Microdosimetry of pulsed radiation fields employing the variance method

Area of Science:

• Medical physics
• Radiation dosimetry
• Particle physics

Background:

• The variance method previously derived dose mean lineal energy (yD) in steady radiation fields.
• Kellerer and Rossi proposed using two detectors for time-varying fields.

Purpose of the Study:

• To report the first measurements of yD for 10 MeV X rays and 9, 18 MeV electrons using the variance method.
• To demonstrate the practicability of the two-detector variance technique in pulsed radiation fields.

Main Methods:

• Utilized two spherical proportional counters and independent analog-to-digital converters synchronized with the beam pulse.
• Applied the variance method to measure yD for various radiation types and energies.
• Investigated site diameters of 1/2, 1, and 2 microns.

Main Results:

• Successfully measured yD for 10 MeV X rays and 9, 18 MeV electrons from a pulsed linear accelerator.
• Demonstrated that accurate yD data can be obtained in under 1 minute.
• Validated the two-detector variance technique for time-varying radiation fields.

Conclusions:

• The two-detector variance method is effective for determining yD in pulsed radiation fields.
• This technique enables rapid, potentially "on line" yD or zD determinations in clinical settings.
• The method offers a significant advancement for real-time radiation dosimetry.