Controlled cutoff frequency analog filter for CT scanners

Details Controlled cutoff frequency analog filter for CT scanners Controlled cutoff frequency analog filter for CT scanners

1984-06-20

1986-10-28

Church, Craig E.

X-ray or gamma ray systems or devices

Specific application

Computerized tomography

378 4, 378901, G03B 4116

Patent

active

046203133

ABSTRACT:
A network for use in a fourth generation CT scanner for noise reduction. The network comprises an active low pass filter whose cutoff frequency is controlled by a scaled signal responsive to the angular velocity of the rotating radiation source of the scanner. In a preferred embodiment a raw signal is generated by an encoder that detects movement of the source. As the source speed changes either in response to an operator's selection of a different scan speed or to systemic variations in the scanner relative to expected performance, the filter's cutoff frequency will automatically change thereby assuring optimum performance regardless of scan speed.

REFERENCES:
patent: 4034223 (1977-07-01), Kowalski
patent: 4181858 (1980-01-01), Moore
patent: 4494141 (1985-01-01), Altebruse
C. B. Lim et al., "CT Image Noise and Resolution Behavior in RC Filter--Based Projection Data Acquisition", IEEE Transactions on Nuclear Science, vol. NS-28, No. 1, Feb. 1981.
R. N. Bracewell, The Fourier Transform and its Applications, New York, McGraw--Hill, pp. 189-197.
"MF10 Universal Monolithic Dual Switched Capacitor Filter", National Semiconductor Corp., Dec. 1981, Product Brochure, IM-B25M121.

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