Three Cases of Primary Hyperparathyroidism (PHP) with Prior Failed Surgery Where Culprit Lesions Were Identified by 11C-Methionine Positron Emission Tomography (PET) and Accurately Localized with PET-MRI Coregistration

This report describes 3 cases of primary hyperparathyroidism (PHP) in which presurgical localization of the culprit lesions was essential. In 2 cases, the initial parathyroid surgery had failed to restore normal levels of either parathyroid hormone (PTH) or calcium (Ca⁺⁺). In each of these cases experienced surgeons performed the initial parathyroid explorations. In one of these 2 cases, a positive ^99mTc sestamibi (MIBI) scan was obtained prior to the initial surgery. ¹¹C-methionine-positron emission tomography (PET) scans and magnetic resonance imaging (MRI) studies were performed prior to repeat surgical exploration with these data coregistered (the digital data sets from each modality were spatially aligned). In each case, the ¹¹C-methionine-PET studies identified metabolically active tumors whose anatomic locations were accurately determined on the PET coregistration. The third case had previously undergone a thyroidectomy and modified right radical neck dissection for removal of a thyroid cancer and regional lymph node metastases. Following the diagnosis of PHP, MIBI, thallium, and ultrasound studies were performed and were all negative. ¹¹C-methionine-PET and MRI were performed identifying a parathyroid adenoma in the prior surgical field. In these 3 cases culprit lesions were readily located at surgery, excised and confirmed as parathyroid neoplasms. This ¹¹C-methionine PET-MRI coregistration technique appears to be effective at localizing parathyroid neoplasms in high risk patients with PHP in the setting of initially failed surgery or when PHP occurs following previous regional neck surgery.