Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. MRA Chest, Abdomen, and Pelvis Without IV Contrast Multiple unenhanced MRA techniques such as time-of-flight, phase-contrast imaging, and steady-state free precision (SSFP) have been developed that allow for the evaluation of aortic dissection and aneurysm [44,45]. Even without IV contrast, MRA can be used to precisely evaluate the thoracoabdominal aorta size, as well as for access vessel size, intraluminal thrombus, and branch vessel involvement [37,39]. A 2017 observational study comparing AAA measurements in CTA and noncontrast MRA showed strong agreement, with intraclass coefficient >0.99 and interobserver reproducibility >0.99 for both CTA and MRA [45]. This study also noted a potential benefit of noncontrast MRA allowing evaluation of the composition of intraluminal thrombus, potentially allowing for risk quantification for disease progression [45]. This finding was also supported by a follow-up 2019 article [52].


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Although some studies have shown more accurate measurements with contrast-enhanced MRA compared with noncontrast MRA, other studies have shown an equal ability to detect aortic pathology and to measure aortic size [44,50,51]. A 2014 study comparing thoracic aortic measurements and pathology in 76 patients undergoing both contrast- and noncontrast-enhanced MRA showed high agreement between study types, with low intra- and interobserver dependency (intraclass correlation coefficient 0.99) [51]. A similar 2017 study comparing thoracic aorta measurements/findings on contrast- and noncontrast-enhanced MRA performed on a group of 50 patients favored noncontrast-enhanced MRA over contrast-enhanced MRA as the technique of choice because of superior image quality and better vessel sharpness in the ascending aorta [44]. Although these existing studies focus on the thoracic or abdominal segments of the aorta rather than the thoracoabdominal aorta, findings can likely be extrapolated to the thoracoabdominal aorta.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. MRA Chest and Abdomen Without and With IV Contrast Compared with MRA of the chest, abdomen, and pelvis, exclusion of the pelvis carries the benefit of faster acquisition time. However, extension to the abdomen without the pelvis involved, results in limited evaluation of the iliofemoral vessels to evaluate suitability for possible endovascular intervention or for aneurysm dilation/dissection of the iliac or femoral arteries if pathology extends to the bifurcation.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Thoracoabdominal Aortic Aneurysm or Dissection MRA Chest and Abdomen Without IV Contrast Compared with MRA of the chest, abdomen, and pelvis, exclusion of the pelvis carries the benefit of faster acquisition time. However, extension to the abdomen without inclusion of the pelvis involved results in limited evaluation of the iliofemoral vessels to evaluate suitability for possible endovascular intervention or for aneurysm dilation/dissection of the iliac or femoral arteries if pathology extends to the bifurcation.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Radiography Chest Chest radiographs demonstrate abnormalities in a large percentage of patients with acute thoracoabdominal pathology. Most commonly, a widened mediastinum is appreciated in patients with pathology extending to the proximal to mid thoracic aorta, and a posteroanterior (PA) projection is found to be significantly more accurate than an anteroposterior (AP) projection [53]. Other studies have found that a chest radiograph is not sensitive (64%) or specific (87%) for thoracic aortic disease [54,55]. Given the relatively low sensitivity and specificity, chest radiography should not substitute for cross-sectional imaging. Furthermore, the role of chest radiography in the follow-up of known thoracoabdominal disease is limited because radiographs would be unlikely to appreciate subtle changes in aortic size.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Radiography Chest, Abdomen, and Pelvis There is no relevant literature for chest, abdomen, and pelvis radiographs for the follow-up of thoracoabdominal aortic dissection or aneurysm.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Chest radiographs demonstrate abnormalities in a large percentage of patients with acute thoracoabdominal pathology. Most commonly, a widened mediastinum is appreciated in patients with pathology extending to the proximal to mid thoracic aorta, and a PA projection is found to be significantly more accurate than an AP projection [53]. Other studies have found that a chest radiograph is not sensitive (64%) or specific (87%) for thoracic aortic disease [54,55]. Given the relatively low sensitivity and specificity, chest radiography should not substitute for cross-sectional imaging. Furthermore, the role of chest radiography in the follow-up of known thoracoabdominal disease is limited because radiographs would be unlikely to appreciate subtle changes in aortic size.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. US Duplex Doppler Aorta Abdomen Duplex ultrasound (US) of the abdominal aorta is an option for evaluation of the thoracoabdominal aorta, although the ability to evaluate the aorta above the diaphragm may be markedly limited by acoustic windows. Prior studies comparing US, CT, and MRI of the abdominal aorta found that US is a reliable method to diagnose and follow AAAs [56]. In the evaluation of thoracoabdominal aortic dissection, US can also be used to evaluate blood flow in the true and false lumens and to directly and dynamically monitor the motion of dissection flaps [43]. As such, abdomen US can be performed serially to evaluate for aortic size changes or dissection hemodynamic changes. However, a limited ability to evaluate the thoracic aorta due to difficult acoustic windows could result in poor image quality or the inability to view changes to the aorta.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. US Echocardiography Transthoracic Resting Transthoracic echocardiogram (TTE) allows visualization of the heart and portions of the thoracic aorta. TTE can be used to evaluate the heart for complications such as pericardial effusion in patients with new symptoms [57]. However, portions of the proximal descending thoracic aorta may be poorly visualized with TTE because of patient acoustic windows and habitus, creating the possibility of false-negative examinations in patients with new symptoms [58]. These characteristics have resulted in a low sensitivity of 31% to 55% for the diagnosis of acute type B aortic dissection on TTE [33]. TTE is also limited by the ability to visualize the abdominal aorta to determine the extent of thoracoabdominal aortic pathology.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Variant 2: Planning for endovascular or open repair of thoracoabdominal aorta aneurysm or dissection. Aortography Chest Abdomen Pelvis There is no relevant literature regarding aortography for the planning of thoracoabdominal aortic endovascular or open repair. Aortogram with DSA for evaluation of the thoracic and abdominal aorta has a sensitivity of up to 90% and a specificity of 95% for acute aortic syndrome [27]. The role of aortography before endovascular or open repair is limited to noninvasive modalities such as CTA and MRA. Furthermore, the projectional nature of catheter angiograms limits its ability to evaluate the 3-D configuration of vessels, increasing the risk of error if procedures are planned based on angiogram [59].


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Thoracoabdominal Aortic Aneurysm or Dissection CT Chest, Abdomen, and Pelvis With IV Contrast There is no relevant literature for venous phase CT chest, abdomen, and pelvis for the planning of thoracoabdominal aortic endovascular or open repair. Most preprocedural CT imaging for thoracoabdominal pathology uses an arterially timed contrast bolus in the form of a CTA (discussed below). Although typically not performed for the purpose of procedural planning, contrast-enhanced CT performed to evaluate for extravascular pathology can often assess for acute changes in thoracoabdominal dissection or aneurysm. If venous phase or unenhanced CT has already been performed, additional imaging with CTA may not be required in some patients but may be needed for preprocedure sizing and evaluation of pathology.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CT Chest, Abdomen, and Pelvis Without and With IV Contrast There is no relevant literature for venous phase CT chest, abdomen, and pelvis with noncontrast phase for the planning of thoracoabdominal aortic endovascular or open repair. Most preprocedural CT imaging for thoracoabdominal pathology uses an arterially timed contrast bolus in the form of a CTA (discussed below). Although typically not performed for the purpose of procedural planning, contrast-enhanced CT performed to evaluate for extravascular pathology can often assess for acute changes in thoracoabdominal dissection or aneurysm. If venous phase or unenhanced CT has already been performed, additional imaging with CTA may not be required in some patients but may be needed for preprocedure sizing and evaluation of pathology.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CT Chest, Abdomen, and Pelvis Without IV Contrast There is no relevant literature for CT chest, abdomen, and pelvis without IV contrast for the planning of thoracoabdominal aortic endovascular or open repair. CT without IV contrast would likely be able to assess aortic size and for nonvascular findings, but utility for preprocedure planning would be markedly limited in the absence of IV contrast. If venous phase or unenhanced CT has already been performed, additional imaging with CTA may not be required in some patients but may be needed for preprocedure sizing and evaluation of pathology.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CT Chest and Abdomen With IV Contrast There is no relevant literature for venous phase CT chest and abdomen for the planning of thoracoabdominal aortic endovascular or open repair. Compared with CT of the chest, abdomen, and pelvis, exclusion of the pelvis from the field of view carries the drawback of precluding evaluation of the iliofemoral access vessels if endovascular repair is considered. Furthermore, if the thoracoabdominal dissection or aneurysm extends into the pelvis, a lack of pelvis evaluation could result in incomplete evaluation of the aortic pathology. In select cases with recent imaging of the pelvis or in cases of planned open repair without extension into the pelvic vasculature, further imaging of the pelvis vasculature may not be needed. If venous phase or unenhanced CT has already been performed, additional imaging with CTA may not be required in some patients but may be needed for preprocedure sizing and evaluation of pathology.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CT Chest and Abdomen Without and With IV Contrast There is no relevant literature for venous phase CT chest and abdomen with noncontrast phase for the planning of thoracoabdominal aortic endovascular or open repair. Most preprocedural CT imaging for thoracoabdominal pathology uses an arterially timed contrast bolus in the form of a CTA (discussed below). Although typically not performed for the purpose of procedural planning, contrast-enhanced CT performed to evaluate for extravascular pathology can often assess for acute changes in thoracoabdominal dissection or aneurysm. However, exclusion of the pelvis from the field of view carries the drawback of precluding evaluation of the iliofemoral access vessels if endovascular repair is considered. Furthermore, if the thoracoabdominal dissection or aneurysm extends into the pelvis, lack of pelvis evaluation could result in incomplete evaluation of the aortic pathology. In select cases with recent imaging of the pelvis or in cases of planned open repair without extension into the pelvic vasculature, further imaging of the pelvis vasculature may not be needed. If venous phase or unenhanced CT has already been performed, additional imaging with CTA may not be required in some patients but may be needed for preprocedure sizing and evaluation of pathology.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CT Chest and Abdomen Without IV Contrast There is no relevant literature CT chest and abdomen without contrast for the planning of thoracoabdominal aortic endovascular or open repair. Compared with CT of the chest, abdomen, and pelvis, exclusion of the pelvis from the field of view carries the drawback of precluding evaluation of the iliofemoral access vessels if endovascular repair is considered. If venous phase or unenhanced CT has already been performed, additional imaging with CTA may not be required in some patients but may be needed for preprocedure sizing and evaluation of pathology.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Thoracoabdominal Aortic Aneurysm or Dissection CTA Chest, Abdomen, and Pelvis With IV Contrast The high spatial resolution and profound, homogenous enhancement of the aorta and branch vessels in CTA allows for excellent preoperative assessment. Prior studies dating back to the 2000s have shown CTA to be a valuable tool to evaluate anatomic suitability for endovascular repair of the thoracic or abdominal aorta [31,60-63]. With anatomic coverage from the aortic root to the superficial femoral arteries, CTA can rapidly evaluate the extent of thoracoabdominal aneurysm or dissection as well as provide information valuable for preoperative planning such as aortic tortuosity, branch vessel location and patency, and suitability of femoral access vessels for endovascular repair. CTA can also readily evaluate for complications related to aortic pathology that could affect surgical or procedural plan including aortic rupture, dissection extension, or malperfusion syndrome.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Although TAAA is traditionally treated with open repair, hybrid and endovascular repair of TAAA or dissections have increasingly been used over the past decade [14,64]. Techniques including snorkels/periscopes to allow perfusion of aortic branches, fenestrated EVAR, and branched EVAR have been used for thoracoabdominal aneurysms, and fenestration, branch vessel stenting, and true lumen stenting have progressively been used for thoracoabdominal dissection [9,14,64,65]. Many of these are complex procedures, and precise measurements of the aortic aneurysm or dissection before the procedure facilitates planning and ensures appropriate device availability at the time of procedure [9,65]. The thin slices, high spatial resolution, and isotropic data acquired with CTA permits advanced reconstruction techniques such as centerline measurements and double orthogonal measurements, permitting precise assessment of the aortic and branch vessel anatomy and detailed procedure planning [60- 62,66,67].


