Parathyroid Imaging

A colloquial saying described the best localization before parathyroid surgery was finding a good surgeon. While it is still important to have a high volume parathyroid surgeon, the trend away from bilateral neck exploration towards that of minimal invasive parathyroidectomy (MIP) has changed the perioperative management of parathyroid disease. The success of MIP depends heavily on the ability of preoperative imaging to localize the abnormal gland(s) and differentiate between single- and multigland disease. Most centers worldwide use a combination of ultrasound and sestamibiscintigraphy (sestamibi). When both are concordant for a single abnormal gland, high cure rates can be achieved. Sensitivity of both sestamibi (varying from 70% to 86%)and ultrasound (76%) are, however, limited. In these scenarios, several second-line imaging modalities have been employed, including Computed Tomography (CT) and Magnetic Resonance Imaging (MRI). More recently, there has been increasing attention to the use of Positron Emitting Tomography (PET), of which the results using 18F-Fluorocholine (FCH) seem most promising. Interestingly, FCH was discovered to localize parathyroid adenomas by incident. It was first described in a patient with prostate cancer, who was found to have a focal hotspot in the neck. Biochemical testing revealed that this patient suffered from primary hyperparathyroidism (pHPT) and during surgery the adenoma was found at exactly the location that was indicated by FCH PET. The aim of this research was to investigate the performance of localization studies for abnormal parathyroid glands in patients with pHPT. Conventional imaging studies and the use of PET are discussed separately

18F-fluorocholine PET/MRI versus ultrasound and sestamibi for the localization of parathyroid adenomas

Purpose: Accurate preoperative localization is imperative to facilitate a minimally invasive parathyroidectomy (MIP) in primary hyperparathyroidism (pHPT). This study aims to compare the diagnostic value of standard-of-care localization techniques (ultrasound [US] and 99mTechnetium (99mTc) -sestamibi scintigraphy) to [F-18]-fluorocholine positron emission tomography/magnetic resonance imaging (FCH-PET/MRI) to determine the additional clinical usefulness of PET/MRI in a Canadian cohort. Methods: We conducted a prospective, appropriately powered, study to compare the diagnostic value of -FCH PET/MRI to that of the US and 99mTc-sestamibi scintigraphy for localization of parathyroid adenomas in a patient with pHPT. The primary outcome was the per-lesion sensitivity and positive predictive value (PPV) of FCH-PET/MRI, US, and 99mTc-sestamibi scintigraphy. Intraoperative surgeon localization, parathormone levels, and histopathological findings were used as reference standards. Results: Forty-one patients underwent FCH-PET/MRI of which 36 patients had parathyroidectomy. In these 36 patients, 41 parathyroid lesions were histologically confirmed as adenomas or hyperplastic glands. Per-lesion sensitivity of FCH-PET/MRI was 82.9% and of US and 99mTc-sestamibi scintigraphy combined at 50.0%, respectively. The sensitivity of FCH-PET/MRI was superior to that of US and 99mTc-sestamibi scintigraphy (p = 0.002). In the 19 patients in whom both US and 99mTc-sestamibi scintigraphy were negative, PET/MRI correctly identified the parathyroid adenoma in 13 patients (68%). Conclusions: FCH-PET/MRI is a highly accurate imaging modality for localization of parathyroid adenomas in a tertiary center in North America. It is a superior functional imaging modality to 99mTc-sestamibi scintigraphy alone and more sensitive for localization of parathyroid lesions than US and 99mTc-sestamibi scintigraphy combined. This imaging modality could become the most valuable preoperative localization study given its superior performance in localizing parathyroid adenomas