Ultrasonic measurement of carotid luminal surface roughness with removal of axial displacement caused by blood pulsation

For early diagnosis of atherosclerosis, we have developed a method to measure the initial minute surface roughness utilizing the natural longitudinal displacement of the intima-media-complex (IMC) on the carotid artery caused by pulsation. However, the IMC displaces not only in the longitudinal direction but also in the axial direction due to the pulsation. In the present paper, we proposed a novel method to remove the pulsation component by spatially convolving a high-pass filter with the measured depths of IMC in the longitudinal direction. The proposed method was validated by a phantom experiment, and the surface roughness with ten saw teeth was correctly measured. Next, the surface roughness of the carotid artery wall was measured for two healthy volunteers. The proposed method reduced the variation of measured surface roughness among beams compared to the previous method.