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Inclusion of the pelvis in the study also aids in procedure planning by allowing evaluation of the iliofemoral access vessels. Femoral access is typically preferred for endovascular repair, although access vessels must typically be suitable in size, tortuosity, and calcification of the iliac vessels to permit device delivery to the aorta. In patients with inappropriate iliofemoral vessels, groin cutdown with conduit, direct aortoiliac access, or brachial access can be used.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Before open or endovascular repair of a thoracoabdominal aneurysm or dissection, some authors have advocated for imaging for identification of the artery of Adamkiewicz, because preoperative identification could potentially reduce the risk of spinal cord ischemia [68,69]. Given the variability of the origin of this artery, preoperative identification of the origin of this vessel allows for operative planning that minimizes the risk of damage and can reduce surgical times [69]. Multiple studies evaluating the ability of CT and MRI to identify the artery of Adamkiewicz show that the artery can be identified and traced in >75% of patients, with some studies finding >90% identification [68,70-72].


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CTA Chest and Abdomen With IV Contrast Compared with CTA of the chest, abdomen, and pelvis, exclusion of the pelvis carries the drawback of precluding evaluation of the iliofemoral access vessels if endovascular repair is considered. Furthermore, if the thoracoabdominal dissection or aneurysm extends into the pelvis, a lack of pelvis evaluation could result in incomplete evaluation of the aortic pathology. In select cases with recent imaging of the pelvis or in cases of planned open repair without extension into the pelvic vasculature, further imaging of the pelvis vasculature may not be needed.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. MRA Chest, Abdomen, and Pelvis Without and With IV Contrast Although the spatial resolution of MRA without and with IV contrast is less than the spatial resolution of CTA with IV contrast, MRA provides good evaluation of the aorta and branch vessels to allow for procedural or operative planning [38,62,67]. A 2011 study compared image quality, vessel measurements, and proposed endograft selection among MRA and CTA in 30 patients scheduled for EVAR [67]. This analysis found small differences in measured aortic diameter at multiple locations, all <1 mm between MRA and CTA [67]. Ultimately, this study concluded that the image quality for both CTA and MRA was, in general, adequate and that differences were not clinically relevant because all 30 patients had the same endograft components selected based on measurements [67]. Although the study was focused on AAA, the result is likely applicable to measurements of thoracoabdominal aneurysm or dissection, with the caveat that the complexity of endovascular thoracoabdominal repair may place a higher value on precise measurements. MRA is thus able to evaluate the extent of thoracoabdominal aneurysm or dissection as well as to provide information valuable for preoperative planning such as aortic tortuosity, branch vessel location and patency, and suitability of femoral access vessels for endovascular repair. MRA can also evaluate for complications related to aortic pathology that could affect surgical or procedural plan including aortic rupture, dissection extension, or malperfusion syndrome.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Thoracoabdominal Aortic Aneurysm or Dissection


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Although TAAA is traditionally treated with open repair, hybrid and endovascular repair of TAAA or dissections have increasingly been used over the past decade [14,64]. Techniques including snorkels/periscopes to allow perfusion of aortic branches, fenestrated EVAR, and branched EVAR have been used for thoracoabdominal aneurysms, and fenestration, branch vessel stenting, and true lumen stenting have progressively been used for thoracoabdominal dissection [9,14,64,65]. Many of these are complex procedures, and precise measurements of the aortic aneurysm or dissection before procedure facilitates planning and ensures appropriate device availability at the time of procedure [9,65]


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Before open or endovascular repair of a thoracoabdominal aneurysm or dissection, some authors have advocated for imaging for identification of the artery of Adamkiewicz because preoperative identification could potentially reduce the risk of spinal cord ischemia [68]. Given the variability of the origin of this artery, preoperative identification of the origin of this vessel allows for operative planning that minimizes risk of damage. Multiple studies evaluating the ability of CT and MRI to identify the artery of Adamkiewicz show that the artery can be identified and traced in >75% of patients, with identification rates typically higher in MRA compared with CTA [68,70-73].


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. MRA Chest, Abdomen, and Pelvis Without IV Contrast A 2012 study by Shaida et al [63] compared aortic measurements in 20 patients undergoing both CTA and noncontrast MRI before EVAR. The study measured vessel diameter at multiple points as well as several vessel lengths and found small discrepancies between MRI and CTA, typically <1 mm for diameters or 5 mm for lengths [63]. The authors concluded such measurements were unlikely to alter planning of the repair but favored CTA in most patients [63]. Although this study focused on AAA, the result is likely applicable to measurements of thoracoabdominal aneurysm or dissection, with the caveat that the complexity of endovascular thoracoabdominal repair may place a higher value on precise measurements. Similar conclusions were reached by a 2013 study comparing pre-EVAR MRI without IV contrast and CTA [61,74].


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. MRA Chest and Abdomen Without and With IV Contrast Compared with MRA of the chest, abdomen, and pelvis, exclusion of the pelvis carries the drawback of precluding evaluation of the iliofemoral access vessels if endovascular repair is considered. Furthermore, if the thoracoabdominal dissection or aneurysm extends into the pelvis, a lack of pelvis evaluation could result in incomplete evaluation of the aortic pathology. In select cases with recent imaging of the pelvis or in cases of planned open repair without extension into the pelvic vasculature, further imaging of the pelvis vasculature may not be needed.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. MRA Chest and Abdomen Without IV Contrast Compared with MRA of the chest, abdomen, and pelvis, exclusion of the pelvis carries the drawback of precluding evaluation of the iliofemoral access vessels if endovascular repair is considered. Furthermore, if the thoracoabdominal dissection or aneurysm extends into the pelvis, a lack of pelvis evaluation could result in incomplete evaluation of the aortic pathology. In select cases with recent imaging of the pelvis or in cases of planned open repair without extension into the pelvic vasculature, further imaging of the pelvis vasculature may not be needed.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Radiography Chest There is no relevant literature regarding the use of radiography for planning thoracoabdominal aortic endovascular or open repair.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Radiography Chest Abdomen Pelvis There is no relevant literature regarding the use of radiography for planning thoracoabdominal aortic endovascular or open repair.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. US Duplex Doppler Aorta Abdomen There is no relevant literature regarding the use of duplex US for planning thoracoabdominal aortic endovascular or open repair. Although US can be used to evaluate the abdominal aorta for dissection or aneurysm, limitations to


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Thoracoabdominal Aortic Aneurysm or Dissection the evaluation of the spatial relationship of the aorta to branch vessels and the inability to visualize portions of the aorta limit its utility as a sole modality for procedural planning.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. US Echocardiography Transthoracic Resting There is no relevant literature regarding the use of TTE for planning thoracoabdominal aortic endovascular or open repair. Although TTE can evaluate for cardiac complications such as aortic valve regurgitation [33] and evaluate portions of the thoracic aorta, limitations to the evaluation of the spatial relationship of the aorta to branch vessels, the inability to visualize portions of the aorta, and a dependence on operator and patient characteristics limit its utility as a sole modality for procedural planning.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Variant 3: Follow-up after endovascular repair of thoracoabdominal aortic aneurysm or dissection. Aortography Chest Abdomen Pelvis Aortogram with DSA for evaluation of the thoracic and abdominal aorta has a sensitivity of up to 90% and a specificity of 95% for acute aortic syndrome [27]. The role of aortography for routine follow-up after endovascular repair is limited in favor of noninvasive modalities such as CTA and MRA, and CTA has been found to have a higher sensitivity than angiogram [75,76]. In cases of increasing aneurysm sac size likely to require treatment of endoleak, aortogram could be considered because it would allow rapid transition from diagnosis to treatment. Additional benefits of angiogram include the ability to evaluate directionality of endoleaks, which can be difficult on CTA [76].


