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Optimized Energy Window Configuration for ²⁰¹Tl Imaging

¹ Department of Medical Physics, School of Medical Sciences, Tarbiat Modares University, Tehran, Iran; and ² Department of Nuclear Medicine, Rajaei Heart Center, Iran University of Medical Sciences, Tehran, Iran

View larger version (102K): [in this window] [in a new window]   FIGURE 1.  Sample images of phantom. (A) One slice of activity distribution in torso phantom. (B) Corresponding attenuation map. (C) 3-Dimensional view of cardiac left ventricle wall. (D) Bull's-eye plot of cardiac left ventricle. Images shown here are very similar to images from real patients.

View larger version (10K): [in this window] [in a new window]   FIGURE 2.  Primary, scatter, and total energy spectra of simulated 201Hg x-ray photons. Graphs were generated by calculating total counts in images acquired in 32 windows from 58 keV to 90 keV at 1-keV resolution. Spectra included 167-keV photopeak counts.

View larger version (18K): [in this window] [in a new window]   FIGURE 3.  Primary counts vs. energy window centers (A) and PTSRs vs. energy window centers (B). Graphs were generated by calculating total counts in images acquired in 48 energy window configurations.

View larger version (12K): [in this window] [in a new window]   FIGURE 4.  Combination of 2 graphs shown in Figure 3 after normalization. This graph simultaneously represents variations in normalized primary counts (Pn) and normalized PTSRs (PTSRn) vs. energy window centers. Maximum point in graph was assumed to represent optimum window configuration.

View larger version (57K): [in this window] [in a new window]   FIGURE 5.  From top to bottom, 3 consecutive slices of cardiac region in NCAT phantom that was used as reference in simulation study (A), images acquired in window of 67 ± 10% keV (B), images acquired in window of 73 ± 15% keV (C), images acquired in window of 75 ± 15% keV (D), and images acquired in window of 77 ± 15% keV (E). From left to right, 3 standard views: horizontal long axis, vertical long axis, and short axis.

View larger version (112K): [in this window] [in a new window]   FIGURE 6.  Reconstructed Jaszczak phantom images acquired in different energy window configurations: 67 ± 10% keV (A), 73 ± 15% keV (B), 75 ± 15% keV (C), and 77 ± 15% keV (D). Left image was used for visual inspection, and next was used for quantitative evaluation. Identical line profiles were used for calculation of average counts at peaks and valleys to calculate image contrast.

View larger version (89K): [in this window] [in a new window]   FIGURE 7.  Two adjacent slices from patient images acquired in window of 67 ± 20% keV (A), window of 73 ± 15% keV (B), window of 75 ± 15% keV (C), and window of 77 ± 15% keV (D). From left to right, 3 standard views (see legend to Fig. 5).