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Cerebral small vessel disease (SVD) is a common accompaniment of ageing. Features seen on neuroimaging include recent small subcortical infarcts, lacunes, white matter hyperintensities, perivascular spaces, microbleeds, and brain atrophy. SVD can present as a stroke or cognitive decline, or can have few or no symptoms. SVD frequently coexists with(More)
Echo-planar imaging (EPI) is an ultrafast magnetic resonance (MR) imaging technique prone to geometric distortions. Various correction techniques have been developed to remedy these distortions. Here improvements of the point spread function (PSF) mapping approach are presented, which enable reliable and fully automated distortion correction of echo-planar(More)
OBJECTIVE To determine whether proton MRS (1H MRS) can detect long-term metabolite abnormalities in abstinent methamphetamine users. BACKGROUND Methamphetamine is toxic to dopaminergic and serotonergic neurons in rodents; however, little data are available on the toxic effects of methamphetamine on the human brain. METHODS 1H MRS was performed in 26(More)
Subject motion and associated artefacts limit the applicability of MRI and the achievable quality of the images acquired. In this paper, a fully integrated method for prospective correction of arbitrary rigid body motion employing an external motion tracking device is demonstrated for the first time. The position of the imaging volume is updated prior to(More)
OBJECTIVES To evaluate the neural correlates of attention and working memory deficits in patients with HIV-1. METHOD fMRI was used to evaluate brain activity in 11 patients with HIV and 11 age-, sex-, education-, and handedness-matched seronegative subjects, while performing a battery of tasks that required different levels of attention for working(More)
A new functional imaging method has been developed and used to measure T2*- and initial intensity (I0)-parameter maps of multiple slices during activation of the cortex with high temporal resolution. Multiple echo-planar images (EPIs) are read out after a single excitation of the spin system, leading to several images with increasing effective echo times.(More)
OBJECTIVE To determine whether cerebral metabolite abnormalities normalize with highly active antiretroviral therapy (HAART). BACKGROUND Patients with HIV-cognitive motor complex (HIV-CMC) show cerebral metabolite abnormalities in the early stages of dementia. METHODS Sixteen patients with HIV-CMC were evaluated before and after HAART, and compared with(More)
The dominant view that perceptual learning is accompanied by changes in early sensory representations has recently been challenged. Here we tested the idea that perceptual learning can be accounted for by reinforcement learning involving changes in higher decision-making areas. We trained subjects on an orientation discrimination task involving feedback(More)
Single-shot echo planar imaging (EPI) acquisitions at 7T are challenging due to increased distortions, signal dropouts, RF-power requirements, and reduced T2*. This study developed and tested pulse sequence and protocol modifications required to allow high resolution EPI for whole brain functional neuroimaging. Using geometric distortion correction methods,(More)
This study aims to determine possible persistent abnormalities in regional cerebral blood flow (relative rCBF) and cognitive function in abstinent methamphetamine (METH) users. Twenty METH-dependent subjects (abstinent for 8+/-2 months) and 20 age- and gender-matched controls were evaluated with perfusion magnetic resonance imaging (pMRI) and(More)