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CT Chest, Abdomen, and Pelvis With IV Contrast There is no relevant literature regarding venous phase CT chest, abdomen, and pelvis for the follow-up of endovascular repair of thoracoabdominal aneurysm or dissection because most follow-up imaging uses an arterially timed contrast bolus in the form of a CTA (discussed below). However, contrast-enhanced CT can provide similar information as CTA in evaluating the size and extent of aortic pathology, although with a reduced sensitivity to delineating endoleak and subtle changes to aorta and branch artery diameter. Although typically not performed for the purpose of follow-up of thoracoabdominal aortic pathology, contrast-enhanced CT performed to evaluate for extravascular pathology can often assess for acute changes after endovascular repair including endoprosthesis migration or aortic rupture. If venous phase or unenhanced CT has already been performed, additional imaging with CTA may not be required in some patients.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CT Chest, Abdomen, and Pelvis Without and With IV Contrast There is no relevant literature for venous and unenhanced CT chest, abdomen, and pelvis without an arterial phase for follow-up after thoracoabdominal endovascular repair. However, contrast-enhanced CT can provide similar information as CTA in evaluating the size and extent of aortic pathology, although with a reduced sensitivity to delineating endoleak and subtle changes to aorta and branch artery diameter. Although typically not performed for the purpose of follow-up of thoracoabdominal aortic pathology, contrast-enhanced CT performed to evaluate for extravascular pathology can often assess for acute changes after endovascular repair including endoprosthesis migration or aortic rupture. The addition of a noncontrast phase would be expected to aid in identifying endoleak and distinguishing endoleak from other sources of sac/false lumen opacification, although a lack of an arterial phase limits sensitivity. If venous phase or unenhanced CT has already been performed, additional imaging with CTA may not be required in some patients.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CT Chest, Abdomen, and Pelvis Without IV Contrast Typical CT follow-up after endovascular thoracoabdominal aortic repair incorporates arterial and delayed venous phases to evaluate for endoleak [77]. However, unenhanced CT can be used to evaluate aortic caliber to detect changes to a thoracoabdominal aneurysm or aneurysmal degeneration of a thoracoabdominal dissection. Drawbacks of unenhanced imaging include an inability to identify endoleak, evaluate branch vessel patency, or evaluate for false lumen thrombosis in aortic dissection. Nonetheless, some authors have advocated for routine use of noncontrast-enhanced CT over contrast-enhanced CT in patients after EVAR with stable aneurysm sac size, with contrast-enhanced CTA used for evaluation if aortic sac size changes [32,76]. If venous phase or unenhanced CT has already been performed, additional imaging with CTA may not be required in some patients.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CT Chest and Abdomen With IV Contrast There is no relevant literature regarding venous phase CT chest and abdomen for the follow-up of endovascular repair of thoracoabdominal aneurysm or dissection. Compared with CT of the chest, abdomen, and pelvis, evaluation of the chest and abdomen only without imaging of the pelvis may fail to detect changing or new


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Thoracoabdominal Aortic Aneurysm or Dissection pathology in the pelvic vasculature. If venous phase or unenhanced CT has already been performed, additional imaging with CTA may not be required in some patients.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CT Chest and Abdomen Without and With IV Contrast There is no relevant literature for venous and unenhanced CT without an arterial phase for follow-up after thoracoabdominal endovascular repair.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Compared with CT of the chest, abdomen, and pelvis, evaluation of the chest and abdomen only without imaging of the pelvis may fail to detect changing or new pathology in the pelvic vasculature. If venous phase or unenhanced CT has already been performed, additional imaging with CTA may not be required in some patients.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CT Chest and Abdomen Without IV Contrast Compared with CT of the chest, abdomen, and pelvis, evaluation of the chest and abdomen only without imaging of the pelvis may fail to detect changing or new pathology in the pelvic vasculature. If venous phase or unenhanced CT has already been performed, additional imaging with CTA may not be required in some patients.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CTA Chest, Abdomen, and Pelvis With IV Contrast CTA is ideal for evaluation after endovascular repair because of its sensitivity in detecting endoleaks, ability to detect changes in aortic diameter, evaluation of false lumen thrombosis, endograft infection, and assessment of branch vessel/stent patency [1,2,77-79]. Because most endovascular repairs of TAAA or dissection are complex, the need for routine surveillance after treatment is crucial, and often, lifelong follow-up is recommended. A 2016 study of 354 patients undergoing endovascular repair for thoracoabdominal aortic pathology underscores the need for close follow-up, because 36% of patients required further intervention within 36 months, most commonly for endoleak [14]. Typically, follow-up imaging is obtained at 1, 3, and 6 months after intervention to evaluate for endoleak, increase in aortic diameter, incomplete false lumen thrombosis (in dissection), and other procedure complications, and prior studies have shown poor compliance with follow-up and increased risk of aortic rupture in these patients with limited imaging follow-up [17,80]. After 6 months, individualized imaging follow-up may be planned based on personal risk factors, with imaging typically at 6- to 12-month intervals.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Although direct evidence comparing CTA to other modalities in endoleak identification after endovascular thoracoabdominal aneurysm repair is lacking, multiple studies and meta-analyses have compared CTA with MRI and US for endoleak identification after EVAR for AAA [78,79,82,83]. A meta-analysis by Guo et al [82] in 2016 evaluated 3,853 patients after EVAR with paired scans of different modalities (CTA, MRA, US) within a 1-month period. In 2,346 paired CTA and duplex US scans, CTA identified 214 additional endoleaks not seen on duplex US (including 26 type I or type III endoleaks), whereas duplex US identified 77 additional endoleaks not seen on CTA (no type I or III endoleaks) [82]. In 1,694 paired CTA and MRA scans, CTA identified 2 additional endoleaks, whereas MRA identified 42 additional endoleaks [82]. A subsequent meta-analysis in 2018 by Zaiem et al [84] also noted that MRI identified more endoleaks than CTA. These findings suggest higher sensitivity of MRI to detect endoleaks, although the authors caution that the increased endoleaks identified could represent false-positive findings or endoleaks that are not clinically important [84].


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CTA Chest and Abdomen With IV Contrast Compared with CTA of the chest, abdomen, and pelvis, evaluation of the chest and abdomen only without imaging of the pelvis may fail to detect changing or new pathology in the pelvic vasculature that could require additional intervention.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. MRA Chest, Abdomen, and Pelvis Without and With IV Contrast The spatial resolution of MRA is less than that of CTA, but the ability to detect branch vessel complications, endoleaks, stent graft complication, or infection has established MRA as an effective modality for imaging after endovascular repair, particularly for nitinol stent grafts, which have reduced susceptibility artifact. Because most thoracoabdominal aortic repairs are complex, the need for routine surveillance after treatment is crucial, and often, lifelong follow-up is recommended. A 2016 study of 354 patients undergoing endovascular repair for


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Thoracoabdominal Aortic Aneurysm or Dissection thoracoabdominal aortic pathology underscores the need for close follow-up, because 36% of patients required further intervention within 36 months, most commonly for endoleak [14]. Typically, follow-up imaging is obtained at 1, 3, and 6 months after intervention to evaluate for endoleak, increase in aortic diameter, incomplete false lumen thrombosis (in dissection), and other procedure complications, and prior studies have shown poor compliance with follow-up with increased risk of aortic rupture in patients with poor follow-up [17,80]. After 6 months, individualized imaging follow-up may be planned based on personal risk factors, with imaging typically at 6 to 12 month intervals.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Early studies evaluating the ability of MRA to evaluate for endoleak or other complication after EVAR established MRI as a suitable alternative to CTA [78,85,86]. Direct evidence comparing MRA with IV contrast to other modalities in endoleak identification after endovascular thoracoabdominal aneurysm repair is lacking, but multiple additional studies and meta-analyses have compared MRA with CTA in identifying endoleaks after EVAR [78,79,82,83,85,86]. A meta-analysis by Guo et al [82] in 2016 evaluated 3,853 patients after EVAR with paired scans of different modalities (CTA, MRA, US) obtained within a 1-month period. In 1,694 paired CTA and MRA scans, CTA identified 2 additional endoleaks, whereas MRA identified 42 additional endoleaks [82]. A subsequent meta-analysis in 2018 by Zaiem et al also noted that MRI identified more endoleaks than CTA [84]. These findings suggest a higher sensitivity of MRI in identification of endoleak compared with CTA, although the authors caution that the increased endoleaks identified could represent false-positive findings or endoleaks that are not clinically important [84].


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. MRA with IV contrast also allows superior evaluation of flow dynamics compared with CTA. Time resolved and 4-D flow MRA can be used to improve detection and classification of endoleaks [76,87,88]. Use of multiple phases of contrast can be used in 4-D flow MRA to ascertain not only the presence of endoleak but also the endoleak type [88]. MRA with IV contrast has also shown value in predicting the persistence of type II endoleak. A retrospective review of MRAs with type II endoleak performed by Katahashi et al determined that the use of flow quantification could be used to accurately predict persistence or resolution of type II endoleak after EVAR, although this algorithm has not been applied prospectively [20].


