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Correction of geometrical distortions and determination of ADC in diffusion sensitive EPI

Borg, Mikael (1998)
Medical Physics Programme
Abstract (Swedish)
Diffusion is a molecular phenomenon and can be described as the process by which matter is transported from one part of a system to another as a result of random molecular motion. The diffusion coefficient is then a quantity that describes the mobility of the molecules in a media. In recent years, methods have been developed to image the diffusion of water in human tissue using magnetic resonance tomography. In tissue, e.g. cellular barriers restrict diffusion. The measured quantity is therefor called apparent diffusion coefficient (ADC). By acquiring a series of images with different diffusion weighting parameters, it is possible to construct an image mapping the ADC. A fast imaging method is requiered and at Lund University Hospital, the... (More)
Diffusion is a molecular phenomenon and can be described as the process by which matter is transported from one part of a system to another as a result of random molecular motion. The diffusion coefficient is then a quantity that describes the mobility of the molecules in a media. In recent years, methods have been developed to image the diffusion of water in human tissue using magnetic resonance tomography. In tissue, e.g. cellular barriers restrict diffusion. The measured quantity is therefor called apparent diffusion coefficient (ADC). By acquiring a series of images with different diffusion weighting parameters, it is possible to construct an image mapping the ADC. A fast imaging method is requiered and at Lund University Hospital, the echo planar pulse sequence is used (EPI). The method involves strong magnetic gradients that are rapidly switched on and off. This results in eddy currents in the object to be depicted. The eddy currents alter the magnetic field, resulting in geometric distortions in the images. In this work, a computer program that implements an algorithm that corrects the geometrical distortions has been written, and another program that calculate and map the ADC. (Less)
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author
Borg, Mikael
supervisor
organization
year
type
H2 - Master's Degree (Two Years)
subject
keywords
MRI
language
English
id
2156917
date added to LUP
2011-09-13 15:25:59
date last changed
2011-09-13 15:25:59
@misc{2156917,
  abstract     = {Diffusion is a molecular phenomenon and can be described as the process by which matter is transported from one part of a system to another as a result of random molecular motion. The diffusion coefficient is then a quantity that describes the mobility of the molecules in a media. In recent years, methods have been developed to image the diffusion of water in human tissue using magnetic resonance tomography. In tissue, e.g. cellular barriers restrict diffusion. The measured quantity is therefor called apparent diffusion coefficient (ADC). By acquiring a series of images with different diffusion weighting parameters, it is possible to construct an image mapping the ADC. A fast imaging method is requiered and at Lund University Hospital, the echo planar pulse sequence is used (EPI). The method involves strong magnetic gradients that are rapidly switched on and off. This results in eddy currents in the object to be depicted. The eddy currents alter the magnetic field, resulting in geometric distortions in the images. In this work, a computer program that implements an algorithm that corrects the geometrical distortions has been written, and another program that calculate and map the ADC.},
  author       = {Borg, Mikael},
  keyword      = {MRI},
  language     = {eng},
  note         = {Student Paper},
  title        = {Correction of geometrical distortions and determination of ADC in diffusion sensitive EPI},
  year         = {1998},
}