***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: There is confusion about how carotid stenosis should be measured on angiograms . If the results of research based on different methods of measurement of stenosis are to be discussed and the results of clinical trials properly applied to routine clinical practice , measurements made by the different methods must be formally compared . Methods The method of measurement of stenosis  used in the European Carotid Surgery Trial ( ECST ) , that used in the North American Symptomatic Carotid Endarterectomy Trial ( NASCET ) , and a method based on measurement of the common carotid ( CC ) artery lumen diameter were compared . Carotid stenosis was measured by two observers , working independently and using the three different methods of measurement , on the angiographic view of the symptomatic carotid stenosis that showed the most severe disease in 1001 patients from the ECST . Results The results of using the ECST and CC methods differed from those of using the NASCET method in the classification of stenoses as mild ( 0 % to 29 % ) , moderate ( 30 % to 69 % ) , or severe ( 70 % to 99 % ) in 51 % of measurements . The ECST and CC methods indicated that twice as many stenoses were severe as did the NASCET method , and classified less than a third of the number of stenoses as mild . The results of the  ECST  and CC methods differed from each other in 15 % of measurements . The relations between measurements made by each method to those made by the others were approximately linear , so a simple equation could be derived to convert measurements made by one method to measurements made by the others . Conclusions There were major and clinical ly important disparities between measurements of stenosis made using different methods of measurement on the same angiograms . However , it is possible to convert measurements made by one method to those of another using a simple arithmetic equation OBJECTIVE The purpose of this study was to compare the abilities of color-coded duplex sonography , CT angiography , and selective digital subtraction angiography to reveal disease requiring surgery in patients with occlusive disease of the carotid bifurcation . MATERIAL S AND METHODS Fifty-six carotid arteries in 28 patients who had 48 carotid stenoses and symptomatic cerebrovascular disease were prospect ively studied by selective digital subtraction angiography , color-coded duplex sonography , and CT angiography . CT data were displayed in maximum intensity projection . The degree of stenoses revealed were grade d as mild , moderate , severe , and occluded according to North American Symptomatic Carotid Endarterectomy Trial criteria . The results of CT angiography and color-coded duplex sonography were correlated with the gold st and ard of digital subtraction angiography . RESULTS Grading of stenoses on CT angiography agreed with grading of stenoses on digital subtraction angiography in 89 % of cases . All high- grade stenoses and occlusions revealed on CT angiography were correctly interpreted by all observers . For stenoses revealed by color-coded duplex sonography and digital subtraction angiography , observers ' agreement was 75 % . Two severe stenoses were incorrectly grade d as occluded by the interpreter of the color-coded duplex sonograms . Also , one occluded carotid artery was misdiagnosed as moderate stenosis . CONCLUSION Our results indicate that CT angiography is superior to color-coded duplex sonography for evaluating carotid disease and determining disease requiring surgery . CT angiography warrants further investigation in a larger group of patients Background and Purpose — Carotid endarterectomy has been shown to be beneficial in symptomatic patients with a severe stenosis ( 70 % to 99 % ) of the internal carotid artery ( ICA ) .  Digital subtraction angiography ( DSA ) is the st and ard of reference in the diagnosis of carotid artery stenosis but has a relatively high complication rate . In a diagnostic study we investigated the accuracy of noninvasive testing compared with DSA . Methods — In a prospect i ve diagnostic study we performed duplex ultrasound ( DUS ) , magnetic resonance angiography ( MRA ) , and DSA on 350 consecutive symptomatic patients .  