ESTRO 2024 - Abstract Book

S3704

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2024

improved from 1.03 to 1.01 for the IMRT opt plan compared to the IMRT 0 plan. Similar results were obtained also for patient 2 and patient 3. For the same conformity index of 1.05 in both plans, the IMRT opt plan reduced brain V 26Gy by 1.3% (22.9 cc vs 23.2 cc) and the mean brain dose by 0.7% (8.07 Gy vs 8.10 Gy) for patient 2, compared to the IMRT 0 plan. For patient 3, brain V 26Gy was reduced from 30.6 cc to 29.3 cc (-4.2%) and the mean brain dose was reduced from 7.57 Gy to 7.52 Gy (-0.7%) for the IMRT opt plan compared to the IMRT 0 plan, while a similar conformity index of 0.84 was obtained for both plans. Using the proposed approach for collimator angle optimization, several different collimator angles were selected for different beam orientations as well as for the same beam orientation. The computation time for optimizing both the IMRT opt and IMRT 0 plans was approximately the same.

Conclusion:

A dosimetrically motivated collimator angle optimization method was implemented and demonstrated for three patients with multiple BMs. The proposed method allows to reduce the bridge dose in between different lesions for SRS-based treatments of patients with multiple BMs and may therefore mitigate the brain toxicities related to SRS. Different from geometrically based collimator angle optimization methods, which determine the collimator angle at each beam orientation prior to the dose optimization, the collimator angles are optimized together with the dose distribution using the proposed approach, and may vary for different planning goals.

Keywords: collimator angle optimization, SRS, IMRT planning

References:

[1] Battinelli C, Fredriksson A, Eriksson K. Technical Note: Collimator angle optimization for multiple brain metastases in dynamic conformal arc treatment planning. Med Phys. 2021;48(9):5414-5422. doi:10.1002/mp.15078

[2] Romeijn HE, Ahuja RK, Dempsey JF, Kumar A. A Column Generation Approach to Radiation Therapy Treatment Planning Using Aperture Modulation. SIAM J. Optim. 2005;15(3):838-862. doi: 10.1137/040606612