How has the diagnostic approach to parathyroid localization techniques evolved in the past decade? Insights from a single-center experience

The standardization of preoperative imaging in primary hyperparathyroidism is one of the current challenges of endocrine surgery. A correct localization of the hypersecretory gland by neck ultrasound and 99mTc-sestamibi (MIBI) scintigraphy are not sufficiently sensitive in some cases. In recent years, CT-4D, 18F-Fluorocholine PET/CT, and radio-guided parathyroidectomy have come into common use. The aim of this study is to evaluate the performance of 18F-Fluorocholine PET/CT after prior negative or discordant first-line imaging in patients with primary hyperparathyroidism undergoing parathyroid surgery. Monocentric observational study on patients affected by pHPT undergoing surgery from July 2009 to April 2024 at the Division of General Surgery, Cattinara Teaching Hospital of Trieste. Preoperative, intra-operative, and follow-up data were collected. The imaging methods used were neck ultrasound, 99mTc-sestamibi (MIBI) scintigraphy, and 18F-Fluorocholine PET/CT (since 2018). 172 patients were included. As first radiologic examination, neck ultrasound (US) was performed in 140 cases and 99mTc-sestamibi (MIBI) scintigraphy in 162. Ultrasound and/or scintigraphy imaging were sufficient for the identification of the gland in 127 patients (73.8%), while in 45 patients (26.2%), the localization was defined with other techniques. Particularly, three patients with negative or discordant first-line imaging underwent neck 4D-CT scan who was useful for parathyroid localization all cases (100%). Only one patient received a neck magnetic resonance (MRI) and resulted positive for preoperative localization. Starting in 2018, 29 out of 45 patients underwent 18F-FCH PET/CT yielding a positive result in 29 patients (100%). In other 16 cases (before the introduction of PET/CT in our preoperative imaging study), the preoperative localization was inconclusive and bilateral neck exploration (BNE) was necessary. The sample was homogeneous in terms of age, anthropometric characteristics, and preoperative biochemical parameters. Male/female ratio was 1:5.1. In the intra-operative site, in the cases of exclusive PET/CT positivity, in 28 cases (96.5%), a diagnostic agreement was confirmed, and the gland was macroscopically smaller or normal in size. The combination of ultrasound and MIBI scintigraphy remains the preferred imaging approach for preoperative studies of pHPT. If secondary imaging is required, 18F -FCH PET/CT stands out as the most advantageous option due to its ability to provide anatomical and functional specificity. FCH PET/CT resulted an effective imaging modality with the highest sensitivity of the available imaging techniques for localizing the hyperfunctioning parathyroid gland. Therefore, this method can be recommended in patients showing negative or inconclusive results in the conventional diagnostic imaging.