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FIGURE 7. Correlations between true defect size and quantified SPECT defect size for SPECT acquisition using 180° and 360° orbits, in center position (A) and in 5- (B), 10- (C), and 15-cm (D) off-center positions. Each phantom position was analyzed with phantom in straight and angled orientations. Data label (
) denotes multiple data points with same (overlapping) SPECT defect value for 180° and 360° acquisitions. Dotted-and-dashed line represents line of identity. With 180° acquisition orbit, quantified SPECT defect size was increasingly overestimated when phantom was placed more eccentrically. With 360° acquisition orbit, quantified SPECT defect size remained in same range of underestimation regardless of whether phantom was positioned in center or off center.
