ESTRO meets Asia 2024 - Abstract Book

S217

Interdisciplinary – Lung

ESTRO meets Asia 2024

381

Digital Poster

a single institutional study: setup accuracy of lung SBRT of different breathing motion management

Wen Xin Er

Cancer Centre, Sunway Medical Centre, Sunway City, Malaysia

Purpose/Objective:

To investigate the inter-fractional motion of lung stereotactic body radiotherapy (SBRT) of different breathing motion management technique used in our centre as well as its impact on setup accuracy of the treatment.

Material/Methods:

96 sets of pre-treatment CBCT from 61 patients with lung metastasis who underwent lung SBRT using different motion management technique from 2021 to 2022 are retrospectively analyzed. The dose prescription ranges from 40-50Gy in 4-5 fractions. Pre-treatment CBCT is acquired daily and image registration based on lesions is performed. Online correction is then performed after image registration regardless of the value of the translational shifts. The translational shift in anterior-posterior (AP), left-right (LR) and superior-inferior (SI) of every fraction are obtained from Eclipse and are recorded. Mean and standard deviation of these translational shifts are then calculated overall and based on each breathing motion management technique (Jean-Pierre Bissonnette et al. 2009).

Results:

There are 48 ITV (35.4%), 9 DIBH (9.4%), 33 abdominal compression (34.4%) and 6 gating (6.3%) performed in our centre in 2021 and 2022. The overall shift of all breathing motion management in LR, SI and AP direction is 0.3±0.2cm, 0.5±0.3 cm and 0.2±0.1cm respectively. The shift using ITV, DIBH, abdominal compression and gating technique in LR, SI and AP direction is 0.3±0.1cm, 0.4±0.2cm and 0.2±0.1cm, 0.3±0.1cm, 0.4±0.1cm and 0.2±0.0cm, 0.3±0.2cm, 0.5±0.2cm and 0.3±0.1cm, 0.4±0.1cm, 0.5±0.2cm and 0.2±0.1cm respectively. In all the breathing motion management technique used, SI direction has the highest inter-fractional translational shift while AP direction has the least inter fractional translational shift. This indicates that inter-fractional motion in SI direction is most affected by breathing motion of patients. All the breathing motion management technique used in lung SBRT in our centre result in optimal patient’s breathing motion as all the technique have mean inter-fractional translational shift of ≤0.5cm in all directions. DIBH has comparable result with ITV, both the technique has the smallest mean inter-fractional translational shift in all directions. DIBH has the highest reproducibility and consistency as it results in the smallest standard deviation in the inter-fractional translational shift in all directions. Abdominal compression has the highest inter-fractional translational shift in SI and AP direction. This reflects that physical restriction of breathing motion is less effective and reproducible technique in restricting patient’s breathing motion (Qi, Y. et al. 2021).

ITV and gating are the easiest and most convenient breathing motion management for patients to cooperate as no active participation from patients is needed. ITV is the most used technique maybe due to it is the easiest to