24.1 ULTRASOUND

What is meant by ultrasound?

• Sound waves with frequencies below 20 Hz

• Sound waves with frequencies in the range of 20 Hz - 20 kHz

• Sound waves with frequencies above 20kHz

• Sound waves with frequencies above 10 MHz

Explain the main principles behind the generation of ultrasound to obtain diagnostic information about internal body structures [6 marks]

The device used to generate and detect ultrasonic waves is called a _____________ crystal.

What is the main application of ultrasound in medicine?

• Communication

• Imaging

• Heating

• Navigation

What is specific acoustic impedance of a medium?​

• The product of density of the medium and the speed of sound in the medium

• The ratio of density of medium to the speed of sound in the medium

• The volume of the medium divided by the acoustic velocity.

• The speed of ultrasound inside the medium.

Specific acoustic impedances for a particular tissue and bone are 1.6 x 10⁶ kgm^-2s^-1 and 7.0 x 10⁶ kgm^-2s^-1 respectively.

What is the ratio of reflected intensity to incident intensity (what is the intensity reflection coefficient) as ultrasound travels through the boundary between the tissue and bone?

• 4.8 cm

• 2.4 cm

• 1.2 cm

• 2.8 cm