ESTRO 2024 - Abstract Book

S4241

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2024

1233

Digital Poster

Surface guided ring gantry radiotherapy in deep inspiration breath hold for breast cancer patients

Mustafa Kadhim 1,2 , André Haraldsson 3,2 , Malin Kügele 3,2 , Hedda Enocson 3,2 , Sven Bäck 1,2 , Sofie Ceberg 2

1 Radiation physics, Department of Hematology, Oncology, and Radiation Physics, Skåne University Hospital, Lund, Sweden. 2 Medical Radiation Physics, Lund University, Lund, Sweden. 3 Radiation Physics, Department of Hematology, Oncology, and Radiation Physics, Skåne University Hospital, Lund, Sweden

Purpose/Objective:

Deep inspiration breath hold (DIBH) is a widely adopted treatment technique for left-sided breast cancer patients which reduces ionising radiation exposure to the heart 1 . By reducing the dose to the heart, the rate of cardiac complications and toxicity associated with radiotherapy can be mitigated 2 . Accurate DIBH treatments can be achieved using surface guided radiotherapy (SGRT), a technology that enables real-time monitoring and motion management of breast cancer patients 3 . In combination with TomoDirectTM (TD), a fixed-angle beam intensity-modulated radiotherapy (IMRT) treatment technique implemented on the Radixact® (Accuray, Madison, USA) 4 , further dose reductions to the heart could potentially be achieved. We investigated as the first in the world the combination of TD and treatment in DIBH using SGRT. Technical challenges for the SGRT system need to be addressed, both the risk of DIBH-signal loss due to camera occlusion in the deep ring gantry bore of the Radixact® and signal stability during constant couch movement. Moreover, a dosimetric investigation motivating the new combination of the techniques is warranted. Thus, the aim of this study is to: 1) investigate the compatibility and feasibility of DIBH utilising SGRT for TD treatments of breast cancer in the Radixact® and 2) measure and compare dosimetric parameters between TD in DIBH and in free breathing (FB) for breast cancer patients. To investigate the camera occlusion in the deep bore ring gantry of the Radixact®, surface images (SI) of four healthy volunteers using the Catalyst + HD TM (C-RAD Positioning AB, Uppsala, Sweden) three-camera system were evaluated. The patient setup was done outside the bore at the virtual iso-center, 70 cm from the treatment iso-center (inside the bore). The SGRT system uses a couch tracking laser to track the reference surface during couch movement. The SI coverage and DIBH-signal were evaluated at and beyond the treatment iso-center of the Radixact® For the dosimetric investigation, 20 left-sided breast cancer patients receiving tangential radiotherapy were retrospectively enrolled. For all patients, treatment plans in both FB and DIBH were generated and measured. The plan quality and surface image accuracy were investigated for simulated respiratory motions using a Delta 4 Phantom+ (ScandiDos, Uppsala, Sweden) installed on a HexaMotion (ScandiDos, Uppsala, Sweden) platform. The absorbed dose to the planning target volume (PTV) and organs at risk (OARs) was evaluated for FB and DIBH, respectively. Two-sided paired Wilcoxon signed-ranks tests were performed on the dose-volume histograms (DVH) to investigate significance difference in dosimetric parameters. Material/Methods:

Results: