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Novel Method for Proton Radiography Using Plastic Scintillation Plate and Beam Energy Modulation Water Phantom

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S Park

S Park*, C Jeong, D Kang, S Cho, J Shin, J Jeong, D Shin, Y Lim, National Cancer Center, Goyang, Gyeonggi-do

SU-E-I-98 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: The purpose of this study is to present the experimental evaluation and quantification of proton radiography using plastic scintillation plate and beam energy modulation (BEM) water phantom.
Methods: Using the newly designed water phantom, proton beam energy was modulated by controlling water depth horizontally. Modulated proton beam which passed through water phantom was measured by dose-measurement system which consists of a plastic scintillation plate, a mirror and a CCD camera in a dark box. A range compensator (RC) was positioned between BEM water phantom and scintillation plate for proton radiography. While a proton beam which has 15 cm range in water was being irradiated on RC, water depth is controlled from 71 to 170 mm in 1 mm increment and radiographs of RC on a scintillation plate were saved in every 1 mm increment using a dose-measurement system. One hundred images were stacked and the position of Bragg peak was found along the stack order. The same radiograph procedure was performed without RC in order to calculate the depth of RC by subtracting the position index of Bragg peak between radiograph of RC and background. This difference was divided by water equivalent thickness value of RC material and then measured depth of RC was compared to plan data, quantifying the precision with the mean absolute depth difference (MADD) and the standard deviation (SD).
Results: The MADD and the SD over the entire areas of RC was calculated as 0.62 mm and 0.67 mm respectively. MADD and SD precisions over chosen flat regions were less than 0.54 mm and 0.25 mm.
Conclusion: Good image quality with high precision of depth measurement was observed by our proton radiography system. These system can also be used as a 3D dosimetry tool.

Funding Support, Disclosures, and Conflict of Interest: This study was supported by funds from research projects of the National Cancer Center of Korea (nos. NCC 1210210) and National Research Foundation of Korea (K1A3A1A21 2010 0026071).

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