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A Clarkson-Based Independent Dose Verification for the Helical Tomotherapy

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H Nagata

H Nagata1,2*, H Hongo1,3 , D Kawai4 , R Takahashi5 , H Hashimoto6 , H Tachibana7 , (1) Shonan Kamakura General Hospital, Kamakura, Kanagawa, (2) Juntendo University, Hongo, Tokyo, (3) Tsukuba University, Tsukuba, Ibaraki, (4) Kanagawa Cancer Center, Yokohama, Kanagawa, (5) Cancer Institute Hospital of Japanese Foundation for Cancer Research, Koto, Tokyo, (6) Shonan Fujisawa Tokushukai Hospital, Fujisawa, Kanagawa, (7) National Cancer Center, Kashiwa, Chiba


SU-F-T-267 (Sunday, July 31, 2016) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: There have been few reports for independent dose verification for Tomotherapy. We evaluated the accuracy and the effectiveness of an independent dose verification system for the Tomotherapy.
Methods: Simple MU Analysis (SMU, Triangle Product, Ishikawa, Japan) was used as the independent verification system and the system implemented a Clarkson-based dose calculation algorithm using CT image dataset. For dose calculation in the SMU, the Tomotherapy machine-specific dosimetric parameters (TMR, Scp, OAR and MLC transmission factor) were registered as the machine beam data. Dose calculation was performed after Tomotherapy sinogram from DICOM-RT plan information was converted to the information for MU and MLC location at more segmented control points. The performance of the SMU was assessed by a point dose measurement in non-IMRT and IMRT plans (simple target and mock prostate plans). Subsequently, 30 patients’ treatment plans for prostate were compared.
Results: From the comparison, dose differences between the SMU and the measurement were within 3% for all cases in non-IMRT plans. In the IMRT plan for the simple target, the differences (Average±1SD) were -0.70±1.10% (SMU vs. TPS), -0.40±0.10% (measurement vs. TPS) and -1.20±1.00% (measurement vs. SMU), respectively. For the mock prostate, the differences were -0.40±0.60% (SMU vs. TPS), -0.50±0.90% (measurement vs. TPS) and -0.90±0.60% (measurement vs. SMU), respectively. For patients’ plans, the difference was -0.50±2.10% (SMU vs. TPS).
Conclusion: A Clarkson-based independent dose verification for the Tomotherapy can be clinically available as a secondary check with the similar tolerance level of AAPM Task group 114.

Funding Support, Disclosures, and Conflict of Interest: This research is partially supported by Japan Agency for Medical Research and Development (AMED)

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