NUCLEAR MEDCENTER-BELO HORIZONTE
AIMS: To demonstrate the usefulness of parathyroid scintigraphy, with sequential static images to define the best relation target/fundus time, for surgical planning of minimally invasive radioguided parathyroidectomy (MIRP).
METHODS: Sixteen patients with clinical and laboratorial diagnosis of either primary or secondary hyperparathyroidism underwent 99mTc-Sestamibi scintigraphy for surgical planning of MIRP. The protocol was based on endovenous administration of the radiotracer at the dose of 740 to 1110 MBq, and images of the cervical region were obtained: immediately; in 10-minute intervals, during the first hour; and in 30-minute intervals until completing three hours of study or after complete thyroid washout. Early and later images of the thorax were also obtained for diagnostic purposes of ectopic parathyroid. After acquiring images, the time of the best relation target/fundus of parathyroid lesion was analyzed, taking into account the degree of thyroid washout throughout the study. Thus, it was possible to determine the best moment for a new administration of the radiotracer before the surgery and, therefore, the best surgery length to parathyroid access using hand-held gamma-probe. In the cases in which the best relation target/fundus occurred in the first 60 minutes (06 out of 16 cases) a new radiotracer injection was performed in the operation theater. To facilitate the surgical incisions, cutaneous marks of the scintigraphy-visible lesions were made.
RESULTS: Out of the 16 cases patients analyzed by scintigraphy and submitted to surgery, anatomopathological examinations revealed 9 patients with parathyroid adenoma, 5 patients with parathyroid hyperplasia, 1 with parathyroid adenocarcinoma and 1 with parathyroid adenocarcinoma associated with papillary thyroid carcinoma. Of the patients under study, 3 cases showed to have normal scintigraphy, without hyperconcentration areas of radiotracer.
CONCLUSION: Thyroid scintigraphy demonstrated its diagnostic usefulness and was very usefull for a best planning the radioguided surgeries, concerning identification of lesions and reduction of the operation length. Out of 16 patients in our casuistic, 6 (37.5%) showed to have the ideal relation target/funds up to 60 minutes post-injection of the radiotracer. Such relation would not be well defined whether only immediate and late (from 2 to 4 h) images were obtained, misleading the ideal moment (maximum target/fundus relation) for gamma- probe guided MIRP.