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

Abstract

Background: 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.

Methods: 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.

Results: 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.

Conclusions: 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.

Keywords: 11C-methionine; Positron emission tomography/computed tomography (PET/CT); computed tomography (CT); primary hyperparathyroidism (PHPT); scintigraphy.

Figure 1

Parathyroid adenoma localization techniques. PHPT, primary hyperparathyroidism; CT, computed tomography; PET/CT, positron emission tomography/computed tomography; TP, true positive; FP, false positive; TN, true negative; FN, false negative.

Figure 2

¹¹C-methionine PET/CT results in a 41-year-old female showed an intrathyroid lesion from the right thyroid gland (white arrows) and a lesion corresponding to left lower parathyroid adenoma (white arrowheads). Those appeared to be double hyperplasia according to histology result. PET/CT, positron emission tomography/computed tomography.

Figure 3

Discordant US results and positive ¹¹C-methionine PET/CT results in a 66-year-old female. (A) US showed 3 lesions (white arrows). The left one (A) was located at the lower pole of the left thyroid gland back side. The lesion in the middle (A) borders with the first one and, presumably, comes out from the lower pole of the left thyroid gland, and descends to the retrosternal region. The right one (A) was located in the middle of the right thyroid gland back side. All of them were suspected to be parathyroid adenomas. (B) However, ¹¹C-methionine PET/CT (B) showed only one focus of high ¹¹C-methionine uptake in a lesion located at the back side of left thyroid gland (white arrows). A retrosternal lesion is showed by white arrowheads. (C) ¹¹C-methionine PET/CT of the lesion from the right thyroid gland back side is showed by black arrowheads, and a focus of high ¹¹C-methionine uptake in a lesion located at the back side of left thyroid gland is showed by white arrows. According to histology results, only the lower left lesion was a parathyroid adenoma. The retrosternal lesion appeared to be a multinodular goiter. The lesion from the right thyroid gland back side was normal thyroid tissue. US, ultrasound; PET/CT, positron emission tomography/computed tomography.