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Feasibility of Dual-Isotope Coincidence/Single-Photon Imaging of the Myocardium

Medical Imaging Research Laboratory, Department of Radiology, University of Utah, Salt Lake City, Utah

View larger version (57K): [in a new window]   FIGURE 1. 18F-only short-axis images of cardiac thorax phantom obtained with axial slat collimators (uniformity, 0.10) (A), LEHR collimators (uniformity, 0.11) (B), and axial slat collimators but without attenuation correction (uniformity, 0.22) (C). Short-axis slices appear somewhat square in (B); this anisotropic resolution effect is detailed in Discussion.

View larger version (109K): [in a new window]   FIGURE 2. Patient data shown by polar maps with attenuation correction (A), polar maps without attenuation correction (B), and short-axis slices without attenuation correction (C). For all images, left side is with axial slat collimators and right side is with LEHR collimators.

View larger version (91K): [in a new window]   FIGURE 3. Four noncontiguous short-axis slices of phantom. Top row shows 18F-only images obtained with LEHR collimators. Middle row shows images with 99mTc also present (99mTc/18F overall ratio, 7:1). Bottom row shows difference images.

View larger version (50K): [in a new window]   FIGURE 4. Phantom study for crosstalk levels. Top row shows images with 99mTc and 18F present (99mTc/18F overall ratio, 9:1) and LEHR collimators. Bottom row shows 99mTc-only images (99mTc/18F overall ratio, 138:1). Arrows are pointing to true 99mTc defect.

View larger version (59K): [in a new window]   FIGURE 5. Phantom study for crosstalk compensation. (A) Reverse grayscale images. Top left shows 99mTc window. Top right shows 162-keV window. Bottom left shows smooth scatter estimate (from Eq. 1). Bottom right shows difference or residual between 99mTc window and smooth scatter estimate. (B) Horizontal profile through row 27 of images in A (162-keV window profile not shown). Scat est. = smooth scatter estimate.

View larger version (111K): [in a new window]   FIGURE 6. Reconstructions from SPECT imaging of volunteer with only sestamibi present (A), with sestamibi and FDG present and crosstalk compensation (B), with sestamibi and FDG present and subtraction of crosstalk estimate (C), and with sestamibi and FDG present and inclusion of crosstalk estimate in iterative reconstruction algorithm (D). Even with correction, artifactual inferolateral defect remains.

View larger version (42K): [in a new window]   FIGURE 7. Comparison of reconstruction using 3-dimensional tilt angle binning and SSRB for 18F data acquired with LEHR collimators. Left image was obtained with axial slat collimators; middle image, with LEHR collimators and SSRB; and right image, with LEHR collimators and 3-dimensional tilt angle binning.