Congress:
EuroSafe Imaging 2021
Keywords:
Radioprotection / Radiation dose, Digital radiography, Equipment, Quality assurance
Authors:
P. Sänger, C. Lappe, M.-A. Weber, M. Lütgens
DOI:
10.26044/esi2021/ESI-10702
Results or findings
The results of dose area product analysis for different anatomies are summarized in Figure 1. For X-rays of the chest, the average dose area product (DAP) for 3-year-old children was reduced from 2.76 µGcm² in 2013-2014 to 0.48 µGcm² in 2017-2019. For adults, the dose reduction was slightly lower. Here, a reduction of 79% was observed instead of 83% for children. In general, the DAP for adults was at a significantly higher level due to the greater absorption length for an adult chest compared to a child chest. A dramatic dose reduction was also observed for other anatomies. In pediatrics, the digital detector system resulted in a 25% reduction in hand dose, 76% reduction in elbow dose, and 86% reduction in abdomen dose. Averaged over all examinations analyzed, a dose reduction of 70% was observed.
To elucidate the change in image quality due to dose reduction, we further investigated spatial resolution as a function of dose. Our sample images are shown in Figure 2, and the results are summarized in Figure 3.
Since the dose depends linearly on the exposure time product (see Fig. 3), systematic variation of the exposure time product is a suitable technique to analyze the dose dependence of spatial resolution. Resolution is evaluated visually by viewing the lead lined grid. Phosphor storage plate systems typically achieve a resolution of 3.4 LP/mm (not shown). To pass the constancy test, a resolution of 2.4 LP/mm is required for digital radiographic systems [2]. In the constancy test, a value of 4.0 LP/mm could be achieved with the conventional parameters (70 kV and 40 mAs) using the digital detector. With one tenth of the original mAs and dose, a resolution was still achieved (2.5 LP/mm) sufficient to pass the constancy test (Fig. 3). The loss of resolution is accompanied by a corresponding increase in the standard deviation of the gray values measured in the homogeneous center of the test image.