Author: Chang Heon Choi, Yoonsuk Huh, Jin Jegal, Seonghee Kang, Jung-in Kim, Inbum Lee, Hyojun Park 👨🔬
Affiliation: Department of Radiation Oncology, Seoul National University Hospital 🌍
Purpose: This study evaluates SpekPy, a Python-based tool for modeling kilovoltage (kV) x-ray spectra, by comparing its calculated energy spectra, half-value layer (HVL), and air kerma with experimental measurements and Monte Carlo simulations. The goal was to explore the reliability of SpekPy for practical kilovoltage beam quality assessment.
Methods: SpekPy was used to calculate the energy spectra, HVL, and air kerma for kV beam energies ranging from 40 to 140 kVp. Energy spectra were compared with those generated by Geant4 Monte Carlo simulations. HVLs were evaluated against measurements from an Exradin A12 ionization chamber (following AAPM TG-61), a Piranha MULTI meter, and GATE simulations. Air kerma values from SpekPy were compared to experimental measurements at 60 and 120 kVp obtained with a Piranha meter.
Results: SpekPy’s energy spectra closely matched those generated by Geant4 simulations, showing consistent spectral shapes and intensities. HVLs calculated by SpekPy differed by no more than 0.4 mm Al from values measured using the ionization chamber, Piranha meter, and GATE simulations across the kVp range. However, air kerma values calculated by SpekPy showed differences of up to 10% compared to experimental measurements with the Piranha meter, indicating the need for further refinement in dosimetric accuracy.
Conclusion: SpekPy demonstrates strong potential as a practical tool for modeling key beam quality metrics, such as energy spectra and HVL. While its accuracy in these areas aligns well with experimental and simulation data, the variability observed in air kerma calculations suggests that additional calibration or adjustments may be necessary for precise dose estimation. Nevertheless, SpekPy remains a promising option for beam characterization in scenarios where experimental measurements are limited or impractical, though further investigation is warranted to enhance its dosimetric applications.