Imaging characteristics following 90yttrium microsphere treatment for unresectable liver cancer

Selective internal radiation therapy (SIRT) with (90)yttrium microspheres - also known as radioembolisation - is a relatively new interventional radiology technique offering symptomatic and survival advantages for patients with unresectable liver cancer. However, in delivering both beta-particle brachytherapy and embolisation of tumour vasculature, SIRT produces biological sequelae and imaging characteristics distinct from other treatment modalities. Current CT interpretation criteria consistently under-report pathological responses to radioembolisation, diminishing both the prognosis and subsequent treatment choices for responding patients. However, newer criteria incorporating both tumour dimensions and enhancement characteristics improve the correlation with histopathology and provide substantially earlier confirmation of response. CT following radioembolisation may also identify parenchymal features that are often benign but may be mistaken for tumour progression. This review outlines imaging criteria specific to SIRT, including assessment of tumour response and interpretation of both lesion and parenchymal characteristics. The adjunctive role of additional modalities such as positron emission tomography is also addressed.