Device and Method for Measuring Beam Quality in CT

Tech ID: 22455 / UC Case 2010-719-0


Researchers at the University of California, Davis have invented a device and methods for half-value layer (HVL) characterization in computed tomography (CT) to allow a medical physicist to measure the HVL of an X-ray system while the X-ray tube is rotating - that is, during its normal operation without the necessity to make the x-ray tube stationery.

Full Description

For medical imaging applications which use X-rays, part of the necessary characterization of the X-ray beam "quality" required the measurement of the half value layer (HVL), which is the thickness, typically in aluminum, which reduces the X-ray intensity of the X-ray beam by 50%.  The HVL is routinely measured in projection X-ray imaging situations such as in mammography, radiography, and fluoroscopy.  However, for computed tomography (CT), the X-ray source rotates around the gantry and this precludes the measurement of HVL using the standard set-up of an exposure meter with aluminum filters.

Researchers at the University of California, Davis have developed a device and methods for measuring HVL in a CT machine while the X-ray tube is rotating.  Therefore, the CT gantry does not need to be placed in a parked position, and a service engineer is not required to help in the measurements.  This invention, therefore, makes the measurement of the HVL in CT practical, automated, accurate, and fast.  Our researchers have prototyped a case device to be used with a real-time dosimeter; accompanying method packages for estimation of the HVL from the real-time doe measurements have also been developed.


Measurement of X-ray beam quality in CT scanners and in projection radiography settings (including fluoroscopy, radiography and mammography) and enable rapid and reliable characterization of the x-ray beam. 


  • Allows HVL measurements to be preformed with one rotation of the CT scanner
  • Enables rapid and reliable characterization of the x-ray beam that is used in CT scanners
  • Adapts easily to stationary X-ray sources (e.g. fluoroscopy, radiography and mammography) to obtain HVL measurements

Patent Status

Country Type Number Dated Case
United States Of America Issued Patent 9,008,264 04/14/2015 2010-719


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  • Boone, John M.
  • Burkett, Jr., George W.
  • McKenney, Sarah E.

Other Information


Computed Tomography (CT), Radiography, X-ray Beam Quality, Half layer value, HVL Characterization

Categorized As

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