Motion correction in treadmill first-pass radionuclide angiography

High-quality, first-pass radionuclide angiography (RNA) of the human heart is performed to study left ventricular function of patient during peak treadmill exercise, by means of a Multiwire Gamma Camera (MWGC) and intravenous injection of ultrashort-lived radionuclide Tantalum-178. The prognostic value of treadmill RNA in patients with coronary artery disease (CAD) is significant compared with other clinical and catheterization variables, but 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 incorporates an electromagnetic motion tracking to monitor the movement of left ventricle (LV) center, based on the real-time six-dimensional position and orientation of the sensor attached on patient's back, and LV center location in patient's chest contour. The method was evaluated in dynamic phantom simulations using an Am-241 point source worn by a volunteer exercising at Bruce Level IV. Accuracy of correction was assessed by calculating root mean square (RMS) error of the locations of the maximum activity pixel (centroid) in uncorrected and corrected images, and by visual comparison of corrected versus uncorrected image sequences. 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.