Background: Magnetic resonance (MR) imaging and measurement of glycosaminoglycan (GAG) have potential for characterization of hyaline articular cartilage. Recently, some reports have demonstrated the potential of direct administration of contrast media for MR imaging of cartilage.
Purpose: To prove the feasibility of intraarticular gadolinium-enhanced MR imaging of cartilage (iGEMRIC) and T1 relaxation mapping of the articular cartilage in vivo with intraarticular injection of Gd-DTPA2−.
Material and Methods: Five healthy beagle dogs underwent MR imaging and T1 relaxation mapping of the knee joints of both hind legs. The delayed gadolinium-enhanced MR imaging of cartilage (dGEMRIC) and iGEMRIC techniques were interchanged with MR imaging. For dGEMRIC, a double routine dose of Gd-DTPA2− (0.2 mM/kg) was administered intravenously. For iGEMRIC, 2.5 and 1.25 mmol/l saline-diluted Gd-DTPA2− solutions were separately injected into the right and left knee joints, respectively, prior to MR imaging. Color-coded T1 maps of 20 femoral condyles were obtained from the dGEMRIC and iGEMRIC images. The signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and glycosaminoglycan (GAG) delineation of articular cartilage were compared between the dGEMRIC and iGEMRIC techniques.
Results: The mean SNR was higher with dGEMRIC than with iGEMRIC, but the difference was not statistically significant (P = 0.174). The mean (±SD) CNR was higher with iGEMRIC (−11.6±3.4) than with dGEMRIC (−16.7±4.0; P = 0.000), although the absolute value of the CNR was higher with dGEMRIC. The layering and gradient distribution of GAG were more clearly visualized on the iGEMRIC images. The mean scores of GAG delineation with dGEMRIC and iGEMRIC were 0.7±0.6 and 2.2±1.7, respectively. The iGEMRIC method better visualized GAG distribution (P = 0.001).
Conclusion: Although the SNR did not differ significantly between the iGEMRIC and dGEMRIC techniques, the color-coded T1 map produced with iGEMRIC allowed better cartilage evaluation. Thus, iGEMRIC exhibits the useful features of both MR arthrography and dGEMRIC, and provides a color-coded T1 map that is useful for diagnosing early articular cartilage damage.
