Ian A. Cunningham PhD, Presenter: Founder, DQE Instruments Inc

Michael McDonald, Abstract Co-Author: Nothing to Disclose

John Henry, Abstract Co-Author: Nothing to Disclose

DQE testing shows differences in the dose efficiency of different systems, and can play a role in usage, service and replacement strategies.

The Image Gently initiative emphasizes the need to minimize patient x-ray exposures by using optimal protocols and exposure techniques tailored to patient size. Complementary to this objective is the need to ensure the best possible image quality for a given dose. The detective quantum efficiency (DQE) is widely accepted by scientific and regulatory communities as a quantitative measure of performance relative to an “ideal” detector, and the only true indicator of a system’s ability to produce the best possible images, but is difficult to measure outside a laboratory environment. We have recently demonstrated the ability to accurately measure the DQE of a wide range of imaging systems in a clinical environment, including DR, CR and mammography, and have incorporated these tests into our quality assurance program.

It is not yet clear whether differences are due to different technologies or degradation with age or use. However, knowing the DQE enables one to specifically choose high-DQE facilities for applications such as pediatric imaging and to identify equipment that might be serviced to restore full performance. We believe the DQE should play a greater role in purchasing decisions, and for evidence-based replacement decisions as there may be no need to replace older equipment that continues to show good DQE tests.

A survey of DQE values identified systems that perform less well than others. The zero-frequency DQE value varied by a factor of 2.5, consistent with expected differences between technologies. In addition, the DQE decreased at low exposure levels more quickly on some systems, and a wide range (factor of 50x) was found in high-frequency DQE values in some cases as illustrated in the figure. On systems that allow image-processing features to be disabled, use of these features (including a range of logarithmic transformation, edge enhancement and gray-scale inversion) did not affect DQE results.

Cunningham, I, McDonald, M, Henry, J, Image Gently, and Use the DQE to Ensure the Best Possible Images with Low Patient Exposures: A DQE Survey of Clinical Systems.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12033825.html