Week #12 Quiz: Bioeffects and QA

bioeffects

change to tissues as US beam travels through

dosimetry

the science of identifying and measuring the characteristics of an ultrasound beam

what dosimetric qualities are measured

pressure

power

intensity

force

pressure=

force/area

peak positive pressure

compression

peak negative pressure

rarefaction

acoustic power=

energy/time

acoustic intensity=

power/beam area

intensity _______________ in the far field

decreases

calorimeter

measures total power in a sound beam

thermocouple

measures sound beams power at a certain location

liquid crystal

measures change in temp

hydrophones

measures pressure at a specific location

________________ has the lowest output power and _______________ has the highest

2D, PW doppler

what are the two types of hydrophones?

hydrophone probes (tiny needle shape)

membrane hydrophone (round disc shape)

radiation force balance

force that is exerted when wave hits a target that absorbs, scatters, or reflects energy

measured radiation force relates to ____________ of the beam

intensity or power

what is used to visualize the shape of a sound beam

schlieren imaging

SPTP

highest intensity

SPTA

measures intensity in tissue

when considering ALARA you should use ____________ gain and _________ output power

high gain and low output power

what are the two important bioeffect mechanisms

thermal and mechanical

thermal

tissue temperature elevation

max heating is related to the beam's _______ intensity

SPTA

SPTA should not exceed...

100mW/cm^2 for unfocused beam

1W/cm^2 for focused beam

mechanical

cavitation

no bioeffect for up to ________ degrees Celsius above normal and exposure time less than __________ hours

2, 50

TIS

thermal index in soft tissue

TIB

thermal index in bone

TIC

thermal index in cranial bone

non scanned modalities

CW

PW

M-mode

A-mode

scanned modalities

2D

color doppler

cavitation

causes formation of gas bubbles in tissue which may pop causing tissue damage

stable cavitation

bubbles do not pop

transient cavitation

larger bubbles cause temperature increase and pop which can cause cell death in the affected area

MI and FRQ are ___________ related

inversely

MI

risk of mechanical bioeffects

what is another way to reduce MI

increase FRQ

radiation force

type of MI; force exerted by sound beam on tissue

microstreaming

type of MI; stresses by fluid surrounding the cells

-useful in therapeutic US

in vivo research

performed on animal or plants

in vitro research

performed in petri dish (glass)

Epidemiology

branch of medicine assoc with population studies

empirical

provides exposure-response using clinical surveys

prospective studies

forward-looking

retrospective studies

from the past

-less accurate

randomized studies create _______ groups which are...

2 groups exposed group and unexposed group

gold standard

it is assumed that the gold standard is "perfect"

what are the most common gold standards for US

angiogram

MRI

where is the gold standard on the factorial table

at the top

where is the test (US) on the factorial table

side

where is TP on the factorial table

top left

where is FN on the factorial table

bottom left

where is FP on the factorial table

top right

where is TN on the factorial table

bottom right

true positive (TP)

US and gold standard are both positive

true negative (TN)

US and gold standard are both negative

false positive (FP)

US result is positive

gold standard is negative

false negative (FN)

US result is negative

gold standard is positive

specificity

tests ability in deciding a normal exam

sensitivity

tests ability to find positive exams when there is a disease

positive predictive value (PPV)

measures likelihood that positive noninvasive exam is correct when disease is present

negative predictive value (NPV)

measure the likelihood that a negative noninvasive exam is correct when a disease is present

accuracy

how good is a tests overall quality

how effective is finding positive and neg results

prevalence

percentage of the population affected by a specified disease at a given time

formula for sensitivity

TP / (TP + FN)

formula for specificity

TN / (TN + FP)

formula for positive predictive value

TP / (TP + FP)

formula for negative predictive value

TN / (TN + FN)

what are the lab accreditation agencies

ACR

AIUM

IAC

ACR focuses on

mammo, MRI, breast

AIUM focuses on

general

IAC focuses on

echo and vascular

what is QA

routine maintenance

standardized procedures

stat tracking of test results

lab accreditation

sonographer cert

what are the 4 requirements for QA program

assessment

repairs

prevention

record keeping

what are the goals for QA programs

proper equipment

detect gradual changes

minimize downtime

reduce non-diagnostic imaging

reduce repeat scans

acoustic exposure is determined by...

beam intensity

exposure time

what is the highest intensity in PW tissue US?

SPTA

what is the highest intensity in PW US?

SPTP

TIS is used in

soft tissue

TIB is used in

bone

TIC is used in

cranium in near field

periodic assessment of machines to make sure they are working properly describes

QA

why do we perform QA tests

asses performance between different systems

monitor wear and tear

minimize artifacts

testing methods

healthy model

phantoms

The acoustic variable defined as force divided by area is called:

pressure

The amount of power divided by area is called:

intensity

To reduce the acoustic exposure to the patient, the sonographer should:

decrease the output control

If the power is doubled, the intensity will be:

doubled

If the amplitude is doubled, the intensity will:

increase by a factor of four

Which of the following units are used to measure intensity?

milliwatts per cm squared

The instrument that measures the intensity of the sound beam is a:

hydrophone

Experiments performed in petri dishes are called:

in vitro

Which of the following is used to measure the MI of the sound beam?

sound interaction with gas bodies

Which of the following intensities is measured during the pulse repetition period?

SATA

Which of the following intensities has the lowest value during pulsed ultrasound?

SATA

Which of the following intensities are equal when using continuous wave ultrasound?

SATP=SATA

The routine, periodic evaluation of the ultrasound system is termed:

QA

The middle rod group of the AIUM phantom scanned from the top measures the:

axial resolution

The testing device composed of a series of 0.75 mm diameter stainless steel rods arranged in groups suspended in fluid is the:

AIUM 100mm test object