Chapter 24

Question 1

is similar to a small hypodermic needle with a tiny piece of PZT material attached to its end; small transducer that measures the characteristics of a sound beam

Answer 1

Hydrophone (or microprobe)

Question 2

The hydrophone also measures the:

Answer 2

-period
-PRP
-PRF
-pulse duration

Question 3

measures the total power in a sound beam through the process of absorption

Answer 3

Calorimeter

Question 4

tiny electric thermometer; inserted into the sound beam and temperature is measured

Answer 4

Thermocouple

Question 5

change color based on their temperature; energy is absorbed when a sound beam strikes

ex: mood rings

Answer 5

Liquid crystals

Question 6

T/F: Low intensity ultrasound has no known bioeffects.

Answer 6

True

Question 7

T/F: Extremely high ultrasound intensities damage biologic tissues.

Answer 7

True

Question 8

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

Answer 8

Dosimetry

Question 9

research preformed within the living body of an animal or plant; “in the living”

Answer 9

In vivo

Question 10

research performed outside of the living body and in an artificial environment; “in glass”

-provide the opportunity to perform research that would be impossible with live, human subjects

-indicated that very high intensities can cause genetic damage and cell death

Answer 10

In vitro

Question 11

2 study techniques used to study bioeffects

Answer 11

1. mechanistic approach
2. empirical approach

Question 12

-begins as a proposal
-theoretical analysis is performed based on proposal
-cause & effect relationship

Answer 12

Mechanistic approach

Question 13

-based on acquisition and review of info from patients/animals exposed to ultrasound
-relationship b/w exposure and response

Answer 13

Empirical approach

Question 14

What are the (+) and (-) of mechanistic approach?

Answer 14

(+): broad exposure

(-): uncertainty about assumptions; are other mechanisms involved?; is the bioeffect clinically significant?

Question 15

What are the (+) and (-) of empirical approach?

Answer 15

(+): no need to understand mechanism; obvious biological significance

(-): no need to understand mechanism; species differences may alter results

Question 16

Which of the study techniques, mechanistic or empirical, is the best w/ regard to ultrasound bioeffects?

Answer 16

The strongest conclusions are made when the mechanistic and empirical conclusions are in agreement.

Question 17

2 important mechanism of bioeffects

Answer 17

1. thermal
2. cavitation (nonthermal)

Question 18

proposes that bioeffects result from tissue temperature elevation

-as sound propagates in body, energy is converted into heat
-core temp of 37C; life processes do not function normally at other temps
-tissue temps are elevated through exercising, sunbathing, fever, etc.

Answer 18

Thermal mechanism

Question 19

1. TIS (soft tissue thermal index): assumes that sound is traveling in soft tissue
2. TIB (bone thermal index): assumes that bone is at or near focus of sound beam
3. TIC (cranial bone thermal index): assumes that cranial bone is in the sound beam’s near field

Answer 19

3 forms of thermal index (TI)

Question 20

useful predictor of max temp increase under most clinically relevant conditions; 3 forms: TIS, TIB, and TIC

Answer 20

Thermal index (TI)

Question 21

T/F: Tissue heating is related to the output characteristics of transducer and the properties of the tissues.

Answer 21

True

Question 22

A combination of _________ and __________ determine the likelihood of harmful bioeffects. With higher temps, harmful effects can occur with shorter exposure times.

Answer 22

temperature; exposure time

Question 23

T/F: Adult tissues appear less tolerant of tissue heating than fetal and neonatal tissues.

Answer 23

False

Fetal and neonatal tissues appear less tolerant of tissue heating than adult tissues.

Numerous fetal defects have resulted from temp elevation.

Question 24

T/F: The temperature rise in soft tissues near bone is significantly higher than in other locations.

Answer 24

True

Bone absorbs more acoustic energy than soft tissue. Ultrasound that strikes fetal bone deserve special attention.

Question 25

interaction of sound waves with microscopic, stabilized, gas bubbles* in tissue; also describes the creation of gaseous nuclei from dissolved gasses in a fluid

*gaseous nuclei

2 forms:
1. stable
2. transient

Answer 25

Cavitation

Question 26

-gaseous nuclei tend to expand and contract (at lower MI levels)

-do not burst

-intercept and absorb acoustic energy

-fluids surrounding the cells undergo microstreaming and the cells are exposed to shear stresses

Answer 26

Stable cavitation

Question 27

-higher MI levels

-bursting bubble

-also called normal or inertial

-shock waves and very high temp

Answer 27

Transient cavitation

Question 28

calculated number that indicates the harmful bioeffects from cavitation

lower:
-less cavitation
-less pressure
-higher frequency

higher:
-more cavitation
-more pressure
-lower frequency

Answer 28

Mechanical index (MI)

Question 29

T/F: A health care professional may proceed when the benefits surpass the risks.

Answer 29

True

Question 30

What are three devices that measure the output of ultrasound transducers by absorption?

Answer 30

1. Calorimeter
2. Thermocouple
3. Liquid Crystal

Question 31

How is the best epidemiological study taken?

Answer 31

By prospective and randomized.

Question 32

What is the most important patient precaution?

Answer 32

To minimize the patient ultrasound exposure. Use ALARA (as low as reasonably achievable) the minimum output power and maximum amplification to optimize image quality.

Question 33

What are two mechanisms that are likely to induce bioeffects?

Answer 33

Two. Most important mechanism associated with ultrasound induced, bioeffects are thermal and non-thermal (mechanical).

Question 34

Which type of Doppler imaging is associated with the highest tissue temperature elevation?

Answer 34

Pulsed Doppler