QA & Phantoms & Elastography Flashcards
Acoustic Power Measurements
A specialized ultrasound transducer referred to as a _________ is placed in the water tank and aligned to the beam to make the various intensity measurements.
hydrophone
What type of hydrophone is this?
“membrane” hydrophone
membrane hydrophones are the gold standard for pulsed wave imaging applications that require a flat response over a broad bandwidth. Flat response over a broad bandwidth. High Sensitivity
What type of hydrophone is this?
The four hydrophones pictured above are called “needle” hydrophones
needle piezoceramic hydrophones are excellent sensors for laboratory use in ultrasonic field mapping, with pinpoint access and good spatial resolution. They exhibit high sensitivity, with decreased sensitivity flatness and slightly narrower directivity.
What is Schlieren Image?
Schlieren imaging is a method to visualize density variations in transparent media.[
Visualization of pressure field produced by ultrasound
The term “schlieren imaging” is commonly used as a synonym for schlieren photography, though this article particularly treats visualization of the pressure field produced by ultrasonic transducers, generally in water or tissue-mimicking media.
QA
Many devices have been created to test system performance. System tests are designed to…..
make certain that there has been no degradation in system performance over time.
QA
What are the 2 categories to test QA devices?
- Used to test instrument operation/performance (diagnostic functionality and the entire US system)
- Used to measure acoustic output (bioeffects and safety & beam former and TDR
The 2 most commonly used hydrophones for diagnostic US TDR testing are:
- needle hydrophone
- membrane hydrophone
important parameters of hydrophones are:
- bandwidth
- sensitivity
- directivity
- flatness of response
What is TE (tissue equivalent) Doppler Phantom?
- used for Doppler
- May contain circulation pump, vibrating strings, moving belt.
- Simulates blood flow through vessels embedded in phantom.
- Used to assess Pulsed Wave, Continuous Wave, Color, and Power Doppler.
Doppler testing presents extraordinary challenges since mimicking the properties of blood in a consistent fashion is extremely difficult. As a result, many different types of Doppler phantoms have been created. The most notable are (3):
- Flow phantoms
- String phantoms
- Vibrating Plate (sensitivity) phantoms
Doppler flow phantom can be used for:
- Directional Discrimination
- Flow velocity
- Sensitivity (varying depth)
- Maximum penetration
- Location of flow
Flow Phantom Controller
What does this phantom do?
detects the maximum velocity and the direction of flow
This device is used to produce the fluid flow and can be used in conjunction with flow phantoms such as the discrimination device shown in the previous slide.
The greatest difficulty with Doppler flow phantoms is producing a fluid with stable reflective properties over long periods of time. Some companies have recognized this problem and now sell __________
blood mimicking fluids
Flow Phantom (Calibrated Flow VolumeFlow Phantom )
This flow phantom produces a known volumetric flow with laminar flow profiles in the center stream of the flow conduit.
A second Doppler sensitivity phantom can be included within the box. The sensitivity phantom has a diving vessel with a variable speed constant velocity flow
String Phantoms
A string phantom uses controlled movement of a string via a motor to create reproducible velocities.
measure velocity within the vessel
String Phantoms
Notice in the upper left hand corner the velocity profile created by the moving string. This type of phantom was designed to test:
- peak velocity accuracy
- gate depth accuracy
- spectral broadening
This phantom creates a Doppler signal by phase modulation of the ultrasound beam through very small vibrations of a target plate
Vibrating Plate Doppler Phantom
Other Test Objects
Beam Profile/Slice Thickness
- contains thin, scattering layer in echo-free material
- Used to show beam width on scan plane or section thickness
- Evaluates elevational resolution (may diminish spatial resolution and reduce visibility of small lesions if too thick).
The purpose of using phantoms
Many phantoms have been created to test various aspects of 2-D and now 3-D imaging characteristics and the various types of resolution. Some of the aspects that can be tested with these phantoms include:
Whan can we test with phantom?
