Introduction: Minimally invasive surgical treatment of primary hyperparathyroidism (PHPT) requires optimal preoperative localisation imaging. Parathyroid four-dimensional CT (4D-CT) has been reported to provide greater sensitivity than MIBI-SPECT/CT in localizing parathyroid adenomas. We analysed the additional value of 4D-CT in our cohort of PHPT patients.
Materials and methods: Patients who attended our parathyroid clinic between February 2016 and April 2017, with biochemically unequivocal PHPT and meeting criteria for surgery were included. All patients underwent Ultrasound and MIBI-SPECT/CT. Patients with inconclusive imaging underwent additional 4D-CT.
Results: Fifty-two patients (77% female) with a mean age of 66.2±14.9 years were included. To date 17/23 patients with inconclusive imaging results underwent additional 4D-CT. Surgical correlation so far has been positive in 4/4 positive 4D-CTs. An intrathyroidal parathyroid adenoma was found in 1 patient with a negative 4D-CT.
|Positive||29/52 (55.8%)||29/52 (55.8%)||13/17 (76.4%)|
|Negative||20/52 (38.5%)||22/52 (42.3%)||3/17 (17.6%)|
|Equivocal||3/52 (5.7%)||1/52 (1.9%)||1/17 (5.9%)|
|MIBI-SPECT/CT||4D-CT vs 4D-CT adjusted protocol||Annual UK Background Exposure|
|Calculated exposure||8.5 mSv||18 mSv vs 12 mSv||2.7 mSv|
Conclusions and discussion: We have been able to radiologically localize a parathyroid adenoma in a majority of our PHPT patients with inconclusive imaging. Surgical correlation is ongoing, but results so far are promising. 4D-CT incurs radiation exposure, particularly to the thyroid and therefore should be used cautiously, especially in younger patients. Population risk for developing any cancer is 1/1000 after 4D-CT, 1/1700 after 4D-CT adjusted protocol and 1/2400 after MIBI-SPECT/CT. Lifetime attributable risk for thyroid cancer after 4D-CT is 1/100,000 in patients >60 years vs 1/2600 in patients of 30 years. MIBI-SPECT/CT is five times more expensive than 4D-CT (£630 vs £125). Currently, first line imaging consists of Ultrasound and MIBI-SPECT/CT. 4D-CT has additional value in PHPT patients with negative conventional imaging. We suggest that 4D-CT should be considered as first line imaging in patients over 60 years presenting with PHPT. Optimising the sensitivity of parathyroid imaging should result in more patients having minimally invasive surgery.