Image interpolation improves the zonal analysis of cartilage T2 relaxation in MRI

Abstract

Background: This project aimed to investigate the improvement in the detection of osteoarthritis (OA) in cartilage by the interpolation of T2 images, in the situation when the native MRI resolution is insufficient to resolve the depth-dependent T2 characteristics in articular cartilage (AC).Methods: Eighteen intact canine knee joints that were healthy or had mild (contralateral) or severe OA were T2-imaged in a 7T/20 cm MRI system at 200 µm/pixel resolution (macro-MRI). Two image analysis methods were used to interpolate the images to 100 µm/pixel, i.e., by Fourier-transforming the time-domain FID (Free Induction Decay) signal using the Varian NMR software and by interpolating the 2D T2 image using the ImageJ software. and the interpolated 100 µm resolutions were subdivided into two equal-thickness regions and three-equal thickness regions based on clinical MRI protocols. A new method divided the T2 profiles into three-unequal thickness zones according to the T2 profiles at 17.6 µm/pixel from the same cartilage imaged in a 7 Tesla/9 cm µMRI system. Both interpolation methods improved the depth-dependent T2 images/profiles in macro-MRI. The unequal zone division in T2 had better OA sensitivity than the equal zone division. The threeequal zone division of T2 profiles had better OA sensitivity than the two-equal zone division. The statistical significant difference between the healthy and mild OA cartilage is detected (P=0.0018) only by the unequal zone division method at 100 µm resolution.Conclusions: Data interpolation improves the T2 sensitivity in MRI of cartilage OA. Unequal division of tissue thickness enables better early stage of OA detection than the equal division.

Structural Morphology of Rabbit Patella and Suprapatella Cartilage by Microscopic MRI and Polarized Light Microscopy

“…14,17 The intact joint imaging used a FOV (field of view) of 25 × 25 mm, a slice thickness of 0.8 mm, and a matrix size of 256 × 256 in 5 echo times (8, 16, 24, 32, 40 ms). The cartilage blocks were imaged with a FOV of 5 × 5 mm and a matrix size of 256 × 128, which was later reconstructed into the size of 256 × 256 in ImageJ 19 (v1.52a). These imaging parameters resulted in a pixel resolution of 97.6 µm per pixel for the intact joint and a higher resolution of 19.5 µm for the cartilage blocks.…”