Search PubMed⌕ Search
Home/Archive/PubMed

PubMed · 8170302

Permeability estimation from T1 mapping.

B Issa·P Mansfield
View original source ↗Export metadata ↓

Abstract

Fluids permeating a solid matrix can interact strongly with the pores in which they are contained. Enhanced relaxation behaviour over that of the bulk water can ensue due to the presence of paramagnetic centres or to exchange with bound water at the pore surface. In the latter case, the ratio of pore surface to the pore volume is effective in the relaxation behaviour. NMR provides an effective tool for investigating the solid matrix properties (e.g., pore size distribution) via indirect measurement of the fluid NMR parameters. In addition to spin density, we use T1 mapping to provide an estimate of the specific permeability of sandstone for a few samples.

Explore related subjects

Echo-Planar ImagingMagnetic Resonance SpectroscopyPermeabilityPorosityWaterJournal ArticleResearch Support, Non-U.S. Gov't

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

B Issa, P Mansfield. 1994. Permeability estimation from T1 mapping.. https://doi.org/10.1016/0730-725x(94)91519-9

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed1998

Non-invasive mapping of placental perfusion.

BACKGROUND: We aim to develop a clinical technique for the non-invasive measurement of placental perfusion, to enable early detection of intrauterine growth restriction (IUGR). Pregnancies with this complication are characterised by low placental perfusion. METHODS: We measured placental perfusion by means of perfusion-sensitive echoplanar imaging (EPI); a rapid method of making magnetic resonance images. Perfusion measurements were done on six healthy volunteers with normal pregnancies and nine with pregnancies complicated by IUGR. Perfusion maps were created to assess the relation between placental perfusion and fetal size at birth. FINDINGS: Pregnancies complicated by IUGR differed significantly from normal pregnancies in patterns of perfusion within the placenta (p<0.0001, ANOVA). Subsequent analysis showed that the proportion of placentas with low perfusion rates was higher in the IUGR group than in the normal group. A significant correlation between areas of reduced placental perfusion and fetal size was demonstrated (p=0.041, Spearman's rank correlation). INTERPRETATION: Non-invasive imaging of placental perfusion by means of EPI has potential as a clinical tool in assessing the dynamics of placental perfusion.

Echo-Planar Imaging↗
PubMed1998

Radial echo-planar imaging.

A new ultrafast magnetic resonance imaging pulse sequence named radial echo-planar imaging (rEPI) is introduced. The sequence is based on a modification of the echo-planar imaging (EPI) sequence to scan k-space radially, in an attempt to combine the speed of EPI with the benefits of radial sampling. Like in EPI, all the desired lines in k-space are scanned consecutively in opposite directions. The unique feature of this new sequence, however, is that the orientation of the readout gradient is incrementally rotated, so that all the echoes are refocused through the center of k-space. Therefore, rEPI data are acquired in a polar grid, and image reconstruction can be done either by means of filtered back-projection or by regridding the data to a Cartesian matrix followed by 2D Fourier transform. First results show that rEPI images can be acquired with the same speed and signal-to-noise ratio of EPI images. rEPI images are also shown to be less sensitive to off-resonance effects than EPI images. Further studies are underway to investigate the usefulness of rEPI for spectroscopic imaging and applications affected by motion.

Echo-Planar Imaging↗
PubMed1998

Echo-planar imaging relaxometry to measure the viscosity of a model meal.

A method for measuring noninvasively the viscosity of a polysaccharide model meal using the known relationship between relaxation times and polysaccharide concentration in solution in vitro is presented. The aim is to develop a method for monitoring digesta viscosity in vivo, using EPI to capture the motion of the gastrointestinal lumen. The transverse relaxation rate T-12 of locust bean gum solutions was calibrated against the zero-shear viscosity at 37 degreesC. Differences in viscosity were distinguished significantly using T-12 measurements. T-12 and viscosity were insensitive to exposure to gastric juice and changes in pH, and the model meal was well received by volunteers and provided good contrast in vivo in EPI images. Therefore it would be possible to use this method to monitor the changes in meal viscosity within the gastric lumen in vivo.

Echo-Planar Imaging↗