Dosimetric comparison of 3D chemical dosimeters for use in modern RT/SRS quality assurance. (September 2016) - Petrokokkinos, L.
Abstract : Introduction: QA of modern radiotherapy/radiosurgery techniques is quite challenging, requiring dosimetric systems with fine spatial resolution, water equivalence, lack of energy/dose rate dependence and, hopefully, 3D dose registering. Purpose: A comparative dosimetric assessment of two 3D dosimeters, one custom and one commercially available, towards a dosimetric system with favorable characteristics for radiotherapy/radiosurgery QA. Materials and methods: MRI scanned VIP Polymer Gel and Optical-CT scanned PRESAGE radiochromic dosimeters were calibrated side by side. Both were subjected to the same irradiation scheme, in an extensive dose range. The dosimetric characteristics compared included dose sensitivity, dose resolution, dose rate dependence, useful dose range, minimum detectable dose and, ultimately, the uncertainty budget of the measured dose distribution. Results & conclusion: Both 3D dosimetric systems exhibited measured dose uncertainty appropriate for clinical dosimetry. The dose sensitivity of PRESAGE/OCT was higher resulting to improved dose resolution. This adds up to the increased ease of use of PRESAGE/OCT and availability of a dedicated optical scanner. However the increased noise in comparison to Polymer Gel/MRI and the occurrence of concentric ring and significant edge artifacts render this favorable characteristics debatable. Moreover indications of dose rate and energy dependence due to higher density have to be further investigated in order to end up with a dosimetric system to be used in the verification of complex radiotherapy/radiosurgery treatment plans. Disclosure: Research conducted with financing by "IKY Postdoc Fellowships of Excellence in Greece – Siemens Programme" in the framework of the Hellenic Republic – Siemens Settlement Agreement.