Purpose: The objective of this work is to perform a retrospective study comparison of the quality of treatment plans generated using static jaw without collimator optimization to those with dynamic jaw tracking and collimator optimization for intracranial SRS treatments in order to test any clinical significance.
Methods: 20 patients with single cranial lesions that were planned on Brainlab Elements ver 1.5 with static jaw and no collimator optimization were replanned in Brainlab Elements ver 3.0 Cranial SRS module with dynamic jaw tracking and collimator optimization. The arc geometry and the planning optimization objectives were kept same for all patient cases. The PTV volumes ranged between 0.58 cc – 35.81 cc. We compared the differences in three treatment plan’s quality parameters CI, GI, V12 cc, V2 cc, Total MU, Dmax, max OAR point doses using a linear mixed effects model. In the event the global test was found to be significant, pairwise treatment plan comparison was done across the three treated plans using Tukey’s multiple comparison test Statistical significance was based on a two-sided p-value of 0.05.
Results: Clinical plan with static jaw and no collimator optimization had a significantly lower mean Dmax (-55.1; 95% CI: -100.054, -10.146; P-value: 0.013); and MU (-793.7; 95% CI: -1407.737, -179.663; P-value: 0.009) as compared to plan with only jaw tracking enabled. The mean Cochlea dose for clinical plan was found to be significantly higher as compared to plan with both jaw tracking and collimator optimization enabled (73.6; 95% CI: 7.076,140.124; P-value: 0.027). There were no significant differences found in the CI, GI, V12 cc, V2 cc and other OAR doses investigated.
Conclusion: Brainlab Elements 3.0 plans has higher beam modulation and helps in generating SRS plans with similar conformity and higher max point dose to target and better Cochlea sparing.