Nuevas técnicas de imagen en la valoración del cartílago articular / New imaging techniques in the evaluation of joint cartilage

La resonancia magnética (RM) brinda una excelente resolución espacial para observar el cartílago y una gran definición de sus principales propiedades. Los equipos de 1,5 teslas (T) y, principalmente, los de 3 T se demuestran muy eficaces para visualizar todo el cartílago articular, y mediante el análisis de propiedades morfológicas, estructurales y físicas estratificar el daño degenerativo. La evaluación mediante RM del cartílago articular tiene una gran relevancia clínica dada la prevalencia de lesiones degenerativas y el desarrollo de nuevos medicamentos y de tratamientos de base quirúrgica. En este trabajo se analizan los avances de la cuantificación mediante RM de las propiedades del cartílago articular, en concreto, los tiempos de relajación T2 y T1, la distribución del primer paso de un medio de contraste (estudio farmacocinético) y el porcentaje de realce tardío. Mediante el empleo de secuencias específicas y técnicas de cuantificación adecuadas, la RM permite evaluar parámetros tan importantes como la superficie, el espesor y el volumen del cartílago; la intensidad de la señal y las propiedades físicas relacionadas con la integridad del colágeno y el edema; la perfusión del cartílago y la permeabilidad de membrana relacionada con la neovascularización y la presencia de áreas con realce tardío, relacionadas con la concentración de proteoglicanos. Esta información puede ayudar al diagnóstico precoz de la enfermedad, establecer el grado de afectación, valorar el pronóstico, incidir en la decisión terapéutica y evaluar la eficacia del tratamiento. El estudio de las alteraciones estructurales y funcionales del cartílago mediante RM es un excelente biomarcador de la degeneración del cartílago (AU)

Magnetic resonance (MR) imaging provides an excellent spatial resolution to visualize cartilage and define its main properties. Both 1.5 and especially 3 Tesla equipments have become very efficient in showing the whole articular cartilage and classifying the degenerative damage by analyzing morphological, structural and physical properties. MR evaluation of articular cartilage is of great clinical importance due to the prevalence of degenerative lesions and the development of new drugs and surgery-based treatments. In this work we explain the advances in the MR quantitation of the articular cartilage properties, particularly focusing on T2 and T1 relaxation times, the distribution of first-pass contrast agent (pharmacokinetic study) and late enhancement percentage. By using specific sequences and adequate measuring techniques, MR allows the evaluation of important parameters such as cartilage surface, thickness and volume; signal intensity and the physical properties related to collagen integrity and edema; cartilage perfusion and endothelial permeability related to neovascularization; and the presence of late enhancement areas, related to proteoglycan concentrations. This information will aid early diagnosis, establishment of the degree of degeneration, assessment of prognosis, definition of therapeutic options and evaluation of treatment effectiveness. The study of the cartilage structural and functional alterations by MR imaging is an excellent biomarker of tissue degeneration (AU)

[New imaging techniques in the evaluation of joint cartilage]. / Nuevas técnicas de imagen en la valoración del cartílago articular.

Magnetic resonance (MR) imaging provides an excellent spatial resolution to visualize cartilage and define its main properties. Both 1.5 and especially 3 Tesla equipments have become very efficient in showing the whole articular cartilage and classifying the degenerative damage by analyzing morphological, structural and physical properties. MR evaluation of articular cartilage is of great clinical importance due to the prevalence of degenerative lesions and the development of new drugs and surgery-based treatments. In this work we explain the advances in the MR quantitation of the articular cartilage properties, particularly focusing on T2 and T1 relaxation times, the distribution of first-pass contrast agent (pharmacokinetic study) and late enhancement percentage. By using specific sequences and adequate measuring techniques, MR allows the evaluation of important parameters such as cartilage surface, thickness and volume; signal intensity and the physical properties related to collagen integrity and edema; cartilage perfusion and endothelial permeability related to neovascularization; and the presence of late enhancement areas, related to proteoglycan concentrations. This information will aid early diagnosis, establishment of the degree of degeneration, assessment of prognosis, definition of therapeutic options and evaluation of treatment effectiveness. The study of the cartilage structural and functional alterations by MR imaging is an excellent biomarker of tissue degeneration.

In vivo trabecular bone morphologic and mechanical relationship using high-resolution 3-T MRI.

OBJECTIVE: The purpose of this study was to investigate the in vivo morphologic and elastic parameters of trabecular bone with high-resolution 3-T MRI in a healthy reference population. SUBJECTS AND METHODS: A series of wrist MR images were acquired with high-spatial-resolution (180 mum) isotropic voxels from 40 subjects without reported bone disease. After image postprocessing, the bone volume-to-total volume ratio, trabecular thickness, trabecular separation, and trabecular number were calculated in the morphologic analysis. Trabecular bone was mechanically simulated using the finite-element method to calculate the apparent elastic modulus parameter. The relationship between morphologic and mechanical parameters was studied. The influence of the analyzed bone volume was also investigated. RESULTS: Statistically significant sex influences were found on the bone volume-to-total volume ratio (p = 0.003), trabecular thickness (p = 0.02), and apparent elastic modulus (p = 0.01); these parameters were lower in women. However, trends were found only on trabecular separation (p = 0.06) and trabecular number (p = 0.07). Age had no statistically significant influence in any morphologic (bone volume-to-total volume ratio, r = -0.24, p = 0.13; trabecular thickness, r = -0.03, p = 0.88; trabecular separation, r = 0.12, p = 0.47; and trabecular number, r = -0.23, p = 0.16) or elastic (apparent elastic modulus, r = -0.18, p = 0.26) parameter. A statistically significant relationship between apparent elastic modulus and the square of bone volume-to-total volume ratio was found (r = 0.968, p < 0.001). This association was not seen (r = 0.185, p = 0.25) and apparent elastic modulus results were considerably different (p < 0.001) if the volume of analyzed bone was reduced. CONCLUSION: We found that bone volume-to-total volume ratio, trabecular thickness, and apparent elastic modulus are parameters significantly influenced by sex. Apparent elastic modulus results show a relationship with bone volume-to-total volume ratio. Trabecular bone volume should be maximized for an appropriate mechanical analysis.