Several basic approaches to digital subtraction radiography have been investigated in the last decade. In one approach, the traditional video chain (image intensifier/TV camera) is modified, and the output of the camera is digitized and analyzed by a computer. A second approach (line and point scanning) utilizes a linear detector array (gas detector or solid-state linear diode array), and a series of line images is generated. These line images are combined to a two-dimensional image while the area of body being investigated is scanned. Other approaches recently developed, in particular the phosphor storage system, offer the potential to be useful in several applications, but their use on a large scale at present is precluded by a lack of clinical experience, cost, and other factors. The two most frequently used approaches also have significant advantages as well as limitations. For example, the image intensifier/TV camera (II- DSA) method is sufficiently fast for clinical needs but has limited spatial resolution, minimal or no scatter reduction, and relatively low latitude (signal-to-noise ratio). Line and point scanning overcomes some of these drawbacks but is too slow for many procedures, and generated x-ray utilization is very low. In addition, patient positioning in this method is complicated, and either the patient or the detector must be moved during the procedure in a synchronized and extremely accurate fashion. It is the purpose of this proposal to carry out a comprehensive feasibility study to investigate an alternative concept in digital subtraction radiography detection systems which would combine many of the advantages of the above mentioned approaches while eliminating some of their disadvantages. We will construct, test, and evaluate a clinically usable digital subtraction radiography system which is based on two-dimensional solid-state diode arrays fiberoptically coupled to a fluorescent screen and/or a scintillating fiberoptic faceplate. Due to unique circumstances at our institution, all three types of systems noted above (II-DSA, line scanning, storage phosphor) and our proposed system will be available to us, and we will therefore also be able to carry out a comparative study of these methodologies as an integral part of this investigation.
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