Pinhole or SPECT Sestamibi Imaging of Parathyroid Lesions?
OBJECTIVE
There is great variation in Tc-99m Sestamibi parathyroid imaging protocols, with advocates for many techniques. A review of data of our SPECT protocol from 2001 to 2004 (presented elsewhere) showed a sensitiviy of 50%. The imaging protocol was changed from dual phase planar with delayed SPECT to dual phase pinhole-based imaging in 2005. We now report our experience with two parathyroid imaging protocols in patients with surgically proven parathyroid adenoma and hyperplasia.
METHOD
A cohort of 32 patients who had parathyroid scintigraphy and parathyroidectomy at our institution since 2004 was identified. These included patients with primary hyperparathyroidism and those with hyperparathyroidism secondary to end stage renal failure.
RESULTS
24 of 32 patients (75%) had a positive finding on Sestamibi imaging, almost all were true positive results on correlation with histology. Pinhole imaging showed abnormal results in 86% (19/22) of patients, while SPECT was abnormal in 50% (5/10). For parathyroid adenomas, pinhole imaging correctly lateralised the lesion in 100% (8/8) of patients, and localised the lesion in 87% (7/8). For parathyroid hyperplasia, both pinhole and SPECT had much lower sensitivity on an analysis by individual abnormal glands. Pinhole imaging however demonstrated at least one abnormal gland in 86% (12/14) of patients.
CONCLUSION
Dual phase Sestamibi pinhole imaging is more accurate than dual phase planar imaging with delayed SPECT in parathyroid adenoma and parathyroid hyperplasia. Individual hyperplastic glands are insensitively imaged with either technique. The improved sensitivity with pinhole imaging is not accompanied by a reduction in specificity.