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Comparison of Myocardial Perfusion ⁸²Rb PET Performed with CT- and Transmission CT–Based Attenuation Correction

¹ Departments of Imaging and Medicine, Cedars-Sinai Medical Center, Los Angeles, California; and ² Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California

View larger version (11K): [in this window] [in a new window]   FIGURE 1.  Protocol for cardiac rest–stress 82Rb PET/CT study with CT-based and TCT-based AC. Total imaging time is approximately 23 min.

View larger version (15K): [in this window] [in a new window]   FIGURE 2.  Stress and rest American Heart Association 17-segment representation of average differences between 82Rb PET data attenuation-corrected with TCT and with CT for studies with no misregistration or with misregistration less than 5 mm. Changes are expressed as percentage of all counts in myocardium (all changes are P < 0.05). Negative change (red) implies that CT-corrected value is smaller.

View larger version (36K): [in this window] [in a new window]   FIGURE 3.  Stress and rest American Heart Association 17-segment representation of average differences between 82Rb PET data attenuation, corrected with TCT and with CT for studies with misregistration greater than 5 mm before (A) and after (B) alignment correction.

View larger version (16K): [in this window] [in a new window]   FIGURE 4.  Frequency and magnitude of misalignment as judged by 2 observers for rest (A) and stress (B) studies.

View larger version (97K): [in this window] [in a new window]   FIGURE 5.  Example of misalignment in rest 82Rb study of female patient (weight, 54.4 kg [122 lb]; age, 76 y; body mass index, 20.9). Images are before alignment correction (A) and attenuation-corrected with aligned CT (aCT) (B). From left to right, figure shows TCT- and CT-corrected original images, positive and negative change images with overlaid contours, raw polar maps, change polar maps, and PET/CT fusion images with blue arrows showing identified misalignment. TCT > CT changes are seen in septal wall (white arrows). Differences between CT- and TCT-corrected studies changed after alignment correction of CT. Two observers identified displacements of x = 10, y = 4, and z = 6 mm and x = 6, y = 11, and z = –1 mm.

View larger version (56K): [in this window] [in a new window]   FIGURE 6.  Example of misalignment in stress study of male patient (weight, 75.9 kg [167 lb]; age, 67 y; body mass index, 25.4), in which AC by aligned CT (aCT) did not eliminate differences between CT- and TCT-corrected images. TCT > aCT changes remain in anterior and septal walls (white arrow), and TCT < aCT changes are shown in inferior wall (yellow arrow), despite manual alignment. Note that irregular heart structure on CT maps (green arrows), which is likely due to respiratory and cardiac motion effects during normal breathing CT, could be likely cause of remaining differences.