Noise introduced by angular reprojection in tomographic image reconstruction

Conference · Wed May 01 04:00:00 EDT 1985 · J. Nucl. Med.; (United States)

OSTI ID:6843169

Chen, C T; Metz, C E

Tomographic image reconstruction requires redistribution of data collected at different projection angles back into the fixed matrix frame. This process normally produces additional noise on the reconstructed images. Three angular reprojection methods have been investigated in the present study. The direct method reprojects the entire rotated pixel (RP) into the fixed pixel (FP) which contains the center of the RP. It is fast but suffers from high noise level. The weighting method redistributes the RP into a number of FPs with weights proportional to the fractional overlaps of these FPs with a shifted FP whose center is that of the RP. This approach reduces the magnitude of the noise but requires more processing time. The matrix method uses matrix coefficients retrieved from a precalculated data bank to transform RPs into FPs. This method introduces least error but demands substantial memory space. Computer simulation studies have been performed to evaluate these three methods. In general, reprojection noise decreases with the use of more projection angles but appears to be independent from both matrix size and object size. Two models have been developed to describe the standard deviation of the noise in reprojected images. For the direct method, this noise can be regarded as a background noise level proportional to count density, which is added to the Poisson image noise. For the weighting and matrix methods the overall effect is as if the Poisson image noise were smoothed by a pixel size 1.5 times as large in each direction as the pixels actually employed, with a background noise level proportional to count density then superimposed. Noise textures also have been studied by Wiener spectral analysis.

• Research Organization: Univ. of Chicago, Chicago, IL
• OSTI ID: 6843169
• Report Number(s): CONF-850611-
• Conference Information: Journal Name: J. Nucl. Med.; (United States) Journal Volume: 26:5
• Country of Publication: United States
• Language: English

Related Subjects

657000* -- Theoretical & Mathematical Physics
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALGORITHMS
CAT SCANNING
COMPUTERIZED SIMULATION
COMPUTERIZED TOMOGRAPHY
DIAGNOSTIC TECHNIQUES
DISTRIBUTION FUNCTIONS
FUNCTIONS
IMAGE PROCESSING
IMAGES
MATHEMATICAL LOGIC
MATRICES
PROCESSING
SIGNAL-TO-NOISE RATIO
SIMULATION
TOMOGRAPHY
WEIGHTING FUNCTIONS