The ability of 99mTc-pertechnetate/sestamibi subtraction, double-phase 99mTc-sestamibi and 99mTc-sestamibi SPECT imaging to localize abnormal parathyroid tissue was compared.
Methods: Fifty-five consecutive patients had parathyroid imaging before surgery for hyperparathyroidism. Imaging consisted of 99mTc-pertechnetate pinhole images of the neck followed by 99mTc-sestamibi pinhole images of the neck and parallel-hole images of the neck and chest (early images). Within 2.5-4.0 hr later pinhole images of the neck, parallel-hole and SPECT images of the neck and chest were obtained (late images). Nodular foci of increased sestamibi activity were considered abnormal.
Results: The sensitivity for abnormal parathyroid glands by visual comparison of early images and pertechnetate images was 72%-75%, late images and pertechnetate images was 73%-78% and double-phase (early and late) sestamibi images was 62%-65%; computer subtraction of pertechnetate from early images was 71%-74%; and SPECT imaging was 79%. The sensitivity for parathyroid adenomas was 89%-98%, while the sensitivity for hyperplastic parathyroid glands was only 47%-58%.
Conclusion: Late imaging, computer subtraction and SPECT may not be necessary since they provided only marginal improvements on visual comparison of early sestamibi with pertechnetate images. Double-phase sestamibi imaging was less sensitive, so baseline thyroid imaging with pertechnetate is recommended.