Chapters 8 and 9

Question 1

hydrophone

Answer 1

a small transducer element mounted on the end of a narrow tube

a piezoelectric membrane with small metallic electrodes

measures pressure amplitude, period, etc

Question 2

phantom

Answer 2

tissue-equivalent device that has characteristics that are representative of tissues (e.g. scattering, propagation speed, attenuation).

Question 3

radiation force

Answer 3

the force exerted by a sound beam on an absorber or a reflector.

Question 4

test object

Answer 4

a device without tissue-llike properties that is designed to measure a specific characteristic of an imaging system

Question 5

ALARA

Answer 5

as low as reasonably achievable

the principle that it is prudent to obtain diagnostic information with the least amount possible of energy exposure to the patient.

Question 6

cavitation

Answer 6

production and dynamics of bubbles in sound

Question 7

mechanical index

Answer 7

an indicator of nonthermal mechanism activity

equal to the peak rarefactional pressure divided by the square root of the center frequency of the pulse bandwidth

Question 8

thermal index

Answer 8

an indicator of thermal mechanism activity (estimated temperature rise)

a value equal to transducer acoustic output power divided by the estimated power required to raise tissue temperature by 1 Celsius.