- Detail resolution (lateral, axial, and elevation)
- Sensitivity
- Contrast resolution
- The dead zone (area close to the transducer dominated by reverberation)
- Dimensional measurement accuracy (depth, diameter, area, volume, etc.)
What can be tested from this?
By placing the transducer on an alternate “face” of the same phantom, different aspects of detail resolution can be tested
The multi-purpose tissue cyst phantom can be used to test many different aspects of the ultrasound system including:
- Dead Zone
- Detail resolution (lateral and axial)
- Depth accuracy
- Measurement accuracy
- Contrast resolution
- Penetration
What is this phantom and its characteristics?
AIUM 100mm Test Object is used to evaluate:
- Axial resolution – pins parallel to beam axis
- Lateral resolution – pins perpendicular to beam axis
- Electronic Caliper accuracy – measured distances between reflectors are compared to known distances on test object
- Dead Zone – pins at top of test object, close to TDR
*This phantom can be used for testing detail resolution (lateral/axial), depth accuracy, the dead zone, measurement accuracy and penetration.
Match the following group of wires with its function for the AIUM test object (Fig. 1–51)
11. registration or B-mode alignment _____
12. axial resolution _______
13. lateral resolution _______
14. dead zone _______
15. depth calibration _______
11. (A, B, C, D, E) All rods must be used to check registration accuracy
12. (A)
13. (B)
14. (D)
15. (C or E) See Fig. 1–24 and Table 1–3, Study Guide
AIUM 100 mm test object is filled with
algae inhibitor, alcohol, and water = ps 1540 m/s
scan face A, evaluate center rods, group a
scan B, evaluate rod group b
7 vertical rods separated 25, 20, 15, 10, 5 and 3 mm, top to bottom
lateral resolution
spacing of 2 closest rods seen separately
lateral resolution
scan face A, evaluate rod group d
6 vertical rods separated 20 mm from top
depth calibration accuracy
depth calibration accuracy measures the
distance between 1st and last rod
depth calibration true distance
100 mm
depth calibration, +/- _____ = call service
2mm
scan face A, evaluate rod group e
system sensitivity a measure of
the weakest echo signal that can be seen on the image display
system sensitivity, any change of _____ or more = call service
6 dB
scan face A, evaluate rod group c
5 rods separated by 10, 8, 6, 4, and 2 mm from top of test object
dead zone
distance from TDR face to first rod image
dead zone
tissue mimicking phantom AKA
tissue equivalent phantom
What is TE phantom used for?
With tissue-mimicking material the phantom can also be used for penetration tests, since this material has attenuation properties similar to tissue.
TE Phantom
Contain materials with properties similar to soft tissue such as (4 properties):
- speed of sound = 1540 m/s
- attenuation
- scattering
- echogenicity
TE Phantom
material
graphite-filled aqueous gels and urethane rubber
TE Phantom
contains
- structures that mimic cysts, and solid masses
- thin nylon lines/rods to test resolution and distance
TE Phantom
used to
evaluate grayscale
ATS Multipurpose Phantom
This phantom can be used for:
- Dead zone (ring down)
- Vertical measurement accuracy
- Horizontal measurement accuracy
- Sensitivity/Penetration
- Focal Zone
- Axial and Lateral Resolution
- Image uniformity
- Gray scale & displayed dynamic range
Curved Linear Image of the ATS Multipurpose Phantom
TE phantoms simulate tissue properties, allowing assessment of (4)
- detail and contrast resolution
- penetration
- dynamic range
- TGC
TE phantom does not assess
beam width
phantom set up _____ MHz or higher
3.5
Doppler phantom accurately evaluates (4)
- PW
- CW
- CFD
- power Doppler
beam profiler/slice thickness info gives
3D reflection amplitude info
CIRS Model 040 Phantom
Image uniformity
Axial and Lateral resolution Depth calibration
Dead zone (ring down) Registration within two different
backgrounds of 0.5 and 0.7 dB/cm/MHz
CIRS Fetal Phantom