1,720,984 research outputs found
Projection reconstruction MR microscopy for the ex vivo evaluation of trabecular bone structure
No full textRole inversion in magnetization exchange between water and macromolecular protons in articular cartilage components at different hydration levels
No full textCondrocyte-alginate bioconstructs: A nuclear magnetic resonance relaxation study
No full textProton nuclear magnetic resonance (NMR)
relaxometry can give informations about hydrogel scaffold
properties. As these properties can be modified with
culture time and conditions according to scaffold biodegradability
and new tissue biosynthesis, the aim of this
research was to test the efficiency of this noninvasive
NMR technique in the follow-up of 3D cultures for tissue
engineering. The distributions of proton relaxation times
T1 and T2 have been measured on cylindrical gel samples
of different types of alginate, in the presence or absence
of hyaluronate, in gels or bioconstructs with encapsulated
chondrocytes cultured for 30 days in normal or
reduced weight conditions. It was found that T2 increases
with the mannuronate/guluronate ratio in alginate samples
and with the presence of hyaluronate. The distributions
of both T1 and T2 result wider for bioconstructs cultured
in normal gravity than for those cultured in
reduced weight conditions. Neither cell growing nor collagen
production but only GAG neosynthesis have been
demonstrated in our experimental conditions. In conclusion,
T2 is sensitive to the gel properties (possibly to the
rigidity of macromolecular components). The homogeneity
of bioconstructs can be monitored by the distribution
of T1 and T2. We propose that nonspatially resolved
NMR relaxometry can efficiently be used in monitoring
tissue development in a biodegradable scaffold for tissue
engineering
Comparison of μCT and high-resolution MRI approaches in the assessment of trabecular bone structure
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Detection and Quantitation of Phosphorus Metabolites in Crude Tissue Extracts by 1H and 31P NMR: Use of Gradient Assisted 1H-31P HMQC Experiments, with Selective Pulses, for the Assignment of Less Abundant Metabolites
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DEGENERATIVE CHANGES OF PORCINE INTERVERTEBRAL DISC INDUCED BY ENDPLATE INJURIES
No full textSTUDY DESIGN: Graded endplate injuries were performed in porcine lumbar discs. The effects of such injuries were compared to control animals in which a sham operation was performed. OBJECTIVES: To investigate the effects of endplate injuries on disc tissue. SUMMARY OF BACKGROUND DATA: Studies have shown that injuries of vertebral endplates are frequently found at autopsy. However, little is known on the effects of acute injuries of vertebral endplates in vivo. METHODS: Ten domestic pigs were included in the study group. Under general anesthesia, the lower three discs of the lumbar spine were exposed and randomly submitted to multiple endplate injuries, isolated endplate injury, and no treatment. A sham operation was performed in 5 pigs used as control group. Animals were killed 7 months after surgery and the harvested lumbar spine submitted to MRI investigations, histologic, and biochemical analysis. RESULTS: MRI showed that all but one discs treated with multiple endplate injuries were markedly degenerated while, of the discs treated with an isolated injury, one was markedly degenerated, five slightly degenerated and two were normal (P = 0.01). Histologic analysis showed severe changes in discs treated with multiple injuries. In those who had an isolated injury, changes were less severe and essentially limited to the posterior anulus or the inner anterior anulus. Biochemical analysis showed an inverse correlation between uronate content in the nucleus pulposus and severity of endplate injuries. CONCLUSIONS: Injuries of vertebral endplates in porcine discs were found to cause degenerative changes in the disc tissue on MRI, histologic, and biochemical investigations. The severity of such degenerative changes was related to the severity of endplate injuries. Injuries of vertebral endplate may be one of the pathomechanisms leading to early changes in the disc matrix and eventually to abnormal biomechanical behavior of the whole disc. The present animal model seems to be a suitable experimental model for disc degeneratio
Segmentation of magnetic resonance microimages of trabecular bone: classifiers and markov random field model
No full textArchitettura trabecolare in vertebre di ratto mediante 3D-μ-MRI e nuovo metodo di segmentazione a soglia variabile
No full textLa microarchitettura dell’osso trabecolare è stata tradizionalmente studiata mediante tecniche di microscopia ottica ed elettronica a scansione [1,2], mentre i parametri strutturali sono determinati tramite misure stereologiche [3]. Recentemente si sono rese disponibili tecniche ad alta risoluzione 3D per misure non distruttive quali la micro-computed tomography (μ-CT) e la micro-Magnetic Resonance Imaging (μ-MRI). Applicate a piccoli animali, queste tecniche forniscono una risoluzione spaziale tale che le dimensioni del voxel risultano più piccole delle strutture da esaminare, fornendo la possibilità di analisi quantitative con parametri in grado di descrivere la complessa struttura 3D dell’osso trabecolare.
In particolare, studi a Risonanza Magnetica Nucleare (NMR) del tessuto osseo stanno assumendo sempre maggiore importanza sia ex vivo che in vivo.
In questo studio sono state analizzate vertebre lombari di ratto con μ-MRI 3D ad una risoluzione spaziale apparente di (20 μm)3.
La segmentazione delle immagini, necessaria per la determinazione quantitativa dei parametri strutturali nei volumi di interesse selezionati, è stata realizzata utilizzando un nuovo metodo semi-quantitativo a soglia variabile [4]. Le eterogeneità strutturali così ottenute entro la vertebra sono state validate mediante confronto con μ-CT
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