Multi-components of T2 relaxation in ex vivo cartilage and tendon.

The multi-components of T2 relaxation in cartilage and tendon were investigated by microscopic MRI (microMRI) at 13 and 26 microm transverse resolutions. Two imaging protocols were used to quantify T2 relaxation in the specimens, a 5-point sampling and a 60-point sampling. Both multi-exponential and non-negative-least-square (NNLS) fitting methods were used to analyze the microMRI signal. When the imaging voxel size was 6.76 x 10(-4)mm3 and within the limit of practical signal-to-noise ratio (SNR) in microscopic imaging experiments, we found that (1) canine tendon has multiple T2 components; (2) bovine nasal cartilage has a single T2 component; and (3) canine articular cartilage has a single T2 component. The T2 profiles from both 5-point and 60-point methods were found to be consistent in articular cartilage. In addition, the depletion of the glycosaminoglycan component in cartilage by the trypsin digestion method was found to result in a 9.81-20.52% increase in T2 relaxation in articular cartilage, depending upon the angle at which the tissue specimen was oriented in the magnetic field.