***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: Purpose The aim of this study was to prospect ively compare the detection rate of 68Ga-DOTATATE PET-CT with 111In-octreotide SPECT-CT and conventional imaging ( CI ) in medullary thyroid carcinoma ( MTC ) patients with increased calcitonin ( Ctn ) levels but negative CI after thyroidectomy . Methods Fifteen patients with raised Ctn levels and /or CI evidence of recurrence underwent 68Ga-DOTATATE PET-CT , 111In-octreotide SPECT-CT and CI . Histopathology , CI and biochemical/ clinical /imaging follow-up were used as the reference st and ard . PET/CT , SPECT/CT and CI were compared in a lesion-based and organ-based analysis . Results PET/CT evidence d recurrence in 14 of 15 patients . There were 13 true positive ( TP ) , 1 true negative ( TN ) , 1 false positive ( FP ) and no false negative ( FN ) cases , result ing in a sensitivity and accuracy of 100 % and 93 % . SPECT/CT was positive in 6 of 15 cases . There were 6 TP , 2 TN , 7 FN and no FP cases , result ing in a sensitivity of 46 % and accuracy of 53 % . CI procedures detected tumor lesions in 14 of 15 patients . There were 13 TP , 1TN , 1 FP and no FN cases with a sensitivity of 100 % and accuracy of 93%.A significantly higher number of lesions was detected by PET/CT ( 112 lesions , p = 0.005 ) and CI ( 109 lesions , p = 0.005 ) in comparison to SPECT/CT ( 16 lesions ) . There was no significant difference between PET/CT and CI for the total number of detected lesions ( p = 0.734 ) . PET/CT detected more lesions than SPECT/CT regardless of the organ . PET/CT detected more bone lesions but missed some neck nodal metastases evidence d by CI . The number of lesions per region demonstrated by PET/CT and CI were similar in the other sites . Conclusion 68Ga-DOTATATE PET/CT is superior to 111In-octreotide SPECT/CT for the detection of recurrent MTC demonstrating a significantly higher number of lesions .  68Ga-DOTATATE PET/CT showed a superior detection rate compared to CI in demonstrating bone metastases Purpose This study sought to evaluate and compare the utility of 18-F-fluorodihydroxyphenylalanine ( 18F-DOPA ) and 18-F-fluorodeoxyglucose ( 18F-FDG ) positron emission tomography/computed tomography ( PET/CT ) for identification of lesions in patients with recurrent medullary thyroid carcinoma ( MTC ) . In addition , we analyzed the correlation between the calcitonin ( Ct ) , carcinoembryonic antigen ( CEA ) levels , each doubling time ( DT ) , and PET positivity . We evaluated the reliability of the 150 pg/mL Ct cutoff set by the American Thyroid Association guidelines for further imaging ( including 18F-DOPA PET/CT ) . Methods We prospect ively recruited 18 patients with recurrent MTC , identified by elevation of Ct or CEA . Each patient underwent a 18F-FDG PET/CT and a 18F-DOPA PET/CT . Results Abnormal uptakes were detected with 18F-DOPA ( n=12 ) and 18F-FDG ( n=9 ) , ( sensitivity of 66.7 % vs. 50 % ; p<0.01 ) . Twenty-eight lesions were detected with 18F-DOPA vs. 16 lesions with 18F-FDG ( 1.56±1.5 vs. 0.89±1.18 lesions per patient ; p=0.01 ) . None of our patients showed additional lesions with 18F-FDG in comparison to 18F-DOPA . Patient-based detection rate increased significantly with Ct levels ≥150 pg/mL vs. Ct<150 pg/mL for both 18F-DOPA ( sensitivity 90.9 % vs. 28.6 % ; p=0.013 ) and 18F-FDG PET/CT ( sensitivity 72.7 % vs. 14.3 % ; p=0.025 ) . Using a CEA cutoff of ≥5 ng/mL , detection rates of 18F-DOPA and 18F-FDG PET/CT were 81.1 % and 72.7 % , respectively . No correlation between Ct-DT or CEA-DT and PET positivity was found . Histological confirmation was obtained in eight patients . Conclusions 18F-DOPA PET/CT appears to be superior to 18F-FDG PET/CT in detecting and locating lesions in patients with recurrent MTC . This technique tends to be especially useful in patients with negative results in other imaging modalities and Ct≥150 pg/mL or CEA≥5 Abstract .Metastases of differentiated