title: Proton-radiography-based quality assurance of proton range compensator.
abstract: The aim of this work was to study the feasibility of proton radiography (pRad) as a patient-specific range compensator (RC) quality assurance (QA) tool and to validate its clinical utility by performing QA on RCs having three kinds of possible defects. In order to achieve pRad for a single EBT film, proton beam currents were modulated with new weighting factors, maximizing the linearity of optical-density-to-thickness ratio. Two RCs, examined to be accurately manufactured as planned, were selected to estimate the feasibility of our pRad. The optical densities of the EBT film on which the RC was irradiated with the modulated proton beam were digitized to pixel values (pv) and then converted to thickness using a thickness-pv calibration curve. The thickness information on the pRad was compared with plan data that had been extracted from treatment planning system. The mean thickness difference (TD) over the flat RC regions was calculated as 0.39 mm, and the standard deviation as 0.22 mm, and the proton scattering effect was analyzed by step phantom measurement. Even proton scattering effected a TD of over 1 mm in the large gradient region, the percentage of pixels over the acceptance criterion was only within 1.11% and 3.49%, respectively, when a 1 mm distance to agreement tolerance limit was applied. The QA results for both precisely and imprecisely manufactured RCs demonstrated the high potential utility and clinical applicability of the pRad-based RC QA tool.
authors.affiliation: Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea.
authors.forename: Seyjoon
authors.initials: S
authors.lastname: Park
authors.forename: Chiyoung
authors.initials: C
authors.lastname: Jeong
authors.forename: Dong Yun
authors.initials: DY
authors.lastname: Kang
authors.forename: Jae-Ik
authors.initials: JI
authors.lastname: Shin
authors.forename: Sungkoo
authors.initials: S
authors.lastname: Cho
authors.forename: Jeong-Hoon
authors.initials: JH
authors.lastname: Park
authors.forename: Dongho
authors.initials: D
authors.lastname: Shin
authors.forename: Young Kyung
authors.initials: YK
authors.lastname: Lim
authors.forename: Joo-Young
authors.initials: JY
authors.lastname: Kim
authors.forename: Byung Jun
authors.initials: BJ
authors.lastname: Min
authors.forename: Jungwon
authors.initials: J
authors.lastname: Kwak
authors.forename: Jiseoc
authors.initials: J
authors.lastname: Lee
authors.forename: Seungryong
authors.initials: S
authors.lastname: Cho
authors.forename: Dae-Hyun
authors.initials: DH
authors.lastname: Kim
authors.forename: Sung Yong
authors.initials: SY
authors.lastname: Park
authors.forename: Se Byeong
authors.initials: SB
authors.lastname: Lee
mesh_terms: D000465:Algorithms; D002138:Calibration; D003198:Computer Simulation; D005373:Film Dosimetry / Q000379:methods; D006801:Humans; D019047:Phantoms, Imaging; D061766:Proton Therapy; D011786:Quality Control; D011859:Radiography / Q000295:instrumentation / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D011522:Protons
chemical_list: D011522:Protons