Biomedical subjects

V Jellús

Publications and source records attributed to V Jellús.

4 recordsLinked to original sources

PubMed2000

Short-TE projection reconstruction MR microscopy in the evaluation of articular cartilage thickness.

The aim of this study was to assess the potential of projection-reconstruction (PR) MR microscopy in the accurate measurement of cartilage thickness. Short-TE PR microimages were acquired at 7.05 T on bone-cartilage cylindrical plugs excised from four regions of two disarticulated femoral heads (i. e. superior, inferior, posterior and anterior), using an NMR instrument equipped with a microimaging accessory. The PR microimages were then correlated with conventional spin-echo (SE) microimages and with histology. On PR microimages, acquired with an echo time of 3.2 ms, the cartilage signal was increased, allowing an accurate delineation of the cartilage from the tidemark/cortical bone region. As a consequence, by the PR method a more precise measurement of cartilage thickness compared with that performed by the conventional SE approach was feasible. An excellent correlation between PR microimages and histology was also obtained (r = 0.90). By the proposed method it is possible to accurately determine the cartilage thickness better than with the conventional SE sequences.

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PubMed1998

Motion artifacts reduction in DWI using navigator echoes: a robust and simple correction scheme.

NMR signal phase variation caused by macroscopic motion of an object during application of the diffusion gradient is a well-known effect in diffusion-weighted imaging (DWI) using the standard pulsed gradient spin-echo sequence (PGSE). This phase error causes severe ghost artifacts in the output image when phase encoding techniques, such as two dimensional Fourier transform (2DFT) imaging, are used. One possible way to eliminate the motion effects is the navigator echo technique. The method is based on estimating the phase error from the navigator echo and using it for the correction of the image echo. The phase errors (zero and first order) for the phase correction of the image echo are usually evaluated from the navigator echo after Fourier transform (FT) in the readout direction, correcting for both translation and rotation. We present here a simple algorithm which enables evaluation and correction in the time domain of phase errors induced by motion. This approach has the advantage of improved correction of motional artifacts and minimized sensitivity to noise and inaccurate setting up of the experiment.

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PubMed1998

Correlation between biochemical composition and magnetic resonance appearance of articular cartilage.

OBJECTIVE: The objective of this study was to find a correlation between magnetic resonance (MR) appearance and biochemical composition of the normal articular cartilage by comparing the laminar aspects with the distribution of the two principal matrix components: proteoglycans and collagen. DESIGN: T2-weighted MR microimages of porcine cartilage-bone plugs, excised from both the habitually loaded and habitually unloaded regions of the proximal end of the humerus, were obtained using a spin-echo sequence. Proteoglycans (PGs) were monitored by histology and by measuring the uronate and the sulfur content of the tissue; a histologic method and the chemical determination of hydroxyproline were used for the evaluation of the collagen content. RESULTS: The 'loaded' cartilage exhibited the expected MR laminar appearance whereas the 'unloaded' tissue appeared to be more homogeneous. The PG content in the 'loaded' cartilage, was found to be 2.4 times higher than in the habitually unloaded tissue, exhibiting an increasing trend from the articular surface to the bone. In the 'unloaded' cartilage the uronate distribution was more uniform with a higher concentration in the intermediate zone. The mean collagen content of both cartilage regions was found to be about 39% of the tissue dry weight. Histology and hydroxyproline distribution pattern showed that collagen was particularly concentrated at the surface and in a central zone of the 'loaded' cartilage whereas in the 'unloaded' tissue collagen was evident only at the surface. In accordance with the collagen distribution, transverse relaxation (T2) times in 'loaded' cartilage showed a minimum value at the articular surface and another minimum in a central region. On the contrary, the average T2 value of the 'unloaded' tissue was high at the surface and decreased rapidly in the deeper zones. CONCLUSION: These results demonstrate that the MR appearance of articular cartilage correlates with the collagen content, but not with that of PGs, of the different zones. Other matrix components might, however, influence the MR appearance by contributing to the macromolecular organization of the tissue.

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PubMedDate not supplied

Short-TE projection reconstruction NMR microscopy of trabecular bone.

The aim of this study was to assess the potential of projection reconstruction (PR) NMR microscopy in the quantitative evaluation of trabecular bone architecture. Short-TE PR spin-echo microimages were acquired at 7.05 T on normal bone explants. The main structural parameters such as bone volume fraction (BVF), trabecular thickness (Tb.Th.) and trabecular separation (Tb.Sp.) were obtained from the 3D microimages using the method of directed secants. Quantitative structural data were then compared with those derived from conventional spin-echo microimages. Our study indicates that projection reconstruction NMR microscopy promises to be more accurate than the conventional FTI method in the analysis of trabecular bone.

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