Tatsuya Kamima1, Hiromi Baba2, Ryo Takahashi3, Mikiko Yamashita4, Yasuharu Sugawara5, Daisuke Kawai6, Toshijiro Yamamoto7, Aya Satou8, Hidenobu Tachibana9. 1. Radiation Oncology Department, The Cancer Institute Hospital, Japanese Foundation for Cancer Research, Tokyo 1358550, Japan. Electronic address: tatsuya.kamima@jfcr.or.jp. 2. Particle Therapy Division, Exploratory Oncology Research and Clinical Trial Center, The National Cancer Center Hospital East, Chiba 2778577, Japan; Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki 3058575, Japan. Electronic address: hibaba@east.ncc.go.jp. 3. Radiation Oncology Department, The Cancer Institute Hospital, Japanese Foundation for Cancer Research, Tokyo 1358550, Japan. Electronic address: ryo.takahashi@jfcr.or.jp. 4. Department of Radiological Technology, Kobe City Medical Center General Hospital, Hyogo 6500047, Japan. Electronic address: m-yamashita@kcho.jp. 5. Department of Radiation Oncology, The National Center for Global Health and Medicine, Tokyo 1628655, Japan. Electronic address: y.sugawara6155@gmail.com. 6. Division of Radiation Oncology, Kanagawa Cancer Center, 2-3-2 Nakao, Asahi, Yokohama, Kanagawa 241-0815, Japan. Electronic address: dkawai0128@gmail.com. 7. Department of Radiological Technology, KKR Otemae Hospital, 1-5-34 Otemae, Chuo, Osaka 540-0008, Japan. Electronic address: edge260@gmail.com. 8. Department of Radiology, Itabashi Chuo Medical Center, 2-12-7 Azusawa, Itabashi, Tokyo, 174-0051, Japan. Electronic address: ayahikita.ims@gmail.com. 9. Particle Therapy Division, Exploratory Oncology Research and Clinical Trial Center, The National Cancer Center Hospital East, Chiba 2778577, Japan. Electronic address: htachiba@east.ncc.go.jp.
Abstract
PURPOSE: No multi-institutional studies of computer-based independent dose calculation have addressed the discrepancies among radiotherapy treatment planning systems (TPSs) and the verification programs for intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). We conducted a multi-institutional study to investigate whether ±5% is a reasonable action level for independent dose calculation for IMRT/VMAT. METHODS: In total, 477 IMRT/VMAT plans for prostate or head and neck (H&N) malignancies were retrospectively analyzed using a modified Clarkson-based commercial verification program. The doses from the TPSs and verification programs were compared using the mean ±1 standard deviation (SD). RESULTS: In the TPS-calculated dose comparisons for prostate and H&N malignancies, the sliding window (SW) technique (-2.5 ± 1.8% and -5.3 ± 2.6%) showed greater negative systematic differences than the step-and-shoot (S&S) technique (-0.3 ± 2.2% and -0.8 ± 2.2%). The VMAT dose differences for prostate and H&N malignancies were 0.9 ± 1.8% and 1.1 ± 3.3%, respectively. The SDs were larger for the H&N plans than for the prostate plans in both IMRT and VMAT. Such plans including more out-of-field control points showed greater systematic differences and SDs. CONCLUSIONS: This study will help individual institutions to establish an action level for agreement between primary calculations and verification for IMRT/VMAT. A local dose difference of ±5% at a point within the planning target volume (above -350 HU) may be a reasonable action level.
PURPOSE: No multi-institutional studies of computer-based independent dose calculation have addressed the discrepancies among radiotherapy treatment planning systems (TPSs) and the verification programs for intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). We conducted a multi-institutional study to investigate whether ±5% is a reasonable action level for independent dose calculation for IMRT/VMAT. METHODS: In total, 477 IMRT/VMAT plans for prostate or head and neck (H&N) malignancies were retrospectively analyzed using a modified Clarkson-based commercial verification program. The doses from the TPSs and verification programs were compared using the mean ±1 standard deviation (SD). RESULTS: In the TPS-calculated dose comparisons for prostate and H&N malignancies, the sliding window (SW) technique (-2.5 ± 1.8% and -5.3 ± 2.6%) showed greater negative systematic differences than the step-and-shoot (S&S) technique (-0.3 ± 2.2% and -0.8 ± 2.2%). The VMAT dose differences for prostate and H&N malignancies were 0.9 ± 1.8% and 1.1 ± 3.3%, respectively. The SDs were larger for the H&N plans than for the prostate plans in both IMRT and VMAT. Such plans including more out-of-field control points showed greater systematic differences and SDs. CONCLUSIONS: This study will help individual institutions to establish an action level for agreement between primary calculations and verification for IMRT/VMAT. A local dose difference of ±5% at a point within the planning target volume (above -350 HU) may be a reasonable action level.