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

Patient motion during brain SPECT studies can degrade resolution and introd uce distortion. We have developed a correction method which incorporates a motion tracking system to monitor the position and orientation of the patie nt's head during acquisition. Correction is achieved by spatially repositio ning projections according to measured head movements and reconstructing th ese projections with a fully three-dimensional (3D) algorithm. The method h as been evaluated in SPECT studies of the Hoffman 3D brain phantom performe d on a triple head camera with fan beam collimation. Movements were applied to the phantom and recorded by a head tracker during SPECT acquisition. Fu lly 3D reconstruction was performed using the motion data provided by the t racker. Correction accuracy was assessed by comparing the corrected and unc orrected 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. We conclude that this method can compensate for head motion under clinical SPECT imaging conditions.