thyroid cancer may show different uptake patterns for fluorine-18 fluorodeoxyglucose and [131I]NaI. FDG positron emission tomography ( PET ) , iodine-131 whole-body scintigraphy ( 131I WBS ) and magnetic resonance imaging were performed in 58 unselected patients , and spiral computed tomography ( CT ) of the lung in 25 patients . Thirty-eight patients presented with papillary carcinomas , 15 patients with follicular carcinomas and five patients with variants of follicular carcinoma . Primary tumour stage ( pT ) was pT1 in 3 , pT2 in 19 , pT3 in 11 and pT4 in 25 cases . For the detection of metastases , FDG PET was found to have a sensitivity of 50 % , 131I WBS a sensitivity of 61 % , and the two methods combined a sensitivity of 86 % . When FDG PET was limited to patients with elevated thyroglobulin ( Tg ) levels and negative 131I WBS , the sensitivity of this algorithm was 82 % . Of the 21 patients with lymph node metastases , seven presented with FDG uptake but no iodine uptake . In four of them , a second FDG hot spot appeared in a lymph node metastasis of normal size . Five of the seven patients underwent surgery . None of the eight patients with pulmonary metastases smaller than 1 cm exhibited FDG uptake , while five of them had iodine uptake . All had positive results on spiral CT . In conclusion , FDG PET can not be substituted for 131I WBS . If the Tg level is elevated and 131I WBS is negative , FDG PET can be used to detect lymph node metastases and complements anatomical imaging . A spiral CT of the lung is useful to exclude pulmonary metastases before planning a dissection of iodine-negative lymph node metastases UNLABELLED 18F-FDG PET has been shown to effectively detect differentiated thyroid carcinoma ( DTC ) metastases with impaired iodine-trapping ability . This article evaluates the potential contribution of FDG PET in the follow-up of patients with differentiated thyroid carcinoma , elevated thyroglobulin ( Tg ) levels , and negative whole-body scan results obtained after high doses of (131)I. METHODS We prospect ively assessed the ability of FDG to detect metastases in 37 DTC patients who had undergone total thyroidectomy and radioactive ablation and presented with persistent disease , as assessed from elevated Tg levels and negative results of whole-body scans performed after therapeutic doses of (131)I. Additional conventional imaging procedures were performed to detect residual disease , and the patients were divided into 2 groups : group 1 , with positive conventional imaging findings ( n = 10 ) , and group 2 , with negative conventional imaging findings ( n = 27 ) . RESULTS FDG PET showed positive findings in 28 patients and accurately localized tumor sites in 89 % of them . In group 1 , FDG PET confirmed 17 of 18 previously known tumor sites and detected 11 additional sites . In group 2 , FDG PET  findings were positive in 19 of 27 patients with no previously detected metastases . PET was effective for both low- and high-stage tumors . The FDG data led to a change in the clinical management of 29 of 37 patients with further surgical resection in 23 patients , 14 of whom achieved disease-free status , and external radiation therapy in 4 patients . CONCLUSION FDG PET is able to detect metastases undetected by (131)I posttherapy whole-body scanning in patients with elevated Tg levels . It should be proposed as a first-line investigation in patients with persistent disease but negative findings on (131)I whole-body scans after treatment Fluorodeoxyglucose-positron emission tomography (FDG-PET)/computed tomography ( CT ) is able to localize persistent or recurrent disease in differentiated thyroid carcinoma ( DTC ) . The aim of the study was to correlate PET/CT results with precise intraoperative localization of persistent or recurrent papillary and follicular thyroid carcinoma . Patients with differentiated thyroid carcinoma who received FDG-PET scans were prospect ively documented . The PET/CT results were correlated with other localization studies ( neck ultrasound , ¹³¹I whole-body scan ) and accurately compared to intraoperative findings and histopathological examinations . FDG-PET/CT scans were performed in 18 patients , between 16 and 84 years of age , from December 2008 to June 2011 . Fourteen patients had papillary thyroid carcinomas and 4 had follicular thyroid carcinomas . All patients had a previous thyroidectomy and radioiodine ablation .  