ESTRO 2024 - Abstract Book

S646

Clinical - Breast

ESTRO 2024

1 Strahlenzentrum Hamburg, Medical Physics, Hamburg, Germany. 2 Strahlenzentrum Hamburg, Oncologists, Hamburg, Germany. 3 Strahlenzentrum Hamburg, RTT, Hamburg, Germany

Purpose/Objective:

Since the installation of the SGRT- system AlignRT by VisionRT at the “Strahlenzentrum Hamburg MVZ” there is a unique possibility to evaluate the patient movement during the treatments, and the therapy as a whole. Furthermore, the comparison between FB vs DIBH allows quantitative conclusions about the accuracy of the planning target volume coverage.

Material/Methods:

For this analysis, finished treatment of the thoracic and mammal regions, with and without DIBH, were used independently of their prescriptions. In total, the surface data of 1400+ DIBH fractions and 4000+ FB fraction were analysed, and consequently evaluated. The focus was set to the three translation dimensions superior-inferior, anterior-posterior, and left-right. Furthermore, the spanning vectors are analysed to determine a margin due to the integrated patient movement.

Results:

The mean deviation over all FB fraction is σ FB (vert./long./lat.)=1.2mm/1.1mm/0.7mm, while the centre position covers a range of Δ FB (vert./long./lat.)=26.4mm/16.9mm/13.5mm. The mean deviation over all DIBH fractions is σ DIBH (vert./long./lat.)=0.7mm/1.3mm/0.8mm, while the centre position covers a range of Δ DIBH (vert./long./lat.)=4.8mm/14.2mm/8.6mm. The analysis of the spanned vectors result in a margin vec FB = 2.7mm±1.06mm and a margin vec DIBH = 1.89mm±0.58mm to envelope the patient movement.

Conclusion:

The surface movement of the DIBH treatments is more stable and less oscillating in comparison to the FB treatments. This can lead to improved local tumour control, lessen the radiation load of organs at risk, and potentially reduce the planning target volume size.

Keywords: SGRT, DIBH, FB

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