Effectiveness of 99Tcm-pertechnetate whole body scan with neck and chest SPECT/CT for the detection of post-surgical pulmonary metastasis in differentiated thyroid carcinoma patients

Abstract

Objective To evaluate the effectiveness of 99Tcm-pertechnetate whole body scan with neck and chest SPECT/CT for detecting post-surgical pulmonary metastasis in differentiated thyroid carcinoma(DTC) patients. Methods A total of 34 DTC patients were evaluated retrospectively. The patients underwent 99Tcm-pertechnetate whole body scan with neck and chest SPECT/CT after surgery and before 131I treatment. The sensitivity and positive predictive value of this imaging in detecting pulmonary metastasis were calculated. Moreover, its impact on formulating therapeutic schedule was analyzed. Results Two of the 34 patients were defined as positive, which was manifested as an anatomical finding from CT with increased radiotracer uptake. Ten patients were equivocal positive, which was manifested as typical abnormal anatomical localization of lung metastasis without radiotracer uptake. The remaining 22 patients were considered as equivocal negative. Considering positive and equivocal results as positive findings, the sensitivity of the 99Tcm-pertechnetate whole body scan with neck and chest SPECT/CT in detecting pulmonary metastasis was 35.3%(12/34), and its positive predictive value was 100%(12/12). Consequently, 11 of 34 patients received increased radioactive dosage in the subsequent 131I treatment. Conclusions Most pulmonary metastasis of DTC manifested as no radiotracer uptake in 99Tcm-pertechnetate planar imaging, and bigger lesions tended to show positive pertechnetate uptake. 99Tcm-pertechnetate whole body scan with neck and chest SPECT/CT could detect several pulmonary metastasis lesions which showed no pertechnetate uptake. Thus, this process can increase the positive detection rate of pulmonary metastasis lesions and adjust the treatment program of some patients. Key words: Thyroid neoplasms; Neoplasm metastasis; Sodium pertechnetate Tc 99m; Single photon emission computed tomography computed tomography