RESUMEN
PURPOSE: This study aims at characterising the properties of TruView™ and ClearView™ two new gel dosimeters (Modus Medical Devices Inc.) and at studying the feasibility of relative dosimetry using these dosimeters and the Vista™ Optical CT scanner to accurately evaluate dose. METHODS: In this work, we investigated key dosimetric aspects (dose response, energy and dose rate dependence) and stability of these radiochromic gels initiated in preliminary works (Huet et al., 2017; Colnot et al., 2017) using spectrophotometric measurements. Moreover, by mean of optical CT scanning (Vista™), their performances to measure relative depth dose (PDD) and cross profiles were analysed. RESULTS: TruView™ and ClearView™ present a linear dose response up to 20â¯Gy and up to 80â¯Gy respectively, independent of both photon beam energy (4-18â¯MV) and dose rate (up to 9.9â¯Gy/min) (Huet et al., 2017; Colnot et al., 2017). ClearView™ response proves to be stable for a week post-irradiation and uniform within the batch whereas TruView™ presents an unstable but uniform response. Optical CT scanning generates errors due to stray light that need to be corrected in order to use these gels; ClearView™ scanning particularly requires important precautions. After corrections, those gels used in combination with the Vista™ scanner show promising spatial and dosimetric precision (dose difference <5%). Finally, TruView™ is reusable and presents excellent reproducible response (maximum 3% difference) and the ClearView™ dosimeter presents good spatial stability (0.5% difference after 6â¯days). CONCLUSION: This study provides important knowledge about two gel dosimeters presenting interesting dosimetric properties. A study is ongoing to benchmark those promising candidates for clinical dose verification.
Asunto(s)
Dosímetros de Radiación , Radiometría/instrumentación , Calibración , Electrones , Estudios de Factibilidad , Imagen Óptica/instrumentación , Imagen Óptica/métodos , Fantasmas de Imagen , Fotones , Espectrofotometría , Tomógrafos Computarizados por Rayos X , Tomografía Computarizada por Rayos X/instrumentación , Tomografía Computarizada por Rayos X/métodos , IncertidumbreRESUMEN
PURPOSE: Synchrotron Radiation Therapy techniques are currently being trialed and commissioned at synchrotrons around the world. The patient treatment planning systems (TPS) developed for these treatments use simulated data of the synchrotron x-ray beam to produce the dosimetry in the treatment plan. The purpose of this study was to investigate a water equivalent PRESAGE® dosimeter capable of 3D dosimetry over an energy range suitable for synchrotron x-ray beams. METHODS: Water equivalent PRESAGE® dosimeters were fabricated with a radiological effective atomic number similar to water over an energy range of 10 keV to 10 MeV. The dosimeters were irradiated at various energies, scanned using optical CT (OCT) scanning and compared to ion chamber measurements. Percentage depth dose and beam profiles of the synchrotron beam were compared to Monte Carlo (MC) model simulations. RESULTS: The PDD profiles of the water equivalent PRESAGE® agreed with ion chamber measurements and MC calculations within 2% for all keV energies investigated. The PRESAGE® also showed good agreement to the MC model for depths below 5 mm of the synchrotron beam where ion chamber data do not exist. The spatial resolution of the OCT was not sufficient to accurately measure the penumbra of the synchrotron beams compared to MC calculations or EBT3 film; however, the water equivalent PRESAGE® was able to verify dose profile characteristics of the MC model. CONCLUSIONS: The radiological response of a water equivalent PRESAGE® dosimeter has been validated for synchrotron x-ray beam energies along with the ability to independently verify dose distributions of a MC model.