Journal of magnetic resonance imaging : JMRI
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J Magn Reson Imaging · Jun 2005
Quantitative perfusion measurements using pulsed arterial spin labeling: effects of large region-of-interest analysis.
To study arterial spin labeling (ASL) MRI techniques and to investigate various problematic issues that still hinder the accurate and robust quantitative analysis of ASL data. ⋯ Analysis of ASL data based on a large ROI may suffer from inaccuracies arising from a distribution of transit times, implying that averaging of ASL kinetic data over such regions should therefore be avoided. When possible, a PBP fit should be performed.
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J Magn Reson Imaging · Jun 2005
Comparative StudyHigh-dose Gd-DTPA vs. Bis-Gd-mesoporphyrin for monitoring laser-induced tissue necrosis.
To compare Bis-Gd-mesoporphyrin (Bis-Gd-MP), a contrast agent with a reported high affinity to necrotic tissue, with high-dose gadopentate dimeglumin (Gd-DTPA) for defining laser-induced muscle and liver necrosis by contrast-enhanced (CE) MRI. ⋯ Bis-Gd-MP and Gd-DTPA are equally well suited for postinterventional lesion assessment in LITT.
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In view of recent applications in cardiovascular and functional brain imaging, this work revisits the basic performance characteristics of spiral imaging in direct comparison to echo-planar imaging (EPI) and conventional rapid gradient-echo imaging. Using both computer simulations and experiments on phantoms and human subjects at 2.9 T, the study emphasizes single-shot applications and addresses the design of a suitable trajectory, the choice of a gridding algorithm, and the sensitivity to experimental inadequacies. ⋯ Moreover, when ignoring parallel imaging strategies that are also applicable to EPI, improvements of image quality via reduced acquisition periods are only achievable by interleaved multishot spirals because partial Fourier sampling and rectangular fields of view (FOVs) cannot be exploited for non-Cartesian trajectories. Taken together, while spiral imaging may find its niche applications, most high-speed imaging needs are more easily served by EPI.
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J Magn Reson Imaging · Jun 2005
Dynamic susceptibility contrast perfusion imaging of radiation effects in normal-appearing brain tissue: changes in the first-pass and recirculation phases.
To identify radiation-induced changes in the cerebral vasculature of healthy tissue in the first four months following radiotherapy through the analysis of dynamic-susceptibility contrast perfusion imaging. ⋯ The observed results suggest a dose-dependent decline in vessel density and increase in vascular permeability and/or tortuosity in irradiated normal-appearing brain tissue at two months following radiotherapy.