High throughput film dosimetry in homogeneous and heterogeneous media for a small animal irradiator

Abstract

Purpose We have established a high-throughput Gafchromic film dosimetry protocol for narrow kilo-voltage beams in homogeneous and heterogeneous media for small-animal radiotherapy applications. The kV beam characterization is based on extensive Gafchromic film dosimetry data acquired in homogeneous and heterogeneous media. An empirical model is used for parameterization of depth and off-axis dependence of measured data. Methods We have modified previously published methods of film dosimetry to suit the specific tasks of the study. Unlike film protocols used in previous studies, our protocol employs simultaneous multichannel scanning and analysis of up to nine Gafchromic films per scan. A scanner and background correction were implemented to improve accuracy of the measurements. Measurements were taken in homogeneous and inhomogeneous phantoms at 220 kVp and a field size of 5 × 5 mm2. The results were compared against Monte Carlo simulations. Results Dose differences caused by variations in background signal were effectively removed by the corrections applied. Measurements in homogeneous phantoms were used to empirically characterize beam data in homogeneous and heterogeneous media. Film measurements in inhomogeneous phantoms and their empirical parameterization differed by about 2%–3%. The model differed from MC by about 1% (water, lung) to 7% (bone). Good agreement was found for measured and modelled off-axis ratios. Conclusions EBT2 films are a valuable tool for characterization of narrow kV beams, though care must be taken to eliminate disturbances caused by varying background signals. The usefulness of the empirical beam model in interpretation and parameterization of film data was demonstrated.

Comprehensive quality assurance phantom for the small animal radiation research platform (SARRP)

“…For the commissioning task, the gafchromic EBT 2 was used. The calibration curve and dose measurement procedures were performed as reported in previous work [10,11]. …”

Advances in Preclinical Research Models of Radiation-Induced Cardiac Toxicity

“…In 2011, members of the Centers for Medical Countermeasures against Radiation (CMCR) outlined specific issues related to small animal irradiator calibration and dosimetry, in order to highlight the importance of "accurate and reproducible dosimetry" in preclinical radiobiology studies [85]. Gafchromic film dosimetry can be a valuable tool for characterization of small kV radiation beams [86]. However, even if the incident radiation field on a given animal is accurately assessed and uniform, the true delivered dose to the target volume will vary based on the incident radiation energy, the atomic number of the radiation source, and density of the tissue (e.g., lung, bone, soft-tissue) [85].…”

Technical Note: Manufacturing of a realistic mouse phantom for dosimetry of radiobiology experiments

“…Small-field dosimetry on commercial small animal irradiators is typically reliant upon two detector typesradiochromic films, commonly used for commissioning of conformal small animal irradiators, and small volume dosimeters. [9][10][11][12] In order to perform reliable dosimetry, modifications to the design of a 3D printed phantom, in the form of custom apertures, may be used to accommodate any variety of small-field portable dosimeters, including TLD/OSLDs, scintillating detectors, and diamond or pinpoint ion chambers. For the purposes of this study, modifications have been made to accommodate both radiochromic film and a 1-mm plastic scintillator dosimeter (PSD).…”