Q1S1 Ch. 5 Ultrasound Physics

Front 1

T/F
Blind (doppler only) transducers have a broad depth of field.

Back 1

True

Front 2

T/F
A phased array transducer must have multiple elements.

Back 2

True

Front 3

T/F
A mechanical system can steer and focus the beam electronically.

Back 3

False

Front 4

T/F
An annular array can be focused electronically but must be steered mechanically.

Back 4

True

Front 5

An annular transducer has the distinct benefit of variable focus in both elevation and lateral planes. A distinct disadvantage with respect to phased transducers is that an annular transducer
a) cannot image deeper than 10 cm
b) is inherently less sensitive
c) must be steered mechanically
d) can not perform Doppler or color flow

Back 5

c) must be steered mechanically

Front 6

Which of the following has a rectangular image?
a) annular
b) sector
c) linear switched array
d) more than one of the above

Back 6

c) linear switched array

Front 7

A fundamental difference between a linear switched array and a linear phased array is that a linear switched array
a) has a fixed focus and cannot steer
b) has a variable focus and can steer.
c) has a lower maximum PRF

Back 7

a) has a fixed focus and cannot steer.

Front 8

.
c) for cost effectiveness.
d) to minimize the time it takes to shoot a frame.

Back 8

a) for rib access.

Front 9

The footprint" of a transducer has two dimensions. The beamwidth is associated with the _____ dimension and the "slice thickness" is determined by the _____dimension.
a) axial, elevation
b) elevation, lateral
c) elevation, axial
d) lateral, elevation

Back 9

d) lateral, elevation

Front 10

Which of the following does not belong?
a) axial
b) longitudinal
c) depth
d) radial
e) azimuthal

Back 10

e) azimuthal

Front 11

Which of the following is not the same as lateral resolution?
a) radial
b) angular
c) azimuthal
d) transverse

Back 11

a) radial

Front 12

In pulsed mode, what determines the operating freequency (equation)?

Back 12

PS of crystal / 2 X thickness of crystal

Front 13

In continuous mode, what determines the operating frequency?

Back 13

the frequency of the "pulser" or the transmitter

Front 14

The near zone length is approximately equal to D squared X f / 6. If the frequency doubles, the NZL
a) increases by a factor of 2
b) decreases by a factor of 2
c) increases by a factor of 4
d) decreases by a factor of 2

Back 14

a) increases by a factor of 2

Front 15

If the diameter of a transducer is increased by a factor of 2, the NZL
a) increases by a factor of 2.
b) decreases by a factor of 2.
c) increases by a factor of 4.
d) decreases by a factor of 2.l

Back 15

c) increases by a factor of 4.

Front 16

Which of the following transducers would give the shallowest focus?
a) D = 2 mm, f = 2 MHz
b) D = 1 mm, f = 2 MHz
c) D = 2 mm, f = 10 MHz
d) D = 1 mm, f = 10 MHz

Back 16

b) D = 1 mm, f = 2 MHz

Front 17

Which focusing technique best improves the focus in the far field?
a) a lens
b) mirrors
c) electronic focusing
d) curved elements
e) none, one can only improve focus in the near field

Back 17

e) none, one can only improve focus in the near field

Front 18

For an unfocused transducer, what is the approximate beamwidth at the focal distance and twice the focal distance, given a crystal diameter of 5 mm?
a) 5 mm, 10 mm
b) 2.5 mm, 10 mm
c) 5 mm, 5 mm
d) 2.5 mm, 5 mm

Back 18

d) 2.5 mm, 5 mm

Front 19

How thick would a crystal have to be for 2 MHz pulsed mode operation given a propagation velocity through the crystal of 5,000 m/sec?

Back 19

Rearrange f equation:
thickness = PS of crystal/ 2 X f
5,000 m/sec / 2 X 2x10 to 6th = 5 X 10 to -3 power/ 4 = 1.25 mm

Front 20

If the thickness of a crystal doubles, the frequency of operation for PW mode
a) doubles.
b) halves.
c) quadruples.
d) quarters.

Back 20

b) halves.

Front 21

Two crystals of the same thickness are used for transducers A and B. The PS on transducer A's crystal is twice that of transducer B's. Which of the following is true?
a) A and B have the same operating f.
b) A operates at twice the operating f as B.
c) B operates at twice the operating f as A.
d) A operates at four times the operating f as B.

Back 21

a) A operates at twice the operating f as B (remember that the operating f is proportional to the PS within the crystal)

Front 22

Radial resolution equals ____.

Back 22

SPL/2

Front 23

Lateral resolution equals the ________ and therefore varies with depth since the ________ varies with depth.

Back 23

Beamwidth

Front 24

A transducer is anything which converts ______ from one form to another form.

Back 24

energy

Front 25

An __________transducer converts voltage into sound above human hearing and sound into a voltage.

Back 25

ultrasound

Front 26

An ultrasound transducer converts electropotential _____ into _______ _______ and mechanical energy into electropotential energy.

Back 26

energy, mechanical energy

Front 27

Ultrasound transducers use the _____ effect.

Back 27

piezoelectric

Front 28

A commonly used material for ultrasound transducers is ____ zirconate Titanate (PZT).

Back 28

Lead

Front 29

If a transducer is heated above its ___ temperature, it will loose its piezoelectric properties.

Back 29

Curie

Front 30

For PZT, the Curie temperature is ______

Back 30

300 degrees