and Solutions

Misregistration between attenuation and emission images causes artifactual abnormalities on cardiac PET images that result in false-positive defects. This study determines the fre-quency and mechanisms of misregistration artifacts, identifies their predictors, and validates a method for their routine clinical identification, prevention, or correction. Methods: We per-formed 1,177 consecutive diagnostic myocardial perfusion PET studies using 1 of 3 protocols: (a) 3 initial consecutive measured attenuation correction (MAC) scans, followed by resting and dipyridamole emission scans; (b) an initial MAC scan (early MAC), followed by emission scans; and (c) a MAC attenuation scan obtained after emission scans (late MAC). Emission im-ages were manually shifted to obtain coregistration with atten-uation and reconstructed again using shifted emission data that eliminated artifactual defects. Measurements on PET images included heart size, heart and diaphragm displacement after dipyridamole, objective quantitative misregistration of attenua-tion and emission images, and size or severity of image defects before and after shifting emission images. Results: Of 1,177 rest-dipyridamole PET perfusion studies, 252 (21.4%) had arti-factual defects due to attenuation–emission misregistration. By shifting emission images, quantitative severity and size of mis-registration and artifactual defects significantly decreased (P 0.001) with visual normalization. Artifactual defects were pre-dicted by horizontal plane misregistration (odds ratio [OR] 1.545, confidence intervals [CI] 1.113–2.145, P 0.009), body mass index (OR 2.659, CI 1.032–6.855, P 0.043), and whole heart area in the horizontal plane at rest (OR 1.096