Module 1 : Quality Assurance Flashcards
main reason for quality assurance
reality of patient misdiagnosis exists if the pages we think we see are not real
quality assurance definition
- program that ensures proper and consistent operation of imaging system
7 things that quality assurance ensures
- proper equipment operation
- detection of gradual degradation of performance
- minimizes machine down time
- minimizes repeat examination s
- sonographer and patient safety
- cost efficiency
- maintains standards
three main people responsible for QA
- physician
- sonographer
- service (biomedical/manufacturer)
the physicians role in QA
- the director
- assess images for overall quality
the sonographers role in QA
- the front line
- may perform routine testing and record keeping
- routine maintenance (cleaning filters and visual inspections)
routine maintenance the sonographer may do
- clean surface
- clean recording devices
- clean air filters
- assess cables and trasnducers
- film/image recording quality
the two types of service personnel
- the manufacturer
- the biomedical personnel
role of the manufacturer in QA
- provide routine preventative maintenance and repair equipment as needed
role of biomedical personnel in QA
- responsible for acceptance testing when machine arrives on site to ensure patient and employee safety
what is acceptance testing
- sophisticated testing when systems are place into operation
- image performance and power output are measured and the system checked to see that it will work with ancillary equipment in the department
what is routine performance testing
- aout measuring image performance
- ASSESSING FOR CHANGES OVER TIME
the key component to a good QA program is
- record keeping
- consistency
+ person, temp, focus, time
AIUM 100
- older testing device
- plastic case contain 0.75mm steel rods arranges in groups and filled with water alcohol and algicide
- inexpensive but have no grayscale and non attenuation
phantoms 2 types
- tissue equivalent phantoms
- AIUM 100
tissue equivalent phantoms
- structure than contains one of more materials to simulate a body of tissue in its interaction with ultrasound
phantoms - purpose and characteristics
- plastic case that contains a gel mixed with graphite poweder and rod groups plus solid and cystic lesions
- give a much better approximation of clinical performance since they allow for testing of gray scale, attenuation , speed of sound
characteristics tissue equivalent phantoms must have to act as soft tissue
- attenuation coefficiente (1/2F)
- speed of sound (1540m/s)
- backscatter coefficient/ relative contrast
- elasticity
- thermal properties
tissue equivalent phantoms can do what testing
- dead zone measurement
- detailed resolution
- distance accuracy
- image uniformity
- depth of penetration
- cyst imaging capabilities
what is the dead zone
- the area in the near field close to the transducer also known as the MAIN BANG
dead zone QA technique
- scan rod group a from side A
- the last pin that you can fully resolve closest to the probe is the dead zone depth
- record measurement and check again over time
what is axial resolution
- ability to separate interfaces along the path of the beam
axial resolution QA technique
- involves measuring the smallest separation visible between the axial resolution pins at various depths
- watch for changes over time
- scan rod group b from side A
- the smallest distance between the pins that we can resolve is the axial resolution
what is lateral resolution
- ability to separate interfaces across the beam
- related to beam width
lateral resolution QA technique
- measuring the lateral resolution pins and is dependant on depth and focus
- need to have the same depth and focus every time
- side A rod group C
- look at which rod has the least amount of point spreading is and measure the beam width
- look for changes over time
what is elevational resolution
- aka slice thickness and Z axis
- ability to resolve echoes in the 3D plane
elevational resolution QA technique
- for quantitative assessment you need a different phantom with a RAMP
- for qualitative assessment look at the cystic structures as see how well they are resolved
- side A cyst group e
- look for number of internal echoes have focus right at the cyst so you know lateral resolution is at its best
- look for changes over time
distance accuracy
- both horizontal and vertical distance accuracy can be measured using pins
- IMPORTANT TO MEASURE OVER LARGE DISTANCE TO DETECT SMALL MARGINS OF ERROR
distance accuracy QA technique
- measuring pins at a known distance with callipers and comparing numbers
- look for changes over time
TGC characteristics
- user specific test where results are based on the observation of the individual performing the test
- images may be captures with different slide pod configurations under different conditions and compared over time
image uniformity
- test a linear arrays consistency along th array
- look for inhomogeneous regions or areas of non uniformity
what is sensitivity
- ability to detect weak echoes
sensitivity QA technique
- maximum depth of visualization
- power and gain are optimized for penetration and the observer records the death where brightness starts to fade
dynamic range
- measures the number of shades of gray displayed the machine
- subjective test need good record keeping
- images compared over time
what is contrast resolution
- measures the ability to distinguish between simulated lesion to similar echogenicity
- controlled by dynamic range
- BIT DEPTH IS ULTIMATELY RESPONISIBLE FOR CONTRAST RESLOLUTION
contrast resolution QA technique
- scanning solid, cystic, hypo echoic, echogenic lesions
- see how well you can differentiate lesions from other surrounding tissue
contrast vs contrast resolution
- can have lots of contrast but still have poor CONTRAST RESOLUTION
registration
- test for older static b scanner to ensure arm positioning is accurate for the reconstruction of an image
registration QA technique
- involves scanning pins from 3 sides to see if the lines intersect at one point
two types of doppler phantoms
- flow = like TE phantom
- string or belt = like AIUM 100 test object
flow doppler phantoms
- like TE phantoms
- close match to clinical experience
- expensive
flow phantoms can measure what factors
- maximum depth (sensitivity for color)
- gate position accuracy
- volume flow and velocity accuracy
- color flow penetration
- image congruency test
string or belt doppler phantoms
- move a string or belt in a water bath
- do not match the clinical experience
- cheap
3 other applications for phantoms
- demonstration
- training
- research
7 other specialty phantoms
- biopsy
- mass
- 3D
- cryosurgery
- brachytherapy
- HIFU (high intensity frequency ultrasound)
- IVUS (intravenous ultrasound)
what are output testing devices
- used by service personnel or manufacturers to evaluate the systems power output
3 types of output testing devices
- hydrophone
- power (force) balancers
- calorimeter
hydrophone also had 4 other parts
- plotter (articulated arm)
- spectrum analyzer
- oscilloscope
- schlieren system (acoustic optical method)
what is a hydrophone
- small (1mm) transducer that produces a voltage proportional to the received acoustic pressure (piezoelectric element)
- used with a plotter to be moved throughout the sound field and produce a beam profiler
hydrophone capabilities with an oscilloscope
- SPL
- PD
- PRP
- PRF
- DF
hydrophone capabilities with a spectrum analyzer
- resonant frequency
- bandwidth
- fractional bandwidth
- Q factor
what is force balance used to measure
- power
what is a force balance
- sophisticated sensitive micro balance that is phased in the sound field and calibrated to determine acoustic power and intensity
what is a calorimeter
- essentially a heat meter used to measure acoustic power
- an enclosed fluid container with a very sensitive thermocouple detects temp change and can determine acoustic power
future QA developments
- as tech changes need new products
- phantoms designed to have increased durability and longevity but have to keep up with advancements to technology
+ thin film phantom
+ smaller resolution point targets - some machines have ability to self evaluate which would help with subjectivity of manual evaluation