Before cervical re-exploration ,  FDG-PET/CT-positive findings were reported in 14 individuals , whereas 4 PET scans provided no evidence of disease . Intraoperatively , 13 of 14 FDG-PET/CT-positive  localizations of recurrent or persistent thyroid carcinomas were verified and confirmed by histopathology ( sensitivity 93 % ) . In another patient lymph node metastases of lung cancer were detected intraoperatively . However , FDG-PET/CT  underestimated the number of lesions in 5 of 6 patients undergoing systematic lymphadenectomy . No lymph node or soft tissue metastases were found intraoperatively in 3 of the 4 patients with negative FDG-PET scans . A solitary cystic lymph node metastasis was found in the fourth patient but was not detected by FDG-PET/CT ( specificity 75 % ) . FDG-PET/CT  has high sensitivity and specificity for the detection of persistent or recurrent differentiated thyroid carcinoma . FDG-PET/CT helps to select patients who might benefit from surgery because it provides precise anatomical details UNLABELLED This study aims to investigate the usefulness of F-18 FDG PET/CT in differentiated thyroid cancer ( DTC ) with elevated serum thyroglobulin ( Tg ) but negative iodine-123 ( I-123 ) scan . METHODS Twenty patients with histopathologically proven DTC , negative diagnostic I-123 scan , and elevated serum Tg levels were prospect ively su bmi tted to F-18 FDG PET/CT evaluation . The histopathologic findings consisted of 19 papillary thyroid cancers , 1 follicular thyroid cancer . RESULTS F-18 FDG PET/CT identified lesions in 18 out of 20 patients , giving a sensitivity of 90 % . Thirteen of the 18 patients revealed limited loco-regional disease . Remaining 5 patients showed distant metastases , consisting of 4 patients with lung metastases and 1 patient with bone metastasis . Two patients revealed negative F-18 FDG PET/CT findings . CONCLUSION F-18 FDG PET/CT is suitable for the detection and precise localization of loco-regional recurrences and distant metastases of DTC in patients with elevated serum Tg but negative I-123 whole body scan Aims This study aim ed ( a ) to determine the clinical and histopathologic factors that are related to FDG avidity in the recurrence/metastases of patients with differentiated thyroid carcinoma ( DTC ) who present with elevated thyroglobulin ( Tg ) levels and negative 131I whole-body scans ( WBSs ) , ( b ) to clarify Tg cutoff levels in this setting , and ( c ) to evaluate the impact of PET/CT on patient management strategies and hence to critically look into the importance of PET/CT in combination with Tg in clinical decision making . Methods A total of 105 patients with DTC with negative 131I WBS and neck ultrasound but elevated Tg , who underwent FDG PET/CT for the suspicion of recurrent/metastatic disease , were included in this analysis . All patients had previously undergone total thyroidectomy and radioiodine ablation/therapy . PET/CT results were correlated with Tg levels and clinical and histopathologic characteristics of the primary tumor compared with the follow-up data . Results PET/CT was true-positive in 69 patients ( of which 23 had surgically amenable disease ) , true-negative in 
    Output:
    
Conclusion : The patient-relevant benefits of PET or PET/CT in thyroid cancer could not be evaluated satisfactorily based on the included studies .
It remains unclear whether higher diagnostic test accuracy leads to changes in therapeutic strategies and better patient-relevant outcomes