Elastography

Question 1

What does elastography measure?

Answer 1

Stiffness of the liver

Question 2

What is used to measure the stiffness of a material?
(hint: the units)

Answer 2

Youngs Modulus in kPa

Question 3

What unit is Young’s modulus measured in?

Answer 3

kPa

Question 4

What is true of materials with a SMALL young’s modulus?

Answer 4

Softer material and a larger strain as it can compress more easily

Question 5

What is true of materials with a LARGE young’s modulus?

Answer 5

Stiffer material and a small strain as it cannot compress very easily

Question 6

What type of ultrasound technology is used for shear wave imaging?

Answer 6

Elastography

Question 7

In shear wave imaging, how is the stiffness of liver quantified?

Answer 7

It is measured in kPa and a HIGHER score indicates a greater stiffness

Question 8

What is the range in kPa for soft tissue?

Answer 8

1-300 kPa

Question 9

What is the value in kPa for fat vs. fibrotic liver?

Answer 9

Fat = 1

Fibrotic liver = 300

Question 10

What is the formula for Young’s modulus?

Answer 10

Force/strain

Question 11

What is the ratio of the applied stress to the resulting strain a result of?

Answer 11

A stress that either compresses or stretches tissue - measured with Young’s modulus

Question 12

Elastography provides an imaging means of?

Answer 12

Palpation

Question 13

What method in elastography involves initiating a MANUAL force to the tissue?

Answer 13

STATIC

Question 14

In using what method can Young’s modulus not be quantified and only uses qualitative information?

Answer 14

Static method

Question 15

Applications of static elastography?

Answer 15

1. Cancer detection of small parts (breast, thyroid, prostate)
2. Myocardium viability
3. Monitoring of therapies that alter tissue composition such as ablation

Question 16

Dynamic methods use what kind of force?

Answer 16

Short transient force or time-varying repetitive force

Question 17

What force is INITIALLY produced in a dynamic method?

Answer 17

Compressional strain

Question 18

What is another term for compressional strain?

Answer 18

Transient or oscillatory

Question 19

Does compressional strain travel at a high or low propagation speed? What is the speed?

Answer 19

High: 1440-1640 m/s

Question 20

Through what kind of force is a compressional strain converted to shear waves?

Answer 20

Radiation force

Question 21

Do shear waves travel at a high or low propagation speed? What is the speed?

Answer 21

Low: 0.5-10 m/s

Question 22

In what direction do shear waves propagate in tissue during shear wave elastography?

Answer 22

Perpendicular to the direction of tissue compression

Question 23

How can shear displacements of propagating shear waves be tracked?

Answer 23

Ultrafast by using high frame rates to determine their propagation speed

Question 24

What does ARFI stand for?

Answer 24

Acoustic Radiation Force Impulse Imaging

Question 25

What is the function of ARFI?

Answer 25

Determining propagation speed of tissue to determine the stiffness

Question 26

How do we determine propagation speeds in shear wave imaging?

Answer 26

Using high frame rates

Question 27

What units is shear wave reported in?

Answer 27

m/s

Question 28

What kind of method is used to determine quantitative information?

Answer 28

Dynamic

Question 29

Where do we scan for shear wave?

Answer 29

Intercostally

Question 30

What segments of the liver are shear wave measurements taken from?

Answer 30

7 or 8

Question 31

Take elastography measurements using what kind of breath on a patient?

Answer 31

Suspended breath hold

Question 32

Where should the shear wave box be located?

Answer 32

1-2 cm below liver capsule

Question 33

T or F? We should always increase the gain in shear wave imaging

Answer 33

FALSE: Do not attempt to increase the gain as it will likely lead to an inaccurate measurement

Question 34

To have a good shear wave measurement, how much colour must be filled in?

Answer 34

>50%

Question 35

F1 Normal to mild fibrosis staging in kPa?

Answer 35

5.48-8.29

Question 36

F2 mild to moderate fibrosis staging in kPa?

Answer 36

8.29-9.4

Question 37

F3 moderate to severe fibrosis staging in kPa?

Answer 37

9.4-11.9

Question 38

F4 Cirrhosis

Answer 38

>11.9

Question 39

What position is the patient usually in during elastrography?

Answer 39

Supine or LLD with R arm above head

Question 40

What method uses both qualitative and quantitative assessment of liver stiffness?

Answer 40

Dynamic - no force applied

Question 41

T or F? Radiation force is most intense at the focal zone?

Answer 41

TRUE

Question 42

Radiation force is a result of a change in wave?

Answer 42

Momentum due to scattering at an obstacle

Question 43

What is measured to equal radiation force?

Answer 43

Rate of momentum change, averaged over the period of the wave