ESTRO 2024 - Abstract Book

S1650

Clinical - Lung

ESTRO 2024

CT scan is performed using Optima CT 580W (GE), and a treatment plan is created using Precision (Acurray). The planning parameters are Planning Method: VOLO Ultra, Field Width: 1.0 cm and 2.5 cm, Calculation grid: 1 x 1.25 x 1 mm 3 , and 50 Gy/5 Fr, D98 prescription for Target A and Target B. First, perform a standard dose evaluation without driving the dynamic phantom or using Synchrony to confirm little deviation from the treatment plan (baseline measurement). Next, we move the dynamic phantom and evaluate the absorbed dose and dose distribution of Synchrony. The phantom drive conditions are primary drive: 10 mm in the IEC-Y direction, secondary drive: 2 mm, 4 mm, 6 mm, and 8 mm in the IEC-Y direction, each driven by a sine wave with a breathing cycle of 3 seconds. Perform Dose Difference and gamma analysis (DD 3%, DTA 2 mm, TH 10%) based on the absorbed dose and dose distribution obtained in the baseline measurement.

Results:

The dose difference was 1.3% under a Jaw Width of 2.5 cm and secondary drive of 8 mm but was less than 1% (- 0.1% to 0.7%) in other cases. Gamma analysis obtained a pass rate of 95.7% to 97.4% for plans with a jaw width of 1.0 cm and a pass rate of 96.4% to 100% for plans with a jaw width of 2.5 cm. This treatment plan had excellent dose uniformity, and no significant changes were observed in the absorbed dose at the center of the tumor, even if Synchrony no longer tracked it. In the dose distribution evaluation, an extremely small dose discrepancy was detected in the IEC-Y direction due to increased secondary drive. Still, it was not large enough to significantly affect the gamma analysis results.

Conclusion:

In Single-Isocenter treatment using Radixact-Synchrony system, it was suggested that even if multiple targets have different respiratory movements, fatal errors in treatment accuracy may not occur.

Keywords: Synchrony,Multiple Target,Different Movements

References:

1) Lana C. Critchfield, Mark E. Bernard, et al. Journal of Applied Clinical Medical Physics. 2021; 22(1): 251 - 260.

2) Guang-Pei Chena, An Tai, Timothy D. Keiper, et al. Medical Physics. 2020; 47(7): 2814 - 2825.

3) William S. Ferris, Wesley S. Culberson, Jennifer B. Smilowitz, et al. Journal of Applied Clinical Medical Physics. 2021; 22(1): 1 - 7.

4) J.E. van Timmeren, M.S. Hoogeman, S. Ehrbar, et al. Radiotherapy and Oncology 2021; 162: 105 - 111.

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Immunomodulatory effects of lung SBRT in the primary and metastatic cancer setting (LAPIS trial).