Use of three-dimensional Gaussian interpolation in the projector/backprojector pair of iterative reconstruction for compensation of known rigid-body motion in SPECT

Abstract

Due to the extended imaging times employed in SPECT and PET, patient motion during imaging is a common clinical occurrence. The fast and accurate correction of the three-dimensional (3D) translational and rotational patient motion in iterative reconstruction is thus necessary to address this important cause of artifacts. We propose a method of incorporating 3D Gaussian interpolation in the projector/backprojector pair to facilitate compensation for rigid-body motion in addition to attenuation and distance-dependent blurring. The method works as the interpolation step for moving the current emission voxel estimates and attenuation maps in the global coordinate system to the new patient location in the rotating coordinate system when calculating the expected projection. It also is employed for moving back the backprojection of the ratio of the measured projection to the expected projection and backprojection of the unit value (sensitivity factor) to the original location. MCAT simulations with known six-degree-of-freedom (6DOF) motion were employed to evaluate the accuracy of our method of motion compensation. We also tested the method with acquisitions of the Data Spectrum Anthropomorphic phantom where motion during SPECT acquisition was measured using the Polaris IR motion tracking system. No motion artifacts were seen on the reconstructions with the motion compensation.

Triply Differential Single Ionization of Argon: Charge Effects for Positron and Electron Impact

“…With regard to atomic interactions, the present work compares how momentum transfer data are influenced by electron exchange (or lack of), polarization effects, and postcollision interactions by comparing positron and electron impact data. More broadly, conclusions derived from the present study impact our understanding of positron interactions, which is important in fields where positrons play important roles, e.g., in the production of antihydrogen and other antiparticles and the subsequent fundamental studies of QED, CPT, gravitational forces on antimatter [9], tomographic imaging in medicine [10,11], characterization of materials, and ionization of biological molecules. With regard to medical and biological effects, knowledge about positron interactions is recognized as being important in improving the spatial resolution of 163201-1 Ó 2010 The American Physical Society positron-emission tomography images [12] plus in accounting for differences in the axial and radial penetrations and doses measured for positron and electron impact [13].…”

Estimation and correction of cardiac respiratory motion in SPECT in the presence of limited‐angle effects due to irregular respiration

“…Motion compensation is performed in a second pass through a MLEM reconstruction method where we use the original ͑not normalized or processed͒ projections for each state and their motion estimates obtained as detailed in Sec. II C. The motion compensation technique is that described by Feng et al 9 Briefly, for all the motion states besides the reference state, the current estimate of the object volume is repositioned from the reference state to that of the motion state. The estimated projections plus the scatter estimate are then compared to the actual projections, the results backprojected and realigned with the reference state.…”

“…Once the motion across the respiratory states has been estimated, we reconstruct using the estimated motion in existing motion-correction iterative-reconstruction methods. [8][9][10] In this last step, all the raw acquired counts are utilized in reconstruction. Section III details the materials, methods, and data analysis used to investigate our algorithm.…”

A flexible multicamera visual‐tracking system for detecting and correcting motion‐induced artifacts in cardiac SPECT slices

“…The change in location as a function of projection angle was used to correct the RB motion of the second acquisition during reconstruction using our previously described methodology which incorporates 3D Gaussian interpolation in the projector/backprojector pair. 24 In this method, 3D Gaussian interpolation moves the current emission estimates and attenuation maps in the global coordinate system to locations in the rotating coordinate system to which the patient moved. It then moves back to the original location the backprojection of the ratio of the measured projections to the projections of the current estimate.…”

“…A singular-value decomposition ͑SVD͒ is applied to the body motion components of the chest markers to obtain an aggregate six-degree-of-freedom ͑6-DOF͒ RB motion estimate which is employed to correct RB motion within iterative reconstruction. 24 The vertical motion of abdominal markers is used to obtain a signal employed in the correction of respiratory motion. This selection was based on the vertical motion of abdominal markers always exhibiting the largest effects of respiration.…”