A method for converting microdosimetric spectra in diamond to tissue in proton therapy

Area of Science:

• Medical Physics
• Radiation Dosimetry
• Nuclear Engineering

Background:

• Diamond's excellent properties make it a promising microdosimeter for radiation protection and radiotherapy.
• Diamond is not tissue-equivalent, necessitating spectral conversion for accurate dose assessment in biological tissues.
• Proton therapy requires precise dose measurements, highlighting the need for reliable microdosimetry techniques.

Purpose of the Study:

• To develop and validate a method for converting microdosimetric spectra from diamond to tissue in proton therapy.
• To investigate the application of the Chapman-Kolmogorov equation for spectral conversion.
• To assess the accuracy of the conversion method using Geant4 simulations.

Main Methods:

• Comparing stopping power and energy deposition distributions between diamond and various tissues.
• Deriving a spectral conversion method based on the Chapman-Kolmogorov equation and a derived scaling factor.
• Utilizing Geant4 simulations to validate the theoretical conversion method.

Main Results:

• The linear stopping power ratio of diamond to tissue adequately converts microdosimetric spectra for identical dimensions.
• Converted spectra for diamond to bone showed good agreement with Geant4 simulations along the Bragg curve.
• Good agreement was observed for water at the Bragg curve plateau and distal peak, but poor agreement at the proximal peak.

Conclusions:

• The developed method shows good results for converting diamond microdosimetry spectra to tissue in most scenarios.
• Deficiencies in spectral conversion accuracy were identified, particularly in specific regions of the Bragg curve for water.
• Further research is essential to enhance the reliability and accuracy of the diamond-to-tissue spectral conversion method.