CORRECTION OF DETECTING DEPTH AND CALCULATION OF SPEED OF MOVING OBJECTS BASED ON TIME OF FLIGHT OF ULTRASOUND PULSES

摘要

During transmission, speed of ultrasound pulses gradually reduces due to their energy loss from acoustic impedance. So, calculating a detecting depth with fixed speed of the ultrasound pulses will distort ultrasound images. Correction of the detecting depth will rectify a depth registration and improve the imaging quality. The thickness and density of piezoelectric elements (PZT) decide a quantity of the ultrasound pulses, which affect their detecting depth. The density and sound speed in PZT elements decide the frequency of the ultrasound pulses, which can be used to increase the detecting depth for a high frequency ultrasound. Moving objects can change speed of reflected ultrasound pulses, which change their TOF and TOF shift. Therefore the TOF shift can be used to calculate the velocity of the moving objects in a continuous and a pulsed wave and a color ultrasound, and correct aliasing of the pulsed wave and the color ultrasound.

主权项

1. A method for rectifying errors of registration of a detecting depth due to speed reduction of ultrasound pulses during a transmission, the method comprising:
obtaining a calculated detecting depth from a general speed of the ultrasound pulses and a traveling time between emitting and receiving ultrasound pulses, wherein the calculated detecting depth is a half value of a multiplication result of the general speed of the ultrasound pulses in a transmitting medium and the traveling time between the emitting and the receiving ultrasound pulses; calculating a speed reducing coefficient of the ultrasound pulses, wherein the speed reducing coefficient of the ultrasound pulses equals to a multiplication result of acoustic impedance and attenuation coefficient; obtaining a depth shift of the ultrasound pulses, wherein the depth shift of the ultrasound pulses equals to a half value of a multiplication result of the speed reducing coefficient and the traveling time; and determining a corrected detecting depth, wherein the corrected detecting depth is a difference between the calculated detecting depth and the depth shift.