Verification of relative output factor measurement using Gafchromic films for small-field radiosurgery photon beams.

International Nuclear Science, Technology and Engineering Conference 2017

原子能学

Abdullah, R.^1,4 ; Sapeei, M.S.^1 ; Shukor, N.S.A.^1 ; Yusof, M.F.M.^1 ; Mohamed, M.^2,3 ; Idris, N.R.N.^2,3 ; Yusoff, A.L.^2,3 ; Zakaria, A.^1 ; Aziz, M.Z.A.^4

School of Health Sciences, Health Campus USM, Universiti Sains Malaysia, Kelantan, Malaysia^1

Department of Nuclear Medicine, Radiotherapy and Oncology, School of Medical Sciences, Health Campus USM, Universiti Sains Malaysia, Kelantan, Malaysia^2

Department of Nuclear Medicine, Radiotherapy and Oncology, Hospital Universiti Sains Malaysia, Kelantan, Malaysia^3

Advanced Medical and Dental Institute, Universiti Sains Malaysia, Bertam, Pulau Pinang, Malaysia^4

关键词: Dosimetric parameter;    Electronic equilibrium;    GafChromic films;    High spatial resolution;    Output factor measurements;    Reliable measurement;    Stereotactic radiosurgery;    Treatment planning;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/298/1/012022/pdf
DOI  :  10.1088/1757-899X/298/1/012022

来源: IOP

【 摘 要 】

Accurate dosimetry of small-field photon beams has always been difficult to achieve, due to the steep dose gradient and absence of lateral electronic equilibrium. The purpose of this study was to verify the measurement of relative output factor (ROF), which is one of the dosimetric parameter required for stereotactic radiosurgery (SRS) treatment planning. The ROFs for Radionics circular cone collimators with diameter in the range of 10.0 to 45.0 mm were measured using Gafchromic EBT2 and EBT3 films. The measurements were then compared with the ROFs obtained using a PinPoint ionisation chamber and Monte Carlo (MC) simulation. From the results, the ROFs measured by the ionisation chamber, EBT2, and EBT3 films were good agreement with the MC simulation, with deviations of less than 1.5, 2.6, and 5.0 % respectively. Based on the film dosimetry, the EBT2 film showed in a more reliable measurement for field size ranging from 15.0 to 45.0 mm, compared with EBT3. As a conclusion, based on the special characteristic of the small-field photon beams, ROF measurement using PinPoint ionisation chamber are being favoured, due to its accuracy. However, the EBT2 film can be used as an alternative, when high spatial resolution is required.