Abstract
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Objectives Perform rigid-body MR-assisted PET motion correction (MC) in an integrated MR-PET scanner.
Methods A prototype MR-PET human brain scanner was recently developed by Siemens [1], allowing the acquisition of MR and PET data simultaneously. This permits the motion of the object to be characterized using the MR and the information to be used to correct the PET data. Rigid-body motion can be tracked using the 3D PACE method [2] or embedded cloverleaf navigators [3]. These methods were used to track the motion of a structured phantom moved in 3 positions. The motion was accounted for in the post-processing step by “moving” the coordinates of all crystals based on the transformation matrix obtained from the MR. Similarly, a time-weighted sensitivity was obtained. Data in LOR space were then rebinned into sinograms and the image was reconstructed using the OP-OSEM 3D algorithm.
Results The transformation matrices were obtained from the MR data for each frame. The first frame was considered the reference frame and the MR provided the transformation parameters for the two subsequent frames relative to the reference frame. Substantial improvement was observed in the image reconstructed after applying the MC.
Conclusions Simultaneous MR-PET data acquisition permits temporal correlation of the data, opening up opportunities impossible to realize using sequentially acquired data, one example demonstrated here being MR-assisted PET MC. As a next step the method will be tested in human volunteers.
- © 2009 by Society of Nuclear Medicine