QA

why are 3 reasons statistics is needed

to look at the history of disease, advance knowledge, assess normal and the point it becomes a pathology

diagnostic test are used to confirm or exclude a

specific diagnosis

the certainty that a specific diagnosis can be confirmed or excluded determines _______of a study

usefulness

no test are ____ accurate

100 percent

how is statistics practiced in sonography

patients are classified as healthy or abnormal, instruments or test can be in perfect, and there are test error

what is a test error

when a patient is incorrectly classified

statistics offers a method to measure the ability of a specific test to give the ____ _____ for both health and ill patient

correct diagnosis

we must compare our lab test to a

gold standard

what is a gold standard

MRI, CT, arteriogram

what is the all important rule to sonography practice statistics

the gold standard is always right

this is when the lab test is positive at the GS is positive

true positive

this is where the lab test is positive but the GS is negative

false positive

this is where the lab lest is negative and the GS is negative

true negative

this is where the lab test is negative but the GS is positive

false negative

the ability to detect a disease when disease is really present, the degree to which it identifies all patients with disease

sensitivity

the ability to determine that there is no disease when the patient is truly normal, the degree to which it defines all patients without disease

specificity

tells use the percent of correct lab test compared to the gold standard, indicates the percent of patients in whom the test results are correct in identifying the presents or absence of disease

accuracy

incidence of disease in total population

prevalence

tells us the likelihood that the disease is really present, indicates the percent of patients with a positive test result who have the suspected disease

positive predictive value

- tells us the likelihood that disease is NOT present

- indicates the % of pts with a negative test result who do not have the suspected disease.

negative predicative value

what is the sensitivity formula

TP/(TP+FN)

what is the specificity formula

TN / (TN + FP)

what is the accuracy formula

TP+TN/(TN+TP+FN+FP)

what is the PPV formula

TP / (TP + FP)

what is the NPV formula

TN/(TN+FN)

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

quality assurance

quality assurance is a ____ and _____ necessity

medical and legal

What are the 4 requirements of quality assurance?

assessment of system components, repairs, preventive maintenance, and record keeping

What are the 5 goals of quality assurance?

guarantee proper operation of the system, detect gradual changes, minimize downtime, reduce the number of non-diagnostic exams, reduce the number of repeat scans

ultimate responsibility for equipment quality assurance fall to the _____ to diagnose and report problems

sonographer

what do competent sonographers look for when looking over their machines

inspect the transducer and cables, clean the transducer and machine, change the filter, check the wheel locks, and check the track ball

quality assurance programs should be based on ____standards

objective

this information is factual, repeatable ,and able to be counted

objective

this information is affected by opinion, belief, or assumptions and frequently varies from person to person

subjective

what are devices we use to check for quality assurance of our machine

tissue equivalent phantom, doppler phantom, and slice thickness phantom

a tissue equivalent phantom is similar to soft tissue what 4 ways

propagation speed, attenuation, scattering characteristics, and echogenicity

what does the tissue equivalent phantom evaluate

grey scale, tissue texture, and multi and adjustable focus

this is a circulation pump that simulates RBC reflections for doppler evaluation

doppler phantoms

what does a phantom doppler evaluate

CW, PW, and color doppler

other types of flow phantoms include:

vibrating strings and moving belts

what does the slice thickness phantom measure

beam thickness and thus thickness resolution

if the thickness of the slice is too thick what will we see

decreased spatial resolution

performance measurements are completed when new equipment is

purchased or installed

what is all checked out in a quality insurance test

sensitivity, dead zone, vertical depth, horizontal calibration, focal zone, axial resolution, lateral resolution, TGC, grey scale, and mock cyst

the ability to detect low level echoes

sensitivity

what are the two types of sensitivity

normal and maximum

this is the sensitivity setting where all pins, sold masses, and cysts structures in the test phantom are accurately displayed

normal

in normal sensitivity ___ ____ and ____ are set to normal sensitivity and are not changed through the remainder of the QA testing

TGC, Power, and amplification

this is the sensitivity where the output power and amplification are set to the max and the depth is the greatest

maximum sensitivity

what is the purpose of maximum sensitivity

to detect very low level signals at maximum depth

the region close to the transducer where images are inaccurate

dead zone

how do they measure the dead zone

roads are placed at varying depths from the top of the phantom 2,4,5,8,10 cm. the distance from the transducer to the first visible rod is the dead zone

what does the dead zone come from

the time it takes for the transducer to switch from talking to listening

what kind of frequency transducer (high or low) has a shallower dead zone

higher

what can be used with low frequency transducer to minimize the dead zone

acoustic standoff or gel pack

if the dead zone is larger then expected what does that indicate

cracked crystal, detached backing material or a longer pulse duration

range accuracy is also called

vertical depth calibration

what is range accuracy

the ability of the system to accuracy place reflectors at the correct depths parallel to the sound beam

what is horizontal calibration

the ability of the system to place reflectors in the correct position perpendicular to the sound beam

this is checking for accurate horizonal and vertical caliper measurements

distance measurements

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

focal zone

the _____ pin indicates the focal zone

narrowest

what type of resolution is best at the focal zone

lateral resolution

Scan from the top where two pins are displayed as two separate reflectors, the distance between the two pins get closer and closer. there are parallel to the sound beam

axial resolution

how close 2 pins can be positioned parallel to the sound be and still be represented as 2 structures

axial resolution

this is taken from and angled corner

lateral resolution

minimum distance that two rods are displayed as two separate images perpendicular to the sound beam

lateral resolution

why does lateral resolution vary at different depth

divergence

the ability of the system to display similar reflectors in the phantom with echoes of equal brightness

compensation operation or uniformity

will proper _____, all echoes should have the same appearance regardless of depth

depth

what do mock cyst and solid masses in the phantom allow us to check for

if the system is accurately displaying the dimension, textures, and fill in

true or false: it is important that the US system, hard copy, work station, and archival system all display the same information and quality of photo

true