¹¹C-methionine PET/CT and conventional imaging techniques in the diagnosis of primary hyperparathyroidism

It is well known that primary hyperparathyroidism (PHPT) is one of the most common endocrine disorders. Precise preoperative adenoma localization is essential for increasing PHPT cure rate. Conventional localization techniques include neck ultrasound, 99m-Tc-sestamibi scintigraphy, and computed tomography (CT). However, all of these methods have limitations. ¹¹C-methionine positron emission tomography/computed tomography (PET/CT) combines both anatomical and functional modalities; it may be useful in terms of lowering the imaging procedures number and improving accuracy.

A retrospective diagnostic accuracy study with sensitivity and specificity evaluation was conducted. We studied the data of 91 patients with PHPT, who were hospitalized at Almazov National Medical Research Centre. Medical records, lab results, and CT imaging of all patients were analyzed. All of them underwent ultrasound. 99m-Tc-sestamibi/99m-Tc-pertechnetate subtraction scintigraphy and CT were performed on 56 and 86 patients, respectively. Since 2020 ¹¹C-methionine PET/CT has been performed on 45 patients. Then, minimally invasive parathyroidectomy (PTX) was carried out in all patients. Histological results were used as a benchmark in order to evaluate diagnostic accuracy of studied methods. Parathyroid adenoma or hyperplasia was confirmed in all patients. Multiple lesions were found in 5 patients. Nineteen lesions were ectopic. All patients with multiple lesions required at least 3 localization techniques, and 2 of them required 4.

The sensitivity of ¹¹C-methionine PET/CT was 98%, CT, 99m-Tc-sestamibi scintigraphy, and ultrasound showed sensitivity at 75%, 79%, and 67%, respectively. The estimated specificities of ¹¹C-methionine PET/CT, CT, 99m-Tc-sestamibi scintigraphy and ultrasound were 93%, 73%, 75%, and 70%, respectively.

Our study showed that ¹¹C-methionine PET/CT has higher sensitivity and specificity than conventional techniques in a group of 19 patients. ¹¹C-methionine PET/CT may take a place in the imaging of parathyroid adenomas, it may replace CT and 99m-Tc-sestamibi scintigraphy while simultaneously providing information about lesion topography and function.