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. MRA Chest, Abdomen, and Pelvis Without IV Contrast Literature supporting the use of MRA without IV contrast for evaluation after endovascular thoracoabdominal aortic repair is limited compared with evidence of MRA with IV contrast. A 2019 study evaluating 8 patients used a noncontrast MRI protocol to assess for endoleak after EVAR [89]. This study compared noncontrast MRA with contrast-enhanced CTA and angiogram and found the MRAs had comparable ability to detect endoleaks and assess aneurysm size [89]. The applicability of these findings to imaging post-thoracoabdominal endovascular intervention is unknown, although applicability may be incomplete because of multiple stents within the aorta and branch vessels. Additionally, the ability of this sequence to obtain widespread use is unclear. As such, noncontrast MRA would generally be expected to have a lower sensitivity for endoleak, false lumen thrombosis, or branch vessel patency, although evidence is lacking.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. MRA Chest and Abdomen Without and With IV Contrast Compared with MRA of the chest, abdomen, and pelvis, evaluation of the chest and abdomen only without imaging of the pelvis carries the advantage of reduced imaging time although may fail to detect changing or new pathology in the pelvic vasculature that could require further intervention.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. MRA Chest and Abdomen Without IV Contrast Compared with MRA of the chest, abdomen, and pelvis, evaluation of the chest and abdomen only without imaging of the pelvis carries the advantage of reduced imaging time although may fail to detect changing or new pathology in the pelvic vasculature that could require further intervention.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Radiography Chest Postintervention radiography can be used to monitor endograft position and integrity, with location relative to bony landmarks used to infer possible stent migration [76]. Additionally, prior studies have reported the value of radiography to evaluate for endograft fracture and kinking [76,90]. However, the low incidence of stent fracture and the inability of radiography to evaluate for increasing aneurysm sac size, branch occlusion, and many other complications limits value in routine use. Additionally, a radiograph of the chest only is likely to include only a portion of the repaired aorta within the field of view.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Thoracoabdominal Aortic Aneurysm or Dissection Radiography Chest Abdomen Pelvis Postintervention radiography can be used to monitor endograft position and integrity, with location relative to bony landmarks used to infer possible stent migration [76]. Additionally, prior studies have reported the value of radiography to evaluate for endograft fracture and kinking [76,90]. However, the low incidence of stent fracture and the inability of radiography to evaluate for increasing aneurysm sac size, branch occlusion, and many other complications limits value in routine use.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. US Duplex Doppler Aorta Abdomen Duplex US of the abdominal aorta carries the advantages of being a readily obtainable bedside examination for evaluation of the distal thoracic and abdominal aorta. After EVAR, duplex US can be used to evaluate aortic diameter and presence of endoleak, with a good correlation of aortic size with CTA in most patients [76,91].


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. US Echocardiography Transthoracic Resting TTE allows visualization of the heart and portions of the thoracic aorta. However, portions of the proximal descending thoracic aorta may be poorly visualized with TTE, and examination may be limited by poor acoustic windows, creating the possibility of false-negative examinations in following patients after endovascular thoracoabdominal aortic repair [58]. These characteristics have resulted in a low sensitivity of 31% to 55% for diagnosis of acute type B aortic dissection on TTE [33]. TTE is also limited by the ability to visualize the abdominal aorta to determine the extent of thoracoabdominal aortic pathology.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Variant 4: Follow-up after open repair of thoracoabdominal aortic aneurysm or dissection. Aortography Chest Abdomen Pelvis There is no relevant literature regarding the use of aortography in the evaluation of follow-up of open repair of TAAA or dissection. Aortogram with DSA for evaluation of the thoracic and abdominal aorta has a sensitivity of up to 90% and a specificity of 95% for acute aortic syndrome [27]. Although it has the advantage of allowing immediate intervention if an abnormality is identified, aortography is an invasive procedure that is now typically performed for treatment after diagnosis of a new or worsening aortic pathology.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CT Chest, Abdomen, and Pelvis With IV Contrast There is no relevant literature regarding venous phase CT chest, abdomen, and pelvis for the follow-up of open repair of TAAA or dissection because most follow-up imaging uses an arterially timed contrast bolus in the form of a CTA (discussed below). However, contrast-enhanced CT can provide similar information as CTA in evaluating the size and extent of aortic pathology and in identifying postsurgical complications. If venous phase or unenhanced CT has already been performed, additional imaging with CTA may not be required in some patients.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CT Chest, Abdomen, and Pelvis Without and With IV Contrast There is no relevant literature regarding venous phase CT chest, abdomen, and pelvis with noncontrast phase for the follow-up of open repair of TAAA or dissection because most follow-up imaging uses an arterially timed contrast bolus in the form of a CTA (discussed below). However, contrast-enhanced CT can provide similar information as CTA in evaluating the size and extent of aortic pathology and in identifying postsurgical complications. If venous phase or unenhanced CT has already been performed, additional imaging with CTA may not be required in some patients.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CT Chest, Abdomen, and Pelvis Without IV Contrast There is no relevant literature for CT chest, abdomen, and pelvis without IV contrast in the evaluation of follow-up of open repair of TAAA or dissection. Although most follow-up after open thoracoabdominal aortic repair is performed with IV contrast [29-31], select groups of patients may be monitored with noncontrast CT to evaluate measurements of aortic size and for surrounding changes that could suggest inflammation or infection. If venous phase or unenhanced CT has already been performed, additional imaging with CTA may not be required in some patients.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Thoracoabdominal Aortic Aneurysm or Dissection CT Chest and Abdomen With IV Contrast There is no relevant literature regarding venous phase CT chest and abdomen for the follow-up of open repair of TAAA or dissection. Compared with CT of the chest, abdomen, and pelvis, exclusion of the pelvis may fail to detect changing or new pathology in the pelvic vasculature. If venous phase or unenhanced CT has already been performed, additional imaging with CTA may not be required in some patients.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CT Chest and Abdomen Without and With IV Contrast There is no relevant literature regarding venous phase CT chest, abdomen, and pelvis with noncontrast phase for the follow-up of open repair of TAAA or dissection. Compared with CT of the chest, abdomen, and pelvis, evaluation of the chest and abdomen only without imaging of the pelvis may fail to detect changing or new pathology in the pelvic vasculature. If venous phase or unenhanced CT has already been performed, additional imaging with CTA may not be required in some patients.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CT Chest and Abdomen Without IV Contrast There is no relevant literature for CT chest and abdomen without IV contrast in the evaluation of follow-up of open repair of TAAA or dissection. Compared with CT of the chest, abdomen, and pelvis, exclusion of the pelvis may fail to detect changing or new pathology in the pelvic vasculature. If venous phase or unenhanced CT has already been performed, additional imaging with CTA may not be required in some patients.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CTA Chest, Abdomen, and Pelvis With IV Contrast CTA of the chest, abdomen, and pelvis with IV contrast uses fast scan times to allow for rapid evaluation of the aorta. Acquisition of thin axial slices with subsequent reconstruction along with extensive and homogenous luminal opacification allows for precise and reproducible measurements of the aorta, which are valuable for monitoring aortic growth and interval changes [33,34].


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. In addition to monitoring aortic size and postsurgical complications such as anastomotic pseudoaneurysm, CTA can evaluate for endograft complications, kinking or occlusion/stenosis of branches of the graft, infection, or complications including thoracoabdominal aneurysm rupture or dissection extension [31,35].


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Evidence comparing CTA with MRA for follow-up after surgical thoracoabdominal aortic repair is limited. A 2015 review of imaging of the thoracic aorta concluded that contrast-enhanced CT was the optimal modality evaluation of the aorta after surgical repair, although MRI is also comparable and with image resolution comparable to CTA [33].


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Compared with CTA of the chest and abdomen, imaging of the pelvis carries the benefit of evaluation of the iliofemoral vessels to assess for new or worsening pathology of the pelvic vessels.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. CTA Chest and Abdomen With IV Contrast Compared with CTA of the chest, abdomen, and pelvis, CTA of the chest and abdomen may fail to identify new or worsening pelvic pathology.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. MRA Chest, Abdomen, and Pelvis Without and With IV Contrast MRA of the chest, abdomen, and pelvis without and with IV contrast can be used as an alternative to CTA for follow-up after open thoracoabdominal aortic repair. Spatial resolution of MRA is not as high as CTA, although some authors have found MRI to be an alternative option for imaging in younger patients [33].


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. In addition to monitoring aortic size and postsurgical complication such as anastomotic pseudoaneurysm, CTA can evaluate for graft complications, kinking or occlusion/stenosis of branches of the graft, infection, or complications including thoracoabdominal aneurysm rupture or dissection extension. MRA can also assess flow dynamics including wall stress and turbulent flow patterns, which may be valuable in certain patients [23,24].


