Abstract
Positron Emission Tomography (PET) images are prone to motion artefacts due to the long acquisition time of PET measurements. Recently, simultaneous magnetic resonance imaging (MRI) and PET have become available in the first generation of Hybrid MR-PET scanners. In this work, the elimination of artefacts due to head motion in PET neuroimages is achieved by a new approach utilising MR-based motion tracking in combination with PET list mode data motion correction for simultaneous MR-PET acquisitions. The method comprises accurate MR-based motion measurements, an intra-frame motion minimising and reconstruction time reducing temporal framing algorithm, and a list mode based PET reconstruction which utilises the Ordinary Poisson Algorithm and avoids axial and transaxial compression. Compared to images uncorrected for motion, an increased image quality is shown in phantom as well as in vivo images. In vivo motion corrected images show an evident increase of contrast at the basal ganglia and a good visibility of uptake in tiny structures such as superior colliculi.
Highlights
Functional magnetic resonance imaging (MRI) is a common tool to assess brain networks by measuring the blood oxygen level dependent (BOLD) effect [1], which is a proxy for cerebrovascular changes caused by neuronal activation [2]
Even when using appropriate motion-restrictions, head motion cannot be avoided during such long studies, as has commonly been experienced in both Functional MRI (fMRI) and positron emission tomography (PET)
We investigated the effect of parallel imaging on motion estimation accuracy and provide an echo planar imaging (EPI) protocol optimised for high accuracy motion parameters suitable for most fMRI experiments
Summary
Functional MRI (fMRI) is a common tool to assess brain networks by measuring the blood oxygen level dependent (BOLD) effect [1], which is a proxy for cerebrovascular changes caused by neuronal activation [2]. The integration of MRI and PET in one instrumentation opens the way for novel multi-parametric studies where different aspects of brain function are observed by MRI as well as PET [6,7]. Such studies are expected to have long acquisition times of more than one hour. Even when using appropriate motion-restrictions, head motion cannot be avoided during such long studies, as has commonly been experienced in both fMRI and PET. In neuroreceptor PET optical systems have been employed to track head motion and different approaches have been applied to correct for this motion [8,9,10,11]
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