4 November 1981 System For Automated Real-Time Generation Of Higher Order Energy Subtraction Images In Digital Fluoroscopy
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Abstract
When energy subtraction methods are employed in digital radiography it is necessary to combine the initial images in a weighted fashion. This paper discusses the instrumentation developed to automatically generate up to quadratic order combinations of x-ray images at realtime video rates in energy subtraction digital fluorography. Although the energy mode used is three-beam K-edge subtraction, the same instrumentation can also be used for dual beam imaging. The method is implemented by first acquiring logarithmically amplified digital fluorographic images of a calibration phantom with each of three spectrally different x-ray beams. The distribution of iodinated contrast material in the phantom is presumed known and the phantom thicknesses cover the range expected to be encountered clinically. Next, individual pixel values from the images are automatically fed to a PDP 11/10 computer where the weighting coefficients are calculated by least squares. The optimum coefficients are next loaded from the computer into a hardware multiplier network capable of combination of 256 x 256 pixel images at realtime video rates. Once loaded with the fitted coefficients the network is then calibrated and ready to generate energy sub-traction images of arbitrary objects. The complexity of the image combination may range from linear to full quadratic combination of differences of the three initial images. The emphasis of this paper is a discussion of the closed form iodine specific fit used to determine the coefficients and the instrumentation aspects of the system: design of the computer interface and design and operation of the multiplier network. Sample experimental results are presented.
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S. J. Riederer, S. J. Riederer, D. L. Ergun, D. L. Ergun, R. A. Kruger, R. A. Kruger, C. G. Shaw, C. G. Shaw, C. A. Mistretta, C. A. Mistretta, "System For Automated Real-Time Generation Of Higher Order Energy Subtraction Images In Digital Fluoroscopy", Proc. SPIE 0314, Digital Radiography, (4 November 1981); doi: 10.1117/12.933048; https://doi.org/10.1117/12.933048
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