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Compared with MRA of the chest and abdomen, imaging of the pelvis carries the benefit of evaluation of the iliofemoral vessels to assess for new or worsening pathology of the pelvic vessels. The drawback of inclusion of the pelvis is increased acquisition time.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. MRA Chest, Abdomen, and Pelvis Without IV Contrast Evidence supporting use of MRA without IV contrast for evaluation after open thoracoabdominal aortic repair is limited compared with evidence of MRA with IV contrast.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Similar to CTA, MRA of the thoracoabdominal aorta allows for precise and reproducible assessment of aortic sac size in aneurysm or extent of dissection in thoracoabdominal aortic dissection [33,37-39]. Multiple unenhanced


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Thoracoabdominal Aortic Aneurysm or Dissection MRA techniques such as time-of-flight, phase-contrast imaging, and SSFP have been developed that allow for evaluation of aortic dissection and aneurysm, including after open surgical repair [44,45]. Even without IV contrast, MRA can be used to precisely evaluate the thoracoabdominal aorta [37,39]. A 2017 observational study comparing AAA measurements in contrast-enhanced CTA and noncontrast-enhanced MRA showed strong agreement, with intraclass coefficient >0.99 and interobserver reproducibility >0.99 for both CTA and MRA [45].


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Although some studies have shown more accurate measurements with contrast-enhanced MRA compared with noncontrast-enhanced MRA, other studies have shown equal ability to detect aortic pathology and to measure aortic size [44,50,51]. A 2014 study comparing thoracic aortic measurements and pathology in 76 patients undergoing both contrast- and noncontrast-enhanced MRA showed high agreement between study types, with low intra- and interobserver dependency (intraclass correlation coefficient 0.99) [51]. A similar 2017 study comparing thoracic aorta measurements/findings on contrast- and noncontrast-enhanced MRA performed on a group of 50 patients favored noncontrast-enhanced MRA over contrast-enhanced MRA as the technique of choice because of superior image quality and better vessel sharpness in the ascending aorta [44]. Although these studies do not focus on postsurgical patients, the findings are likely applicable to this patient population.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. MRA Chest and Abdomen Without and With IV Contrast Compared with MRA of the chest, abdomen, and pelvis, imaging of the chest and abdomen reduces acquisition time, although is unable to assess for new or worsening pathology within the pelvis.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. MRA Chest and Abdomen Without IV Contrast Compared with MRA of the chest, abdomen, and pelvis, imaging of the chest and abdomen reduces acquisition time, although is unable to assess for new or worsening pathology within the pelvis.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Radiography Chest There is no relevant literature for radiography in the evaluation of follow-up of open repair of TAAA or dissection. After surgical repair of the thoracoabdominal aorta, radiography is unlikely to carry a sufficient sensitivity or specificity to be used routinely.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Radiography Chest Abdomen Pelvis There is no relevant literature for radiography in the evaluation of follow-up of open repair of TAAA or dissection. After surgical repair of the thoracoabdominal aorta, radiography is unlikely to carry a sufficient sensitivity or specificity to be used routinely.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. US Duplex Doppler Aorta Abdomen Duplex US of the abdominal aorta is an option for evaluation of the thoracoabdominal aorta, although the ability to evaluate the aorta above the diaphragm may be markedly limited by acoustic windows. Prior studies comparing US, CT, and MRI of the abdominal aorta found that US is a reliable method to diagnose and follow AAAs [56]. In the evaluation of thoracoabdominal aortic dissection, US can also be used to evaluate blood flow in the true and false lumens and to directly and dynamically monitor the motion of dissection flaps [43]. As such, abdomen US can be performed serially to evaluate for aortic size changes or dissection hemodynamic changes. However, a limited ability to evaluate the thoracic aorta with dependence on patient acoustic windows could result in poor image quality or the inability to view changes to the aorta.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Thoracoabdominal Aortic Aneurysm or Dissection


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Supporting Documents The evidence table, literature search, and appendix for this topic are available at https://acsearch.acr.org/list. The appendix includes the strength of evidence assessment and the final rating round tabulations for each recommendation.


Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. For additional information on the Appropriateness Criteria methodology and other supporting documents go to www.acr.org/ac.


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Introduction/Background Spine infection is a disease that occurs when either microorganisms or viruses invade and involve one or more structures within or surrounding the spine [1-7]. Although uncommon, the incidence of spine infection appears to be increasing because of a combination of predisposing factors, such as an increasing number of susceptible hosts, an increase in the number of interventional and surgical spine procedures, and an increase in diagnostic testing [5,8- 11]. Potential host factors include preexisting extraspinal infection (endocarditis, HIV, pulmonary infection), intravenous (IV) drug use, diabetes mellitus, hepatic or renal failure, rheumatologic disease, or immunosuppression [12,13]. Spine infection presents a diagnostic and management challenge [14]. Diagnostic delay is not uncommon because of an often indolent clinical presentation with nonspecific presenting signs and symptoms such as back pain, fever, and, less commonly, neurologic compromise [3,8,10]. The location of the spine infection is also important because it may influence the clinical presentation and the subsequent imaging evaluation. One or more spine structures and/or compartments may be infected, and this also influences the imaging findings [1,14]. Spine infection is often extradural, initially invading the vertebral endplate in adults via a hematogenous route and centering about the vertebral endplate (osteomyelitis) and intervertebral disc (discitis). Spine infection may also arise initially within a facet joint. Spine infection occurs less frequently in children and initially affects the intervertebral disc [15]. Epidural and paraspinal soft tissue involvement are not uncommon [16,17]. Other important clinical manifestations of spine infection with imaging and management implications include epidural (abscess), subarachnoid (meningitis) space involvement, or spinal cord involvement (myelitis) [18,19]. Multilevel or multifocal spine infection may be observed in specific patient groups, such as IV drug users, postoperative spine patients, or in geographic regions with endemic infections such as tuberculosis, coccidioidomycosis, or neurocysticercosis [5,20-22]. The type of infection, whether pyogenic, granulomatous, parasitic, or viral, will likewise influence the clinical and imaging presentation [2,4,5,7,23-26].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Imaging is important for suggesting the diagnosis of spine infection, guiding percutaneous spine biopsy procedures, defining the full extent of infection for the purposes of determining medical and/or surgical management, and for possible clinical follow-up [27-31]. Diagnostic imaging can be used to assess suspected spinal cord compression as well as to evaluate for potential spinal instability, either of which, if present will influence surgical intervention [8,32]. Several diagnostic imaging examinations have been previously utilized in the evaluation and management of spine infection and include radiography, CT, nuclear scintigraphy with various radionuclides, and MRI [20,31,33-37]. Recently, PET/CT has seen increasing application in the evaluation of suspected spine infection, particularly in the postoperative spine [38-45]. PET/MRI is undergoing preliminary investigation for possible use in spine infection [46].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through representation of such organizations on expert panels. Participation on the expert panel does not necessarily imply endorsement of the final document by individual contributors or their respective organization.


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Reprint requests to: publications@acr.org


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Suspected Spine Infection Although imaging studies have a role in the diagnostic evaluation of suspected spine infection, a high index of clinical suspicion for an infectious etiology is required in order to initiate the clinical workup [47]. Important laboratory parameters that may be assessed include serum erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), white blood cell (WBC) count with differential, and blood cultures [37,48-50]. Other testing such as for brucella or mycobacterium may be helpful if the patient is from the appropriate endemic area [2,4,5,7]. Because the imaging appearance of spine infection may overlap with other noninfectious pathologic entities, such as degenerative disc disease, inflammation, trauma, or neoplasm, spine biopsy with microbiologic and histopathologic analysis of the infected tissue is often required for diagnostic confirmation [35,51-58].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Special Imaging Considerations Although the clinical presentation and physical examination can help localize the level of suspected spine infection, in specific clinical situations it may be beneficial to image the entire spine [21,59]. This may be influenced by clinical presentation and patient factors such as a history of IV drug use, specific pathogens such as tuberculosis, or initial imaging findings that demonstrate multilevel spine involvement [21,59-61].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Like other spine infections, spinal epidural abscess has increased in incidence and is now seen in 2.5 to 3/10,000 patients [3,60]. Epidural abscess is often associated with diagnostic delay that can potentially lead to significant neurologic morbidity and mortality. Patients with preexisting risk factors, such as having a potential source for infection (preexisting infection, IV drug use, recent spine procedure) or a reason for being immunosuppressed (diabetes, steroid use) and patients with an elevated ESR, may be at increased risk for epidural abscess [18,21,22,62].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. OR Discussion of Procedures by Variant Variant 1: Suspected spine infection (such as epidural abscess or discitis osteomyelitis), with new or worsening back or neck pain, with or without fever, who may have one or more of the following red flags (diabetes mellitus, IV drug use, cancer, HIV, or dialysis) or abnormal lab values. Initial imaging. The annual incidence of spine infection ranges from 4 to 24 per million per year [10]. In the presence of red flag conditions (diabetes mellitus, IV drug use, cancer, HIV, or dialysis) or abnormal lab values, imaging may be indicated if there is a clinical suspicion for spine infection in a patient with neck or back pain with or without fever. Clinically, it may be difficult to differentiate spine infection from other causes of neck or back pain such as degenerative disease, trauma, inflammatory spondyloarthropathy, or neoplastic involvement of the spine [3,35,55]. As any one of these clinical entities has the potential to mimic the imaging appearance of spine infection, it is important to use the combination of clinical presentation, laboratory values such as an elevated ESR and CRP and imaging findings in order to consider the diagnosis of spine infection [8].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. The body regions covered in this clinical scenario are the cervical, thoracic, and lumbar spine. These body regions might be evaluated separately or in combination as guided by physical examination findings, patient history, and other available information.


