Exam 1 Ultrasound Flashcards
Ultrasound is defined as sound with a frequency above _________ Hz.
What is the frequency range for human hearing?
20,000 Hz
20 to 20000 Hz
Describe a Linear Probe
High Frequency
Great Resolution
Poor Penetration
Ideal for imaging vessels, muscles, tendons, breast, and thyroid. Anything just below the surface of the skin.
Describe a Curved/ Curvilinear Probe
Medium to Low Frequency
Wider and deeper field of view, sacrifice resolution.
Ideal for OB/Pelvic exams.
Describe a Phased Array Probe
Medium to Low Frequency
Deeper image, sacrifice resolution
A smaller footprint allows easier imaging between rib spaces, perfect for cardiac scanning, and can be used for the abdomen as well.
What piece of item in the ultrasound probe will convert electricity to sound?
The piezoelectric element will vibrate and produce sound waves that will send sound waves to the body.
Don’t drop the probe
What is the relationship between frequency and wavelengths?
Inverse relationship
High Frequency = Short Wavelength
High Resolution, Superficial Image
Low Frequency = Long Wavelength
Low Resolution, Deep Image
The maximum height of the wave is called the __________.
Amplitude (dB)
(as described as the max particle displacement dB)
___________ is the speed at which the wave propagates through a medium.
Velocity (m/s)
Vibrations will move through solids a lot faster than air
Why is there a delay in imaging with an ultrasound?
Sound waves are produced in pulses that are spaced apart. We need to allow time for echoes to be reflected back to the transducer and processed before emitting a new pulse.
Move slowly and scan
What is the relationship between stiffness and speed?
What is the relationship between density and speed?
Proportional.
Increase stiffness, Increase Speed
Inverse relationship.
Increase density, Decrease speed
Because mediums within the body have varying density and stiffness, the propagation speed of sound will change between different mediums.
Which type of ultrasound uses a beam sweep?
Linear Transducer
Curvilinear Transducer
Beam sweep refers to the waves working down the transducer and receiving echoes to produce an image
Which type of ultrasound does not use a beam sweep?
Phase Array
The Piezoelectric elements are packed near the center of the transducer and produce a focus beam that originates from the center
What is the Fraunhofer Zone?
Far field, area distal to the focal point.
Beam is diverging, poor image quality.
Higher frequency, less divergence in far field.
Lateral resolution is greatly reduced.
What is the Freshnel Zone?
Near field, area proximal to the focal point.
Beam diameter is same as transducer.
Higher frequency = longer near field zone.
Lateral resolution is good.
What is the resistance to ultrasound?
Impedance (density x propagation speed of sound)
Increase tissue density, increase impedance.
High impedance, high reflection. (bone)
This image is showing good _______.
Reflection
Reflection occurs when sound strikes the interface of two mediums with significant impedance values
Why do we use ultrasound jelly?
Sound waves are unable to penetrate/travel through the air, the gel is used to reduce the air between the patient and the transducer which reduces the impedance and reflection to allow a clear image to be produced.
A reflection coefficient of 0 corresponds to _________ reflection.
No reflection, total transmission.
What causes mirror artifacts?
Mirror image artifacts occur when the transmitted pulse and returning echo reflect off of a highly reflective interface (diaphragm) and change direction before returning to the transducer.
What is going on here?
What kind of artifacts will this lead to?
How do you mitigate this?
Refraction
Edge artifacts
Tilt the probe to reduce refraction.
What are these?
Attenuation and Absorption
Attenuation is when sound waves travel through tissue, the intensity and amplitude decrease.
Absorption occurs when soundwaves loses energy as it travels through a medium.
Refers to the ability to reflect or transmit ultrasound waves in the context of surrounding tissues
Echogenicity
What is anechoic?
Anechoicrefers to structures that appear black, meaning that there are no internal echoes.
Think fluid-filled vessels, bladder, gallbladder
What is hypoechoic?
Hypoechoicstructures appear darker than surrounding structures; gives off fewer echoes. Often seen in tissues with increased density such as fibrous masses. Can also be used to describe the appearance of one organ in relation to another.
The kidney (outlined in blue) is hypoechoic to the adjacent splenic tissue
What is hyperechoic?
It is used to describe structures that appear brighter than surrounding structures; these structures give off more echoes. This can be seen in structures with lower density than the surrounding structures allowing for increased propagation speeds.
What is isoechoic
Isoechoicis used to describe a structure that gives off similar echoes relative to another structure in the same image.
In this image of the kidney/liver interface the kidney (outlined in blue) is isoechoic to the adjacent liver tissue.
What is shadowing?
Occurs when sound waves encounter a structure that has a very high attenuation coefficient (such as bone or solids). We know that the vast majority of the sound waves that strike solids are reflected back to the transducer, but the remaining sound waves attenuate very quickly causing a shadow.
Radius (highlighted in blue) demonstrates shadowing deep to a dense reflector. The sound is unable to continue through the bone causing a black appearance void of echoes
What is posterior acoustic enhancements?
Opposite of shadowing. It occurs when sound waves pass through a structure with a very low attenuation coefficient (fluid filled structures). Because sound passes through fluid filled structures exceptionally well, there is an increase in the brightness of posterior echoes.
Bladder demonstrates posterior acoustic enhancement (highlighted in blue) deep to the bladder
What is reverberation?
Reverberation occurs in the presence of highly reflective surfaces (usually a hardware like a needle). This causes the image to record and display multiple evenly spaced echoes on the screen which are not real.
What is gain?
Gain is the contrast.
High gain brighter, low gain darker.
What is 2D or B-mode?
Standard grayscale mode.
The “B” stands for brightness. This mode of ultrasound imaging provides structural information using different shades of gray in a 2D (two dimensional) image.
Here is the view of the liver
What is M-mode?
Motion mode imaging to look at things that are moving (lung).
For color doppler mode what does red indicate what does blue indicate?
Color red, indicating blood flow toward the transducer.
Color blood, blood flow away from transducer.
The red color does not signify the vessel is arterial.
What is the movement called?
Sliding
Moving the transducer along its long axis.
What is the movement called?
Sweeping
Moving the transducer along its short axis.
What is the movement called?
Tilting or Fanning
While maintaining a fixed position on the body, the transducer is moved along its short axis to change the angle of incidence < 90°.
What is the movement called?
Rocking or Heeling
While maintaining a fixed position on the body, pressure is applied to one side of the transducer to move in the long axis and reduce the incident angle < 90°.
What is the movement called?
Rotating
Turning the transducer in a clockwise or counterclockwise direction over a fixed point on the body to change between a short and long-axis view.
An interscalene block will most likely cause what syndrome?
Horner Syndrome
What view is this?
Long axis
What technique is this?
Out-of-plane technique:a needle is inserted perpendicular to the imaging plane, resulting in only a “slice” of the needle being visible on the screen (tip or shaft), where the needle tip can be visualized approaching the target of interest by sequentially tracking the needle during its insertion.
Out-of-plane vascular access. A short axis view of a peripheral vein model demonstrating the needle tip as a hyperechoic point immediately above the vein.
What technique is this?
In-plane probe positioning:A needle is inserted parallel to the imaging plane.
A long axis view of a peripheral vein model demonstrating the entire needle as a hyperechoic line above and cannulating the vein.
What view is this?
Short axis
What are the focal zone and focal point?
The focal point is where the US beam is the narrowest and beam intensity is the greatest.
The focal zone is the area around the focal point.
Lateral resolution is best within the focal zone.
