Physics and Physiology of 90Y Radioembolization for Liver Tumors

Abstract

Transarterial radioembolization with yttrium-90 (90Y) microspheres is an intra-arterial brachytherapy approved for the treatment of hepatocellular carcinoma and metastatic colorectal cancer. 90Y is a pure beta particle-emitting radionuclide with a 64.1 hours physical half-life and a maximum energy of 2.27 MeV. Selective hepatic arterial infusion allows preferential treatment of tumor cells while limiting damage to normal liver parenchyma. Glass microspheres and resin microspheres with high specific activities of 90Y are commercially available for radioembolization. Dosimetry refers to the process of calculating and prescribing the activity of 90Y to administer to a specific patient to result in a tumoricidal dose while maintaining a safe dose to the liver and lung parenchyma. The 90Y treatment plan requires an initial angiographic procedure to map the hepatic arterial anatomy, eliminate potential routes of nontarget embolization, and administer a simulation dose of 99mTc-macroaggregated albumin (99mTc-MAA) to calculate the lung shunt fraction and delineate intrahepatic distribution, and a second procedure to administer the therapeutic 90Y dose.