SU-E-J-128: Liver Motion during CBCT-Guided SBRT.

Purpose of this study was to investigate the motion characteristics of liver during SBRT, based on fiducial markers tracked with X-ray projections of CBCT scans, taken immediately prior to each treatment. Purpose of this study was to investigate the motion characteristics of liver during SBRT, based on fiducial markers tracked with X-ray projections of CBCT scans, taken immediately prior to each treatment. The range of motion for twenty patients were 3.00 ± 2.04 mm, 5.08 ± 3.12 mm and 17.93 ± 5.11 mm in the planning 4DCT, and 2.77 ± 1.6 mm, 5.29 ± 3.10 mm and 16.46 ± 5.69 mm in the treatment CBCT, for LR, AP, and CC directions, respectively. The range of respiratory period was 3.94 ± 0.65 and 4.18 ± 0.75 seconds during 4DCT simulation and CBCT scans, respectively. We found that breathing-induced AP and CC motions are highly correlated. The absolute difference in motion magnitude between the markers, had a positive correlation with absolute distance between the markers (R2=0.69, linear-fit). The inter-fractional gating window varied significantly for some patients, with the largest having 29.5-56.4% range between fractions. This study analyzed the liver motion characteristics of 20 patients undergoing SBRT. A large variation in motion was observed, inter- and intra-fractionally, and that as the distance between the markers increased, the difference in the absolute range of motion also increased. This suggests that marker(s) in closest proximity to the target be used. This project was supported by Varian Medical Systems.

Park JC ，Park SH ，Song B ，Song WY ... -  《-》

Liver motion during cone beam computed tomography guided stereotactic body radiation therapy.

Park JC ，Park SH ，Kim JH ，Yoon SM ，Song SY ，Liu Z ，Song B ，Kauweloa K ，Webster MJ ，Sandhu A ，Mell LK ，Jiang SB ，Mundt AJ ，Song WY ... -  《MEDICAL PHYSICS》

Tumor motion changes in stereotactic body radiotherapy for liver tumors: an evaluation based on four-dimensional cone-beam computed tomography and fiducial markers.

Shimohigashi Y ，Toya R ，Saito T ，Ikeda O ，Maruyama M ，Yonemura K ，Nakaguchi Y ，Kai Y ，Yamashita Y ，Oya N ，Araki F ... -  《Radiation Oncology》

Respiration correlated cone-beam computed tomography and 4DCT for evaluating target motion in Stereotactic Lung Radiation Therapy.

Purdie TG ，Moseley DJ ，Bissonnette JP ，Sharpe MB ，Franks K ，Bezjak A ，Jaffray DA ... -  《ACTA ONCOLOGICA》

Interfraction and intrafraction changes in amplitude of breathing motion in stereotactic liver radiotherapy.

Interfraction and intrafraction changes in amplitude of liver motion were assessed in patients with liver cancer treated with kV cone beam computed tomography (CBCT)-guided stereotactic body radiation therapy (SBRT). A total of 314 CBCTs obtained with the patient in the treatment position immediately before and after each fraction, and 29 planning 4DCTs were evaluated in 29 patients undergoing six-fraction SBRT for unresectable liver cancer, with (n = 15) and without (n = 14) abdominal compression. Offline, the CBCTs were sorted into 10 bins, based on phase of respiration. Liver motion amplitude was measured using liver-to-liver alignment from the end-exhale and end-inhale CBCT and four-dimensional CT reconstructions. Inter- and intrafraction amplitude changes were measured from the difference between the pre-SBRT CBCTs relative to the planning four-dimensional CT, and from the pre-SBRT and post-SBRT CBCTs, respectively. Mean liver motion amplitude for all patients (range) was 1.8 (0.1-7.0), 8.0 (0.1-18.8), and 4.3 (0.1-12.1) mm in the mediolateral (ML), craniocaudal (CC), and anteroposterior (AP) directions, respectively. Mean absolute inter- and intrafraction liver motion amplitude changes were 1.0 (ML), 1.7 (CC), and 1.6 (AP) mm and 1.3 (ML), 1.6 (CC), and 1.9 (AP) mm, respectively. No significant correlations were found between intrafraction amplitude change and intrafraction time (range, 4:56-25:37 min:sec), and between inter- and intrafraction amplitude changes and liver motion amplitude. Intraobserver reproducibility (sigma, n = 29 fractions) was 1.3 (ML), 1.4 (CC), and 1.4 (AP) mm. For the majority of liver SBRT patients, the change in liver motion amplitude was minimal over the treatment course and showed no apparent relationships with the magnitude of liver motion and intrafraction time.

Case RB ，Moseley DJ ，Sonke JJ ，Eccles CL ，Dinniwell RE ，Kim J ，Bezjak A ，Milosevic M ，Brock KK ，Dawson LA ... -  《-》