Validation of an improved helical diode array and dose reconstruction software using TG-244 datasets and stringent...

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• The helical ArcCHECK (AC) diode array is crucial for 3D dose reconstruction in radiation therapy.
• Recent design modifications to the AC reduced diode overresponse to scattered radiation, improving accuracy but impacting existing dose reconstruction models.
• This necessitated a re-evaluation and adaptation of the measurement and reconstruction processes.

Purpose of the Study:

• To characterize and validate the updated ArcCHECK (AC) diode array and its associated 3D dose reconstruction software (3DVH).
• To introduce and assess a software correction mechanism to account for design changes in the AC without altering model parameters.
• To ensure continued accuracy in radiation dose measurements and reconstruction following AC hardware revisions.

Main Methods:

• A correction factor was implemented in the 3DVH software to compensate for differences in out-of-field response between new and old AC designs.
• The optimal correction factor was determined by minimizing dose differences using an ionization chamber.
• Verification utilized AAPM TG-244 standard cases and comparisons with ionization chambers and a Delta4 diode array using gamma analysis.

Main Results:

• A single correction factor of 1.17 provided satisfactory results across multiple radiation energies (6X, 15X, 10XFFF).
• Reconstructed dose in targets showed minimal difference (0.0% ± 1.4%) compared to ionization chamber measurements in a water-equivalent phantom.
• Gamma analysis with a Delta4 system demonstrated high agreement rates (96.7% ± 3.7% overall, 98.3% ± 0.8% for common plans).

Conclusions:

• The implemented software correction mechanism effectively addresses the dosimeter response changes due to AC design modifications.
• The updated system maintains high accuracy for 3D measurement-guided dose reconstruction.
• This ensures the reliability of the ArcCHECK system for clinical applications following hardware revisions.