Ch. 24 Bioeffects

Question 1

amount of acoustic energy the patient receives

Answer 1

acoustic exposure

Question 2

Lowest to highest intensities for various imaging modalities

Answer 2

gray scale, m-mode, color doppler, pulsed wave doppler

Question 3

measures period, PRP, PRF and pulse duration, amplitude and beam shape

Answer 3

hydrophone

Question 4

What devices measure output of ultrasound trdx by absorption

Answer 4

calorimeter, thermocouple, liquid crystal

Question 5

uses absorption, the sound beams total power is calculated by measuring the temperature rise and time of heating

Answer 5

calorimeter

Question 6

uses a tiny electric thermometer, temperature rise is related to the power of the sound beam at the particular location where the device is positioned

Answer 6

themocouple

Question 7

change color based on temp, provides insight into the shape and strength of the sound beam

Answer 7

liquid crystal

Question 8

the ______ must outweigh the _______

Answer 8

benefit, risk

Question 9

what are standard intensities

Answer 9

50-500 W/cm2

Question 10

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

Answer 10

dosimetry

Question 11

research that is preformed with in the living body of an an animal or plant

Answer 11

in vivo

Question 12

research that is preformed outside the living body and in an artificial evironment, indicate high ultrasound intensities can cause genetic damage and cell death

Answer 12

in vitro

Question 13

something has the potential to produce bioeffects, searches for a relationship between cause and effect

Answer 13

mechanistic approach

Question 14

based on acquisition and review of information from patients or animals exposed to ultrasound, seeks a relationship between the exposure and response

Answer 14

empirical approach

Question 15

bioeffects that result from temperature elevation

Answer 15

thermal

Question 16

interaction of the sound waves with microscopic, stabilized, gas bubbles in the tissues

Answer 16

cavatation

Question 17

two forms of cavatation

Answer 17

stable, transient

Question 18

useful predictor of maximum temp increase under most clinical relevant conditions, combination of temp and exposure time, related to output power and properties of the tissue

Answer 18

thermal index

Question 19

thermal index three forms

Answer 19

TIS, TIB, TIC (soft tissue, bone, calvarium-head).
TIS-, or soft tissue thermal index, assumes that sound is traveling in soft tissue
TIB-or bone thermal index, assumes that bone is at or near the focus of the sound beam (think fetal exams)
TIC-or cranial bone thermal index, assumes that cranial bone is in the sound beam’s near field

Question 20

maximal heating is related to the beams ______ intensity

Answer 20

SPTA

Question 21

Current FDA regulation for max intensity is

Answer 21

720 mW/cm2

Question 22

A temp increase of up to ______C has not shown any bioeffects

A ___to___C rise in testicular temp can cause infertility

No fetal defects have been observed at temperatures less than

Answer 22

2

2 to 4

39C

Question 23

pressure changes that cause the formation of bubbles, can produce severe tissue damage

Answer 23

cavitation

Question 24

gaseous nuclei already present, expand and collapse with pressure, bubbles can absorb a large amount of acoustic energy

the fluids surrounding the cells undergo____and the cells are exposed to _____

Answer 24

stable cavitation

Question 25

will stable cavitation bubbles bust

Answer 25

no, low MI

Question 26

dependent on the pressure of the ultrasound pulse, produces highly localized violent effects (shock waves and high temp) AkAs: inertial or normal cavitation

Answer 26

transient cavitation

Question 27

will transient cavitation bubbles burst

Answer 27

yes

Question 28

a calculated number related to the likelihood of harmful bioeffects from cavitation

Answer 28

mechanical index

Question 29

Lower MI: _______ cavitation _______ pressure _______ frequency

Answer 29

less, less, higher

Question 30

Higher MI: _______ cavitation _______ pressure _______ frequency

Answer 30

more, more, lower

Question 31

indicator of cavitation, equal to the peak rarefractional pressure divided by the square root of the frequency

Answer 31

MI

Question 32

ratio of acoustic power produced by the trdx and the power required to raise the temp of tissue 1 degree C, relates to attenuation (heat) and SPTA

Answer 32

TI

Question 33

Preventing Bioeffects: _______ the machine you use Keep the exam as ____ as possible Always start with lowest possible ______ Follow _______ principles Use ________ _____ to optimize image Keep track of ______ and ____ values on screen Be extremely cautious when using doppler in ______ trimester of pregnancies

Answer 33

know, short, power, alara, receiver gain, mi, ti, first

Question 34

Keep TI values below

Answer 34

1

Question 35

Keep MI values below

Answer 35

1

Question 36

branch of medicine associated with population studies, it is an empirical survey method,

Answer 36

epidemiology