| 摘要 |
<p>PROBLEM TO BE SOLVED: To shorten the filtering processing time when a CT image is formed and dispense with a pre-scan using a reference phantom. SOLUTION: The ideal projection data Rij ,s to be obtained when multiple ideal phantoms different in size are scanned are calculated by simulation and held, the ideal projection data Rij ,s of the ideal phantom most approximate to a testee in size are selected (B2), the selected data are subtracted from the projection data Projij obtained when the testee is scanned (B4), and the filtering process (B5-B7) and back protection process (B8) are applied to the difference projection data P'rojij . No low-frequency component is left in the difference projection data P'rojij , no cupping occurs on a CT image when the number of FFT points is decreased in the filtering process, and the calculating time can be shortened. The ideal projection data are obtained by simulation, and a pre-scan using a reference phantom is not required.</p> |
