Which accelerator photon beams are "clinic-like" for reference dosimetry purposes?

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• Traditional beam quality specifiers like TPR10(20) may not be universally adequate for all bremsstrahlung beams, particularly lightly filtered ones.
• Assessing the suitability of TPR10(20) for modern clinical linear accelerators and standards laboratory beams is crucial for accurate dosimetry.

Purpose of the Study:

• To evaluate if TPR10(20) is an adequate beam quality specifier for all modern clinical therapy accelerators.
• To determine conditions under which nonclinical beams can calibrate ion chambers or measure kQ factors.
• To assess the efficacy of %dd(10)x as a beam quality specifier.

Main Methods:

• Detailed Monte Carlo simulations were performed for Varian, Siemens, Elekta, and GE (Saturn) accelerators.
• Analysis included evaluating stopping-power ratios as a function of TPR10(20).
• Comparison of TPR10(20) and %dd(10)x for clinical and standards laboratory beams was conducted.

Main Results:

• TPR10(20) is an adequate beam quality specifier for modern clinical accelerators and heavily filtered standards laboratory beams.
• %dd(10)x is shown to be a good beam quality specifier for a broad range of bremsstrahlung beams.
• A criterion based on TPR10(20) and %dd(10)x is proposed for specifying nonclinical beams.

Conclusions:

• TPR10(20) is suitable for modern clinical accelerators and filtered standards laboratory beams.
• A proposed criterion helps determine if nonclinical beams are well-specified by TPR10(20).
• Further investigation into discrepancies between calculated and published data for clinical accelerators is warranted.