Improvement of lesion detection in patients with differentiated thyroid carcinoma using 131I SPECT/CT

Abstract

Objective To evaluate the incremental value of 131I SPECT/CT over 131I whole body scan (WBS) in the patients with DTC.Methods A total of 97 patients with DTC (31 males,66 females,mean age:44.1 years,age range:17 to 74 years) were retrospectively reviewed.All subjects underwent 131I WBS and SPECT/CT after 131I treatment.The images were interpreted by 2 experienced nuclear medicine physicians.The final diagnosis was based on the pathologic findings and clinical follow-up.The diagnostic accuracies between 131I WBS and 131I SPECT/CT were compared using x2 test with SPSS 13.0.Results 131I WBS detected 175 lesions (128 neck and 47 distant lesions),while 131I SPECT/CT found 176 lesions (128 neck and 48 distant lesions).Out of the 176 lesions,78 were confirmed as benign and 95 as malignant,including 51 lesions in thyroid bed,67 cervical lymph nodes or local residual lesions,7 lesions related to local physiological uptake,30 distant metastases and 18 distant foci due to physiological uptake.The other 3 lesions were still in follow-up.The sensitivity and specificity of 131 I WBS was 73.7％ (70/95) and 78.2％ (61/78),respectively.The accuracy of 131I WBS (106/173,61.3％) was lower than that of 131I SPECT/CT (171/173,98.8％; x2=72.3,P＜0.05).131I SPECT/CT corrected the diagnosis of 131I WBS in 67 lesions,including 37 local lesions (37/128,28.9％) and 30 (30/48,62.5％) distant metastases.The sources of error for the 67 lesions were due to wrong location (n =27) or wrong characterization (n =40).Compared with 131I WBS,131I SPECT/CT changed the location in 27 lesions,clinical staging in 8 cases and therapeutic strategy in 14 cases.Conclusions 131 I SPECT/CT could improve the differentiation of malignant local lesions from residual thyroid,of distant metastatic lymph node,lung or bone lesions from physiological uptake.Such incremental values would be valuable to the management of DTC patients compared with WBS. Key words: Thyroid neoplasms; Radionuclide imaging; Iodine radioisotopes; Diagnosis, differential