Y-90 PET/CT for localization of Yttrium-90 microspheres - Post radioembolization

Objectives Yttrium-90 microspheres are used for the treatment of unresectable liver tumors. Yttrium-90 results in pair production ( e+e- ) in 32 out of 1 million decays. This characteristic allows us to acquire PET images in patients treated with Y-90 microspheres. The aim of this study was to analyze the utility of Y-90 PET to localize the distribution of microspheres in relation to the hepatic tumor foci and also detect sites of non-targeted delivery.

Methods Y-90 PET/CT was performed on 49 patients (30 males and 19 females, age range 34 -83 years) 2-12 hrs after Y-90 microsphere radioembolization. PET imaging of abdomen was performed using time of flight (TOF) reconstruction and without use of additional shielding. Thirty patients had hepatocellular cancer and 19 had hepatic metastasis ( colorectal 9, carcinoid 3, melanoma 3, esophageal 2 , breast 1, lung 1).

Results In 41 of 49 cases Y- 90 distribution matched the tumor foci in the liver with high target to background ratio. In 14 of the 49 patients (29%) management was modified based on the distribution of Y-90 microspheres on PET scan. Eight patients had incomplete coverage of the tumor foci needing further intervention. Complications from non targeted delivery of Y-90 were able to be predicted in 6 cases (gallbladder related 3 cases, bowel 2 and omentum one case).

Conclusions Y-90 PET/CT is a useful noninvasive tool to map out the distribution of Y-90 microspheres delivered to the liver via radioembolization procedure. Localization of Y-90 microsphere distribution by Y-90 PET, impacts management and helps in predicting potential complications