Parathyroid nuclear scan. A focused review on the technical and biological factors affecting its outcome.

OBJECTIVE: Technetium Parathyroid Scintigraphy (TS) is the most popular noninvasive localization procedure in patients with primary hyperparathyroidism (PHPT). Awareness of various factors involved in technetium uptake helps understand the outcome of TS. METHODS: We utilize a case of changing TS scans in a patient to review the literature on the various biological and technical factors involved in technetium uptake by the abnormal parathyroid tissue. A 56 year female was diagnosed with PHPT and osteopenia. An initial scan using (99m)Tc-Tetrofosmin showed no definite areas of abnormal parathyroid tissue. Patient refused surgical exploration, was started on Bisphosponates and subsequently monitored. Five years later she suffered fracture of her right wrist. A repeat TS using (99m)Tc-Sestamibi revealed hypervascular parathyroid lesion in the right lower neck. She underwent successful removal of a right lower parathyroid adenoma. RESULTS: Technical factors like the type of Tc isotope used, imaging techniques and biological factors like biochemical parameters (calcium, vitamin D levels), adenoma size, content of oxyphilic cells, vascularity can affect the outcome of the scan. CONCLUSION: Clinicians should be aware of technical and biological factors that could result in negative scan in parathyroid nuclear scintigraphy.