RT Journal Article SR Electronic T1 Residual Set Up Errors of the Surrogate-guided Registration Using Four-dimensional CT Images and Breath Holding Ones in Respiratory Gated Radiotherapy for Liver Cancer JF In Vivo JO In Vivo FD International Institute of Anticancer Research SP 2089 OP 2098 DO 10.21873/invivo.12478 VO 35 IS 4 A1 YOSHIHIRO UEDA A1 MARI TSUJII A1 SHINGO OHIRA A1 IORI SUMIDA A1 MASAYOSHI MIYAZAKI A1 TERUKI TESHIMA YR 2021 UL http://iv.iiarjournals.org/content/35/4/2089.abstract AB Background/Aim: To evaluate the surrogate-guided registration accuracy of two computed tomography (CT) image sets, expiratory phase four-dimensional (Ex4D) CT and breath-holding CT (BHCT), in respiratory-gated radiotherapy for liver cancer. Materials and Methods: The surrogate-guided registration errors were defined as the differences between the diaphragm- and fiducial-guided registrations or the differences between upper and lower fiducial registrations in three directions: left–right (LR), anterior–posterior (AP), and cranio–caudal (CC). Results: The mean±SDs of the absolute errors for diaphragm-guided registration were 1.9±1.3, 2.7±1.8, and 2.6±1.7 mm with Ex4D and 1.8±1.8, 2.6±1.9, and 1.8±1.7 mm with BHCT in the LR, AP and CC directions, respectively (CC direction, p<0.01). In the fiducial-guided registration, there were no significant differences in any direction. In registration with Ex4D, there were positive correlations between registration errors and the respiratory irregularity during 4D scanning (correlation coefficient; diaphragm: 0.65, fiducial: 0.54). Conclusion: BHCT has the advantage of accurate surrogate-guided registration compared with Ex4D.