14 Ultrasound

Question 1

__________ is defined as the peak maximum or peak minimum value from the average pressure on the medium in the
absence of a sound wave.

Answer 1

Pressure amplitude

Question 2

1 occurs at tissue boundaries where there is a difference in the acoustic impedance of adjacent materials.

Answer 2

1 Reflection

Question 3

__________ describes the
change in direction of the transmitted ultrasound energy with nonperpendicular
incidence.

Answer 3

Refraction

Question 4

__________ occurs by reflection or refraction, usually by small particles
within the tissue medium, causes the beam to diffuse in many directions, and gives rise to the characteristic texture and gray scale in the acoustic image.

Answer 4

Scattering

Question 5

__________
refers to the loss of intensity of the ultrasound beam from absorption and scattering
in the medium.

Answer 5

Attenuation

Question 6

__________ is the process whereby acoustic energy is converted to
heat energy, whereby, sound energy is lost and cannot be recovered.

Answer 6

Absorption

Question 7

stiffness and flexibility of a compressible medium

rayl, where 1 rayl is equal
to 1 kg/(m2s)

Answer 7

acoustic impedance (Z)

Question 8

__________ of ultrasound energy at a boundary between two tissues occurs
because of the differences in the acoustic impedances of the two tissues.

The __________ describes the fraction of sound intensity incident on an interface that is reflected.

Answer 8

reflection

reflection coefficient

Question 9

A conduit of tissue that allows ultrasound

transmission through structures such as the lung is known as an “__________ “

Answer 9

Acoustic window

Question 10

__________
in units of dB/cm, is the relative intensity loss per centimeter of travel for a given
medium.

approximately proportional to frequency

Answer 10

Ultrasound attenuation coefficient, µ,

Question 11

__________ the
thickness of tissue necessary to attenuate the incident intensity by 50%, which is
equal to a 3 dB reduction in intensity

Answer 11

ultrasound HVT

Question 12

Ultrasound Transducer Major components

include the

Answer 12

piezoelectric material, matching layer, backing block, acoustic absorber,
insulating cover, tuning coil, sensor electrodes, and transducer housing.

PIEzoelectric material
Matching layer,
Insulating cover
Sensor electrodes

BACKing block
Acoustic absorber,
Tuning coil
Transducer housing.

Question 13

Curie temperature

Answer 13

328 to 365 Celsius

Question 14

__________ a crystal or ceramic) is the functional component of
the transducer. It converts electrical energy into mechanical (sound) energy by physical deformation of the crystal structure. Conversely, mechanical pressure applied
to its surface creates electrical energy. They are characterized by a
well-defined molecular arrangement of electrical dipoles

Answer 14

Piezoelectric materials

Question 15

__________ are molecular entities containing positive and negative electric charges that have an overall neutral charge. When mechanically compressed by an externally applied pressure, the alignment of the dipoles is disturbed from the
equilibrium position to cause an imbalance of the charge distribution

Answer 15

Electrical dipoles

Question 16

Ultrasound transducers for medical imaging
applications employ a synthetic piezoelectric ceramic, most often _____ -a compound with the structure of molecular dipoles.

Answer 16

lead-zirconate-titanate (PZT)—

Question 17

natural piezoelectric material is __________ , commonly used in watches and
other timepieces to provide a mechanical vibration source at __________ kHz for interval
timing.

Answer 17

quartz crystal

32.768 kHz

Question 18

natural piezoelectric material is __________ , commonly used in watches and
other timepieces to provide a mechanical vibration source at 32.768 kHz for interval
timing.

Answer 18

quartz crystal