Abstract
This work provides an insight into positron emission tomography (PET) joint image reconstruction/motion estimation (JRM) by maximization of the likelihood, where the probabilistic model accounts for warped attenuation. Our analysis shows that maximum-likelihood (ML) JRM returns the same reconstructed gates for any attenuation map (μ-map) that is a deformation of a given μ-map, regardless of its alignment with the PET gates. We derived a joint optimization algorithm accordingly, and applied it to simulated and patient gated PET data. We first evaluated the proposed algorithm on simulations of respiratory gated PET/CT data based on the XCAT phantom. Our results show that independently of which μ-map is used as input to JRM: (i) the warped μ-maps correspond to the gated μ-maps, (ii) JRM outperforms the traditional post-registration reconstruction and consolidation (PRRC) for hot lesion quantification and (iii) reconstructed gated PET images are similar to those obtained with gated μ-maps. This suggests that a breath-held μ-map can be used. We then applied JRM on patient data with a μ-map derived from a breath-held high resolution CT (HRCT), and compared the results with PRRC, where each reconstructed PET image was obtained with a corresponding cine-CT gated μ-map. Results show that JRM with breath-held HRCT achieves similar reconstruction to that using PRRC with cine-CT. This suggests a practical low-dose solution for implementation of motion-corrected respiratory gated PET/CT.
Highlights
P ATIENT respiratory motion during positron emission tomography (PET) acquisition degrades image resolution [1] and results in reconstruction errors due to pos-Manuscript received April 23, 2015; revised July 22, 2015; accepted July 28, 2015
We reported an initial evaluation on patient data, where joint image reconstruction/motion estimation (JRM) was applied with a breath-held high resolution computed tomography (CT) (HRCT) derived -map and the results were compared with post-registration reconstruction and consolidation (PRRC), where each gate was reconstructed using cine-CT gated -maps
We demonstrated that it is possible to extend existing JRM methods [23], [24] to a more complete model that includes an attenuation map affected by the same motion
Summary
P ATIENT respiratory motion during positron emission tomography (PET) acquisition degrades image resolution [1] and results in reconstruction errors due to pos-. Manuscript received April 23, 2015; revised July 22, 2015; accepted July 28, 2015. Date of publication August 03, 2015; date of current version December 29, 2015. Thielemans are with the Institute of Nuclear Medicine, University College London, NW1 2BU London, U.K
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