A method for matching NBS x-ray beam qualities with a half- or full-wave rectified generator

Area of Science:

• Medical Physics
• Radiological Physics
• X-ray Metrology

Background:

• Older x-ray generators (half- and full-wave rectified) produce beam qualities that differ from modern standards.
• The National Bureau of Standards (NBS) has revised its standard x-ray beam qualities, necessitating updated calibration methods.
• Accurate x-ray beam quality matching is crucial for consistent and reliable diagnostic and therapeutic applications.

Purpose of the Study:

• To develop a rapid method for matching revised National Bureau of Standards (NBS) x-ray beam qualities using conventional x-ray equipment.
• To enable users of half- and full-wave rectified x-ray sets to achieve NBS beam quality specifications.
• To validate the developed method through blind calibrations using NBS-owned ion chambers.

Main Methods:

• Devised a method to determine the necessary added filtration for half- and full-wave rectified x-ray sets.
• Focused on matching the first half-value layer (HVL) and homogeneity coefficient (Hv) to NBS standards.
• Validated the method by duplicating NBS beam qualities ranging from 100 to 250 kilovoltage peak (kVcp).

Main Results:

• Successfully developed a rapid technique for filter determination.
• Achieved matching of first HVLs and near-matching of homogeneity coefficients to NBS standards.
• Performed successful blind calibrations at four beam qualities on two NBS ion chambers, demonstrating method efficacy.

Conclusions:

• The devised method effectively enables users of older x-ray equipment to match revised NBS beam qualities.
• The technique provides a fast and accurate way to determine filtration for precise x-ray beam calibration.
• The successful blind calibrations confirm the method's reliability for ensuring metrological traceability in x-ray dosimetry.