Purpose: To retrospectively determine the incremental diagnostic value of adding single photon emission computed tomography/ computed tomography (SPECT/CT) to whole-body scintigraphy with iodine 131 (131I) compared with scintigraphy alone after radioiodine therapy in patients with well-differentiated thyroid carcinoma. Materials and Methods: This retrospective study was institutional review board approved; written informed consent was waived. The study included 147 patients (94 female, 53 male patients; mean age, 51 years) with well-differentiated thyroid carcinoma treated with radioiodine therapy between October 2009 and August 2010. Whole-body scintigraphy and SPECT/CT were performed on the same day in all patients receiving radioiodine therapy. Each radioactive focus at whole-body scintigraphy was classified as positive or equivocal with respect to thyroid bed, lymph node, and distant metastasis uptake. Differences between whole-body scintigraphy and SPECT/CT findings were assessed with the generalized McNemar test. Results: At SPECT/CT, origin was clearly determined of all five "hot spots" in the thyroid bed (remnant thyroid tissue or metastatic lymph node) that were judged as equivocal at wholebody scintigraphy. Interpretation of 24 (22.2%) of 108 radioactive foci for lymph node metastases was changed with SPECT/CT (P < .0001). One of 85 foci that were thought to be positive findings at whole-body scintigraphy turned out to be a negative finding (false-positive finding), and 13 and seven of 20 equivocal foci at whole-body scintigraphy were positive and negative findings, respectively, after adding SPECT/CT findings. Three false-negative findings at whole-body scintigraphy were corrected with SPECT/CT. For the detection of distant metastasis, the interpretations of 21 (40%) of 52 foci were corrected with SPECT/CT (P < .0001). One of 32 foci thought to be a positive finding at whole-body scintigraphy was a negative finding, and 11 and nine of 20 equivocal foci at whole-body scintigraphy were positive and negative findings, respectively, after SPECT/CT. At a patient-based analysis, SPECT/CT findings helped change the clinical staging in nine (6.1%) of 147 patients and therapeutic planning in three (2.0%) of 147 patients. Conclusion: SPECT/CT improved detection and localization of 131I accumulation in lymph node metastases and distant metastases, compared with whole-body scintigraphy.
All Science Journal Classification (ASJC) codes
- Radiology Nuclear Medicine and imaging