A comprehensive physical image quality evaluation of a selenium based digital x‐ray imaging system for thorax radiography

A selenium based digital x-ray system dedicated to chest radiography has been installed by the UK Department of Health’s Medical Devices Agency at Leeds General Infirmary, UK, to undergo a comprehensive evaluation, including the physical image quality. The underlying characteristics which define the overall image quality of a system are the following: sensitometric response, modulation transfer function, and noise power spectrum. These have been measured objectively on preprocessed digital data acquired under relevant radiographic conditions. The image data is further processed prior to hard copy display. The displayed image quality may only be measured subjectively; threshold contrast detail detectability is such a measure which can be related to the objective measures of image quality. The objective imagingcharacteristics suggest that Thoravision has a significant advantage over conventional radiographyimaging systems. However, subjective measures have demonstrated that the image processing can have a significant effect on the perceived image quality. Thoravision has the potential to deliver a significantly improved image quality to clinicians with no increase in radiation exposure to the patient, or image quality may be maintained with a reduction in radiation exposure. Digital image processing is central to the efficiency with which it achieves this.