Producing High Quality Cranial SRS Plans with 4Pi Planning Technique
G Narayanasamy1*, N Shrestha1, M Bimali2, P Sabouri1, F Kalantari1, Z Su1, (1) University of Arkansas for Medical Sciences, Little Rock, AA, (2) Nexus Institute for Research and Innovation, Lalitpur, Nepal
Presentations
TU-B-202-6 (Tuesday, 7/12/2022) 8:30 AM - 9:30 AM [Eastern Time (GMT-4)]
Room 202
Purpose: This dosimetric study on SRS planning of single cranial lesion with 4Pi planning technique is proposed to produce high quality clinically deliverable plan.
Methods: Ten schwannoma patients with Eclipse RapidArc ver 15.5 based SRS plans were replanned twice with Brainlab Elements ver 3.0 – one using the same treatment geometry (denoted as “ArcMatch”), and another using 4Pi treatment geometry restricted to using same number of arcs (denoted as “4Pi”). Differences in the plan evaluation metrics included target CI, GI, max dose to the Brainstem and number of monitor units (MU) were analyzed using a linear mixed effects model. A pairwise treatment plan comparison was done across the three treated plans using Tukey’s multiple comparison test, in case global test was found to be significant. Statistical significance was based on a two-sided p-value of 0.05
Results: Brainlab Elements based ArcMatch plans has higher CI than clinical Eclipse plans (mean difference: 0.127; 95% CI: 0.02, 0.234, P-value=0.018), but the other two plans did not differ. Both Brainlab plans had significantly lower GI than clinical plans (mean difference: -1.147; 95% CI: -1.49, -0.8, P-value<0.001 for ArcMatch and mean difference: -1.148; 95% CI: -1.49, -0.8, P-value<0.001 for 4Pi). Both Brainlab plans had significantly lower max dose to the Brainstem (Gy) compared to clinical plans (mean difference: -1.34; 95% CI: -2.64, -0.04, P-value<0.05 for ArcMatch and mean difference: -1.83; 95% CI: -3.13, -0.53, P-value=0.006 for 4Pi). Likewise, both Brainlab plans had significantly lower MU than clinical plans (mean difference: -3198; 95% CI: -4478.8, -1917.6, P-value<0.001 for ArcMatch and mean difference: -3002; 95% CI: -4282.6, -1721.4, P-value<0.001 for 4Pi).
Conclusion: 4Pi planning technique has been shown to produce cranial SRS plans for single lesion with similar conformity but superior dose falloff, OAR sparing with lower MUs and also lower collision risk.
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