Semi-3D dosimetry of high dose rate brachytherapy using a novel Gafchromic EBT3 film-array water phantom

7th International Conference on 3D Radiation Dosimetry

Palmer, A.L.^1,2 ; Nisbet, A.^1,3 ; Bradley, D.A.^1

Department of Physics, Faculty of Engineering and Physical Science, University of Surrey, United Kingdom^1

Medical Physics Department, Queen Alexandra Hospital, Portsmouth Hospitals NHS Trust, Portsmouth, United Kingdom^2

Medical Physics Department, Royal Surrey County Hospital NHS Foundation Trust, Guildford, United Kingdom^3

关键词: Calibration functions;    Dose distributions;    Dose verification;    Dosimetry measurement;    Equipment performance;    High-dose rate brachytherapy;    Monte Carlo calculation;    Radiochromic film;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/444/1/012101/pdf
DOI  :  10.1088/1742-6596/444/1/012101

来源: IOP

【 摘 要 】

There is a need to modernise clinical brachytherapy dosimetry measurement beyond traditional point dose verification to enable appropriate quality control within 3D treatment environments. This is to keep pace with the 3D clinical and planning approaches which often include significant patient-specific optimisation away from 'standard loading patterns'. A multi-dimension measurement system is required to provide assurance of the complex 3D dose distributions, to verify equipment performance, and to enable quality audits. However, true 3D dose measurements around brachytherapy applicators are often impractical due to their complex shapes and the requirement for close measurement distances. A solution utilising an array of radiochromic film (Gafchromic EBT3) positioned within a water filled phantom is presented. A calibration function for the film has been determined over 0 to 90Gy dose range using three colour channel analysis (FilmQAPro software). Film measurements of the radial dose from a single HDR source agree with TPS and Monte Carlo calculations within 5 % up to 50 mm from the source. Film array measurements of the dose distribution around a cervix applicator agree with TPS calculations generally within 4 mm distance to agreement. The feasibility of film array measurements for semi-3D dosimetry in clinical HDR applications is demonstrated.