| Objective: To evaluate the value of 18F-FDG PET/CT imaging in diagnosisof thyroid cancers, to study ability of PET/CT in differentiating benign andmalignant thyroid lesions, and explore the technique to improve the accuracy ofdiagnosis of thyroid cancers with PET/CT imaging.Materials and methods: There were 29 volunteers, who suffered thyroidmass(es), from the inpatient of Surgery Department, Tianjin Medical UniversityGeneral Hospital and Head and Neck Department, Tianjin Medical UniversityCancer Hospital. 12 of them suffered bilateral thyroid masses. In total, there were30 malignant and 11 benign lesions. All patients performed whole body 18F-FDGPET/CT imaging 1 week before the surgery. PET/CT Images of 40 healthyvolunteers, who received PET/CT scan for health examination, were served asnormal control group. Discovery LS PET/CT were used, manufactured by GeneralElectric Company. Maximum of SUVs (Standard uptake value) of lesions werecalculated. SUV=2.5 was set as thyroid cancer diagnosis cutoff for benign andmalignant lesions. The SUV of delay imaging, performed 2.5h after injection, wascompared with ordinary imaging SUV, which performed 1h after injection.Malignant, benign and control group SUV were compared, and, the SUV indifferent pathological thyroid lesions were analyzed, respectively. Analysis ofvariance, paired-sample t test, independent samples t test and bivariate correlationwere calculated with SPSS statistic software.Results: (1)30 malignant thyroid lesions included 19 (Papillary thyroidcancer) PTCs, 5 (Follicular thyroid cancer) FTCs, 5 (Medullary thyroid cancer)MTCs and 1 (Squamous cancer) SC. 12 benign thyroid lesions included 9(Nodular goiter) NGs and 3 (Hashimoto's thyroiditis) HTs. Of them, 11 were stageâ… , 1 was in stageâ…¡, 8 were in stageâ…£A, 3 were in stageâ…£B and 3 were in stageâ…£C. (2) The SUV of malignant, benign and control group was 11.73±10.38,3.04±1.37 and 1.46±0.31, respectively. There was significant differencebetween any two of these three groups (P=0.000). (3)The SUV of each type ofdisease was 11.55±8.02(n=19) in PTCs, 7.72±3.66(n=5) in FTCs, 10.56±15.23(n=5) in MTCs, 41.00(n=1) in SC, 2.60±0.60(n=9) in NGs, 4.37±2.35(n=3)in HTs. SC was excluded from further analysis because of only 1 case. There weresignificant difference between the SUVs of thyroid cancers and NGs (P＜0.05).The SUVs of thyroid cancers, HTs and NGs were significant higher than that ofnormal control group, respectively (P=0.000). (4)In malignant group, there wassignificant difference between the SUVs of ordinary imaging and delayimaging(P=0.007, t=3.131). But, no significant difference was found in that ofbenign group(P=0.123, t=-1.855). In thyroid cancer group, SUV of delayimaging was higher than ordinary imaging SUV in 87.5%(14/16) cases. In benigngroup, delay imaging SUV was lower than that of ordinary in 83.33%(5/6) cases.(5)In malignant group, there was no significant difference between the SUV ofprimary lesion and lymph node metastasis(P=0.488, r=0.289). (6)In malignantgroup, there was significant difference between the volume and the SUV ofprimary cancer(P=0.003, r=0.554, n=27). (7)If SUV=2.5 was set as cutoff ofPET/CT imaging to diagnose primary thyroid cancer, the sensitivity, specificity,accuracy, positive predictive value and negative predictive value was 96.67%,45.45%, 82.93%, 82.86% and 83.33%, respectively.Conclusions: The SUV of malignant group was significant higher than thatof benign one. And, they were both significant higher than that of normal group.Except for SC, the SUVs of thyroid cancers were significant higher than that ofnodular goiter. The SUVs of thyroid cancers, NG and HT were significant higherthan that of normal people. There was no significant difference between the SUVof thyroid cancer primary lesion and SUV of lymph node metastasis. And, there was significant difference between the SUV and volume of primary disease. TheSUV of delay imaging was significant higher than that of ordinary one inmalignant group, but no significant difference in benign group. If SUV=2.5 wasset as diagnosis cutoff of in thyroid cancer, the examination sensitivity was good,compared with a relative poor specificity. Delay imaging technique may improveits specificity. SUV=3.0 was better than 2.5 for thyroid cancer diagnosis as cutoffvalue.
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