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R Luypaert

Publications and source records attributed to R Luypaert.

42 records · Page 3Linked to original sources
PubMedDate not supplied

In vivo comparison of MR phase distribution and 1/T2* with morphologic parameters in the distal radius.

A new approach based on the calculation of the phase variance in a region of interest on the phase images of a simple gradient echo sequence, was used to assess the properties of trabecular bone in the distal radius. The phase variance reflects the distribution of field inhomogeneities due to the difference in magnetic susceptibility between bone and marrow in a way similar to T2*. However, the phase variance monitors the intervoxular differences, whereas T2* studies the intravoxular inhomogeneities. In this study of the radius of seven volunteers, both techniques were compared with parameters characterizing trabecular bone structure derived from high resolution MR images. Parameters such as the apparent bone area fraction, trabecular number, thickness and spacing, and box-counting fractal dimension were determined.

Adult↗
PubMedDate not supplied

Absolute quantification of 31P liver metabolites in rat using an external reference and a surface spoiling magnetic field gradient.

A simple method for measuring absolute concentrations of 31P metabolites in rat liver using an external reference is described. It neutralizes systematic errors due to conductive losses by calibration of the matching capacitor and selects liver signals via an electrically driven, surface spoiling magnetic field gradient. The technique avoids the chemical shift problems associated with linear field gradient localization methods at 4.7 T and allows combination with the double standard method for absolute metabolite concentration determination. Application of the method to the in vivo measurement of the absolute concentrations of ATP and P(i) in eight rat livers yields results that are in good agreement with literature values. Absolute phosphomonoester concentrations were also obtained, but no literature data were available.

Adenosine Triphosphate↗
PubMedDate not supplied

Fat fraction of lumbar bone marrow using in vivo proton nuclear magnetic resonance spectroscopy.

Localized proton spectra of the human lumbar vertebral body were recorded in vivo at 1.5 T, using the STEAM (stimulated echo acquisition mode) pulse sequence. Thirty-seven patients (18 men, 19 women) were examined, ranging in age from 21 to 68 years (mean = 40, SD = 13). The fat fraction of the bone marrow was calculated from the areas of the fat and water peaks in the spectrum. The results demonstrate that, in the course of aging, there is a systematic increase in measured fat percentage of about 7% per decade of age. No sex difference could be established on the basis of our results.

Adult↗