A practical 3D tomographic method for correcting patient head motion in clinical SPECT

Patient motion during brain SPECT studies can degrade resolution and introduce distortion. The authors have developed a correction method which incorporates a motion tracking system to monitor the position and orientation of the patient´s head during acquisition. Correction is achieved by spatially repositioning projections according to measured head movements and reconstructing these projections with a fully three-dimensional (3D) algorithm. The method has been evaluated in SPECT studies of the Hoffman 3D brain phantom performed on a triple head camera with fan beam collimation. Movements were applied to the phantom and recorded by a head tracker during SPECT acquisition. Fully 3D reconstruction was performed using the motion data provided by the tracker. Correction accuracy was assessed by comparing the corrected and uncorrected studies with a motion free study, visually and by calculating mean squared error (MSE). In all studies, motion correction reduced distortion and improved MSE by a factor of 2 or more. It is concluded that this method can compensate for head motion under clinical SPECT imaging conditions