Attenuation and speed of 10 MHz ultrasound in canine blood of various packed-cell volumes at 37°C

The attenuation coefficient and the speed of 10 MHz ultrasound were determined in canine blood at 37°C by a differential path-length technique. Blood specimens with packed-cell volumes (p.c.v) ranging from 0 to 53% were prepared by separating the cells from the plasma and mixing the two components. The mean attenuation coefficient increased linearly with packed-cell volume, the least squares regression function being α=0·992+0·039 PCV with a standard error of the estimate=0·255. The speed of 10 MHz ultrasound c in millimetres per second, increased with packed-cell volume, the regression function for a wave equation model being 1/c²=0·418+2·09×10⁻⁴ (PCV)−1·75×10⁻⁵ (PCV)² with a standard error of the estimate=0·0049 (mm/s)⁻². Both the attention coefficient and speed of 10 MHz ultrasound were greater in blood than in plasma to a degree dependent on the packed-cell volume.