Leeds X-ray Imaging Research
Digital Image Quality, Evaluation and Enhancement
We are currently examining the image quality performance of an Philips Integris Allura FD10 flat-panel based cardiac imaging system in cooperation with Philips Medical Systems (in the Netherlands) and the Yorkshire Heart Center in the General Infirmary at Leeds.
We are performing a comprehensive set of image quality measurements under clinical representative conditions using a patient equivalent phantom. For a range of phantom thicknesses we measure a number of image quality and dose related quantities.
We measure the entrance surface dose to the phantom and entrance dose to the detector for a number of fluoroscopy modes available on the system. These measurements, performed over a range of phantom thickness, have given us a good insight into the way the system regulates kVp and mA for different operating modes, field sizes and system geometries.
In conjunction with these measurements we also measured the contrast of an iodine equivalent detail placed within the phantom by imaging the detail on the system and calculating the contrast from the digital data. These measurements, therefore, account for the presence of x-ray scatter which substantially degrades the primary contrast and have given an insight on the way that the visual contrast might change under the studied conditions.
We also measured the x-ray scatter fraction incident on the detector by using thick lead circular disks placed before the entrance of the phantom. These were imaged on the system and an estimate of the scatter fraction was calculated from the digital data. In addition, we measured the noise power of the image data from image sequences obtained during the experiments.
The aim of this study is to relate the image quality and dose to the system variables employed with a view to developing optimum image quality at minimum patient dose.