Nuclear imaging for improved radioembolization treatment planning

Abstract

Radioembolization is a minimally invasive treatment for liver cancer. During a radioembolization procedure small radioactive spheres (microspheres) are administered in the vasculature of the liver. These microspheres lodge (mostly) in the tumorous tissue, where they locally irradiate liver tumours, whilst (mostly) sparing the healthy liver tissue. Prior to the treatment procedure, a pre-treatment safety procedure is performed in which surrogate particles, technetium-99m labelled macroaggregated albumin (99mTc-MAA), are administered to simulate the distribution of the microspheres. These 99mTc-MAA particles are visualised using nuclear imaging. Based on the amount of 99mTc-MAA shunting to the lungs (lung shunt fraction), the unwanted accumulation of 99mTc-MAA elsewhere outside the liver (extrahepatic depositions), and the distribution of 99mTc-MAA within the liver (intrahepatic dose distribution), a nuclear medicine physician decides whether or not it is safe to proceed with the treatment procedure. When considered safe, the treatment will usually take place 1-2 weeks later. The microspheres that are administered during the radioembolization treatment have a certain level of radioactivity, measured in becquerel (Bq). Deciding where and how much activity needs to be administered for treatment is called treatment planning. The calculation of the amount of activity that needs to be administered is based on physical models, but these are generally not tailored to individual patients. This thesis introduced several ways to improve radioembolization treatment planning using nuclear imaging.