Chapter 22

QA

the ability of the system to detect weak echoes is called …

sensitivity

target used for measuring axial resolution are

closely spaced targets of varying distances

poor elevation resolution will cause

You will not be able to clear anechoic tubes oriented with their axis in the scan plane

what describes the dead zone

distance from transducer to the first identifiable echo

region of best lateral resolution

at the focal point

what is evaluated using a doppler flow phantom

• accuracy of velocity estimation

• accuracy of sample volume placement

• ability to discriminate different flow directions

• accuracy of color registration

all of the above

with using a phantom, which series of pins would be helpful in distinguishing radial resolution

axial resolution

set of curved pins

with using a phantom, what series of pins determine the dead zones

slanted line of pins closest to the top

with a phantom, which set of pins determine vertical depth calibration

pins going up and down in the middle

an abdominal ultrasound scan result reveals a pancreatic mass. CT (gold standard) report states a normal abdominal findings. the US exam is a …

FP, false positive

the ability of a test to correctly identify those without the disease

specificity

__ __ is routine, periodic evaluation of US system to guarantee optimal image quality

quality assurance

what are the four requirements of QA

component testing

repairs

preventive maintenance

record keeping

what are the goals of QA

proper equipment operation

detect gradual changes

minimize downtime

reduce number of repeat scans

reduce number of non-diagnostic exams

what does objective mean

facts, hard evidence that something is going on

what does subjective mean

opinions or feelings

quality assurance programs should be based on ___ standards

objective

what are three deivces used for quality assurance

tissue equivalent phantom

doppler phantom

beam profile / slice thickness phantom

the tissue equivalent phantom evaluates

gray scale

tissue texture

multi and adjustable focus

the tissue equivalent phantom is similar to soft tissue how

prop speed

attenuation

scattering characteristics

echogenicity

a __ __ is a circulation pump stimulate RBC reflections for doppler evaluation

flow phantom

a flow phantom evaluates

CW, PW, and doppler

what are other types of flow phantoms

vibrating string

moving belt

the __ __ phantom measures beam thickness

slice thickness

the greater the slice thickness the __ the spatial resolution is

poorer

what does slice thickness look like

pulls in weak echoes into other structures (thick plane)

for maximum sensitivity, what adjustments should be made

output power and amplification set at max

depth set at its deepest

what is the dead zone

region close to TRX where image is inaccurate

distance from TRX to first visible

with higher f transducers, there will be a __ __ dead zone

more shallow

how to help visualize superficial structures

use an acoustic standoff or gel pack

creates anechoic aerea

what is range accuracy or vertical depth calibration

accuracy in placing reflectors at correct depth parallel to sound beam

what is horizontal calibration

accuracy in placing reflectors in the correct positions perpendicular to sound beam

performance measurements are needed to determine the …

registration accuracy

what is distance measurement accuracy

check for accurate horizontal and vertical caliper measurements from phantom

the distance along the US beam where intensity is the greatest and beam width is narrowest

focal zone

the focal zone improves __ resolution

lateral

since our beam width varies with depth so our __ resolution will also vary at different depths

lateral

a cyst will be

anechoic

a solid structure / tumor will be

solid, filled in, hyperechoic

we must compare our laboratory test to a ….

gold standard

what is included in the gold standard

CT

MRI

arteriogram

surgery

ultrasound is __ accurate in determining gallstones

98%

the gold standard is __ __

always right

what is a true positive result

lab test and gold standard are both positive

what is a false positive

lab test was postive

gold standard was normal or negative

what is a false negative

lab test normal or negative

gold standard postitive

what is a true negative

lab test and gold standard both normal or negative

__ is the percent of correct laboratory tests compared to the gold standard

accuracy

__ is the incidence of disease in the total population

prevalence

the __ __ __ tells us the likelihood that the disease is REALLY present

positive predictive value

the __ __ __ tells us the likelihood that disease is NOT present

negative predictive value

what is the equation for sensitivity

TP / TP + FN

what is the equation for specificty

TN / TN + FP

equation for accuracy

TP + TN / TN + TP + FN + FP

equation for PPV

TP / TP + FP

equation for NPV

TN / TN + FN

what axis of the table are the lab tests presented on

Y axis - side

what axis is the gold standard presented on

x axis - top

what does the statistics table look like

…. +. _

+ . TP. FP

-. FN. TN