Usefulness of 4D SPECT/CT 99mTc-sestamibi imaging in patients with primary hyperparathyroidism

Introduction: 4D SPECT/CT with multi-phase dynamic contrast enhanced CT has been proven to aid the localisation of parathyroid adenomas, and can be performed at the same timeas the 99mTc-sestamibi SPECT/CT study.

4D-CT is a three phase CT study, with the 4th dimension being the contrast perfusion analysis.

My aim was to evaluate the added value ofmulti-phase high resolution CT in the SPECT/CT study by investigatingcorrelation in relation to the SPECT planar static images and SPECT/CT as well as the prior ultrasound thyroid scan.

Methods: A retrospective review was peformed on 16 patientswho had undergone 4D SPECT/CT with dynamic high resolution CT from it's implementaion in Autumn of 2019 to currently. The proportion of patients who had correlative imaging with dynamic enhanced CT was evaluated.

Results: 7 of 16 patients, the positive dymanic CT correlated with the positive planar SPECT and SPECT/CT, and also the prior positive thyroid ultrasound.

In 5 of 16 patients, the negative dynamic CT correlated with the negative planar SPECT and SPECT/CT and of these 4 correlated with a negative prior ultraound.

4 of 16 cases did not correlate and of these, 1 of 16 had a postive dynamic CT with a negative SPECT/CT (possibly early washout) and positive prior ultrasound.

3 of 16 patients has a negative ultrasound, and a positive enhancing lesionon 4D-Ct which correlated on SPECT/CT.

Conclusions: Overall in many cases the combined approach has localised the precise anatomical location of the suspected parathyroid adenoma (11/16).

This helps give an accurate 3D roadmap for the surgeon.

Studies have shown 4D CT is a highly sensitive and useful study in localising parathyroid lesions. However sestamibi can help in locating ectopic parathyroid tissue, which may be difficult to find in the first instanceon standard 4D-CT.

Dynamic multiphase CT showed very good correlation with both SPECT and SPECT/CT (15/16=94%), as well as ultrasound (12/16=75%). In many cases it localises the precise anatomical locationof the suspected parathyroid adenoma, providing an accurate 3D roadmap for the surgeons, in 1 case to support the prior ultrasound, whilst planar SPECT, and SPECT/CT showed suspected early wash-out.