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Updated: Jul 28, 2026
08:30
X-ray Dose Reduction through Adaptive Exposure in Fluoroscopic Imaging
Published on: September 11, 2011
Photon buildup in orthovoltage X-ray beams
R F Hill1, P J Keall, W A Beckham
1Cancer Therapy Centre, Liverpool Hospital, NSW.
Australasian Physical & Engineering Sciences in Medicine
|September 24, 1998
Summary
Orthovoltage x-ray beams show unexpected depth dose buildup due to scattered photons and electron disequilibrium. This phenomenon, not fully detailed in literature, can lead to higher-than-prescribed doses near the skin surface.
Area of Science:
- Medical Physics
- Radiation Oncology
Background:
- Orthovoltage x-ray beams present a depth dose buildup phenomenon not well-documented.
- This effect is primarily attributed to secondary (Compton) scattered photons initiating electron motion within the phantom.
Purpose of the Study:
- To elucidate the mechanisms behind depth dose buildup in orthovoltage x-ray beams.
- To investigate a secondary order primary dose buildup effect undetectable by conventional detectors.
Main Methods:
- Experimental validation and Monte Carlo simulations were employed.
- Monte Carlo techniques were used to describe a second-order primary dose buildup effect.
Main Results:
- The primary buildup is caused by secondary Compton scattered photons and longitudinal electronic disequilibrium.
- A second-order primary dose buildup effect, due to longitudinal electronic disequilibrium, was identified.
- The magnitude of dose buildup varies with beam parameters and measurement detectors.
Conclusions:
- Radiation oncology departments should evaluate depth dose buildup in their clinical data.
- Ensure accurate dose delivery by accounting for potential higher doses a few millimeters below the skin surface.
- Consider the impact of detector type and data collection methods on measured buildup.
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