Dual-isotope motion correction technique for gated exercise scintigraphy

In exercise multigated blood-pool imaging, significant degradation of image quality occurs as a result of patient movement under the gamma camera. Motion correction devices using centroid tracking of x-y events emanating from the organ of interest cannot be applied to blood-pool studies, because cardiac contraction and rotation masks the correctable patient motion component. We have developed a dual-isotope motion correction technique (DIMC) which utilizes a second point source of dissimilar energy (241Am) to monitor movement. Positional centroids from events incident in the 241Am window are used to develop correction coordinates which are applied to the 99mTc blood-pool events. The ability of DIMC to reduce blur due to motion has been evaluated qualitatively with phantoms and quantitatively by using spatial resolution measurements obtained from stationary line sources and from sources moving at varying rates. Based on these criteria, we have found the device to be capable of reducing over 90% of the image blur of objects moving at 5.1 cm per sec. In preliminary gated exercise studies, subjective perception of image quality was shown to be significantly improved in the DIMC corrected image, when compared to images obtained without DIMC. Improvement in image quality for exercise gated studies is of particular importance because of the low count density obtained during these procedures.