Ch 19 Elastography

Question 1

What is SWE?

Answer 1

It quantifies tissue stiffness by measuring the speed/amplitude of shear waves in tissue

Question 2

Tissue stiffness can be used as a marker for ___?

Answer 2

Fibrosis

Question 3

SWE is a useful tool for evaluating what 3 pathologies?

Answer 3

-Liver fibrosis
-Portal hypertension
-Development of HCC

Question 4

What is the gold standard for staging liver fibrosis?

Answer 4

Liver biopsy

Question 5

The stiffer the tissue, the ___ the shear wave propagates?

Answer 5

Faster

Question 6

Shear wave velocity is expressed in ___?

Answer 6

M/s or kPs using young modulus

Question 7

What is transient elastography (fibroscan)?

Answer 7

-Uses an u/s probe mounted on the axis of a vibrator
-Vibrations induce elastic shear waves in the tissues
-Uses pulse echo technique

Question 8

List a pro + con to using transient elastography?

Answer 8

Pro: rapid + reproducible

Con: limited in pt’s with ascites

Question 9

Where is transient elastography often used?

Answer 9

Outside of medical imaging departments, in specialist’s offices

Question 10

What is real time elastography?

Answer 10

-Uses radiation force from a focused u/s beam to generate shear waves
-Uses doppler like technique to measure SW propagation

Question 11

Is fibroscan or real time elastography integrated into conventional u/s?

Answer 11

Real time (incorporated into routine liver u/s exam)

Question 12

What type of elastography is NOT limited by ascites?

Answer 12

Real time

Question 13

Where is real time elastography typically used?

Answer 13

In medical imaging departments

Question 14

Which type of elastography is commercially available by several u/s vendors?

Answer 14

Real time

Question 15

What are the main differences b/w real time elastography + fibroscan?

Answer 15

Real time: (commercially available)
-integrated into conventional u/s
-not limited by ascites
-used in medical imaging departments

Fibroscan:
-limited by ascites
-used in specialists offices, not imaging departments

Question 16

SWE findings for focal liver lesions are ___?

Answer 16

Non-specific

(the overlap in values b/w benign + malignant make this technique unreliable for diagnosis)

Question 17

What liver segments can we measure in?

Answer 17

7 or 8

Question 18

Our SWE box must be ___ cm below liver capsule?

Answer 18

1-2cm

Question 19

The middle of our SWE box must be ___ cm deep?

Answer 19

4-5cm

Question 20

What must we avoid when using SWE?

Answer 20

Rib shadows, vessels + breathing

Question 21

Can we increase our gain when using SWE?

Answer 21

NO! Do not change any image parameter setting

Question 22

Up to ___ measurements can be taken?

Answer 22

12 (min of 3 obtained)

Question 23

The measurement analysis circle must be at least ___cm in diameter?

Answer 23

1cm

Question 24

The kPa + m/s measurements should be within what percentage for the IQR/Median to be accurate?

Answer 24

kPa: <30%

M/s: <15%

Question 25

Can we overlap measurements?

Answer 25

No!

Question 26

Can the measurement analysis circle extend outside of the SWE box?

Answer 26

Yes, does not affect measurements

Question 27

How to know when our image is good enough to measure on?

Answer 27

-When >50% of the SWE box has color fill with default gain
-When box has uniform color fill

Question 28

Is <5kPa normal?

Answer 28

Yes

Question 29

Is >5kPa normal?

Answer 29

No:

5.1-9: low probability chronic liver disease (CLD)
9.1-13: suggests CLD
>13: high probability CLD
>17: advanced CLD
>25: advanced CLD at risk of complications from portal hypertension