Plan Quality and Optimized Treatment Planning Technique for Single-Isocenter VMAT Brain Stereotactic Radiosurgery/Radiotherapy Using Photon Optimizer

Introduction: This study aims to analyze different dosimetric indices using various formulae in cranial Stereotactic Radiosurgery/Radiotherapy treatment planning.Material and Methods: ۴۲ targets were constructed from ۲۳ patients with brain metastases (≤۳۰ cc) treated at our institution, selected for this study. The PTVs were generated using a ۳.۰ mm isotropic margin from the CTV. Sequential boost prescriptions of ۵-۱۵ Gy were delivered using ۶ MV FFF beams with full, partial, and non-coplanar arcs. The Acuros XB algorithm with a ۱.۲۵ mm grid size was optimized to calculate the dose distribution. The Conformity Index Homogeneity Index, and Gradient Index were evaluated using a DVH with different mathematical formulae.Results: RTOG, Van’t Riet, and Paddick, and the Inverse of RTOG values were close to ۱.۰. Whereas Lomax & Scheib and SALT were ۰.۹۲ ± ۰.۰۶, ۰.۹۴±۰.۰۵, respectively, they achieved lower than ۱.۰. The results of different types of HI values achieved similar ideal values. For GI data scored, each target is in the case of multiple lesions. The effective radius and modified GI results for the dose GI are ۴.۶۱ ± ۱.۱۲ and ۴.۲۸ ± ۱.۲۴, respectively.Conclusion: This study analyzed various CI, HI, and GI definitions to assess dose distribution quality in brain SRS/SRT plans. CI, HI, and GI are valuable tools for evaluating treatment plans by quantifying conformity, dose uniformity, and dose gradient. However, these indices have limitations. Future research should investigate these correlations, linking CI, HI, and GI with local control rates and toxicity outcomes.

Keywords:

Radiosurgery Brain Neoplasms / secondary Radiotherapy Intensity , Modulated