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. CT Spine Area of Interest As a result of its excellent delineation of osseous detail and greater sensitivity than radiography, CT can be used in the evaluation of spine infection [3]. The addition of IV contrast increases the conspicuity of paraspinal soft tissue abnormalities, such as inflammation or abscess that may be caused by infection. In those cases in which a contrast- enhanced CT is to be performed, it is not necessary or useful to perform a noncontrast-enhanced CT first, because this latter examination does not add more diagnostic information. The sensitivity and specificity of CT for spine infection is 79% and 100%, respectively [33]. CT has low sensitivity (6%) for the identification of epidural abscess


Suspected Spine Infection PCAs

Suspected Spine Infection

Suspected Spine Infection PCAs. Suspected Spine Infection


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. [33]. CT is often utilized to evaluate suspected spine infection when MRI is equivocal [3]. It is also of value in presurgical planning for patients with suspected infection-related spine instability, cord compression, as well as follow-up evaluation of the instrumented spine [30]. CT is often used to facilitate percutaneous image-guided spine biopsy [52,57].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Radiography Spine Area of Interest Radiography can be used as part of the initial evaluation in patients with suspected spine infection. Radiographs may not show any abnormalities during the early course of spine infection [3]. Imaging findings such as disc space narrowing, vertebral endplate erosion, and gross paraspinal soft tissue changes that can be seen on radiography lag behind the clinical course of spine infection by at least 2 to 8 weeks [3,10,31]. Nevertheless, the possible presence of one or more of these findings may increase the clinical suspicion for infection and may help guide subsequent imaging management. Radiographs, however, provide an overall view of the status and alignment of the vertebral column and can be used to assess for spinal instability [8].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. 3-Phase Bone Scan Complete Spine A 3-phase bone scan with Tc-99m-methylene diphosphonate (MDP) has variable moderate-to-high sensitivity (81.4%) and low specificity (40.7%) for spine infection [31]. The advantages of skeletal scintigraphy include that it can be performed and completed in 1 day. Because of the imaging time required for a 3-phase bone scan, it tends to be utilized in select situations [3].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Gallium Scan Whole Body Ga-67 scintigraphy combined with single-photon emission computed tomography (SPECT) can be used to evaluate suspected spine infection. Ga-67 is less sensitive (73%) but more specific (61%) than skeletal scintigraphy [31]. The disadvantages of the gallium examination include a requirement for delayed images (24 to 72 hours). [31]. A Tc-99m-MDP study can be combined with Ga-67-citrate in order to improve the overall specificity of the examination (81%) while maintaining a sensitivity of 78% [31,36]. This combined examination may be utilized in select clinical situations such as when multifocal infection is suspected [3].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. WBC Scan and Sulfur Colloid Scan Complete Spine A labeled leukocyte and sulfur colloid study is limited in the evaluation of spine infection as areas of infection often demonstrate decreased or absent radionuclide uptake [31].


Suspected Spine Infection PCAs

Suspected Spine Infection


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Variant 2: Suspected spine infection (such as epidural abscess or discitis osteomyelitis), with recent intervention (such as surgery with or without hardware, pain injection, or stimulator implantation). Initial imaging. The mean incidence of postoperative instrumented spine infection is approximately 2% to 3% [40]. The diagnosis of postintervention spine infection is a clinical challenge given an overlap of clinical symptoms such as neck or back pain between postoperative and spine infection patients. The identification of abnormal laboratory parameters, such as leukocytosis or elevated ESR or CRP, may increase the clinical suspicion for spine infection in the postintervention patient [8,9]. The timing of the imaging examination with respect to when the spine intervention is performed is particularly important, because expected findings such as alteration of soft tissue and osseous structures, edema, and small paraspinal fluid collections such as seromas may represent the normal sequelae of an intervention shortly (a few days to weeks) after the procedure [28,29,48,69].


Suspected Spine Infection PCAs


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. CT Spine Area of Interest CT may be used to assess the spine for suspected infection, particularly following any surgical or interventional procedure, without or with spinal implants [3,30]. When initially considering the diagnosis of spine infection, it is important to use a combination of clinical presentation in the context of these red flags, abnormal laboratory values such as elevated ESR and CRP or leukocytosis, and abnormal imaging findings [8].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. In the postoperative spine, CT may show implant loosening or malpositioning as well as malalignment and imaging findings that may be caused by infection. The addition of IV contrast increases the conspicuity of paraspinal soft tissue abnormalities, such as inflammation or abscess that may be caused by infection. In those cases in which a contrast-enhanced CT is to be performed, it is not necessary or useful to perform a noncontrast-enhanced CT first, because this latter examination does not add more diagnostic information. The sensitivity and specificity of CT for spine infection is 79% and 100%, respectively, but CT has low sensitivity (6%) for the identification of epidural abscess [33].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. MRI Spine Area of Interest Because of its excellent tissue characterization and anatomic delineation, MRI without and with IV contrast has a sensitivity of 96% and a specificity of 94% for the evaluation of patients with suspected spine infection [3,7,14,16,24,37,51]. MRI without and with IV contrast is often utilized for the evaluation of patients who have undergone recent spine interventions and have suspected spine infection [3,7,14,16,24,37,51]. Artifact reduction techniques are often required in patients who have spinal instrumentation. MRI also provides optimal depiction of


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Radiography Spine Area of Interest Radiographs are insensitive during the early course of spine infection [3]. In the subacute or chronic phase of infection, radiographs can be helpful in the follow-up evaluation of the posttreatment spine because serial radiographic studies may show new abnormalities such as implant loosening or alteration in spinal alignment that might be caused by infection [10].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. 3-Phase Bone Scan A 3-phase bone scan with Tc-99m-MDP has variable moderate-to-high sensitivity (81.4%) and low specificity (40.7%) for spine infection [31].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Gallium Scan Whole Body Ga-67 scintigraphy combined with SPECT can be used to evaluate suspected spine infection in patients who have undergone recent spine interventions. Ga-67 is less sensitive (73%) but more specific (61%) than skeletal scintigraphy [31]. A dual Ga-67 and Tc-99m-MDP study can increase the overall specificity of the examination to 81% with a sensitivity of 73% [3,10,31,36]. This combined study can be used to assess the postoperative or postprocedure spine in cases of suspected spine infection when MRI imaging findings are equivocal [3,10].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. WBC Scan and Sulfur Colloid Scan Complete Spine A labeled leukocyte and sulfur colloid study is limited in the evaluation of spine infection because areas of infection often demonstrate decreased or absent radionuclide uptake [31].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. FDG-PET/CT Whole Body FDG-PET with CT has seen increasing application for the assessment of suspected spine infection in select cases as a complementary examination [10,31]. Increased FDG uptake is seen at sites of infection with an elevated SUVmax value. FDG-PET/CT can be used in the evaluation of the postsurgical or postprocedure spine for suspected infection when the MRI examination is inconclusive. Initial studies with FDG-PET/CT have shown the utility of this study in the initial evaluation of potentially infected spinal implants in selected patients [40].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Variant 3: Suspected spine infection (such as epidural abscess or discitis osteomyelitis), with new neurologic deficit or cauda equina syndrome. Initial imaging. The presence of a new neurologic deficit or cauda equina syndrome may be due to spinal cord or cauda equina compromise by either epidural abscess, displaced infected vertebral and/or disc material, or infection-mediated spinal malalignment or instability. The incidence of epidural abscess is 2.5 to 3 per 10,000 hospital admissions [14,60]. Although neurologic deficits are seen in 10% to 15% of cases of spine infection, these clinical situations require immediate imaging attention because the imaging evaluation helps to determine the location and extent of the spinal canal compromise [3,60].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. The body regions covered in this clinical scenario are the cervical, thoracic, and lumbar spine. These body regions might be evaluated separately or in combination as guided by physical examination findings, patient history, and other available information.


Suspected Spine Infection PCAs

Suspected Spine Infection

Suspected Spine Infection PCAs. Suspected Spine Infection


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. CT Spine Area of Interest Noncontrast and contrast-enhanced CT have an overall low sensitivity (6%) for the identification of epidural abscess [33]. Gross spinal cord compression with compromise of the spinal canal (>50% canal narrowing) may be seen in more advanced cases of spine infection [71]. The addition of IV contrast increases the conspicuity of paraspinal soft tissue abnormalities, such as inflammation or abscess that may be caused by infection. In those cases in which a contrast-enhanced CT is to be performed, it is not necessary or useful to perform a noncontrast-enhanced CT first, because this latter examination does not add more diagnostic information. The sensitivity and specificity of CT for spine infection is 79% and 100%, respectively [33]. CT with multiplanar reformations is often used in surgical planning and follow-up [8].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. MRI Spine Area of Interest Because of its excellent tissue characterization and anatomic delineation, MRI without and with IV contrast has a sensitivity of 96% and a specificity of 94% for the evaluation of patients with suspected spine infection [3,7,14,16,24,37,51]. MRI also provides optimal depiction of the intraspinal contents including the epidural space and the spinal cord [6,17,18].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. The use of MRI without and with IV contrast on an emergent or urgent basis, in patients with preexisting risk factors for possible spine infection and with an elevated ESR, may facilitate a more prompt diagnosis of spinal canal compromise by epidural abscess or other infected displaced structures. Epidural abscess is a feared complication of spine infection that may result in spinal cord and or cauda equina compression. The use of IV contrast helps to identify these abnormal epidural fluid collections, define their size and extent, and determine the presence of spinal cord and/or cauda equina compression [3]. MRI when performed without IV contrast may have utility, because it can show findings that are suggestive of possible spine infection, including marrow or paraspinal muscle edema, abnormal fluid collections, areas of abnormal signal, abnormality within the intervertebral disc, and adjacent vertebral endplates and gross structural abnormalities of the involved spine segment(s) [3,10,14,16,17,30,63-66,69]. MRI performed with IV contrast only is not considered to be useful because the precontrast MRI study is required for comparison in order to confirm areas of suspected abnormality within the spine segment(s) of interest. The presence and extent or the absence of contrast enhancement are important imaging features in suspected spinal infection and are best evaluated by comparing the pre- and postcontrast MRI examinations.


