Hybrid SPECT/CT imaging with 99mTc-MIBI

Metastable Technetium 99-labeled Methoxy-IsoButyl-Isonitrile (99mTc-MIBI) single-photon emission computed tomography (SPECT/CT) is recommended for the preoperative workup of hyperparathyroidism to guide minimally invasive surgery. Nevertheless, the introduction of a CT scan, even at low dose, increases the total radiation dose delivered to the patient. The aim was to evaluate the additional effective dose delivered by CT to 99mTc-MIBI parathyroid scintigraphy. This prospective study included 100 adults with primary hyperparathyroidism who received 99mTc-MIBI SPECT/CT. The mean age was 55.6 years with a M/F sex ratio of 0.28. The effective scintigraphic dose was 9.77 mSv. The mean CT effective dose was 1.77mSv. The mean total effective dose from the hybrid examination was 11.54 mSv and ranged from 10.66 to 12.88 mSv. The contribution of the additional radiation induced by CT ranged from 8.3 to 24.1% with a mean of 15%. This dose is not negligible. But taking into account the benefit of hybrid imaging, this additional radiation is still justifiable.