Evaluation of cartilage repair tissue after biomaterial implantation in rat patella by using T2 mapping.

To evaluate the ability of MR T2 mapping (8.5 T) to characterize ex vivo longitudinally, morphologically and quantitatively, alginate-based tissue engineering in a rat model of patellar cartilage chondral focal defect. Calibrated rat patellar cartilage defects (1.

Effect of proteoglycan depletion on T2 mapping in rat patellar cartilage.

Purpose: To evaluate experimentally the sensitivity of T2 mapping with magnetic resonance (MR) imaging at 8.5 T in depicting variations in proteoglycan content and concurrent extracellular matrix of rat patellar cartilage.

Materials And Methods: The study was performed in 36 immature (age, 5 weeks) and 36 mature (age, 10 weeks) Wistar rats.

T2 mapping: an efficient MR quantitative technique to evaluate spontaneous cartilage repair in rat patella.

Objective: To evaluate the ability of T2 mapping on an 8.5 T imager to characterize morphologically and quantitatively spontaneous repair of rat patellar cartilage following full thickness defect.

Methods: Patellar cartilage defects were created in 24 rats knees on D0.

The biochemical content of articular cartilage: an original MRI approach.

The MR aspect of articular cartilage, that reflects the interactions between protons and macromolecular constituents, is affected by the intrinsic tissue structure (water content, the content of matrix constituents, collagen network organization), imager characteristics, and acquisition parameters. On the T1-weighted sequences, the bovine articular cartilage appears as an homogeneous tissue in high signal intensity, whatever the age of animals considered, whereas on the T2-weighted sequences, the articular bovine cartilage presents variations of its imaging pattern (laminar appearance) well correlated to the variations of its histological and biochemical structure. The T2 relaxation time measurement (T2 mapping), which reflects quantitatively the signal intensity variations observed on T2 weighted sequences, is a way to evaluate more precisely the modifications of cartilage structure during the aging and maturation processes (rat's study).

T2 mapping of rat patellar cartilage.

Purpose: To investigate the usefulness of magnetic resonance (MR) T2 mapping in characterizing the evolution of cartilage matrix content and thickness during the maturation and aging process.

Materials And Methods: Patellae from four groups of rats aged 4 weeks, 8 weeks, 4 months, and more than 6 months ("old rats") were studied ex vivo with an 8.5-T microimager.

Bone labelling on micro-magnetic resonance images.

The study of trabecular bone is receiving increasing interest within the medical community working in the field of skeletal diseases, such as osteoporosis. Quantification of trabecular bone structure usually requires as a starting point a correct segmentation of the trabecular network. We have developed a probabilistic relaxation labelling technique, which uses local features of the trabecular bone images to improve segmentation.

In vitro magnetic resonance microimaging of experimental osteoarthritis in the rat knee joint.

Objective: To visualize articular changes during iodoacetate induced osteoarthritis (OA) of the rat knee using high resolution magnetic resonance imaging (MRI).

Methods: All images were acquired on a 8.5T microimager on ex vivo rat knees.

Q optimization of RF inductors for use in NMR probes.

Radiofrequency inductors are important components of many NMR probe circuits, and a high quality factor Q of these inductors is necessary to achieve good signal-to-noise ratios. We have designed high Q inductors using an optimum coil diameter to coil length ratio of the order of 2.54.

Parallel-plate split-conductor surface coil: analysis and design.

A split-conductor circular parallel-plate resonator with one end shorted to ground can be used to one's advantage as a surface coil for NMR imaging experiments. It can be easily constructed by a printed-circuit method and possesses a relatively high loaded Q with negligible frequency detuning. From the proposed equivalent circuit, an equation was derived that relates the self-resonance frequency of the resonator to the split distance measured from a reference point.

A UHF probe for NMR micro-imaging experiments.

A long solenoid is capable of producing, at least theoretically, a B1 field that is relatively more homogeneous than other known structures. This paper describes the design of a UHF probe incorporating a one-turn solenoid associated with a pair of parallel-plate transmission line feeders and presents a practical example used in a 360-MHz spectrometer for micro-imaging experiments. Numerical evaluation of the solenoid inductance using King's method for direct calculation of elliptic integrals is also included.

Automatic NMR field-frequency lock-pulsed phase locked loop approach.

A self-contained deuterium frequency-field lock scheme for a high-resolution NMR spectrometer is described. It is based on phase locked loop techniques in which the free induction decay signal behaves as a voltage-controlled oscillator. By pulsing the spins at an offset frequency of a few hundred hertz and using a digital phase-frequency discriminator this method not only eliminates the usual phase, rf power, offset adjustments needed in conventional lock systems but also possesses the automatic pull-in characteristics that dispense with the use of field sweeps to locate the NMR line prior to closure of the lock loop.