Authors:
T. Lehnert, M. Kissner, H. Korkusuz, U. Voigt-Koop, M. G. Mack, T. J. Vogl; Frankfurt a. Main/DE
DOI:
10.1594/ecr2010/C-2989
Methods and Materials
Study concept:
Extremities of a cadaver, not preserved in formaldehyde, were selected as radiographic imaging objects, in particular the hand, wrist, forearm, foot, ankle and the tibia/fibula. The cadaver was supplied by the Department of Forensic Medicine at the Frankfurt University Hospital.
Image acquisition:
Study objects were imaged in two standard projections using stepwise decreasing dose levels and variation of added filtration (no filtration, 1.0 mm aluminum, 1.0 mm aluminium + 0.1 mm copper) under digital projection radiography. The initial dose level for all body parts imaged was the current x-ray technique. Dose levels considered were 100%, 75%, 50% and 25% of the normal and customary x-ray techniques used for the particular body part and projection. Thus, a total of more than 100 radiographic examinations were performed for this study.
Radiographic system:
The radiographic system (Kodak DirectView DR7500, Rochester, NY, USA) was based on a flat-panel CsI-detector. Matrix size was 3000 x 3000 pixels, with a pixel pitch of 143 µm, which produced an active imaging area of 43 x 43 cm. The inherent filtration provided by the tube housing, collimator, dose-area measuring chamber, and light localizer was equivalent to 2.9 mm of aluminum. For additional filtration a 1-mm-thick aluminum filter or a 1-mm aluminum/0.1-mm-copper filter was integrated in the tube housing on the tube side of the dose-area measuring chamber.
Blinding:
All readers were blinded, so that they were not aware of any technical features of the examinations.
Evaluation:
The images were presented in random order. Four readers, including two senior radiologists and two residents, participated in the image evaluation process. Images were reviewed on a clinical diagnostic workstation. Readers were able to change the image presentation by adjusting the window width and level, and were free to vary their viewing distance on the basis of individual preferences. A time limit for image review was not imposed. Each reader assigned a score to the images without knowledge of the other readers' scores. Image quality was assessed subjectively by using a predefined scoring system considering the image’s resolution and contrast, the sharpness of spongiosa and evaluation of cortical bone and soft tissues (Fig.1, Tab.1).