Lacrimal gland dosimetry for the brain imaging agent technetium-99m-HMPAO.

We calculated lacrimal gland dosimetry for the brain imaging agent 99mTc-HMPAO. One hundred thirty-eight patients were studied using a dedicated brain imaging device. Only 11% of the patients showed lacrimal gland uptake. For a 740-MBq (20 mCi) injected dose of 99mTc-HMPAO, the radiation exposure to the lacrimal glands is 10.2 mGy (1.02 rad), or 0.0138 mGy/MBq (0.051 rad/mCi). These values are five times lower than the ones reported by the manufacturer of HMPAO. As the dosimetry calculation is only for subjects showing 99mTc-HMPAO uptake in the lacrimal gland, the average radiation dose to all subjects is considerably lower, 1/10 of the estimated value.