Comparison of ultrasound speed in articular cartilage measured by different time-of-flight methods.
The purpose of this study was to investigate whether different time-of-flight (TOF) methods including amplitude-related methods, which determine tissue borders from the reflected wave itself, and the cross-correlation method, which requires reference signals to determine borders, influence speed of sound (SOS) values for articular cartilage. Left femoral condyle samples from a 6-month-old pig and a 3-year-old pig were used. Radiofrequency signals from the cartilage surface and cartilage-bone interface were acquired using the ultrasound transducer for nine points in each sample. TOF was calculated by three amplitude-related methods (peak amplitude, peak envelope, signal phase) and a cross-correlation method. Cartilage thickness was measured microscopically, and SOS was calculated at each point. Mean (± standard deviation) SOSs in cartilage from the 9-point measurement by the four TOF methods were 1488 ± 51, 1488 ± 48, 1487 ± 54, and 1466 ± 51 m/s (for peak amplitude, peak envelope, signal phase, and cross-correlation methods, respectively) for the 6-month-old pig, and 1709 ± 107, 1717 ± 104, 1713 ± 105, and 1695 ± 138 m/s, respectively, for the 3-year-old pig. Paired t testing identified no significant differences between the amplitude-related methods and the cross-correlation method, although SOS values yielded by the amplitude-related methods tended to be higher than those from the cross-correlation method. These results suggest that amplitude-related methods of TOF measurement and the cross-correlation method are equivalently applicable to articular cartilage SOS measurement when a wave is clearly reflected from cartilage. TOF methods should thus be considered in studies on SOS measurement.
Sensory and Motor System Medicine, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan. soohashi-tky@umin.ac.jp.
Satoru
S
Ohashi
Sensory and Motor System Medicine, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Isao
I
Ohnishi
Sensory and Motor System Medicine, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Takuya
T
Matsumoto
Sensory and Motor System Medicine, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Juntaro
J
Matsuyama
Sensory and Motor System Medicine, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Masahiko
M
Bessho
Sensory and Motor System Medicine, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Kenji
K
Tobita
Sensory and Motor System Medicine, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Masako
M
Kaneko
Sensory and Motor System Medicine, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Kozo
K
Nakamura
Articular cartilage; Cartilage thickness; Time-of-flight method; Ultrasound speed