Elastography (Lesson 8b) Flashcards
What is elastography?
Presents qualitative or quantitative information regarding the stiffness, hardness, or softness of tissue
What 3 qualities of tissue does elastography assess?
Stiffness, hardness, softness
What is Young’s Modulus?
E = force/strain
What does Young’s Modulus measure?
The stiffness (hardness or softness) of a material
Do soft materials have a small or large Young’s Modulus?
Small, a given stress results in large strain
Do hard materials have a small or large Young’s Modulus?
Large, a given stress results in little strain
What is the unit for Young’s Modulus?
kPa
What is the range in kPa for Young’s Modulus?
1 for fat and 100 for fibrotic
Can Young’s Modulus be calculated int he STATIC method of elastography?
No, the stress force is known (sonographer’s arm pushing down)
What is the static method of elastography?
The sonographer physically pushing on the transducer and the instrument tracks the movement of tissue by spatial corrlation
Is the static method of elastography qualitative or quantitative?
Qualitative, cannot use equation to find exact answer as measured force is unknown
What is the dynamic method of elastography?
Uses a short transient force or a time-varying repetitive force applied to the transducer
What are shear waves?
Transverse waves, they travel at slower speeds in directions perpendicular to the travel of the compressional wave (0.5-10m/s for shear waves vs the usual 1440-1640m/s for compressional waves)
Using shear waves to measure stiffness is called what?
ARFI; acoustic radiation force impulse imaging
What measurement is shear waves reported in?
m/s
