• Lijun Ma, Erica Mason, Penny K Sneed, Michael McDermott, Alexei Polishchuk, David A Larson, and Arjun Sahgal.
• Department of Radiation Oncology, University of California, San Francisco, California. Electronic address: lijunma@radonc.ucsf.edu.
• Int. J. Radiat. Oncol. Biol. Phys. 2015 Mar 1; 91 (3): 661-8.

PurposeTo demonstrate the clinical feasibility and potential benefits of sector beam intensity modulation (SBIM) specific to Gamma Knife stereotactic radiosurgery (GKSRS).Methods And MaterialsSBIM is based on modulating the confocal beam intensities from individual sectors surrounding an isocenter in a nearly 2π geometry. This is in contrast to conventional GKSRS delivery, in which the beam intensities from each sector are restricted to be either 0% or 100% and must be identical for any given isocenter. We developed a SBIM solution based on available clinical planning tools, and we tested it on a cohort of 12 clinical cases as a proof of concept study. The SBIM treatment plans were compared with the original clinically delivered treatment plans to determine dosimetric differences. The goal was to investigate whether SBIM would improve the dose conformity for these treatment plans without prohibitively lengthening the treatment time.ResultsA SBIM technique was developed. On average, SBIM improved the Paddick conformity index (PCI) versus the clinically delivered plans (clinical plan PCI = 0.68 ± 0.11 vs SBIM plan PCI = 0.74 ± 0.10, P=.002; 2-tailed paired t test). The SBIM plans also resulted in nearly identical target volume coverage (mean, 97 ± 2%), total beam-on times (clinical plan 58.4 ± 38.9 minutes vs SBIM 63.5 ± 44.7 minutes, P=.057), and gradient indices (clinical plan 3.03 ± 0.27 vs SBIM 3.06 ± 0.29, P=.44) versus the original clinical plans.ConclusionThe SBIM method is clinically feasible with potential dosimetric gains when compared with conventional GKSRS.Copyright © 2015 Elsevier Inc. All rights reserved.

29 keywords...

hide…