High-resolution ultrasonography for analysis of age- and disease-related cartilage changes

Because of their limited spatial resolution, current clinical noninvasive imaging modalities (radiography, computed tomography, conventional echography, and magnetic resonance imaging) are able to detect only the late stages of the cartilage degradation. To detect early lesions and follow their evolution in time with imaging, higher resolution is necessary. Recent work suggest that high-frequency ultrasound may serve as a useful means for the investigation of cartilage matrix structural changes occurring under various experimental and clinical circumstances, like the growing process and osteoarthritis. In this chapter, an experimental 50-100-MHz ultrasound scanner is described for high-resolution echographic imaging of articular cartilage. The procedures of data acquisition and signal processing are detailed for the quantitative evaluation of ultrasonic reflection and backscatter coefficients, which have been reported to be sensitive to subtle surface and internal disease-related alterations. Further technological developments and miniaturization of the echographic probes may lead to extension of this technique to the study of living small animals or to the clinical field in combination with conventional arthoscopy.