Ultrasound (Exam I) Flashcards
Ultrasound is defined as sound with a frequency greater than ___________ hz (the human hearing limit).
What range do ultrasound devices operate at?
- 20,000 hz
- 2 - 18 megahertz
What type of ultrasound probe provides the best resolution in exchange for poor penetration?
What frequency is seen with this probe?
- Linear
- High frequency
What type of ultrasound probe provides the decent resolution and decent penetration?
- Curvilinear
What type of ultrasound probe provides the best penetration in exchange for poor resolution?
What frequency is seen with this probe?
- Phased
- Low frequency
What aspect of the ultrasound probe converts electricity into sound?
- Piezoelectric elements
Is the output from the ultrasound probe constant? Why or why not?
- No because a “listening” period is needed for returning signals.
What tissue allows for the quickest sound conduction?
What then would have the slowest conduction speed?
- Bone
- Air
What zone is indicated by 1 in the figure below?
What is it’s importance?
- Fresnel Zone (near field)
- Decent lateral resolution in this region
What zone is indicated by 2 in the figure below?
What is it’s importance?
- Fraunhofer Zone (far field)
- Poor lateral resolution in this region
What zone is indicated by 3 in the figure below?
What is it’s importance?
- Focal Zone (ultrasound is narrowest and beam intensity is greatest here.)
- Best lateral resolution in this region
What is impedance?
What has the greatest impedance?
The least?
- The resistance to ultrasound propagation as it moves through a medium.
- Greatest impedance = bone
- Least impedance = air
What is ultrasound reflection?
- Reflection of ultrasound waves back to the probe
What has the highest reflection property?
What tissue is highest?
- Bone has highest reflection
- Air
What is mirror artifact?
- Artifact where tissue is mirrored on the other side of a structure (diaphragm/liver example)
What is refraction?
- Occurs when ultrasound strikes two tissues with different impedance values.
What is edge artifact?
- Artifact occurring at the edges of smooth or rounded structures creating a shadow at structures edge.
What is ultrasound attenuation?
What probe would be most affected by attenuation?
- Loss of amplitude & intensity the deeper ultrasound waves penetrate. (due to absorption, refraction, & reflection)
- Linear probe (due to higher frequency)
What is ultrasound absorption?
- Occurs as ultrasound wave travels through a medium losing energy.
What is Anechoic? What is an example?
- Structures that appear black due to having no internal echoes.
- Ex. Blood vessels, bladder, cysts, etc.
What is hypoechoic? What are tissue examples?
- Structures that appear darker than surrounding tissue.
- Ex. kidney compared to spleen.
What is hyperechoic? What are tissue examples?
- Structures that are brighter than the surrounding tissue.
Ex. Fatty tumors & bone
What type of artifact is noted in the picture below?
- Shadowing (occurs from bone reflecting back most ultrasound waves, and the rest attenuating quickly).
What type of artifact is noted in the picture below?
Posterior Acoustic Enhancement (occurs from passing through low impedance tissue).
What does M-mode do in the ultrasound machine?
What is it useful for?
- Gives a motion over time display.
- Lung sliding, fetal heart rate, etc.
