RESUMEN
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. T2 values were calculated on transverse rat patellar sections and displayed with a color scale (the T2 map) on a pixel-by-pixel basis. Biochemical and histologic studies were performed to evaluate the influence of proteoglycans and collagen contents on T2 values of the patellar cartilage. RESULTS: On the T2 map, the maturation process until 10 weeks was characterized by a decrease in T2 values and in cartilage thickness. The biochemical data revealed a global decrease in proteoglycans and a progressive global increase in collagen content, whereas the histologic study revealed subtle zonal variation in matrix constituents with depth. As aging progressed, the T2 values were low, without important variations, whereas the global cartilage thickness decreased. The cartilage matrix became globally more fibrotic, especially in the deepest zone. Biochemical analysis revealed that collagen content was more determinant of MR signal intensity than was proteoglycans content during maturation and aging. CONCLUSION: T2 mapping allows characterization of variations in cartilage matrix constituents and thickness.
Asunto(s)
Envejecimiento , Cartílago Articular/química , Cartílago Articular/crecimiento & desarrollo , Imagen por Resonancia Magnética , Rótula , Animales , Cartílago Articular/citología , Proteoglicanos Tipo Condroitín Sulfato/análisis , Colágeno/análisis , Hidroxiprolina/análisis , Masculino , Ratas , Ratas WistarRESUMEN
RATIONALE AND OBJECTIVES: The authors evaluated the image quality on delayed CT arthrography images with the use of the nonionic dimeric contrast agent, iodixanol 270 mg I/mL, compared with iohexol 300 mg I/mL. METHODS: A total of 132 patients with shoulder pain were included in a randomized, parallel, double-blind study. Sixty seven patients received iodixanol and 65 patients received iohexol. Patients underwent two CT-arthrography examinations: the first was performed 20 to 30 minutes after contrast injection and the second, 50 to 70 minutes after contrast injection. Data from 31 patients were excluded from the efficacy analysis. The overall quality of CT arthrography images was graded into four categories: excellent, good, moderate, and bad. RESULTS: The overall quality of delayed CT arthrography images was significantly better in the iodixanol group (P = 0.001, alpha = 0.05). On the first CT examination, image quality was good or excellent in 88% of the cases in the iodixanol group and in 96.1% in the iohexol group. The results on the delayed CT arthrography examination indicated that image quality was good or excellent in 88% of the cases when iodixanol was used and in 63.5% when iohexol was used. CONCLUSIONS: The overall quality of delayed images was significantly better with iodixanol than with iohexol.