Abstract
Preoperative localisation of the diseased parathyroid gland(s) in primary hyperparathyroidism (PHP) is a prerequisite for subsequent minimally invasive surgery. Recently, as alternatives to conventional sestamibi parathyroid scintigraphy, the 11C-based positron emission tomography (PET) tracers methionine and choline have shown promise for this purpose. We evaluated the feasibility of using the 18F-based PET tracer fluoroethyl-l-tyrosine (FET), as the longer half-life of 18F makes it logistically more favourable. As a proof-of-concept study, we included two patients with PHP in which dual-isotope parathyroid subtraction single photon emission computed tomography had determined the exact location of the parathyroid adenoma. A dynamic FET PET/CT scan was performed with subsequent visual evaluation and calculation of target-to-background (TBR; parathyroid vs. thyroid). The maximum TBR in the two patients under study was achieved approximately 30 min after the injection of the tracer and was 1.5 and 1.7, respectively. This ratio was too small to allow for confident visualisation of the adenomas. FET PET/CT seems not feasible as a preoperative imaging modality in PHP.
Highlights
In primary hyperparathyroidism (PHP), excessive secretion of parathyroid hormone (PTH) from one or more hyperactive parathyroid glands causes elevated levels of blood Ca2+
90% of cases, PHP is caused by a single parathyroid adenoma
As the location of the parathyroid adenoma is variable, preoperative imaging is often performed in order to permit a minimally-invasive surgical approach
Summary
In primary hyperparathyroidism (PHP), excessive secretion of parathyroid hormone (PTH) from one or more hyperactive parathyroid glands causes elevated levels of blood Ca2+. The 18 F-based PET tracers are much easier to handle and distribute due to the longer half-life of 2 h, and they provide better spatial resolution due to a shorter positron range, making them more appealing for diagnostic use. We considered it likely that FET would perform comparably to MET, as both are amino acid derivatives. We carried out a “proof-of-concept” study in two patients, aiming to verify or refute the feasibility of further evaluation of FET-PET in the preoperative workup in PHP.
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