Organ‐level internal dosimetry for intra‐hepatic‐arterial administration of 99mTc‐macroaggregated albumin

Purpose There are no published data on organ doses following intra‐hepatic‐arterial administration of 99mTc‐macroaggregated‐albumin (IHA 99mTc‐MAA) routinely used in 90Y‐radioembolization treatment planning to assess intra‐ and extra‐hepatic depositions and calculate lung‐shunt‐fraction (LSF). We propose a method to model the organ doses following IHA 99mTc‐MAA that incorporates three in vivo constituent biodistributions, the 99mTc‐MAA that escape the liver due to LSF, and the 99mTc‐MAA dissociation fraction (DF). Methods The potential in vivo biodistributions for IHA 99mTc‐MAA are: Liver‐Only MAA with all activity sequestered in the liver (LSF = 0&DF = 0), Intravenous MAA with all activity transferred intravenously as 99mTc‐MAA (LSF = 1&DF = 0), and Intravenous Pertechnetate with all activity is transferred intravenously as 99mTc‐pertechnetate (LSF = 0&DF = 1). Organ doses for Liver‐Only MAA were determined using OLINDA/EXM 2.2, where liver was modeled as the source organ containing 99mTc‐MAA, while those for Intravenous MAA and Intravenous Pertechnetate were from ICRP 128. Organ doses for the general case can be determined as a weighted‐linear‐combination of the three constituent biodistributions depending on the LSF and DF. The maximum‐dose scenario was modeled by selecting the highest dose rate for each organ amongst the three constituent cases. Results For Liver‐Only MAA, the liver as source organ received the highest dose at 98.6 and 126 mGy/GBq for the adult male and adult female phantoms, respectively; all remaining organs received