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Radiography Spine Area of Interest Radiography is insensitive to the evaluation of the epidural space and to possible spinal cord compression and is therefore not useful as the initial imaging examination in patients presenting with neurologic compromise. As a complementary imaging study, radiography may help guide the imaging evaluation in those cases in which frank disc and vertebral body involvement by an infectious process is evident. Radiography can serve as a complementary test in order to assist with surgical management in those patients who may require surgical decompression and stabilization of the affected spinal segment [72].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. 3-Phase Bone Scan There is no relevant literature regarding the use of bone scans in the initial imaging evaluation of a suspected spinal infection with a new neurologic deficit or cauda equina syndrome.


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. WBC Scan and Sulfur Colloid Scan Complete Spine There is no relevant literature regarding the use of WBC scans in the initial imaging evaluation of a suspected spinal infection with a new neurologic deficit or cauda equina syndrome.


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Gallium Scan Whole Body There is no relevant literature regarding the use of gallium scans in the initial imaging evaluation of a suspected spinal infection with a new neurologic deficit or cauda equina syndrome.


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. FDG-PET/CT Whole Body There is no relevant literature regarding the use of FDG-PET/CT in the initial imaging evaluation of a suspected spinal infection with a new neurologic deficit or cauda equina syndrome.


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Variant 4: Suspected spine infection (such as epidural abscess or discitis osteomyelitis), with decubitus ulcer or wound overlying spine. Initial imaging. Decubitus ulcers are often encountered at the level of the sacrum in chronically bedridden patients but may also be seen at other pressure sites along the back in immobile patients. When there is a clinical concern for possible spine infection extending from a decubitus ulcer or wound due to surgery or other causes [14], imaging may be necessary


Suspected Spine Infection PCAs

Suspected Spine Infection


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. for further evaluation of the involved spinal segment. Imaging can be utilized to distinguish between superficial infection or cellulitis and deeper infections including osteomyelitis and paraspinal or epidural abscess formation [31,48].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. The body regions covered in this clinical scenario are the cervical, thoracic, lumbar spine, and sacrum. These body regions might be evaluated separately or in combination as guided by physical examination findings, patient history, and other available information.


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. CT Spine Area of Interest As a result of its excellent delineation of osseous detail and greater sensitivity than radiography, CT can be used in the evaluation of suspected osteomyelitis as a complication from a decubitus ulcer or wound overlying the spine [3]. The addition of IV contrast increases the conspicuity of paraspinal soft tissue abnormalities, such as inflammation or abscess that may be caused by infection. In those cases in which a contrast-enhanced CT is to be performed, it is not necessary or useful to perform a noncontrast-enhanced CT first, because this latter examination does not add more diagnostic information. The sensitivity and specificity of CT for spine infection is 79% and 100%, respectively [33]. CT may be used to assess the spine for suspected infection following any surgical or interventional procedure [3,30].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. MRI Spine Area of Interest Because of its excellent tissue characterization and anatomic delineation, MRI without and with IV contrast can be utilized for the evaluation of patients with suspected spine infection at the site of a decubitus ulcer or wound [3,7,14,16,24,37,51]. The sensitivity and specificity of MRI for spine infection is 96% and 94%, respectively [14]. The use of IV contrast not only increases lesion conspicuity, characterized by foci of abnormal soft tissue enhancement and peripherally enhancing fluid collections within and/or surrounding the affected spinal segment, but also helps to define the extent of the infectious process [3]. MRI is also used to help distinguish expected postoperative changes at the surgical skin site from infection and contrast-enhanced MRI can be used to assess postoperative fluid collections for suspected infection [28,29,69,70]. MRI when performed without IV contrast may have utility, because it can show findings that are suggestive of possible spine infection, including marrow or paraspinal muscle edema, abnormal fluid collections, areas of abnormal signal, abnormality within the intervertebral disc, and adjacent vertebral endplates and gross structural abnormalities of the involved spine segment(s) [3,10,14,16,17,30,63-66,69]. MRI performed with IV contrast only is not considered to be useful because the precontrast MRI study is required for comparison in order to confirm areas of suspected abnormality within the spine segment(s) of interest. The presence and extent or the absence of contrast enhancement are important imaging features in suspected spinal infection and are best evaluated by comparing the pre- and postcontrast MRI examinations.


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Radiography Spine Area of Interest Radiography provides a quick survey of the soft tissues and underlying osseous structures at the site of suspected spine infection when either a decubitus ulcer or wound is present [3]. Radiography can be used to tailor a subsequent cross-sectional imaging examination especially in patients with prior spine surgery or interventions [8].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. 3-Phase Bone Scan A 3-phase bone scan with Tc-99m-MDP has variable moderate-to-high sensitivity (81.4%) and low specificity (40.7%) for suspected spine infection with decubitus ulcer or wound overlying the spine [31].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Gallium Scan Whole Body Ga-67 scintigraphy combined with SPECT can be used to evaluate suspected infection involving a decubitus ulcer or wound overlying the spine. Ga-67 is less sensitive (73%) but more specific (61%) than skeletal scintigraphy [31]. The disadvantages of the gallium examination include a requirement for delayed images (24 to 72 hours) [31]. A dual Ga-67 and Tc-99m-MDP examination has a similar sensitivity (73%) and an increased specificity (81%) [31]. This combined examination may be utilized in select clinical situations such as when spine infection is suspected adjacent to a decubitus ulcer or wound [31].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. WBC Scan and Sulfur Colloid Scan Complete Spine A labeled leukocyte and sulfur colloid study is limited in the evaluation of spine infection because areas of infection often demonstrate decreased or absent radionuclide uptake [31].


Suspected Spine Infection PCAs

Suspected Spine Infection

Suspected Spine Infection PCAs. Suspected Spine Infection


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. FDG-PET/CT Whole Body FDG-PET with CT has seen increasing application for the assessment of suspected spine infection in select cases as a complementary examination [10,31]. Increased FDG uptake is seen at sites of infection with an elevated SUVmax value. FDG-PET/CT can be used in the evaluation of the postsurgical spine for suspected infection of the skin wound when MRI is inconclusive.


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Variant 5: Suspected spine infection (such as epidural abscess or discitis osteomyelitis). Abnormal radiographs or CT findings. Next imaging study. When an imaging study such as a radiograph or CT of the spine raises a concern for possible spine infection, additional imaging may be required. Because there are other pathologic entities, such as degenerative, traumatic, or inflammatory spondyloarthropathy, which can simulate spine infection on the initial radiographs or CT images, additional imaging is used in conjunction with the clinical evaluation in order to make the appropriate diagnosis [55].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. The body regions covered in this clinical scenario are the cervical, thoracic, and lumbar spine. These body regions might be evaluated separately or in combination as guided by physical examination findings, patient history, and other available information, including prior imaging.


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. MRI Spine Area of Interest Because of its excellent tissue characterization and anatomic delineation, MRI without and with IV contrast is often utilized for the evaluation of patients with suspected spine infection [3,7,14,16,24,37,51]. MRI without and with IV contrast has a sensitivity of 96% and a specificity of 94% for the evaluation of patients with suspected spine infection [3,7,14,16,24,37,51]. MRI also provides optimal depiction of the intraspinal contents, including the epidural space and the spinal cord [6,17,18]. The use of IV contrast increases lesion conspicuity, characterized by foci of abnormal soft tissue enhancement and peripherally enhancing fluid collections within and/or surrounding the affected spinal segment, and also helps to define the extent of the infectious process [3]. MRI can be performed as the next imaging study when the initial radiographs and/or CT examination show abnormal findings that may be indicative of spine infection. MRI when performed without IV contrast may have utility, because it can show findings that are suggestive of possible spine infection, including marrow or paraspinal muscle edema, abnormal fluid collections, areas of abnormal signal, abnormality within the intervertebral disc, and adjacent vertebral endplates and gross structural abnormalities of the involved spine segment(s) [3,10,14,16,17,30,63-66,69]. MRI performed with IV contrast only is not considered to be useful because the precontrast MRI study is required for comparison in order to confirm areas of suspected abnormality within the spine segment(s) of interest. The presence and extent or the absence of contrast enhancement are important imaging features in suspected spinal infection and are best evaluated by comparing the pre- and postcontrast MRI examinations.


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. 3-Phase Bone Scan A 3-phase bone scan with Tc-99m-MDP can be used to evaluate abnormal radiographic or CT findings in a patient with suspected spine infection [31].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Gallium Scan Whole Body Ga-67 scintigraphy combined with SPECT can be used to evaluate abnormal radiographic or CT findings in a patient with suspected spine infection. Ga-67 is less sensitive (73%) but more specific (81%) than skeletal scintigraphy [31]. The disadvantages of the gallium examination include a requirement for delayed images (24 to 72 hours) [31]. A combined Ga-67 and Tc-99m-MDP examination has a sensitivity (73%) and specificity (81%) [31] and can also be used to assess the abnormal imaging findings in cases of suspected spine infection when MRI findings are equivocal [3,10].


Suspected Spine Infection PCAs


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. FDG-PET/CT Whole Body FDG-PET with CT may be considered as a complementary imaging study in select patients with suspected spine infection who already have an abnormal radiographic or CT examination [10,31]. Specifically, these are patients in whom the MRI is inconclusive, such as postsurgical spine patients. FDG-PET with CT shows increased FDG uptake at sites of suspected spine infection and has a sensitivity of 94.8% with a specificity of 91.4% [44].


