Program Information
Reduction of the Skin Surface Dose for Megavoltage Photon Beams Passing Carbon Couch
M Tamura1*, H Monzen1 , K Matsumoto1 , M Okumura2 , Y Nishimura3 , (1) Kindai University, Osakasayama, Osaka, (2) Kindai University Hospital, Osakasayama, Osaka, (3) Kindai University, Osakasayama, Osaka
Presentations
SU-I-GPD-T-504 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: The aim of this study was to reduce skin injure in radiotherapy. We measured surface doses using a carbon couch with or without comfort tool and immobilization device, and investigated the dose reduction with a novel couch (H-M board).
Methods: We measured the absorbed surface doses for 6 and 10 MV photon beams passing a carbon couch (iBeam Couchtop STANDARD; BrainLab) with or without comfort tools (cloth mat and 5 cm Styrofoam board) and immobilization device (vacuum-fixed cushion), and an H-M board which made of polycarbonate foam sandwiched between two glass fiber layers by a plane-parallel ionization chamber. The prescribed dose at 5.0 cm depth (SCD = 100 cm) was irradiated 2.0 Gy with a field size of 10 × 10 cm². We verified the depth dose distributions for 6 and 10 MV photon beams with/without various devices and whether the H-M board could reduce the surface dose.
Results: The absorbed surface doses were 2.209, 2.200, 2.169, 2.079, and 2.027 Gy for the carbon couch alone, with cloth mat, vacuum-fixed cushion, and 5 cm Styrofoam board, and the H-M board alone, respectively, with 6 MV photon beams. With 10 MV photon beams, the absorbed surface doses were 1.980, 1.998, 1.958, 1.823, and 1.741 Gy, respectively. The 5 cm Styrofoam board reduced the surface dose by 5–7%. The H-M board, with a tissue equivalent thickness 0.4 cm less than carbon couch, reduced the surface dose approximately 3–4% compared with the carbon couch with 5 cm Styrofoam board. The H-M board could be more useful in clinical situations instead of carbon couch since tolerance error was less than couch plus the Styrofoam board.
Conclusion: The surface dose can be reduced with a low-absorption, more than 5 cm thickness from couch, and the novel H-M board in clinical setting.
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