Motion correction of respiratory-gated SPECT image and clinical usefulness of the extracted motion information

A respiratory-gated SPECT allows image reconstruction at various phase of the respiration and therefore the blur in an image can be avoided. However, it requires long time to accumulate sufficient number of counts at each phase. If the acquisition time is not long enough, the detected count becomes inadequately small and hence the reconstructed image becomes noisy. We have been proposed a method for correcting the motion between different phase images obtained with the respiratory-gated SPECT. By summing motion-corrected phase images, a less noisy and less blurred SPECT image can be obtained. In this paper, the other advantage of motion correction information produced in the middle of motion correction and summation process is described in addition to the review of the proposed method. We found that there are clear differences in respiratory motion between normal lung and lung with disorder, especially, emphysema. Detail analysis of the motion of the lung may serve as an aid for diagnosis. In this paper, the clinical usefulness is discussed through investigation including quantitative evaluation of the respiratory motion, comparison with ventilation planar images and physician's observation on them.