Lecture 11 Flashcards
Perpendicular facts (2)
Reflection between 2 different boundaries depends on media z
Large difference between z, large reflection
2 examples of contrast agents
Levovist
Sonovue
Contrast agents are ___, ____ ,____
Easy administration, non toxic, stable
Why are contrast agents good in blood stream
Small enough to perfuse through blood vessels
Most contrast agents contain
Microbubbles of air stabilized by a protein, lipid, polymer shell
Contrast agents increase
Reflectivity from blood
Why do contrast agents cause a very high reflection
Impedance (z) of the bubbles (air) is different than the surrounding medium (blood)
How do contrast agent produce strong harmonics
Bubbles contact and expand unequally and create non-linear propogation.
Known as harmonic contrast imaging
T/F tissue lesions can be very difficult to delineate
T
What is seen with the introduction of contrast agents
Increase in the echogenisity in the perfused tissue but not in the lesions
Sometimes the opposite occurs
Important to know it increases contrast
What else can you do with contrast agents
Track perfusion rate by filling area with contrast agent, pop the bubbles with high amp US and then watch the organ fill back up with low amp US
2 pieces of info needed to position echo on the display
The direction the echo came from
The distance to the reflector/ structure that created the echo
Can the instrument measure distance directly?
No
The instrument measures the
Travel time
Speed is assumed to be
1540 m/s
