Abstract
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Objectives We have performed respiratory motion (RM) compensation in clinically acquired Tc-99m SPECT/CT stress cardiac perfusion studies. Herein we summarize the magnitude of the estimated motion, and the impact on image fidelity of RM correction in combination with correction for attenuation, scatter, and system spatial resolution.
Methods Patient motion was visually tracked at 30 Hz using 7 retro-reflective markers and 5 near infrared cameras (Vicon Motion Systems, Inc.) during a list mode acquisition employing a BrightView SPECT/CT (Philips Healthcare). One marker tracked abdominal excursion while the others monitored body motion. Both the visual tracking system and list mode data were folded down to 100 ms temporal segments with the latter framed into 128x128 with a pixel size of 0.466 cm. Seven respiratory amplitude projection sets were created and reconstructed. After RM estimation, a final reconstruction combined the respiratory amplitude projection sets to a location between end in- and expiration. The frequency and extent of estimated RM was correlated with visual markers of improvement in image fidelity such as reduced elliptical eccentricity of left-ventricular shape, reduction in cooling of the inferior and/or anterior walls and reduction in myocardial merging with extra-cardiac activity.
Results We have completed 150+ (45.4% female) patients with an average age of 59.5 (28-85), a body-mass-index (BMI) of 32.8 (19.1-55.8), and respiratory estimates summarized in the Table below. Visual improvement in count uniformity and shape occur with respiratory estimates as low as 1 cm, are more marked in smaller hearts, and apical thinning more pronounced. Quantitatively, count differences are seen for even smaller respiratory estimates with increased counts in the inferior and anterior walls, and decreased counts in the septal and lateral walls.
Conclusions RM correction diminished motion artifacts and improved image quality with the extent of improvement related to the magnitude of RM.
Research Support R01-EB001457 and Philips Healthcare