Article Figures & Data
Figures
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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).
Tables
Value at the following window center ± width (keV): Parameter 68 ± 10% 73 ± 15% 75 ± 15% 77 ± 15% Reference Relative sensitivity 1 1.18 1.08 0.97 PTSR 0.59 0.88 1.04 1.21 Myocardium-to-cavity contrast 0.52 0.57 0.62 0.62 0.91 Myocardium-to-defect contrast 0.19 0.19 0.19 0.23 0.35 Images were acquired with SimSET SPECT simulator in 4 energy window configurations. Reference values were directly derived from NCAT activity distribution images. Difference between conventional window setting and window setting of 77 ± 15% keV was highly significant (P < 0.01), except for relative sensitivity.
- TABLE 2
Quantitative Parameters Derived from Jaszczak Phantom Images Acquired in Different Energy Windows
Value at the following window center ± width (keV) Parameter 68 ± 10% 73 ± 15% 75 ± 15% 77 ± 15% Relative sensitivity 1 1.28 1.14 1.05 Contrast 0.42 0.52 0.45 0.45 Physicians* 0 1 1 2 ↵* Number of physicians who accepted corresponding images as best among 4 sets of images.
Difference between conventional window setting and window setting of 77 ± 15% keV was highly significant (P < 0.01), except for relative sensitivity.
- TABLE 3
Averages of Parameters Derived from Clinical Images Acquired in Different Energy Windows
Value at the following window center ± width (keV) Parameter 77 ± 15% 75 ± 15% 73 ± 15% 68 ± 10% Relative sensitivity 1.05 ± 0.02 1.15 ± 0.02 1.24 ± 0.02 1 Relative myocardium-to-cavity contrast 1.17 ± 0.10 1.12 ± 0.09 1.07 ± 0.04 1 Relative myocardium-to-defect contrast 1.54 ± 0.37 1.33 ± 0.26 1.28 ± 0.24 1 Marks by physicians* 2.65 2.1 1.0 0.25 ↵* Average of marks (0–3) given by physicians to images in corresponding window settings.
Except for relative sensitivity, difference between conventional window setting and window setting of 77 ± 15% keV was highly significant (P < 0.01).
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