Abstract
Our aim was to decrease geometric distortion artifact in DWI on brain by using different MR techniques such as ramp sampling and parallel imaging. The study was done on 15 patients, They were subject to routine brain MRI examination for different symptoms, examination was done on 1.5 T scanner, patients were divided to three group five patient in each group, geometric distortion in frontal and occipital lobe measured in the routine acquired DWI and after used the interested strategy compared to anatomical T2-FSE acquired in the routine examination then reduction percentage for each strategy was calculated. Application of parallel technique imaging showed significant artifact reduction in frontal lobe with approximately 54.36 % and about 34.8% in occipital lobe, while ramp sampling showed reduction with approximately 19% in frontal lobe and reduced artifact by 41.58% in the occipital lobe.
 
 Finally we conclude that using new techniques such as ramp sampling and parallel imaging used with EPI data acquisition reduced geometric distortion artifact and increased geometric resolution.
Highlights
Magnetic field gradient was used in diffusion MRI to generate brain image and considered as the clinical domain routine when (Echo Planar Imaging) was available on MRI devices [1]
As seen in figure (5) DWI acquired without ramp sampling (B) suffer from blurring and low resolution unlike image (C) that acquired with ramp sampling which shows increase in resolution, better contrast between different tissue and incensement in signal strength
Figure (15) shows the second case in this group, we showed that using ramp sampling decrease geometric distortion artifact in EPI-DWI, using both techniques together (15- C) shows more reduction in this artifact in addition to increase in resolution
Summary
Magnetic field gradient was used in diffusion MRI to generate brain image and considered as the clinical domain routine when (Echo Planar Imaging) was available on MRI devices [1]. Mapping of water molecules Diffusion MRI non-invasively (magnetic resonance imaging) helps in imaging of brain microstructural characteristics in-vivo [2]. Two sharp intense magnetic fields were used to generate MR signals which are very sensitive to water movements [2]. Diffusion-weighted magnetic resonance imaging uses echo-planner technique as gold standard procedure imaging in MRI of brain [3]. The main disadvantage of EPI is artifact caused by main magnetic field inhomogeneity as investigated by many clinical [4], [5], [6].This artifacts is major problem in air rich tissues or air edges which separates bones and muscles this artifact is known as susceptibility distortion [7], [8]. It was recognized that maximum error happen in phase encoding direction which generated by phase-encoding steps [11]
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