Chp 3 - Pulse-Echo Intrumentation

Question 1

How long does it take for sound to travel 1cm in soft tissue

Answer 1

13 us (1way)

Question 2

What is apodization?

Answer 2

A technique used to vary the voltage to individual elements used to reduce grating lobes

Question 3

What is the smallest unit of memory in a digital device?

Answer 3

a bit

Question 4

What is the smallest compoenent of a 3D device?

Answer 4

a voxel

Question 5

What is a byte

Answer 5

8 bits of memory

Question 6

What is the difference between B mode comet tail and ring down?

Answer 6

Comet tail - is reverb from small reflectors

Ring down - is an artifact of reverb from gas/air

Question 7

Where is amplitude mode used today?

Answer 7

in echocardiography and ophthalamogy

Question 8

What is the range/distance equation

Answer 8

d = c x time /2

Question 9

What is the assumed distance in soft tissue?

Answer 9

d = 0.77t

Question 10

What is the main function of the beam former?

Answer 10

controls timing of the elements and apodization

Question 11

What is coded excitation?

Answer 11

sends a series of encoded pulses to form one SL (instead of one pulse per SL)

Question 12

What does the master synchronizer do?

Answer 12

part of the machine responsible for controlling the timing of the echoes

Question 13

What is rectification?

Answer 13

turns negative voltages into positive voltages

Question 14

What is the formula to determine the shades of grey?

Answer 14

2^n

n = number of bitd

Question 15

What produces the step ladder appearance?

Answer 15

reverb

Question 16

In a standard cathode ray tube used to display ultrasound images, what
are the charged particles that are emitted from a “gun” from the rear of
the tube?

Answer 16

Electrons

Question 17

How does a cathode ray tube steer the charged particles emitted by
the electron so that they sweep across the front screen?

Answer 17

By using a magnetic field

Question 18

How many fields are in a frame?

Answer 18

2

Question 19

An increase in compression results in what happeneing to the DR?

Answer 19

Decreases

Question 20

An advantage of coded excitation is improved:

Answer 20

signal to noise ratio

Question 21

Additional reflectors on the screen (with an array transducer) that are
from extraneous sound waves off the primary axis of the beam are:

Answer 21

Grating lobes

Question 22

When will a reflector be placed too close to the transducer than it should be?

Answer 22

when the sound beam goes through anything faster than 1540 m/s

Question 23

When will a reflector be placed farther than it should to the transducer?

Answer 23

when the sound beak travels through anything slower than 1540 m/s

Question 24

The part of the machine responsible for timing the reception of the
pulses to determine their location is the:

Answer 24

The master synchronizer

Question 25

When does edge shadow occur?

Answer 25

when sound strikes a curved reflector (ex GB or carotid artery)

Question 26

What is the difference between side lobe and grating lobe?

Answer 26

side lobe occurs with all transducers while grating lobe only occurs with linear transducers

Question 27

How can you reduce grating lobes?

Answer 27

harmonics, subdicing, apodization