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Peter van Gelderen

Publications and source records attributed to Peter van Gelderen.

25 records · Page 2Linked to original sources
PubMed2002

Design of a SENSE-optimized high-sensitivity MRI receive coil for brain imaging.

An 8-channel receive-only detector array was developed for SENSE MRI of human brain. The coil geometry was based on a gapped element design and used ultra-high impedance preamplifiers for mutual decoupling of the elements. Computer simulations of the electric and magnetic fields showed that excellent signal-to-noise ratio (SNR) and SENSE performance could be achieved by placing the coil elements close to the head and maintaining a substantial gap between the elements. Measurements with a 1.5 T prototype coil showed a 2.7-fold improvement of the SNR averaged over the brain compared to a conventional quadrature birdcage receive coil and an average geometrical noise amplification factor (g-value) of 1.06 and 1.38 for rate-2 and rate-3 SENSE, respectively.

Brain↗
PubMed2002

Imaging cortical anatomy by high-resolution MR at 3.0T: detection of the stripe of Gennari in visual area 17.

The brain can be parcellated into numerous anatomical and functional subunits. The classic work by Brodmann (Vergleichende Lokalisationslehre der Grosshirnrinde in ihren Prinzipien dargestellt auf Grund des Zellenbaues. Leipzig: Barth; 1909) identified areas of the cerebral cortex based on histological differences. An alternative to his cytoarchitectonic approach is the myeloarchitectonic approach. MRI has excellent white/gray matter contrast in the brain due to the presence of myelin, and thus seems uniquely suited for in vivo studies of cortical myeloarchitecture. Here it is demonstrated that the stripe or stria of Gennari can be consistently detected in human occipital cortex. T(1)-weighted images obtained at 3T from six of 10 normal volunteers, with resolutions of 350 x 350 x 600 mu clearly demonstrate this myelin-rich intracortical layer. It is concluded that the striate cortex (area 17 of Brodmann) of the human brain can be delineated in vivo on T(1)-weighted images, potentially enabling detection of specific cortical boundaries within individual brains.

Brain Mapping↗
PubMed2002

Application of sensitivity-encoded echo-planar imaging for blood oxygen level-dependent functional brain imaging.

The benefits of sensitivity-encoded (SENSE) echo-planar imaging (EPI) for functional MRI (fMRI) based on blood oxygen level-dependent (BOLD) contrast were quantitatively investigated at 1.5 T. For experiments with 3.4 x 3.4 x 4.0 mm(3) resolution, SENSE allowed the single-shot EPI image acquisition duration to be shortened from 24.1 to 12.4 ms, resulting in a reduced sensitivity to geometric distortions and T(*)(2) blurring. Finger-tapping fMRI experiments, performed on eight normal volunteers, showed an overall 18% loss in t-score in the activated area, which was substantially smaller than expected based on the image signal-to-noise ratio (SNR) and g-factor, but similar to the loss predicted by a model that takes physiologic noise into account.

Brain↗
PubMed2002

Reduction of gradient acoustic noise in MRI using SENSE-EPI.

A new approach to reduce gradient acoustic noise levels in EPI experiments is presented. Using multichannel RF receive coils, combined with SENSE data acquisition and reconstruction, gradient slew-rates in single-shot EPI were reduced fourfold for rate-2 and ninefold for rate-3 SENSE. Multislice EPI experiments were performed on three different scanner platforms. With 3.4 mm in-plane resolution, measuring 6 slices per second (12 slices with 2000 ms TR), this resulted in average sound pressure level reductions of 11.3 dB(A) and 16.5 dB(A) for rate-2 and rate-3 SENSE, respectively. BOLD fMRI experiments, using visually paced finger-tapping paradigms, showed no detrimental effect of the acoustic noise reduction strategy on temporal noise levels and t scores.

Adult↗
PubMed2002

Reduced N-acetylaspartate in prefrontal cortex of adult rats with neonatal hippocampal damage.

Previous studies in animals suggested that neonatal lesions of the ventral hippocampus disrupt development of prefrontal cortex and its regulation of dopaminergic activity. In the present study, we assayed an in vivo chemical marker of neuronal integrity (proton magnetic resonance spectroscopy signal of N-acetylaspartate, NAA) in prefrontal cortex and striatum of rats with neonatal excitotoxic lesions of the ventral hippocampus. We also measured in post-mortem tissue expression of EAAC1 mRNA, a molecular marker of intrinsic neurons. In the cohort studied at juvenile age and again at young adulthood [postnatal day (PD) 37 and 71], we found selective reductions of NAA in the prefrontal cortex only at PD 71. Emergence of neuronal pathology was temporally associated with emergence of amphetamine-induced hyperlocomotion. Reduced prefrontal NAA was confirmed in the second cohort studied at an older age (PD 120). Expression of EAAC1 mRNA was significantly reduced in prefrontal cortex of the lesioned rats. No changes in NAA were found in the striatum in either cohort and cortical area size was not changed. These results suggest that early ventral hippocampal lesions produce developmental neuronal pathology in prefrontal cortex that is temporally associated with dysregulation of dopamine behaviors and is reminiscent of the temporal profile of the onset of schizophrenia.

Age Factors↗