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Nuclear Magnetic Resonance for Diffusion Imaging Development and evaluation of spin-echo-based pulse sequences for in vivo studies of water self-diffusion

Brockstedt, Sara, (författare)
Lunds universitet, Lund University, Medicinska fakulteten, Faculty of Medicine, Institutionen för kliniska vetenskaper, Lund, Department of Clinical Sciences, Lund, Sektion V, Section V, Medicinsk strålningsfysik, Lund, Medical Radiation Physics, Lund
ISBN 91-628-3234-4
Department of Radiation Physics, Lund university, 1998
Engelska 78 s.
  • Doktorsavhandling (övrigt vetenskapligt)
Abstract Ämnesord
  • The interest in diffusion imaging with nuclear magnetic resonance techniques has increased during the last few years. The main reason is the possibility of early diagnosis of acute ischaemic stroke, at a time when conventional MR techniques and computerised tomography fail. The purpose of this study was to develop and evaluate methods for the measurement of water self-diffusion <i>in vivo</i> using magnetic resonance imaging (MRI). The main objective was to design pulse sequences that allow quantification of the diffusion coefficient, and provide diffusion-weighted (DW) images of high quality. DW-MRI is highly sensitive to macroscopic motion, which causes severe image artifacts and makes quantification difficult. This problem was addressed through pulse sequence design and image post-processing techniques. The use of first-order motion-compensating diffusion-encoding gradients in combination with DW spin-echo (SE) imaging proved to increase image quality and accuracy in quantitative data. Further more, quantitative diffusion imaging was found to be possible with fast-SEs, a method that does not require any high-performance gradient systems. Using a segmented echo-planar imaging (SEPI) technique high-resolution DW-images and ADC maps were obtained, showing no proof of susceptibility artifacts or geometrical distortions, problems normally associated with EPI. Navigator-echo phase-corrections were found to reduce motion artifacts present in images obtained with SE, FSE and SEPI techniques. The use of electro-cardiographic triggering for DW-EPI was also evaluated, and found to be relevant in quantitative measurements. Assessment of the perfusion fraction <i>in vivo</i> from DW-images might be helpful in diagnosis and characterisation of acute stroke and can be performed whenever enough data are available. Finally, the performance of DW-SE and DW-EPI for diagnosis of ischaemic stroke in the acute phase was evaluated. DW-EPI and DW-SE in combination with ADC maps were compared with respect to diagnostic accuracy. It was found that although DW-SE methods suffer from limited diffusion sensitivity and limited numbers of slices, it can be used for diagnosis of acute stroke, but ADC maps are essential in discriminating between acute and chronic infarcts.


MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Radiologi och bildbehandling (hsv//swe)
MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Radiology, Nuclear Medicine and Medical Imaging (hsv//eng)


perfusion fraction
electrocardiographic triggering
segmented EPI (SEPI)
echo-planar imaging (EPI)
fast spin-echo (FSE)
spin-echo (SE)
navigator echoes
phase corrections
Magnetic resonance
ischaemic stroke
Medicine (human and vertebrates)
Medicin (människa och djur)

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Brockstedt, Sara
Om ämnet
och Klinisk medicin
och Radiologi och bi ...
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Lunds universitet

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