Thomas Lehnert MD, Presenter: Nothing to Disclose

Huedayi Korkusuz MD, Abstract Co-Author: Nothing to Disclose

Ralf W. Bauer MD, Abstract Co-Author: Research Consultant, Siemens AG Speakers Bureau, Siemens AG

Josef Matthias Kerl MD, Abstract Co-Author: Research Consultant, Siemens AG Speakers Bureau, Siemens AG

Martin Georg Mack MD, Abstract Co-Author: Nothing to Disclose

Thomas Josef Vogl MD, PhD, Abstract Co-Author: Nothing to Disclose

To determine the degree to which the skin entrance dose could be lowered (by adjusting exposure parameters and filtration) and the subsequent effect on readers’ confidence levels of digital radiographs.

The study was prospectively performed on a cadaver. Digital radiographs of bones were evaluated and scored (9 point-scale) separately by 4 radiologists blinded to the filtration and doses used. The study entailed 3 phases: phase I - random dose and filter; phase II - fixed filter and varying radiation doses (100%, 75%, 50% and 25% of the standard recommended dose); phase III - fixed dose and varying filtration (no-filtration, aluminum and aluminum-copper). The thickness of the aluminum filter used was 1 mm while that of the aluminum-copper filter was 1 mm aluminium and 0.1 mm copper. Skin entrance dose was measured using a dosimeter placed at the level of the cadaver part to be imaged. Differences in scores were tested using a Friedman-Test.

The mean scores given to images with 100%, 75%, 50% and 25% recommended standard dose were 6.18, 6.1, 5.11 and 4.07 respectively. No significant difference was noted between 100% and 75% doses images (p=0.1). A significant difference (p<0.0001) was noted when comparing the 100% and 75% images with the 50% and 25% images. The mean score given to no filtration, aluminum and aluminum-copper was 5.67, 5.43 and 5.18 respectively. No significant difference between no filtration and aluminum (p=0.411) was noted. A significant difference was detected between no-filtration and aluminum-copper (p = 0.012). The combination of aluminum-filter and 75% standard dose achieved 31.1% reduction in skin entrance dose.

It is possible to achieve 31.1% reduction in skin entrance dose for imaging bony structures by using 75% of the standard dose and 1 mm aluminum filtration without significantly affecting image quality.

Images of extremities obtained with digital projection radiography are diagnostically acceptable at lower doses than is currently being utilised.

Lehnert, T, Korkusuz, H, Bauer, R, Kerl, J, Mack, M, Vogl, T, Image Quality Perception as a Function of Dose in Digital Radiography.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11008074.html