Edge Phantom Measures Sharpness of X-Ray Detectors

The corrected digital image can be used to enable computer-assisted diagnosis.

Digital radiography makes use of Xray detectors that yield a radiographic image of the object or patient between the X-ray source and the detector. Tools have been developed to assess the image quality characteristics of radiation images. One tool is an edge phantom, placed between source and detector, to assess the sharpness of the radiation image obtained. The edge-like, spatial step-response of the system resulting from a sudden change in irradiation level, invoked by the phantom, can be used to calculate the modulation transfer function (MTF) in a particular direction. In this way, the sharpness of the detector can be assessed.

The edge phantom design is such that X-rays either go through the full thickness of the phantom, or do not go through the phantom at all. Semi-shadow effects at the absorber’s edges due to reduced attenuation during passage through a shorter absorber material trajectory are thus cancelled by the design.

Another advantage of the proposed design is that the sharpness of the system can be assessed in multiple directions within the detector plane using only a single radiation exposure. The phantom is used for X-ray radiation, but other forms of penetrating radiation are also possible.

In the field of digital radiography, image quality performance measurement tools have been developed that consist of measuring or assessing image quality characteristics of radiation images of test phantoms. Specially designed edge phantoms or edge devices allow the assessment of sharpness in multiple spatial directions using a single radiation exposure. The focus point of the X-ray source is the top of a three-dimensional geometric shape, the envelope of which comprises all edge faces of the phantom.

This technology is offered by AGFA HealthCare. For more information, view the yet2.com TechPak at http://info.hotims.com/28049-140.

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