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Figure 1. Transaxial images of simulated lung nodules. The three images that include all four nodule locations are shown for all modalities. 1 = non–attenuation-corrected dedicated PET scans, 2 = attenuation-corrected dedicated PET scans, 3 = non–attenuation-corrected camera-based PET scans, 4 = attenuation-corrected camera-based PET scans, 5 = non–attenuation-corrected SPECT scans, 6 = attenuation-corrected SPECT scans. All four nodules can be seen on the dedicated PET scans obtained with attenuation correction (row 2). The 22-mm-diameter nodule (curved arrow) is in the posterior part of the right lung on the middle image, the 13-mm-diameter nodule (open arrow) is in the anterior part of the left lung on the right image, the 10-mm-diameter nodule (straight solid arrow) is in the anterior part of the right lung on the left image, and the 6-mm-diameter nodule (arrowhead) is in the posterior part of the left lung on the middle images in rows 1–6. Attenuation correction reduces the apparent lung uptake, makes the lesions spherical instead of elongated, and corrects the artificially bright and inaccurate outer body contours. The improved lesion contrast with attenuation correction is most apparent for the small lesion.
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