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. Supporting Documents The evidence table, literature search, and appendix for this topic are available at https://acsearch.acr.org/list. The appendix includes the strength of evidence assessment and the final rating round tabulations for each recommendation.


Suspected Spine Infection PCAs

Suspected Spine Infection PCAs. For additional information on the Appropriateness Criteria methodology and other supporting documents go to www.acr.org/ac.


Suspected Spine Infection PCAs

Suspected Spine Infection


Clinically Suspected Vascular Malformation of the Extremities. Introduction/Background Vascular anomalies encompass a broad range of pathologies histologically composed of vascular type cells. These lesions are most commonly classified by the International Society for the Study of Vascular Anomalies according to their underlying histology as either vascular malformations or vascular tumors. Vascular malformations represent focal structural abnormalities of the vascular tree, typically related to developmental errors during vasculogenesis [1], whereas, vascular tumors are caused by neoplastic cellular proliferation of the endothelium [1]. The extremities are the most common site of these vascular lesions outside of the head and neck [1,2].


Clinically Suspected Vascular Malformation of the Extremities. Vascular malformations more commonly represent isolated spontaneous lesions yet can be part of one of several syndromes such as Parkes Weber syndrome [1,3]. These typically grow commensurate with patient age, often in conjunction with hormonal changes, such as puberty and pregnancy [3-6]. Therefore, vascular malformations that are present at birth may not present clinically until adolescence or adulthood. These lesions can be broadly divided into high- and low-flow lesions. High-flow malformations include arteriovenous malformations and arteriovenous fistulas, both of which demonstrate arterial flow and arteriovenous shunting. The former tend to be congenital lesions, and the latter are typically acquired as sequela of prior trauma or surgery. High-flow lesions comprise approximately 10% of peripheral vascular malformations and may present with pain, skin discoloration, warmth, or mass with palpable thrill or bruit [6]. Compression neuropathy, soft-tissue ulceration, bleeding, arterial steal phenomenon, and high-output cardiac failure may be seen in extreme cases [4,7]. Low-flow lesions include capillary, venous, and lymphatic malformations and are overall more common than high-flow lesions. Of these, capillary malformations are the most common but rarely require imaging for diagnosis because of their characteristic cutaneous manifestations [3,4]. Venous and lymphatic malformations have a reported prevalence of 1% in the general population with 40% involving the extremities [6]. Although symptomatology is variable, these lesions may present with focal or more generalized extremity pain, swelling, or compressible mass with or without associated skin discoloration. Involvement of the deep tissues, including bone, is not uncommon, and physical examination often underestimates their full extent [2,5].


Clinically Suspected Vascular Malformation of the Extremities. Vascular tumors are subclassified based on propensity for aggressive and malignant behavior; however, the majority are benign [3]. Infantile hemangiomas are among the most common type of vascular neoplasm. These benign lesions present in infancy or early childhood and demonstrate rapid proliferative growth followed by eventual involution, most often not requiring treatment [7]. Less commonly, vascular tumors such as the intramuscular hemangioma, can present in adulthood with swelling, pain, or mass.


Clinically Suspected Vascular Malformation of the Extremities. The diagnosis of a vascular malformation or neoplasm is frequently made clinically when classic signs and symptoms are present. Imaging is used for confirmation, particularly if the clinical presentation is atypical or vague [3,8] and is generally required for characterization of these lesions. Imaging also plays a critical role in treatment planning, which is often required because of growth, limb deformity, and decreased function, as well as pain. Lesion characteristics such as subtype (high flow versus low flow), depth, and invasion of adjacent structures, as well as inflow and outflow vessels, help in optimal treatment selection [9]. Treatment approach spans the spectrum of conservative to aggressive options, which include compression dressings, sclerotherapy,


Clinically Suspected Vascular Malformation of the Extremities. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through society representation on expert panels. Participation by representatives from collaborating societies on the expert panel does not necessarily imply individual or society endorsement of the final document.


Clinically Suspected Vascular Malformation of the Extremities. Reprint requests to: publications@acr.org


Clinically Suspected Vascular Malformation of the Extremities. Vascular Malformation of the Extremities


Clinically Suspected Vascular Malformation of the Extremities. transarterial or transvenous embolization, and surgical resection. Sclerotherapy is often used for low-flow lesions, whereas high-flow lesions are most effectively treated with embolization [8,10].


Clinically Suspected Vascular Malformation of the Extremities. All elements are essential: 1) timing, 2) reconstructions/reformats, and 3) 3-D renderings. Standard CTs with contrast also include timing issues and recons/reformats. Only in CTA, however, is 3-D rendering a required element. This corresponds to the definitions that the CMS has applied to the Current Procedural Terminology codes.


Clinically Suspected Vascular Malformation of the Extremities. Discussion of Procedures by Variant Variant 1: Upper or lower extremity. Suspected vascular malformation presenting with pain or findings of physical deformity including soft-tissue mass, diffuse or focal enlargement, discoloration, or ulceration. Initial imaging. The body regions covered in this clinical scenario are shoulder, humerus, elbow, forearm, wrist, hand, hip, femur, knee, tibia/fibula, ankle, and foot.


Clinically Suspected Vascular Malformation of the Extremities. Radiography Extremity Radiographs are often used as the initial imaging modality in the workup of a patient presenting with nonspecific extremity complaints and may be useful for the exclusion of more common causes of extremity pain and deformity. However, radiographs are of limited utility for the specific purpose of vascular malformation imaging. In the setting of a vascular malformation, radiographs may be normal or show a soft-tissue mass [5,12]. Phleboliths may also be seen and provide a clue to the diagnosis of venous malformations and hemangiomas, which are reported to contain phleboliths in 20% to 67% of cases [3,12]. Lesions located adjacent to bone may be associated with bone changes, including periosteal reaction, remodeling, or signs of destruction, such as cortical scalloping and lucencies. Although such findings may be visible radiographically, they are not specific for the diagnosis of vascular malformations [6,12].


Clinically Suspected Vascular Malformation of the Extremities. US Duplex Doppler Extremity Ultrasound (US) with duplex Doppler imaging can be useful for the initial assessment of suspected vascular malformation, particularly if a focal mass or other targetable superficial symptomatology is present. US with Doppler can differentiate high-flow from low-flow malformations, and often provides a specific diagnosis in cases where characteristic vascular malformation features are present [3,5,13,14]. US may also be diagnostic of other lesions within the differential diagnosis for nonspecific extremity complaints [3,15]. Ultimately, this modality is limited in regards to tissue penetration and a small imaging field of view, which may lead to suboptimal evaluation of lesion extent and size, particularly if located deep in the extremity or adjacent to bone [2,8,13]. As a result, cross-sectional imaging, such as MRI, may be needed for more complete evaluation and definitive diagnosis [1,3,13], especially in cases without a targetable focal abnormality.


Clinically Suspected Vascular Malformation of the Extremities. US Extremity Area of Interest with IV Contrast There is limited evidence regarding the utility of contrast-enhanced US (CEUS) in evaluating suspected peripheral vascular malformations, but this modality may be considered in select cases. The addition of microbubble contrast may enhance visualization of small arteriovenous shunts and low-flow vessels compared with US with Doppler [16]. CEUS also has potential for quantifying perfusion in vascular malformations, which could be helpful in assessing treatment response [17].


Clinically Suspected Vascular Malformation of the Extremities. CT Extremity CT offers the benefit of high spatial resolution and provides comprehensive anatomic detail in the workup of extremity complaints. For the specific purpose of vascular malformation imaging, CT may reveal a soft-tissue mass with or without phleboliths, as well as provide information about size and lesion extent [12]. Bone involvement and acute complications like hemorrhage can also be assessed with CT [3,6]. Intravenous (IV)


Clinically Suspected Vascular Malformation of the Extremities. Vascular Malformation of the Extremities contrast administration improves lesion delineation and allows for the assessment of enhancement patterns, which may help narrow the differential diagnosis of a focal finding [3]. However, in general, MRI is the preferred imaging modality when evaluating suspected vascular malformations that are due to its greater soft-tissue contrast and ability to obtain dynamic flow information with MR angiography (MRA) [10].


Clinically Suspected Vascular Malformation of the Extremities. CTA Extremity CTA with IV contrast can be used to evaluate a suspected vascular malformation. It is generally of greater utility for a high-flow lesion, such as an arteriovenous malformation, as CTA is capable of delineating the feeding arteries, nidus, and draining veins, which typically characterize these lesions [10]. CTA may also provide some information in regards to lesion extent and invasion into muscular compartments and bones [10]. However, MRI or MRA is the preferred method for suspected vascular malformation imaging that is due to superior soft-tissue contrast and potential for dynamic blood flow imaging [2,10,18].


Clinically Suspected Vascular Malformation of the Extremities. MRI Extremity MRI offers superior soft-tissue contrast compared with CT and plays an important role in the workup of suspected vascular malformations and soft-tissue masses. Lesion morphology and internal signal characteristics can be assessed, often allowing for definitive diagnosis [2-4,6,7,9,19]. MRI accurately determines lesion extent and involvement of surrounding structures, both of which are underestimated clinically in up to 76% of cases [2,5,7]. Contrast-enhanced sequences may not be necessary if typical features, such as flow voids, are present; however, the use of IV contrast is preferred for improved specificity and more complete characterization [3,6,8,20]. IV contrast also allows better visualization of the feeding and draining vessels in high-flow lesions, although this is best performed using an MRA protocol [1-3,6,7,21]. Additionally, MRI is useful for the evaluation of other soft- tissue lesions and musculoskeletal pathologies that might be considered in the differential diagnosis for a mass, enlarged extremity, or pain [19,20,22,23].