Chapter 5, 21, 24

Question 1

What is an artifact?

Answer 1

Anything that is not real or an error in imaging.

Question 2

What are the 6 assumptions of imaging systems?

Answer 2

1. sound travels in a straight line. 2. sound travels directly to reflector and back. 3. it is exactly 1540m/s. 4.reflections only arise if structure is positioned in the beam’s main axis. 5. imaging plane is thin. 6. strength of reflection is related to tissue’s characteristics.

Question 3

what causes reverberation

Answer 3

The bouncing of the sound waves
between two strong reflectors positioned parallel to the beam

Question 4

which of the echoes are real during reverberation? Which are artifact?

Answer 4

The first two are real. Any others are artifact.

Question 5

What are characteristics of reverberation?

Answer 5

It appears in multiples, equally spaced, parallel to main axis, and at increasing depth.

Question 6

What is Spacial Average Intensity

Answer 6

the average intensity across the
beams whole cross section. This average is less intense than a peak.

Question 7

What is spacial peak intensity?

Answer 7

The beams intensity at the location where it is at its maximum. Will always have a higher intensity than an average.

Question 8

Does an ultrasound beam have the same intensity at different depths?

Answer 8

No. Intensity weakens with depth

Question 9

Which is stronger? Average or Peak

Answer 9

Peaks are stronger

Question 10

What is Time Average (TA)

Answer 10

The average measurement of intensity over the whole pulse

Question 11

What is pulse average

Answer 11

Pulse average is the average intensity over the whole pulse (not a cycle)

Question 12

What is temporal peak (TP?)

Answer 12

the peak intensity over the very highest cycle in the pulse.

Question 13

List the temporal intensities from strongest to weakest

Answer 13

TP, PA, TA

Question 14

When we combine the temporal intensities with the part of the beam we are measuring, what are the possibilities from strongest to weakest?

Answer 14

SPTP, SPPA, SPTA
SATP, SAPA, SATA

Question 15

How is SPTA relevant in DMS?

Answer 15

The most relevant intensity measurement with respect to tissue heating

Question 16

How is SPSA relavant in DMS? Why is this importamt?

Answer 16

It describes the spread of a beam in a particular space. It’s important because an unfocused beam is more harmful than focused.

Question 17

What tool is used to measure the characteristics of a sound beam?

Answer 17

A hydrometer or hydrophone

Question 18

What does a calorimeter measure?

Answer 18

measures total power in a a
beam through absorption

Question 19

What does a thermocouple measure?

Answer 19

measures temperature of the
sound beam

Question 20

What do Liquid Crystals measure?

Answer 20

measures temperature by
liquid crystals that change color based on the temperature

Question 21

Which is more important: The risk of doing an exam or the benefit to a patient’s health? Explain.

Answer 21

The benefit must outweigh the risk. Ultrasounds are very safe, but that doesn’t mean we should be doing them when they aren’t medically necessary.

Question 22

What is dosimetry?

Answer 22

The science of identifying and measuring the characteristics of an ultrasound beam that are relevant
to its potential for producing biological effects.

Question 23

What two methods of research are used with dosimetry?

Answer 23

In-vivo (within the living body) or In-vitro (outside the living body)

Question 24

What does the American Institute of Ultrasound in Medicine (AIUM) say in their statement?

Answer 24

Even though ultrasound imaging is currently identified as safe, we should never uszse ultrasound for non-medical purposes.

Question 25

What are thermal mechanisms of bioeffects?

Answer 25

Bioeffects from tissue temperature elevation

Question 26

What are cavitation mechanisms of bioeffects?

Answer 26

the interaction of ultrasound waves with microbubbles which are stabilized gas bubbles in tissue

Question 27

What is the thermal index?

Answer 27

a predictor of maximum temperature increase under most clinically relevant conditions

Question 28

What do TIS, TIB, and TIC stand for?

Answer 28

Thermal index in soft tissue, bone, and cranial bone respecively.

Question 29

Which is safer: Focused or Unfocused beams?

Answer 29

Focused beams are safer.

Question 30

At what temperature elevation might begin to present harm to an embryo? What could reach these levels?

Answer 30

1.5 C or higher may cause harm. Spectral pulsed Doppler and COlor Doppler might reach these levels.

Question 31

What are factors of stable caviation?

Answer 31

Oscillating bubbles, lower MI

Question 32

What are factors of transient (normal or inertial) caviation?

Answer 32

bursting bubbles, shock waves, high temp, high MI

Question 33

MI is directly related to the potential for Caviation. What is MI inversely related to?

Answer 33

Frequency

Question 34

What is epidemiology?

Answer 34

studies of population

Question 35

What is a prospective study?

Answer 35

hypothesis first and then set up and collect info for the study

Question 36

What is a retrospective study?

Answer 36

having a hypothesis and then going and looking for date to support. A less desirable option.

Question 37

What is a randomized study?

Answer 37

a control group and a study group- compare the two for differences

Question 38

What are two possible causes of Comet Tail artifact?

Answer 38

1. sound bouncing between two closely spaced objects. 2. resonance of gas bubbles vibrated by the beam

Question 39

What assumption is violated to cause Comet Tail?

Answer 39

The assumption that sound travels directly to a reflector and back

Question 40

What is the cause of Ring Down artifact? What diagnosis could this indicate?

Answer 40

The sound bounces between bubbles. It could indicate infection.

Question 41

What happens with reflection when shadowing occurs? What assumption is being violated?

Answer 41

100% reflection and 0% transmission is occuring. The assumption that the intensity of a reflection is related to the tissue creating the reflection.

Question 42

What assumption is being violated with edge shadowing?

Answer 42

Intensity of a reflection is related to the characteristics of the tissue creating the reflection

Question 43

What assumption is being violated with enhancement?

Answer 43

the intensity of a reflection is related to the characteristics of the tissue

Question 44

What is focal enhancement

Answer 44

Hyperechoic side-to-side region that results from increased intensity at the focus

Question 45

Which mirror artifact is real?

Answer 45

The top is real, the bottom is artifact

Question 46

What assumptions are broken with mirror images?

Answer 46

Sound travels in a straight line, to the reflector and back.

Question 47

What happens when sound travels at a speed other than 1540m/s?

Answer 47

A speed error. The correct number of reflectors appear at incorrect depths and may appear split or cut off.

Question 48

What happens when the speed in a tissue is faster than expected

Answer 48

Go-return time is too short and the system writes the reflection too shallow on the screen.

Question 49

What happens when the speed in a tissue is slower than expected

Answer 49

Go-return time is too long and the system writes the reflection too deep on the screen.

Question 50

What is a lobe artifact

Answer 50

An extra or multiple copies of the reflector. All are side by side at the same depth.

Question 51

what assumption is broken by lobe artifacts?

Answer 51

Reflections arise from structures along the beam’s main axis

Question 52

Lobe artifacts are reduced through subdicing and apodization. What do these terms mean?

Answer 52

Subdicing- dividing each element into small pieces. Apodization- central elements are excited with higher voltages than the outermost elements

Question 53

What reduces lobe artifacts

Answer 53

Apodization and Subdicing

Question 55

What assumption