Stenoses were measured with the observers blinded for clinical information and other test results . Separate and combined test results of DUS and MRA were compared with the reference st and ard DSA . Only the stenosis measurements of the arteries on the symptomatic side were included in the analyses . Results — DUS analyzed with previously defined criteria result ed in a sensitivity of 87.5 % ( 95 % CI , 82.1 % to 92.9 % ) and a specificity of 75.7 % ( 95 % CI , 69.3 % to 82.2 % ) in identifying severe ICA stenosis ( 70 % to 99 % ) . Stenosis measurements on MRA yielded a sensitivity of 92.2 % ( 95 % CI , 86.2 % to 96.2 % ) and a specificity of 75.7 % ( 95 % CI , 68.6 % to 82.5 % ) . When we combined MRA and DUS results , agreement between these 2 modalities ( 84 % of patients ) gave a sensitivity of 96.3 % ( 95 % CI , 90.8 % to 99.0 % ) and a specificity of 80.2 % ( 95 % CI , 73.1 % to 87.3 % ) for identifying severe stenosis . Conclusions — MRA showed a slightly better accuracy than DUS in the diagnosis of  carotid artery stenosis  . To achieve the best accuracy , however , both tests should be performed subsequently Purpose This study was undertaken to prospect ively evaluate the diagnostic performance of colour Doppler ultrasonography ( CDUS ) , first-pass ( FP ) and steady-state ( SS ) contrast-enhanced magnetic resonance angiography ( MRA ) and computed tomography angiography ( CTA ) of the carotid arteries using digital subtraction angiography ( DSA ) as the reference st and ard . Material s and methods A total of 170 patients with previous cerebrovascular events and suspected carotid artery stenoses underwent CDUS , blood-pool MRA , CTA and DSA .  Accuracy , sensitivity , specificity , positive predictive value ( PPV ) and negative predictive value ( NPV ) were calculated for CDUS , FP MRA , SS MRA and CTA . The McNemar and Wilcoxon tests and receiver operating characteristic ( ROC ) curve analysis were used to determine significant differences ( p<0.05 ) between the diagnostic performances of the four modalities , and the degree of stenosis was compared using linear regression . Results A total of 336 carotid bifurcations were studied . The area under the curve ( AUC ) for degree of stenosis was : CDUS 0.85±0.02 , FP MRA 0.982±0.005 , SS MRA 0.994±0.002 and CTA 0.997±0.001 . AUC analysis showed no statistically significant difference between CTA and MRA ( p=0.0174 ) and a statistically significant difference between CDUS and the other techniques ( p<0.001 ) . Plaque morphology analysis showed no significant difference between CTA and SS MRA ; a significant difference was seen between CTA and SS MRA versus FP MRA ( p=0.04 ) and CDUS ( p=0.038 ) . Plaque ulceration analysis showed a statistically significant difference between MRA and CTA ( 0.04 < p<0.046 ) versus CDUS ( p=0.019 ) . Conclusions CTA is the most accurate technique for evaluating carotid stenoses , with a slightly better performance than MRA ( 97 % vs. 95 % for SS MRA and 92 % for FP MRA ) and a greater accuracy than CDUS ( 97 % vs. 76 % ) . Blood-pool contrast-enhanced SS sequences offer improved evaluation of degree of stenosis and plaque morphology with accuracy substantially identical to CTA.RiassuntoObiettivoL’obiettivo di questo studio è stato di valutare prospetticamente l’accuratezza dell’eco-color Doppler ( ECD ) , dell’angiografia con risonanza magnetica ( angio-RM ) , ottenuta con sequenze di primo passaggio ( PP ) ed allo stato stazionario ( SS ) e dell’angiografia con tomografia computerizzata ( angio-TC ) nella diagnostica della stenosi carotidea utilizz and o l’angiografia con sottrazione digitale ( DSA ) come metodica di riferimento . Material i e metodiCentosettanta pazienti sintomatici e con sospetta stenosi carotidea sono stati sottoposti ad ECD , angio-RM , angio-TC e DSA . Accuratezza , sensibilità , specificità , valore predittivo positivo ( VPP ) e valore predittivo negativo ( VPN ) sono stati calcolati per ECD , angio-RM ed angio-TC . Le differenze di performance tra le metodiche sono state valutate utilizz and o il test di McNemar , il test di Wilcoxon e l’analisi delle curve receiver operating characteristic ( ROC ) ( p<0,05 ) . Inoltre il valore di stenosi attribuito dalla valutazione dell’ECD , dell’angio-RM e dell’angio-TC è stato confrontato con il valore della DSA tramite regressioni