Projection completion method of partial area scan

Details Projection completion method of partial area scan Projection completion method of partial area scan

1979-11-29

1981-12-08

Krass, Errol A.

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250445T, G01N 2300

Patent

active

043051278

ABSTRACT:
A method of preprocessing incomplete or truncated projections obtained from high resolution CT scanning of a small scan circle corresponding to a limited region of interest within the scanned object. An air calibration is performed to obtain a set of air values. The intensity values obtained during the partial area scan are subtracted from the air values to convert the intensity values to attenuation values. The approximate slope at either end of the truncated projection is then calculated. Based on the attenuation values and the slope the necessary extrapolation of the truncated projection is performed to complete the projection. No measurements, ionizing or otherwise, are required from the region outside of the small scan circle.
The completed projection is ready for conventional reconstruction techniques involving convolution and back projection.

REFERENCES:
patent: 4136388 (1979-01-01), Lindquist
patent: 4189775 (1980-02-01), Inouye et al.
Lewitt, "Processing of Incomplete Measurement Data in Computed Tomography", Med. Image Proc. Group Tech. Rep. MIPG22, Feb. 1979, Comp. Sci. Dept-SUNY.
Nelcioclu et al., "Limited Field of View Reconstruction in Computerized Tomography", Dept. of Rad. Sci., Univ. of Calif., IEEE Trans. on Nuc. Sci. vol. NS-26, No. 1, Feb. 1979.
Ethier et al., "Development of High Resolution Computed Tomography of the Spinal Cord", Dept. of Rad., Montreal Neur. Hosp., Jnl. of Comp. Assis. Tomography, vol. 3, #4, Aug. 1979.
Lewitt et al., "Image Reconstruction from Projections: III: Projection Completion Methods (Theory)", EE Dept. Univ. of Canterbury, Optik 50 (1978) No. 3, pp. 189-204.
Lewitt et al., "Image Reconstruction from Projections: IV: Projection Completion Methods (Computational Ex.)", EE Dept., Univ. of Canterbury, Optik 50 (1978) #4, pp. 269-278.
Oppenheim, "More Accurate Algorithms for Iterative 3-D Reconstruction", Univ. of Chicago, IEEE Trans. on Nucl. Sci., vol. NS-21, Jun. 1974.
Burton, "Computed Tomographic Scanning and the Lumbar Spine": Part 1: Economic and Historical Review, Spine, vol. 4, No. 4, Jul./Aug. 1979, pp. 353-355.

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