Beam quality assessment: Evaluating aluminum purity's effects.

Area of Science:

• Medical Physics
• Radiological Sciences
• Radiation Protection

Background:

• Beam quality assessment is crucial for safe and effective ionizing radiation delivery in medical imaging.
• Variations in national and international standards for beam quality assessment can lead to measurement ambiguities and regulatory compliance issues.

Purpose of the Study:

• To evaluate the impact of aluminum (Al) purity on Half Value Layer (HVL) measurements and radiographic beam quality.
• To assess these effects across both mobile and fixed radiographic units.

Main Methods:

• Utilized aluminum filters of 99.0% and 99.5% purity for beam filtration measurements.
• Followed International Electrotechnical Commission (IEC) standards for HVL measurements using radiation detectors from three manufacturers.
• Determined HVL through exponential fitting of exposure versus aluminum thickness and performed single-shot HVL measurements.

Main Results:

• Increasing aluminum purity from 99.0% to 99.5% resulted in a 1.35% to 4.82% rise in HVL measurements (median increase of 3.26%).
• Deviation between single-shot and interpolated HVL measurements varied, with higher deviations observed for 99.0% purity aluminum.
• Results demonstrate a clear sensitivity of HVL measurements to aluminum purity.

Conclusions:

• A discrepancy exists between FDA (≥99.0% purity) and IEC (≥99.9% purity) standards for reference aluminum purity.
• Variations in aluminum purity can lead to radiographic units falsely failing minimum HVL regulatory requirements.
• Medical physicists must be aware of aluminum purity's influence on HVL testing for regulatory compliance.