Correlation of liver reserve capacity before and after carbon-ion radiotherapy using 99mTc-GSA SPECT in patients with liver tumor

[Objective] 99mTc-GSA SPECT is performed for patients before and after carbon-ion radiotherapy (CIRT) for liver tumors in our hospital. It is essential to assess reduced liver reserve capacity and prediction of post-CIRT value before treatment. In this study, we evaluated the usefulness of the liver reserve capacity estimation using GSA SPECT and CT/MRI fusion images in patients before and after CIRT for liver tumors.[Materials and Methods]Eight patients who received 99mTc-GSA SPECT imaging before and 3 months after CIRT were enrolled in this investigation. After intravenous injection of 99mTc-GSA, dynamic and SPECT imaging was performed using a gamma camera. All acquired SPECT images were fused with CT or MRI images using fusion viewer software, followed by evaluation of liver reserve capacity by the maximal GSA removal rate (GSA-Rmax) and GSA-Rmax of the predicted residual liver after CIRT (GSA-RL) using multicompartment analysis. Then we assessed correlation between GSA-RL before CIRT and GSA-Rmax after CIRT to evaluate the usefulness of residual liver function estimation with 99mTc-GSA SPECT.[Results]GSA-Rmax before and after CIRT were 0.302±0.189 and 0.264±0.172, respectively. GSA-RL before CIRT was 0.266±0.174, which was estimated using GSA SPECT-CT/MRI fusion images before CIRT. There was a high correlation between GSA-RL before CIRT and GSA-Rmax after CIRT (r=0.93, p