Absorbed dose determination in kilovoltage X-ray synchrotron radiation using alanine dosimeters

Determination of beam quality correction factors for alanine dosimetry in clinical proton beams

INTRODUCTION

With the advent of FLASH radiotherapy, alanine dosimetry has gained attention as a promising dosimeter owing to its dose-rate independence. However, before utilized in radiotherapy, procedures for determining the absorbed dose to water using alanine under clinical proton beams must be established. This study sought to develop a formula for alanine dosimetry by deriving beam quality correction factors and validating them through Monte Carlo simulations and experimental measurements.

MATERIALS AND METHODS

To calculate the absorbed dose to water using alanine dosimeters, a formula was developed specifically for the plateau region. Alanine dosimeters were irradiated under both a reference beam (Cobalt-60) and clinical proton beams. Beam quality correction factors were calculated and subsequently validated through Monte Carlo simulations using the Tool for Particle Simulation (TOPAS), which is based on GEANT4, as well as through experimental measurements. During the simulations, both crystalline and bulk densities of alanine were considered.

RESULTS

The simulation results showed that the average beam quality correction factors for alanine were 1.005 for crystalline density and 1.012 for bulk density. Experimental measurements under clinical proton beams yielded a beam quality correction factor of 1.014, with a standard uncertainty of 2.2%.

CONCLUSIONS

These results suggest that alanine dosimeters provide reliable and reproducible measurements for proton therapy. The robust methodology demonstrated here highlights the potential of alanine dosimeters in clinical applications, demonstrating their effectiveness and reliability in determining the absorbed dose to water under clinical proton beam conditions.

Absorbed dose evaluation of a blood irradiator with alanine, TLD-100 and ionization chamber

Irradiation of blood bags using X-ray irradiators and dosimetry services are required to ensure uniform dose levels in the range 25-50 Gy to prevent Transfusion Associated Graft versus Host Disease (TA-GvHD). An absorbed dose characterization of a Raycell MK2 X-Irradiator was performed using three different dosimetric systems. Results showed a dosimetric accuracy of the ionization chamber together with the Alanine dosimeter. TLDs measurements exhibited a small overestimation by 4% of the absorbed dose. The Dose Uniformity Ratio (DUR), between maximum and minimum dose levels in the canister, was in good agreement with the manufacturer specifications (≤1.5).