Joint estimation of activity, attenuation and motion in respiratory-self-gated time-of-flight PET.

Motivation: Whole-body Positron Emission Tomography (PET) imaging is often hindered by respiratory motion during acquisition, causing significant degradation in the quality of reconstructed activity images. An additional challenge in PET/CT imaging arises from the respiratory phase mismatch between CT-based attenuation correction and PET acquisition, leading to attenuation artifacts. To address these issues, we propose two new, purely data-driven methods for the joint estimation of activity, attenuation, and motion in respiratory self-gated time-of-flight (TOF) PET.

Relationship between sodium and diffusion MRI metrics in multiple sclerosis.

Sodium MRI can measure sodium concentrations in people with multiple sclerosis, but the extent to which these alterations reflect metabolic dysfunction in the absence of tissue damage or neuroaxonal loss remains uncertain. Increases in total sodium concentration and extracellular sodium concentration are believed to be indicative of tissue disruption and extracellular space expansion. Conversely, increase in intracellular sodium concentration may represent early and transient responses to neuronal insult, preceding overt tissue damage.

Early-Frame [F]Florbetaben PET/MRI for Cerebral Blood Flow Quantification in Patients with Cognitive Impairment: Comparison to an [O]Water Gold Standard.

Cerebral blood flow (CBF) may be estimated from early-frame PET imaging of lipophilic tracers, such as amyloid agents, enabling measurement of this important biomarker in participants with dementia and memory decline. Although previous methods could map relative CBF, quantitative measurement in absolute units (mL/100 g/min) remained challenging and has not been evaluated against the gold standard method of [O]water PET. The purpose of this study was to develop and validate a minimally invasive quantitative CBF imaging method combining early [F]florbetaben (eFBB) with phase-contrast MRI using simultaneous PET/MRI.

Resolution enhancement, noise suppression, and joint T2* decay estimation in dual-echo sodium-23 MR imaging using anatomically guided reconstruction.

Purpose: Sodium MRI is challenging because of the low tissue concentration of the Na nucleus and its extremely fast biexponential transverse relaxation rate. In this article, we present an iterative reconstruction framework using dual-echo Na data and exploiting anatomical prior information (AGR) from high-resolution, low-noise, H MR images. This framework enables the estimation and modeling of the spatially varying signal decay due to transverse relaxation during readout (AGRdm), which leads to images of better resolution and reduced noise resulting in improved quantification of the reconstructed Na images.

Improved reconstruction of crossing fibers in the mouse optic pathways with orientation distribution function fingerprinting.

Purpose: The accuracy of diffusion MRI tractography reconstruction decreases in the white matter regions with crossing fibers. The optic pathways in rodents provide a challenging structure to test new diffusion tractography approaches because of the small crossing volume within the optic chiasm and the unbalanced 9:1 proportion between the contra- and ipsilateral neural projections from the retina to the lateral geniculate nucleus, respectively.

Methods: Common approaches based on Orientation Distribution Function (ODF) peak finding or statistical inference were compared qualitatively and quantitatively to ODF Fingerprinting (ODF-FP) for reconstruction of crossing fibers within the optic chiasm using in vivo diffusion MRI ( healthy C57BL/6 mice).