AbstractID: 9496 Title: Measurements of kVp and HVL for CT scanners
In order to assure that the radiation doses to patients and image quality are consistent and
reasonable, both the beam quality (HVL) and the x-ray tube voltage (kVp) should be
assessed during routine clinical QC testing of CT scanners. These measurements are
complicated by the rotating geometry of the x-ray tube and the unknown added filtration
of the CT scanner. A special stand was developed to enable the measurement of HVL
with standard filters while the CT scanner was operated in clinical 2-D localizer, axial
and helical mode. This stand restricts the CT x-ray beam to a small solid-angle field-ofview similar to a conventional radiographic exposure. Semi-empirical calculations of the
x-ray beam permit the total x-ray beam filtration to be estimated from the measured
HVLs at various kVp stations. These data are necessary to compensate for errors in noninvasive kVp measurements introduced by variations in the x-ray beam filtration. In this
manner, the tube voltage can then be determined with non-invasive kVp meter during 2D localizer scans or utilizing the previously mentioned CT stand in axial or helical mode.
No intervention into specialized service software is required. Data obtained with several
clinical CT scanners agreed well with manufacturer’s specifications.