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Problems Created in Attenuation-Corrected SPECT Images by Artifacts in Attenuation Maps: A Simulation Study

¹ Division of Nuclear Medicine, Vancouver Hospital and Health Sciences Centre, Vancouver, British Columbia, Canada
² Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada
³ Department of Mathematics and School of Computing Science, Simon Fraser University, Burnaby, British Columbia, Canada

View larger version (55K): [in a new window]   FIGURE 1. Examples of patient attenuation maps displaying problems discussed in this study: truncation from Beacon system seen in posterior torso (A and B), area of decreased attenuation in center of thorax (C), truncation from Profile system seen as large variation in attenuation coefficient across abdomen (D), appearance of "false" lungs near anterior abdominal surface (E), right lung appears as 2 lungs ("third lung" effect) (F), anterior wall of chest showing attenuation coefficients appreciably lower than those in central and posterior regions (G and H).

View larger version (55K): [in a new window]   FIGURE 2. Example of poor-quality patient attenuation map (A) and same map after segmentation (B). Profiles drawn through center of each map show effect of considerable mismatch in determination of lung boundaries (C).

View larger version (68K): [in a new window]   FIGURE 3. Attenuation maps reconstructed using FBP (top row) and OSTG (bottom row) from transmission data with 200 counts (A and E), 500 counts (B and F), 2,000 counts (C and G), and 10,000 counts (D and H) per pixel in blank scan.

View larger version (90K): [in a new window]   FIGURE 4. Attenuation maps and corresponding emission images of myocardial perfusion study showing increased sizes of true septal defect (A has larger defect than B) caused by insufficient counts in maps. Maps were reconstructed using FBP from 500 counts/pixel (A) and 2,000 counts/pixel (B) from transmission data obtained with profile system.

View larger version (68K): [in a new window]   FIGURE 5. Attenuation maps reconstructed using 500 counts/pixel (top row) and 2,000 counts/pixel (bottom row) transmission data with no correction (A and E), cross-talk subtraction and FBP reconstruction (B and F), cross-talk subtraction and OSTG reconstruction (C and G), and OSTG-S reconstruction with cross-talk incorporated in iterations (D and H).

View larger version (77K): [in a new window]   FIGURE 6. Attenuation maps and corresponding emission images of myocardial perfusion study for truncated attenuation map (visible on right side of maps). Data created with profile transmission system and 500 counts/pixel (A) and 2,000 counts/pixel (B). Inferior defect is closer to its true size in image B.

View larger version (83K): [in a new window]   FIGURE 7. Attenuation maps and corresponding emission images of myocardial perfusion study for normal attenuation map (A) and truncated map (B) as may be created using incomplete rotation of Beacon system. Heart image in B shows excessive size of true inferior and false lateral defects. Data created with 2,000 counts/pixel and uniform transmission systems.