A dedicated digital processor is described capable of digitizing a high resolution video signal from a fluoroscopic TV camera into an 810 x 600 matrix in real time. For less demanding applications, a 512 x 512 matrix can be substituted. The sampling clock frequency is 15 Megahertz giving a Nyquist bandwidth limit of 7.5 MHz. A 7 MHz phase equalized eliptical filter at the input prevents aliasing and the production of false artifacts in the picture. Eleven bit digital processing follows an 8 bit analog to digital converter. Noise reduction is accomplished by a one frame recursive filter in which the filter coefficients are adjusted by a patented motion detector on a pixel by pixel basis to reduce motion smear. The lower perceived noise permits X-ray dose reduction of 2 to 8 times while retaining high quality pictures. A noise reduced spot picture can be frozen by a foot controlled switch permitting a further reduction of dosage and eliminating the need for a troublesome disc recorder. This noise reduced picture can also be used as a subtraction mask in an optional version of the equipment. A minimum of front panel operator controls for best human interface is accomplished by the use of a programmed read only memories to control all functions including noise reduction and frame storage.

Date Published: 4 November 1981
PDF: 10 pages
Proc. SPIE 0314, Digital Radiography, (4 November 1981); doi: 10.1117/12.933071

Published in SPIE Proceedings Vol. 0314:
Digital Radiography
William R. Brody M.D., Editor(s)