There is provided a PET-MRI hybrid apparatus and method for integrating a PET image and an MRI image so that anatomical, hemodynamical and molecular information on human tissues are simultaneously presented in a single image. The PET-MRI hybrid system comprises a first scanner for obtaining anatomical and hemodynamical information, and a second scanner for obtaining molecular and functional information on the human tissues. Along a path between the first scanner and the second scanner, a transferring railway system which includes runs, and a movable bed for supporting a subject installed on the railway. The PET-MRI hybrid system also comprises a “RF+ magnetic” shield and a “magnetic” shield between path between the first scanner and the second scanner, which switch between an open status and a close status in a completely synchronized manner to assure a complete magnetic shield for the PET system at any given time. The subject is fastened on the bed and transferred along the railway between the first and second scanner to provide accurately fused MRI and PET images.