Joseph A. Helpern

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A magnetic resonance imaging method is presented for quantifying the degree to which water diffusion in biologic tissues is non-Gaussian. Since tissue structure is responsible for the deviation of water diffusion from the Gaussian behavior typically observed in homogeneous solutions, this method provides a specific measure of tissue structure, such as(More)
Quantification of non-Gaussianity for water diffusion in brain by means of diffusional kurtosis imaging (DKI) is reviewed. Diffusional non-Gaussianity is a consequence of tissue structure that creates diffusion barriers and compartments. The degree of non-Gaussianity is conveniently quantified by the diffusional kurtosis and derivative metrics, such as the(More)
Conventional diffusion tensor imaging (DTI) measures water diffusion parameters based on the assumption that the spin displacement distribution is a Gaussian function. However, water movement in biological tissue is often non-Gaussian and this non-Gaussian behavior may contain useful information related to tissue structure and pathophysiology. Here we(More)
This article presents two related advancements to the diffusional kurtosis imaging estimation framework to increase its robustness to noise, motion, and imaging artifacts. The first advancement substantially improves the estimation of diffusion and kurtosis tensors parameterizing the diffusional kurtosis imaging model. Rather than utilizing conventional(More)
Abnormalities in the P300 ERP, elicited by the oddball task and measured using EEG, have been found in a number of central nervous system disorders including schizophrenia, Alzheimer's disease, and alcohol dependence. While electrophysiological studies provide high temporal resolution, localizing the P300 deficit has been particularly difficult because the(More)
Elevated iron levels in the substantia nigra (SN) of the brain in Parkinson's disease (PD) may mediate lipid peroxidative reactions, promoting SN neuronal death. To assess SN iron accumulation in living PD patients and its relation to motor performance, we measured, in 13 nondemented PD patients and 10 normal control subjects, simple reaction time (SRT) and(More)
Diffusional kurtosis imaging (DKI) is a clinically feasible extension of diffusion tensor imaging that probes restricted water diffusion in biological tissues using magnetic resonance imaging. Here we provide a physically meaningful interpretation of DKI metrics in white matter regions consisting of more or less parallel aligned fiber bundles by modeling(More)
In this paper a new method is presented for the relative assessment of brain iron concentrations based on the evaluation of T2 and T2*-weighted images. A multiecho sequence is employed for rapid measurement of T2 and T2*, enabling calculation of the line broadening effect (T2'). Several groups have failed to show a correlation between T2 and brain iron(More)
Quantitative determination of cerebral blood volume (CBV) is important for understanding brain physiology and pathophysiology. In this work, a novel approach is presented for accurate measurement of absolute CBV (aCBV) using vascular-space-occupancy (VASO) MRI, a blood-nulling pulse sequence, in combination with the T(1) shortening property of Gd-DTPA. Two(More)
PURPOSE To investigate non-Gaussian water diffusion using diffusional kurtosis imaging (DKI) to assess age effects on gray matter (GM) and white matter (WM) microstructural changes in the prefrontal cortex (PFC) of adolescents with attention-deficit hyperactivity disorder (ADHD) compared to typically developing controls (TDC). MATERIALS AND METHODS In(More)