QA Testing Apparatus for Rotating Tomography X-Ray Sources

Tech ID:

A method and apparatus have been developed by researchers at UT Health San Antonio to allow easier, reliable, and frequent calibration of rotating x-ray source radiological equipment (i.e. computed tomography machines – CTs).  The invention adapts the currently accepted method for fixed x-ray sources, the Half-Value Layer (HVL), to provide accurate quality measurements on rotating systems. 



X-ray images are created by the exposure of X-ray film to radiation that passes through the body. Higher energy radiation passes through the tissues more readily, but lower energy radiation is scattered and absorbed by the tissues, causing cellular damage. To minimize the amount of harmful radiation absorbed by the body, it is critical to limit the radiation used to as narrow of a spectrum as possible around the effective wavelength.


Currently, HVL is used as a method to determine the quality of a radiation source to produce an intended image. The HVL is defined as the thickness of a specific material (usually aluminum or copper) that will reduce the radiation beam produced by a particular voltage source to half of its original intensity.


Most diagnostic X-ray equipment has a fixed X-ray source; however, some X-ray devices (such as CTs) use an X-ray source that rotates around the patient, making quality control on these devices more difficult. Currently, QA verification on CT machines involves locking the X-ray source in a fixed position (requiring a trained service engineer) to be able to use the standard non-rotating HVL procedure. This constraint results in QA checks being performed less frequently than on standard, fixed x-ray equipment.


This invention allows measurement of the HVL while the x-ray source is rotating normally. It provides the capability for radiology staff to measure the HVL on-demand.


Commercial Application & Advantages:

This invention would be useful for ensuring the quality of rotating x-ray equipment in doctor’s offices, hospitals, and imaging centers. This invention provides the following advantages:

  • On-demand testing by staff without service engineer present
  • More frequent routine quality assurance testing
  • Earlier detection of failing/deteriorating equipment
  • More accurate values for calculating effective dosages
  • Characterization of scatter pattern of device for calculation adjustments
For information contact:
John Fritz
Sr. Business Development Manager
Nestor A. Ruiz Gonzalez
Geoffrey David Clarke
Patent Information:

United States - Provisional

Patent No.

Status: Pending