This study aimed to determine the absorbed doses in the tumoral-liver and non-tumoral liver of hepatocellular carcinoma (HCC) patients undergoing radioembolization with Yttrium-90 (Y) resin microspheres, and compared with those derived from Tc-MAA using the partition model.
A total of 42 HCC patients (28 males and 14 females, mean age 65 ± 11.51 years) who received 45 treatment sessions with Y-microspheres between 2016 and 2021 were included. Pre-treatment Tc-MAA and post-treatment Y-bremsstrahlung SPECT/CT were acquired for each patient. Semi-automated segmentation of regions of interest (ROIs) was performed using MIM Encore software to determine the tumor-liver ratio (TLR) encompassing the liver volume, tumoral-liver, and lungs, and verified by both nuclear medicine physician and interventional radiologist. A partition dosimetry model was used to estimate the administered activity of Y-microspheres and the absorbed doses to the tumoral-liver and non-tumoral liver. The student’s paired t test and Bland-Altman plot were used for the statistical analysis.
The mean TLR values obtained from Tc-MAA SPECT/CT and Y-bremsstrahlung SPECT/CT were 4.78 ± 3.51 and 2.73 ± 1.18, respectively. The mean planning administered activity of Y-microspheres based on Tc-MAA SPECT/CT was 1.56 ± 0.80 GBq, while the implanted administered activity was 2.53 ± 1.23 GBq (p value < 0.001). The mean absorbed doses in the tumoral-liver estimated from Tc-MAA and Y-bremsstrahlung SPECT/CT were 127.44 ± 4.36 Gy and 135.98 ± 6.30 Gy, respectively. The corresponding mean absorbed doses in the non-tumoral liver were 34.61 ± 13.93 Gy and 55.04 ± 16.36 Gy.
This study provides evidence that the administered activity of Y-microspheres, as estimated from Y-bremsstrahlung SPECT/CT, was significantly higher than that estimated from Tc-MAA SPECT/CT resulted in increased absorbed doses in both the tumoral-liver and non-tumoral liver. However, Tc-MAA SPECT/CT remains a valuable planning tool for predicting the distribution of Y-microspheres in liver cancer treatment.

© 2023. The Author(s) under exclusive licence to The Japanese Society of Nuclear Medicine.