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Dosimetric Comparison Between Portrait and Landscape Orientations in Radiochromic Film Dosimetry

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Y Kakinohana

Y Kakinohana1*, T Toita2 , G Kasuya3 , T Ariga4 , J Heianna5 , S Murayama6 , (1) University of the Ryukyus, Okinawa, ,(2) University of the Ryukyus, Nishihara-cho, Okinwa, (3) University of the Ryukyus, Nishihara-cho, Okinwa, (4) University of the Ryukyus, Nishihara-cho, Okinwa, (5) University of the Ryukyus, Nishihara-cho, Okinwa, (6) University of the Ryukyus, Nishihara-cho, Okinwa

Presentations

SU-E-T-123 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To compare the dosimetric properties of radiochromic films with different orientation.
Methods: A sheet of EBT3 film was cut into eight pieces with the following sizes: 15x15 cm2 (one piece), 5x15 cm² (two) and 4x5 cm² (five). A set of two EBT3 sheets was used at each dose level. Two sets were used changing the delivered doses (1 and 2 Gy). The 5x15 cm² pieces were rotated by 90 degrees in relation to each other, such that one had landscape orientation and the other had portrait orientation. All 5x15 cm2 pieces were irradiated with their long side aligned with the x-axis of the radiation field. The 15x15 cm² pieces were irradiated rotated at 90 degrees to each other. Five pieces, (a total of ten from two sheets) were used to obtain a calibration curve. The irradiated films were scanned using an Epson ES-2200 scanner and were analyzed using ImageJ software. In this study, no correction was applied for the nonuniform scanner signal that is evident in the direction of the scanner lamp. Each film piece was scanned both in portrait and landscape orientations. Dosimetric comparisons of the beam profiles were made in terms of the film orientations (portrait and landscape) and scanner bed directions (perpendicular and parallel to the scanner movement).Results: In general, portrait orientation exhibited higher noise than landscape and was adversely affected to a great extent by the nonuniformity in the direction of the scanner lamp. A significant difference in the measured field widths between the perpendicular and parallel directions was found for both oientations. Conclusion:Without correction for the nonuniform scanner signal in the direction of the scanner lamp, a landscape orientation is preferable. A more detailed investigation is planned to evaluate quantitatively the effect of orientation on the dosimetric properties of a film.



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