Effect of collimator angle on HyperArc stereotactic radiosurgery planning for single and multiple brain metastases |
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| Affiliation: | 2. Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, Suita, Japan;3. Division of Medical Physics, Oncology Center, Osaka University Hospital, Suita, Japan;2. Department of Radiation Oncology, University of Toronto, Toronto, ON M4N 3M5, Canada;3. Department of Medical Physics, Trillium Health Partners, the Credit Valley Hospital, Mississauga, Canada;4. Department of Medical Physics, Marshfield Clinic Health System, Marshfield, WI 54449, USA;5. Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Canada;2. Department of Radiation Medicine and Applied Sciences, University of California San Diego, La Jolla, CA 92093, USA;3. Department of Radiation Oncology, Unit 97, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA;2. Duke University Medical Center, Durham, NC, USA;3. Duke Kunshan University, Kunshan, Jiangsu, China;4. King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia;5. University of Virginia Health System, Charlottesville, VA, USA |
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| Abstract: | We assessed the effect of collimator angle on the dosimetric parameters for targets and organs at risk (OARs) for collimator-optimized HA (CO-HA) and non-CO-HA (nCO-HA) plans. The nCO-HA and CO-HA plans were retrospectively generated for 26 patients (1 to 8 brain metastases). The dosimetric parameters for planning target volume (homogeneity index [HI]; conformity index [CI]; gradient index [GI]) and for OARs were compared. The modulation complexity score for volumetric modulated arc therapy (MCSV) and monitor units (MUs) were calculated. Doses were measured using the electronic portal imaging device and compared with the expected doses. Dosimetric parameters of the HI, CI, and GI for single (n = 12) and multiple (n = 14) metastases cases were comparable (p > 0.05). For multiple metastases cases, the CO-HA plan provided lower V4Gy, V12Gy, V14Gy, V16Gy for brain tissue compared to the nCO-HA plan (p < 0.05). Doses for OARs (D0.1cc) (brainstem, chiasm, Hippocampus, lens, optic nerves, and retinas) were comparable (p > 0.05). For multiple metastases cases, the CO-HA plan resulted in less complex multileaf collimator (MLC) patterns (MCSV = 0.19 ± 0.04, p < 0.01), lower MUs (8596 ± 1390 MUs, p < 0.01), and shorter beam-on time (6.2 ± 1.0 min, p < 0.01) compared to the nCO-HA plan (0.16 ± 0.04, 9365 ± 1630, and 6.7 ± 1.2 for MCSV, MUs, and beam-on time, respectively). For both treatment approach, the equivalent gamma passing rate was obtained with the 3%/3 mm and 2%/2 mm criteria (p > 0.05). The collimator optimization in the HA planning reduced doses to brain tissues and improved the treatment efficacy. |
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