Embolization is a cancer treatment procedure where small particles are injected into the artery that feeds the tumour, blocking the microvasculature and blood flow to the tumour. Size range of the microspheres is such that microspheres are trapped in the pre-capillary arterioles, and cannot be redistributed to other organs.

In (trans-arterial) radioembolization (RE, TARE), selective internal radiation therapy (SIRT), or radiomicrosphere therapy (RMT), microspheres are loaded with a beta emitter, such as 90Y, and injected to a small artery that supplies the tumour. The β- travels only short distances in the tissue, providing localized radiotherapy and saving the surrounding tissue.

Radioembolization is especially used for treatment of liver cancers; tumour in the liver usually gets most of their blood supply from the arteries, while normal liver tissue get most of the blood supply from the portal vein (Gulec, 2016).

Tumour vasculature is immature, devoid of well-developed smooth muscle and innervation, and therefore vasoconstrictors, such as angiotensin-II, adrenaline, and noradrenaline, can be used to further reduce the blood flow and effect of RE on the healthy tissue (van den Hoven et al., 2014).

Small fraction of 90Y decays produces high-energy photons and positron-electron pairs, which can be detected with bremsstrahlung SPECT and PET, respectively. PET provides better resolution, and can be used to assess the in vivo absorbed dose to the tumour in detail.

Usual PET imaging agents, such as [18F]FDG and hypoxia tracers can also be used after embolization to assess the treatment effect.

CT angiography could be used to locate the best arteries for microsphere injection (Simoncini et al., 2018).

See also:


Alrfooh A, Patel A, Laroia S. Transarterial radioembolization agents: a review of the radionuclide agents and the carriers. Nucl Med Mol Imaging 2021; 55: 162-172. doi: 10.1007/s13139-021-00709-3.

D'Arienzo M, Filippi L, Bagni O. Quantitative postradioembolization imaging using PET/CT. In: Handbook of Radioembolization - Physics, Biology, Nuclear Medicine, and Imaging. Pasciak AS, McKinney JM, Bradley YC (eds.), CRC Press, 2017, pp 229-249. ISBN 978-1-4987-4201-6.

Dezarn WA, Cessna JT, DeWerd LA, Feng W, Gates VL, Halama J, et al. Recommendations of the American Association of Physicists in Medicine on dosimetry, imaging, and quality assurance procedures for 90Y microsphere brachytherapy in the treatment of hepatic malignancies. Med Phys. 2011; 38: 4824-4845. doi: 10.1118/1.3608909.

Tags: ,

Updated at: 2022-12-16
Created at: 2016-03-18
Written by: Vesa Oikonen