Physics

Question 1

Reflection and propagation of sound waves through tissues depend on 2 parameters: _________ and ___________.

Answer 1

Acoustic impedance and attenuation.

Question 2

Acoustic impedance

Answer 2

Resistance to propagation of sound waves through tissues. A fixed property of tissues.

Question 3

What percent of sound waves transmitted by ultrasound probe are reflected back to the transducer?

Answer 3

1%

Question 4

Attenuation

Answer 4

Loss of energy as sound waves travel through tissues, mostly due to absorption.

Question 5

List the following in order of attenuation coefficient (smallest to largest): Soft tissue, blood, air, water, bone.

Answer 5

Water (0.0022 dB/cm/MHz)
Blood (0.15)
Soft tissue (0.75)
Air (7.50)
Bone (15.00)

Question 6

List the following in order of acoustic impedance (smallest to largest): blood, air, liver, fat, metal, bone.

Answer 6

Air (0.0004 [kg/(s m^2)]x10^6)
Fat (1.38)
Blood (1.66)
Liver (1.69)
Bone (7.75)
Metal (e.g. titanium) (22.9)

Question 7

List the 3 variables that determine the amount of Doppler shift.

Answer 7

1) Frequency of ultrasound beam
2) Velocity of blood flow
3) Angle of insonation

Question 8

The maximum Doppler frequency or velocity that can be measured before aliasing occurs is called the _____________.

Answer 8

Nyquist limit.

Question 9

Axial resolution depends on __________.

Answer 9

Transducer frequency.