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Effect of Mechanically Simulated Diaphragmatic Respiratory Motion on Myocardial SPECT Processed With and Without Attenuation Correction

¹ Department of Nuclear Medicine, The Alfred Hospital, Prahran, Victoria, Australia
² Department of Nuclear Medicine, The Queen Elizabeth Hospital, Woodville, South Australia, Australia

View larger version (131K): [in a new window]   FIGURE 1. Photograph of phantom shows its components: 1, acrylic tub; 2, cardiac insert; 3, acrylic diaphragm; 4, saline bags; 5, Teflon (DuPont, Wilmington, DE) spine.

View larger version (26K): [in a new window]   FIGURE 2. (A) Schematic diagram of midcoronal section through phantom shows relationship between saline bags and cardiac insert. Components of phantom are numbered same as in Figure 1. (B) Respiratory patterns used for phantom experiments. x-axis: time (s); y-axis: position of diaphragm. Cranial is up.

View larger version (154K): [in a new window]   FIGURE 3. Photograph of gantry assembly on gamma-camera bed: 1, fixed frame; 2, sliding frame; 3, L-shaped detectors; 4, transmission source; 5, phantom (oriented supine, cranial to left). Push-pull handle has been removed for photography.

View larger version (53K): [in a new window]   FIGURE 4. Four illustrative slices of transmission map for vertical short axis with no motion (top left) and with 2 cm of motion (bottom left) and for vertical long axis with no motion (top right) and with 2 cm of motion (bottom right). Heart was at 30° caudal angulation; cold liver and spleen inserts were present. Respiratory pattern was normal respiration.

View larger version (58K): [in a new window]   FIGURE 5. Demonstration of respiratory motion artifact and its dependence on respiratory pattern. For these experiments, myocardial inferior wall self-attenuation was avoided by positioning heart truly horizontally (perpendicular to face of detector), and no liver or spleen inserts were present. Myocardial insert contained 40 MBq 99mTc. Midshort-axis (SA) slices are illustrated. Normal, Even, Reverse = respiratory pattern (see Fig. 2B); AC = measured transmission AC with iterative reconstruction and scatter correction; 0, 1, 2, and 3 cm = respiratory amplitude of phantom.

View larger version (68K): [in a new window]   FIGURE 6. Interaction of attenuation artifact and respiratory motion artifact. Heart was at 30° caudal angulation; cold liver and spleen inserts were present. Myocardial insert contained 4.5 MBq 201Tl. Respiratory pattern was normal respiration. Distance-weighted polar plots and midvertical long-axis slices are illustrated. Normal = respiratory pattern (see Fig. 2B); AC = measured transmission AC with iterative reconstruction and scatter correction; 0, 1, and 2 cm = respiratory amplitude of phantom.

View larger version (27K): [in a new window]   FIGURE 7. Representative graphs of inferior-to-anterior myocardial activity ratio (A) and anterior-to-lateral activity ratio (B) as function of respiratory amplitude. Heart was at 30° caudal angulation; cold liver and spleen inserts were present. Myocardial insert contained 4.5 MBq 201Tl. Respiratory pattern was normal respiration. FBP = FBP processing; AC = measured transmission AC with iterative reconstruction and scatter correction processing.