Bastiana Piras

SPECT/CT in hyperparathyroidism

Hybrid SPECT/CT imaging is playing an increasingly important role in nuclear medicine in several oncological and non-oncological fields. This review presents a literature survey on the use of SPECT/CT as an adjunct to parathyroid scintigraphy in patients with hyperparathyroidism (HPT), highlighting the certainties and the controversies that have so far emerged in this regard. SPECT/CT, providing both functional and anatomical data, has proved to be superior to conventional planar parathyroid scintigraphy and to SPECT for the precise localization and characterization of areas of marked uptake of radiotracers (MIBI or tetrofosmin) corresponding to abnormal parathyroid glands, thus facilitating their surgical treatment. The major benefits of SPECT/CT have been observed in patients with ectopic adenomas, mainly in the mediastinum, and in those with previous neck surgery. In some studies, SPECT/CT has also demonstrated a higher sensitivity than conventional planar or SPECT scans particularly in the detection of low-weight parathyroid adenomas and in the presence of concomitant nodular goiter. In other studies, SPECT/CT has also been found to be more specific, with the anatomical data provided by the CT component shown to be of help in correctly categorizing MIBI-avid non-parathyroid lesions. No definitive conclusions on the clinical value of SPECT/CT in patients with secondary HPT and multiglandular disease can be done due to the small number of studies thus far conducted, but the current available data nevertheless seem to suggest that hybrid imaging is able to detect a significantly higher number of hyperplastic glands than planar scanning can.

Role of Diagnostic 131I SPECT/CT in Long-Term Follow-up of Patients with Papillary Thyroid Microcarcinoma

Papillary thyroid microcarcinoma (PTMC) usually has a favorable prognosis but can also be aggressive, with neck and distant metastases. We evaluated the diagnostic role of 131I SPECT/CT in detecting metastases in PTMC patients during long-term follow-up and whether the procedure should be included in the current diagnostic protocol. Methods: We retrospectively studied 351 consecutive PTMC patients who had undergone thyroidectomy and radioiodine therapy; 21 were at high risk, 94 at low risk, and 236 at very low risk. During follow-up, the patients underwent diagnostic 131I whole-body scanning (WBS) followed by SPECT/CT. Results: WBS found 248 radioiodine-avid foci in 126 patients, and SPECT/CT found 298 in 139 patients, confirming all foci found on WBS. SPECT/CT also correctly classified 76 of the avid foci as unclear or wrongly classified on WBS. Globally, SPECT/CT detected and correctly classified 64 neoplastic lesions in 27 of 30 patients with metastases, and WBS evidenced 39 of 64 lesions, 28 of which were unclear or wrongly classified, in 16 of the 30 patients. Nineteen of 27 patients, including 13 at very low risk, had only neck metastases, 9 of 19 being T1aN0M0 with an undetectable thyroglobulin level. Three of 27 patients, including 1 at very low risk, had only distant metastases with an undetectable or very low thyroglobulin level. Five of 27 patients had neck and distant metastases with a thyroglobulin level <2.5 ng/mL in 1 case, between 2.5 and 10 in 3 cases, and >10 in the remaining case. SPECT/CT also reduced WBS false-positive results in 15 of 139 patients (10.8%). SPECT/CT had an incremental value over WBS in 38.1% of patients with positive findings and changed the classification and therapeutic management in 21.6%. Conclusion: Metastases occurred in 8.5% of patients during long-term follow-up. SPECT/CT performed better than WBS, particularly in patients at very low risk with inconclusive WBS results, a TNM stage of T1aN0M0, and an undetectable or very low level of thyroglobulin. Prolonged surveillance is justified in PTMC patients, and wider use of 131I SPECT/CT in the diagnostic protocol is suggested.