Study of Fricke gel dosimeter response for different gel quality

Cavinato, Christianne Cobello; Campos, L.L.

doi:10.1088/1742-6596/249/1/012064

Cited by 8 publications

(2 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Previous studies have described the effects of various parameters on the R 1 -dose response of FXG dosimeters, including the spontaneous oxidation of Fe 2+ (Keller 1994, Healy et al 2004, applied dose rate and energy dependence (Kron et al 1993, Cavinato et al 2010, chemical impurities (Keller 1994, Duzenli et al 1994 and the relaxation mechanisms at different MR field strengths (Podgorsak andSchreiner 1992, Duzenli et al 1994). Additionally, compositional effects have been investigated for gelling agents (Olsson et al 1989), chelator additives (Kelly et al 1998, Penev andMequanint 2013), and the relationship between initial ferrous sulfate concentration and dose sensitivity (Olsson et al 1990, Schulz et al 1990, Hazle et al 1991.…”

Section: Mr Based Fricke Gel Dosimetersmentioning

confidence: 99%

“…The small fields, complex geometries and kV x-rays used during pre-clinical radiation studies challenge traditional clinical dosimetry techniques that are designed for use with larger radiation fields and MV photon energies. Previously developed 3D gel-based ferrous xylenol-orange (FXG) dosimeters provide a means of accommodating these complex geometries (Olsson et al 1990, Schreiner et al 1994, De Deene et al 2000a, Schreiner 2004, while accurately reporting relative dose measurements at kV energies (Soares et al 1987, Cavinato et al 2010. However, the accuracy of doses reported by MR-based FXG dosimeters are vulnerable to time and temperature dependencies.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The correction of time and temperature effects in MR-based 3D Fricke xylenol orange dosimetry

Welch

Jaffray

2017

Phys. Med. Biol.

View full text Add to dashboard Cite

Previously developed MR-based three-dimensional (3D) Fricke-xylenol orange (FXG) dosimeters can provide end-to-end quality assurance and validation protocols for pre-clinical radiation platforms. FXG dosimeters quantify ionizing irradiation induced oxidation of Fe ions using pre- and post-irradiation MR imaging methods that detect changes in spin-lattice relaxation rates (R = [Formula: see text]) caused by irradiation induced oxidation of Fe. Chemical changes in MR-based FXG dosimeters that occur over time and with changes in temperature can decrease dosimetric accuracy if they are not properly characterized and corrected. This paper describes the characterization, development and utilization of an empirical model-based correction algorithm for time and temperature effects in the context of a pre-clinical irradiator and a 7 T pre-clinical MR imaging system. Time and temperature dependent changes of R values were characterized using variable TR spin-echo imaging. R-time and R -temperature dependencies were fit using non-linear least squares fitting methods. Models were validated using leave-one-out cross-validation and resampling. Subsequently, a correction algorithm was developed that employed the previously fit empirical models to predict and reduce baseline R shifts that occurred in the presence of time and temperature changes. The correction algorithm was tested on R -dose response curves and 3D dose distributions delivered using a small animal irradiator at 225 kVp. The correction algorithm reduced baseline R shifts from -2.8 × 10 s to 1.5 × 10 s. In terms of absolute dosimetric performance as assessed with traceable standards, the correction algorithm reduced dose discrepancies from approximately 3% to approximately 0.5% (2.90 ± 2.08% to 0.20 ± 0.07%, and 2.68 ± 1.84% to 0.46 ± 0.37% for the 10 × 10 and 8 × 12 mm fields, respectively). Chemical changes in MR-based FXG dosimeters produce time and temperature dependent R values for the time intervals and temperature changes found in a typical small animal imaging and irradiation laboratory setting. These changes cause baseline R shifts that negatively affect dosimeter accuracy. Characterization, modeling and correction of these effects improved in-field reported dose accuracy to less than 1% when compared to standardized ion chamber measurements.

show abstract