Risto-Projections TOF Data Non-Rigid Motion Estimation and Correction

With advancements in PET technology, scanners with a very good time-of-flight (TOF) resolution became available. In addition, scanners with long axial extent are now commercialized. Although raw data sizes increase significantly with such scanners, good TOF resolution allows substantial data compression without any loss of spatial resolution: for example, the histo-projections with relatively coarse sampling in the TOF direction in the Siemens Biograph Vision and Vision Quadra PET/CT scanners. The patient motion during the scan is unavoidable. The pattern caused by breathing may result in a relatively large displacement of organs and the consequent blurring of clinically relevant features in regions affected by the motion. As was shown in our previous work, non-rigid motion correction can be performed in the quasi-image space of histo-projections. The TOF locality property can be used to locally perform motion correction; that is, the approximation of motion as locally rigid on a scale of TOF resolution. In this work, we investigate motion estimation in the TOF data space from histo-images by histogramming the data into a 3D array consistent (in geometry and size) with the reconstruction image. The histo-image estimated motion is then used in histo-projections motion correction. Initial results using an XCAT digital phantom showed that the presented methodology accommodates for changes in non-rigid body movements for a typical pattern of patient motion. The patient scan on newly developed Biograph Vision Quadra PET/CT scanner was used in validation of presented motion correction.