lineari . RisultatiSono state valutate 336 biforcazioni carotidee . Per la valutazione del grado di stenosi è stata calcolata l’area sotto la curva ( AUC ) delle quattro metodiche che è risultata : ECD 0,85±0,02 , angio-RM PP=0,982±0,005 , angio-RM SS=0,994±0,002 ed angio-TC=0,997±0,001 con sostanziale equivalenza tra angio-TC ed angio-RM ( p=0,0174 ) ed una differenza statisticamente significativatra l’ECD e le altre metodiche ( p<0,001 ) . Per la valutazione della morfologia di placca l’analisi delle AUC delle quattro metodiche ha evidenziato una sostanziale equivalenza tra angio-TC ed angio-RM con SS , ma ha evidenziato una lieve differenza di entrambe le metodiche nei confronti dell’angio-RM con PP ( p=0,04 ) e dell’ECD ( p=0,038 ) . La valutazione delle ulcere ha evidenziato una differenza statisticamente significativa tra l’angio-RM e l’angio-TC ( p=0,04–0,046 ) e l’ECD ( p=0,019 ) . Conclusion iL’angio-TC è la metodica più affidabile con una leggera superiorità diagnostica rispetto all’angio-RM ( 97 % vs. 95 % per le sequenze SS e 92 % per le sequenze PP ) ed una superiorità molto marcata rispetto all’ECD ( 97 % vs. 76 % ) . L’angio-RM con l’utilizzo delle sequenze allo stato stazionario ottenute con mezzo di contrasto intravascolare ad alta relassività tende sostanzialmente ad eguagliare l’accuratezza dell’angio-TC BACKGROUND Contralateral occlusion ( CLO ) occurs in approximately 8 % of patients undergoing intervention for carotid artery stenosis . Patients with CLO have increased stroke risk compared with patients without CLO , but st and ard carotid duplex ultrasonography ( CDUS ) criteria are not a reliable manner to screen or follow patients with CLO . Because appropriate duplex criteria for these patients are not well understood , this article defines CDUS parameters that accurately predict carotid artery stenosis at our institution . METHODS Sixty-five patients with ipsilateral carotid stenosis and CLO were identified from our institutional data base . Fifteen of sixty-five patients had arteriography , computed tomography angiography , or magnetic resonance angiography within 6 mo of CDUS . We determined accuracy of our laboratory 's criteria for determining stenosis category compared with three-dimensional imaging . Receiver operating characteristic curves were used to determine optimal peak systolic velocity ( PSV ) , end diastolic velocity ( EDV ) , and systolic ratio ( SR ) cutoff values for diagnosing ≥50 % stenosis in this pilot cohort . Finally , the revised criteria were prospect ively applied to a validation cohort ( n = 8) from the same institution . RESULTS Categorization of stenosis by st and ard PSV , EDV , and SR criteria saw similar accuracy trends in both pilot ( 46.7 , 53.3 , and 66.7 % ) and validation ( 25 , 25 , and 62.5 % ) cohorts . Receiver operating characteristic curve analysis in the pilot cohort identified optimized PSV , EDV , and SR cutoffs ( ≥250 , ≥90 , and ≥2.3 cm/s , respectively ) for diagnosing ≥50 % stenosis . In the pilot cohort , new PSV criteria increased specificity ( 60%-100 % ) with minimal decreased sensitivity ( 90%-80 % ) , whereas new EDV criteria increased specificity ( 40%-71.4 % ) and maintained 100 % sensitivity . New SR criteria failed to improve sensitivity or specificity above 80 % . Similar trends for the new CDUS velocity criteria were observed in the validation cohort . CONCLUSIONS Increasingly stringent ultrasound parameters can provide reliable criteria for determining ≥50 % carotid stenosis in patients with CLO . Further prospect i ve validation that includes more patients with high- grade ipsilateral stenosis will help identify the role of SR in segregating high 
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Results The sensitivity and specificity of CTA and CDU are comparable .
CDU is safe and readily available in the clinical environment hence its use in the initial preoperative assessment of carotid stenosis .
CDU is an adequate imaging modality for determining stenosis greater than 70 % ; sensitivity and specificity are improved when the criteria for determining greater than 70 % stenosis are adjusted .
Either modality can be used to determine greater than 70 % stenosis , although a secondary imaging modality may be required for cases of greater than 50 % stenosis