Study guide 9-11

Question 1

The near zone is the region from

Answer 1

the transducer to the smallest cross-sectional area of a sound beam.

Question 1

The Fraunhofer zone starts at the

Answer 1

beams smallest diameter and extends deeper.

Question 2

Near zone & ____ have the same meaning.

Answer 2

Fresnel zone

Question 3

Fraunhofer and ___ have the same meaning.

Answer 3

Far zone

Question 4

Focus is the point or location where

Answer 4

a beam reaches its smallest dimension

Question 5

The focal zone is the region of the sound beam where

Answer 5

focusing is most effective

Question 6

The focus is at the

Answer 6

end of the near zone and the beginning of the Fraunhofer.

Question 7

PZT crystal with small diameter/ low frequency will create a

Answer 7

beam with the shallowest focus.

Question 8

PZT crystal with large diameter/high frequency will create

Answer 8

beam with the deepest focus

Question 9

Ultrasound systems with a larger diameter crystal will have a deeper focus/higher frequency systems will have a

Answer 9

deeper focus

Question 10

Terms that describe the shape of a sound wave created by a tiny fragment of PZT include:

Answer 10

spherical, Huygens’ wavelet and V-shape.

Question 11

Huygens’ principle is based on

Answer 11

interference

Question 12

Huygens’ principle explains the difference in

Answer 12

sound beam shape created by a disc-shaped crystal from that of a small chip of PZT.

Question 13

A-mode

Answer 13

places time of flight information on the x-axis and echo amplitude on the y-axis accurately displays reflector depth.

displays a single jagged line of varying heights.

Question 14

B-mode

Answer 14

strength of the reflection is put on the z-axis

places dots of dissimilar gray scale on the display.

Question 15

M-mode

Answer 15

produces lines related to the changing positions of reflectors in the body with respect to time.

Question 16

Axial resolution

Answer 16

accuracy visualizing two structures that are parallel to a sound beams main axis

Question 17

An axial resolution of 0.3 mm (lower numerical value)

Answer 17

will produce a better quality image than an AR of 0.6 mm

Question 18

The lower the numerical value of the longitudinal resolution

Answer 18

the better the picture

Question 19

An ultrasonic pulse has a pulse repetition period of 1.9 msec, a spatial pulse length of 4.0 mm, and wavelength of 0.3 mm. What is the axial resolution of the system?

Answer 19

AR = spl/2 (2.0mm)

Question 20

Higher frequency of the cycles within a pulse

Answer 20

the lower the numerical value of the axial resolution

Question 21

The shorter the pulse length

Answer 21

the better the picture

Question 22

The lateral resolution of an ultrasound system is 5 mm. Two structures are separated by 2 mm and lie side by side in relation to the sound beams main axis. What will most likely appear on the systems display?

Answer 22

one echo

Question 23

Using an acoustic lens will

Answer 23

lower the value of an ultrasound systems lateral resolution

Question 24

Using a curved crystal is an

Answer 24

internal focusing technique

Question 25

The use of a lens is a technique for

Answer 25

external focusing

Question 26

Both variable or multi-focusing are

Answer 26

electronic techniques for focusing

Question 27

The diameter of a disc-shaped, unfocused piezoelectric crystal is 1.4 cm. The near zone length is 5 cm. What is the best estimate for the lateral resolution at a depth of 10cm?

Answer 27

1.4, at two near zone lengths the LR is again the same as the crystal width.