Mathematics and Physics of Emerging Biomedical Imaging (1996) / Chapter Skim
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2 X-RAY PROJECTION IMAGING
2 X-RAY PROJECTION IMAGING
Pages 13-22
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From page 13... ...
In subsequent (leca(les techniques were (levelope(1 involving the use of contrast materials to enhance the images of blood vessels, gastrointestinal structures, and other anatomy. In 1930 the technique of film subtraction angiography was develope(1 and, in spite of the inconvenient delay required to complete the film processing, enjoyed widesprea(1 use for many (lecades.i Before the invention of the image intensifier in 1950, x-ray diagnosis was accomplished using either static film images or fluoroscope, which involve direct viewing of fluorescent screens after the viewer adapted to the clerk.
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From page 14... ...
The availability of rapidly obtained digital images has led to investigations of dual energy techniques for chest radiography and cardiac imaging.3 Although most of these investigations have been carried out using conventional x-ray sources, there are ongoing investigations of alternative sources for producing narrow band radiation for applications of this type. While it is recognized that film is unique in its ability to serve as detector, display mechanism, and archival storage medium, the availability of digital techniques offers the possibility of separately optimizing these functions.
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From page 15... ...
In the case of digital detectors, which enable manipulations of the contrast after image acquisition, scanning equalization still offers the potential advantage of a spatially uniform signal-to-noise ratio and more efficient dose utilization. 4Stereotaxic localization is the three-dimensional localization of lesions for biopsies or surgery using imaging techniques, usually requiring the fixation of the organ under investigation within a mechanical frame during imaging and surgery.
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From page 16... ...
There are several slot or multisIot scanning systems reported or under development.5 Detector schemes for such systems include phosphor fiber optically coupled to charge coupled devices (CCDs) , systems utilizing direct detection of x-rays by glass or plastic scintillation fibers coupled to CCDs, or silicon photodiode arrays.
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From page 17... ...
The use of x-ray capillary optics is being investigated as a means for achieving magnifications of up to 2.0 without additional focal spot blurring. The capillary optics, which channel the radiation detected at the opposing side of the patient to conventional phosphor plates, prevent focal spot blurring beyond that which exists at the exit plane.
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From page 18... ...
The dynamic range of the detector is very good and the DOE is reported to be better than that for either phosphor plates or conventional film/screen combinations. Photostimulable phosphor plate systems are continuing to gain acceptance for bedside chest radiography but are not widely used for dedicated chest radiography, which has much higher requirements for image quality.
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From page 19... ...
Developments in this area inclucle the use of higher-resolution vicleo cameras, potentially higher resolution detectors, image acquisition strategies to permit imaging of moving tables or multiple angles during an angiographic injection, and Tower-lag CCD camera systems for cardiac applications. Compensation for bright spots in the cletectecT x-ray fielcT by means of a selectable configuration of a basic series of spatially variable filter wheels has been investigated and holds promise for solving one of the most important ~- cat problems in the imaging of Tow-contrast objects.
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From page 20... ...
Other linear scanning array detectors are being developed that use C4Te or zinc tungstate crystals coupled to a photocTiode. 2.6 Research Opportunities · Development of electronic planar array detectors with adequate resolution, size, reliability, and quantum efficiency.
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From page 21... ...
2. Barnes, G.T., Wu, X., and Sanders, P.C., Scanning slit chest radiography: A practical and efficient scatter control design, Radiology 190 (1994)
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From page 22... ...
12. van Lysel, M., Optimization of beam parameters for dual energy digital subtraction angiography, Med.
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