A new method for evaluating the degeneration of articular cartilage using pulse-echo ultrasound

• Published in: Review of scientific instruments 2015-03, Vol.86 (3), p.034301-034301
• Main Authors: Sun, Anyu, Bai, Xiaolong, Ju, Bing-Feng
• Format: Article
• Language: English
• Subjects: Acoustic impedance; Acoustics; Animals; Cartilage; Cartilage Diseases - diagnostic imaging; Cartilage Diseases - physiopathology; Cartilage, Articular - diagnostic imaging; Cartilage, Articular - physiopathology; Cattle; Correlation analysis; Degeneration; Dependence; Echoes; Elastic Modulus; Equipment Design; Feasibility Studies; Fourier Analysis; Fourier transforms; Microscopy; Models, Biological; Modulus of elasticity; Nondestructive testing; Optical Imaging; Patella; Reflectance; Reflection; Scientific apparatus & instruments; Signal Processing, Computer-Assisted; Sound; Transfer functions; Trypsin; Trypsin - metabolism; Ultrasonic imaging; Ultrasonic transducers; Ultrasonography - methods
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/1.4914044

This paper presents a novel nondestructive ultrasonic technique for measuring the sound speed and acoustic impedance of articular cartilage using the pulsed Vz,t technique. Vz,t data include a series of pulsed ultrasonic echoes collected using different distances between the ultrasonic transducer and the specimen. The 2D Fourier transform is applied to the Vz,t data to reconstruct the 2D reflection spectrum Rθ,ω. To obtain the reflection coefficient of articular cartilage, the Vz,t data from a reference specimen with a well-known reflection coefficient are obtained to eliminate the dependence on the general system transfer function. The ultrasound-derived aggregate modulus (Ha) is computed based on the measured reflection coefficient and the sound speed. In the experiment, 32 cartilage-bone samples were prepared from bovine articular cartilage, and 16 samples were digested using 0.25% trypsin solution. The sound speed and Ha of these cartilage samples were evaluated before and after degeneration. The magnitude of the sound speed decreased with trypsin digestion (from 1663 ± 5.6 m/s to 1613 ± 5.3 m/s). Moreover, the Young's modulus in the corresponding degenerative state was measured and was correlated with the ultrasound-derived aggregate modulus. The ultrasound-derived aggregate modulus was determined to be highly correlated with the Young's modulus (n = 16, r>0.895, p