Description
To model the kilovoltage (kV) x-ray source of a superficial x-ray unit and to validate a rapid and accurate in-house software (kVDoseCalc) tool for computing absorbed radiation dose from superficial x-ray therapy energies. To validate kVDoseCalc, we measured central axis percent depth-doses (PDDs) and profiles using an Xstrahl 150 x-ray system (Gulmay Medical Inc.). We also compared the measured and calculated PDDs to those from the British Journal of Radiology Supplement 25 (BJR 25). The Xstrahl source was characterized as a point spectral source with varying spatial fluence, and this source model was used in kVDoseCalc to compute absorbed radiation dose at points of interest (POIs). The spectrum was derived by inputting half-value layers (HVLs) and kVps into third party software Spektr and SpekCalc. Doses for the PDDs and profiles were measured using 2, 5, and 15 cm cone sizes at 80, 120, 140, and 150 kVp energies in a scanning water phantom (IBA Blue Phantom2) using Scanditronix Wellhofer farmer-type and compact chambers of volumes 0.65 and 0.13 cc, respectively. The percent difference in the computed PDD doses compared with our measurements range from -4.76% to 4.78% with an overall mean percent difference and standard deviation of 1.52% and 0.74%, respectively. The percent difference between our PDD measurements and those from BJR 25 range from -13.98% to 15.7% with an overall mean percent difference and standard deviation of 4.94% and 2.10%, respectively; showing that our measurements agree much better with kVDoseCalc than BJR25. The range in percent difference between kVDoseCalc and measurement for profiles was -5.89% to 5.92% with an overall mean percent difference and standard deviation of 1.35% and 1.42%, respectively. The results demonstrate that using our source model, kVDoseCalc can rapidly and accurately compute absorbed radiation dose for superficial x-ray therapy. The results demonstrate that using our source model, kVDoseCalc can rapidly and accurately compute absorbed radiation dose for superficial x-ray therapy. An instruction manual for kVDoseCalc is also accompanied.
