(Sunday, 7/29/2018) 3:00 PM - 6:00 PM
Room: Exhibit Hall
Purpose: To investigate the accuracy and efficiency of our routine-beamline and patient-specific quality assurance (QA) programs by utilizing depth/planar multi-element detection arrays in proton pencil-beam-scanning (PBS) system.
Methods: During commissioning our first PBS beamline, multi-layer ionization-chamber (MLIC) array for depth doses, and planar multi-element ionization-chamber (MEIC) array and optical-scintillator dosimeter for lateral-profile doses were utilized. Our routine-beamline and patient-specific QAs were established around used detection systems. For daily QA, a flat-surface optical dosimeter with configured build-up and a chamber allows tracking variations of output, proton penetration-range, single-spot size/shape, and flatness/symmetry of scanning field. For patient-specific QA, a water-proof planar MEIC array imbedded in water-phantom scanner allow measuring multiple depths without entering into treatment room. For monthly QA, a cone-shape optical dosimeter was utilized for the coincidence between X-ray and proton-beam defined isocenters, MLIC for penetration-range and MEIC for symmetry/flatness of modulated scanning field.
Results: Daily and patient-specific QA without its full function and robustness were established prior to first patient’s treatment. At second week of treatment, required specific spot-scanning pattern was finalized to achieve its full function for daily QA, and accurate setup of MEIC was aligned by X-ray imaging for patient-specific QA. At end of 1st month, overall time for daily QA performance and patient-specific setup was largely reduced to 30 minutes. And, cone-shape optical dosimeter was used to largely reduce required beam/room time for monthly QA. With improved efficiency of both daily/monthly routine-beamline and patient-specific QAs, the accuracy of QAs were not compromised as shown measurement trends of daily/monthly QA, and measurement pass rate of patient-specific QA.
Conclusion: With reliable detection systems, the accuracy and efficiency of robustness QAs were well established that allow facing a busy proton clinic at near future for largely restricted beam/room time but still having high quality of assurance of each patient’s treatment.
Keywords
Protons, Quality Assurance, Dosimetry
Taxonomy
TH- External Beam- Particle therapy: Proton therapy - quality assurance
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