BACKGROUND AND PURPOSE: Vacuum cushion immobilization is commonly used during stereotactic body radiotherapy (SBRT) to reduce intrafraction motion. We investigated target and bony anatomy intrafraction motion (translations and rotations) during online adaptive SBRT on an MR-linac for pelvic/para-aortic lymph node metastases with and without vacuum cushion. MATERIALS AND METHODS: Thirty-nine patients underwent 5x7 Gy SBRT on a 1.5T MR-linac, 19 patients were treated with vacuum cushion, 19 without and 1 patient sequentially with and without. Intrafraction motion was calculated for target lymph nodes (GTVs) and nearby bony anatomy, for three time intervals (pre-position verification (PV), pre-post, PV-post, relating to the online MRI scans) per treatment fraction. RESULTS: Vacuum cushion immobilization significantly reduced anterior-posterior translations for the pre-PV and pre-post intervals, for bony anatomy and pre-post interval for GTV (p < 0.05). Mean GTV intrafraction motion reduction in posterior direction was 0.7 mm (95% confidence interval 0.3-1.1 mm) for pre-post interval (mean time = 32 min). Shifts in other directions were not significantly reduced. More motion occurred in pre-PV interval than in PV-post interval (mean time = 16 min for both); vacuum cushion immobilization did not reduce intrafraction motion during the beam-on period. CONCLUSION: A vacuum cushion reduces GTV and bony anatomy intrafraction motion in posterior direction during pelvic/para-aortic lymph node SBRT. This motion reduction was found for the first 16 min per session. For single targets this motion can be corrected for directly with an MR-linac. Intrafraction motion was not reduced during the second half of the session, the period of radiotherapy delivery on an MR-linac. Vacuum cushion immobilization may not be necessary for patients with single lymph node oligometastases undergoing SBRT on an MR-linac.
BACKGROUND AND PURPOSE: Vacuum cushion immobilization is commonly used during stereotactic body radiotherapy (SBRT) to reduce intrafraction motion. We investigated target and bony anatomy intrafraction motion (translations and rotations) during online adaptive SBRT on an MR-linac for pelvic/para-aortic lymph node metastases with and without vacuum cushion. MATERIALS AND METHODS: Thirty-nine patients underwent 5x7 Gy SBRT on a 1.5T MR-linac, 19 patients were treated with vacuum cushion, 19 without and 1 patient sequentially with and without. Intrafraction motion was calculated for target lymph nodes (GTVs) and nearby bony anatomy, for three time intervals (pre-position verification (PV), pre-post, PV-post, relating to the online MRI scans) per treatment fraction. RESULTS: Vacuum cushion immobilization significantly reduced anterior-posterior translations for the pre-PV and pre-post intervals, for bony anatomy and pre-post interval for GTV (p < 0.05). Mean GTV intrafraction motion reduction in posterior direction was 0.7 mm (95% confidence interval 0.3-1.1 mm) for pre-post interval (mean time = 32 min). Shifts in other directions were not significantly reduced. More motion occurred in pre-PV interval than in PV-post interval (mean time = 16 min for both); vacuum cushion immobilization did not reduce intrafraction motion during the beam-on period. CONCLUSION: A vacuum cushion reduces GTV and bony anatomy intrafraction motion in posterior direction during pelvic/para-aortic lymph node SBRT. This motion reduction was found for the first 16 min per session. For single targets this motion can be corrected for directly with an MR-linac. Intrafraction motion was not reduced during the second half of the session, the period of radiotherapy delivery on an MR-linac. Vacuum cushion immobilization may not be necessary for patients with single lymph node oligometastases undergoing SBRT on an MR-linac.
Authors: Anita M Werensteijn-Honingh; Petra S Kroon; Dennis Winkel; J Carlijn van Gaal; Jochem Hes; Louk M W Snoeren; Jaleesa K Timmer; Christiaan C P Mout; Gijsbert H Bol; Alexis N Kotte; Wietse S C Eppinga; Martijn Intven; Bas W Raaymakers; Ina M Jürgenliemk-Schulz Journal: Phys Imaging Radiat Oncol Date: 2022-06-30
Authors: Tomas M Janssen; Katharine Aitken; Filippo Alongi; Aisling Barry; Uffe Bernchou; Simon Boeke; William A Hall; Ali Hosni; Petra S Kroon; Marcel Nachbar; Hina Saeed; Ina M Jürgenliemk-Schulz; Tine Schytte; Helena M Verkooijen; Marlies E Nowee Journal: Tech Innov Patient Support Radiat Oncol Date: 2022-05-10
Authors: Fabian Weykamp; Charlotte Herder-Wagner; Sebastian Regnery; Philipp Hoegen; C Katharina Renkamp; Jakob Liermann; Carolin Rippke; Stefan A Koerber; Laila König; Carolin Buchele; Sebastian Klüter; Jürgen Debus; Juliane Hörner-Rieber Journal: Strahlenther Onkol Date: 2021-09-01 Impact factor: 3.621
Authors: Maaike T W Milder; Alba Magallon-Baro; Wilhelm den Toom; Erik de Klerck; Lorne Luthart; Joost J Nuyttens; Mischa S Hoogeman Journal: Phys Imaging Radiat Oncol Date: 2022-07-28