Implementation and performance of a motion tracking system for treadmill MWGC imaging studies

A Multiwire Gamma Camera (MWGC) images the generator-produced Ta-178 radiopharmaceutical, which is intravenously injected and utilized as a blood labeling agent. Via this approach; high-quality, first-pass imaging of the human heart is performed to study left ventricular function of patients during peak exercise on a treadmill, as an efficient and cost effective method of assessment of patients presenting with chest pain symptoms. Patient motion and resulting image blurring during the treadmill exercise can degrade resolution and introduce serious image distortion. We have developed a correction method which utilizes an electromagnetic motion tracking system to continuously record the six-dimensional position and orientation of the torso during imaging. Correction is achieved by spatially repositioning imaging data, utilizing the simultaneously acquired six dimensional position data. The method was evaluated in dynamic phantom simulations using an Am-241 point source worn by a volunteer exercising at Bruce Level V. Accuracy of correction was assessed by calculating root mean square (RMS) error of the positions of the maximum activity pixel in uncorrected and corrected images, and by visual comparison of corrected versus uncorrected images. The results show that the motion artifact can be effectively removed with source movement simulating that of a patient´s heart at peak exercise. We conclude that this method shows promise to compensate for body motion under clinical MWGC imaging conditions during treadmill exercise.