Clinical Value of 18F-FCH PET in Localizing Parathyroid Lesions: Comparison With MIBI Scan.

Hyperparathyroidism is a common endocrine disorder. Primary hyperparathyroidism is due to over-secretion of parathyroid hormone and subsequently hypercalcemia, phyophosphatemia and osteoporosis, while secondary hyperparathyroidism is due to physiological secretion of parathyroid hormone by the parathyroid glands in response to hypocalcemia. Surgical approach is the major treatment modality for majority of these patients with hyperparathyroidism. Pre-operative localization of hyperfunctioning glands may lead to minimally invasive surgery. The most commonly used imaging modality for this purpose is 99mTc-sestaMIBI, and supplemented by ultrasonography of the neck. However, the sensitivity and specificity is significantly lower in patients with multiple parathyroid lesions.

Recently, some investigators reported cases of parathyroid adenoma discovered incidentally on choline PET images performed for prostate cancer. 11C or 18F choline is a PET probe used in imaging prostate cancer and hepatocellular carcinoma. As a phospholipid analog, choline is integrated into newly synthesized membranes of proliferating cells by up-regulation of choline kinase. In addition, a previous study showed that the activity of phospholipid/Ca2+-dependent protein kinase was also higher in hyper-functioning parathyroid tissue than in atrophic parathyroid gland. Both mechanisms may be responsible for the uptake of choline tracers in hyperfunctioning parathyroid tissue. Up to now, there are only 3 original reports with limited patients using choline PET in the evaluation of hyperparathyroidism.

This prospective study aims to

• compare the detection rates among sonography, MIBI scan and 18F-FCH PET for localization of the parathyroid lesions including adenoma, hyperplasia or carcinoma;
• evaluate the usefulness of 18F-FCH PET as a second-line tracer in MIBI scan negative patients.

Inclusion criteria

• Parahyperthyroidism (serum iPTH 65 pg / mL; normal range : 12-65), merged with normal or high serum calcium concentration (serum calcium 2.35 mmol / L; normal range: 2.15-2.58) and normal or low serum phosphate concentration (serum phosphorus 3.75 mg / dL; normal range : 2.5-5.0).
• High serum calcium concentration (serum calcium 2.58 mmol/L), but the blood parathyroid hormone concentration in normal range (serum iPTH 12-65pg / mL), hyperthyroidism is suspected.
• MIBI scan has been performed or arranged.
• Age：above 20 years old.

Exclusion criteria

• Patient with Familial hypocalciuric hypercalcemia：daily calcium excretion < 100 mg/24h and fractional excretion of calcium < 1%.
• taking or was taking lithium.
• vitamin D deficiency (25-OH vitamin D < 10 ng/mL).
• Patients with pregnancy or recently having a plan for pregnancy.