The goal of the proposed research is to develop a new digital radiographic imaging system which employs a novel scanning x-ray tube, multiple slit assembly and image intensifier (I.I.)-TV system. This system has the potential to improve diagnostic accuracy in cancer detection, while reducing patient exposure. The proposed approach represents a practical method that should avoid problems such as tube overloading, mechanical motion or long exposure times that have complicated the implementation of other slit imaging systems. Specifically, we plan to (1) construct a prototype digital chest unit having these components; (2) design efficient combinations of multiple slit assemblies and antiscatter grids using Monte Carlo simulations; (3) determine the MTFs, noise Wiener spectra and signal-to-noise ratios of digital images obtained with the I.I.-TV systems; (4) quantitate the effects of pixel size, structured noise and spatial filtering on the detection of simulated radiographic patterns; and (5) investigate the effect of physical image quality on diagnostic accuracy, by using the dual-film cassette technique which provides standard and low-dose radiographs with one exposure. Initially, we plan to employ a film-based digital system in conjunction with a mechanical moving slit assembly, in order to study the synthesis of multiple slit images and the effects of scatter reduction. Secondly, the software needed for the reconstruction of multiple slit images recorded on the I.I.-TV digital system will be developed using a shifting conventional x-ray tube as the x-ray source. Finally, a prototype unit will be designed with the data produced from the various basic studies above (2)-(5) serving as a guide. The new scanning x-ray tube will be incorporated into this prototype unit and the system will be evaluated with the use of phantoms.
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