Quantitative assessment of articular cartilage using high-frequency ultrasound: research findings and diagnostic prospects.

Osteoarthritis (OA) is a universal joint disease with significant socioeconomic effects. No cure for OA is available, but its early diagnosis could enable more efficient treatment. Currently, conventional, noninvasive ultrasound (<10 MHz) examination does not provide access to all joint surfaces and is limited to morphological information, with inadequate spatial accuracy to reveal cartilage microstructure. However, high-frequency (>10 MHz) ultrasound with a minimally invasive intra-articular approach enables not only enhanced resolution for imaging the diseased joint, but also assessment of biochemical and structural changes that affect the acoustic wave-tissue interactions. Therefore, several ultrasound parameters may be beneficial in examining tissue pathology. Ultrasound refection and backscatter from the superficial cartilage are sensitive to alterations in the collagen content and architecture. This enables high-resolution imaging and quantification of the surface fibrillation. Further, ultrasound attenuation (ranging from 1-147 dB/mm in the frequency range 5-100 MHz in normal tissue), speed (typically 1630 m/s in normal tissue), and backscatter from the internal cartilage depend on the tissue structure and composition and thus vary along with tissue degeneration. Ultrasound-assisted techniques such as mechano-acoustic indentation, elastography, and swelling measurements could enable the quantification of impaired mechanical properties of articular cartilage in disease. Although a number of challenges have to be met before the clinical use of ultrasound techniques in cartilage diagnostics is realistic, ultrasound and ultrasound-assisted techniques may enable assessment of the very early tissue changes in OA, so further studies are highly recommended.