Ch 19 Elastography Flashcards
What is SWE?
It quantifies tissue stiffness by measuring the speed/amplitude of shear waves in tissue
Tissue stiffness can be used as a marker for ___?
Fibrosis
SWE is a useful tool for evaluating what 3 pathologies?
-Liver fibrosis
-Portal hypertension
-Development of HCC
What is the gold standard for staging liver fibrosis?
Liver biopsy
The stiffer the tissue, the ___ the shear wave propagates?
Faster
Shear wave velocity is expressed in ___?
M/s or kPs using young modulus
What is transient elastography (fibroscan)?
-Uses an u/s probe mounted on the axis of a vibrator
-Vibrations induce elastic shear waves in the tissues
-Uses pulse echo technique
List a pro + con to using transient elastography?
Pro: rapid + reproducible
Con: limited in pt’s with ascites
Where is transient elastography often used?
Outside of medical imaging departments, in specialist’s offices
What is real time elastography?
-Uses radiation force from a focused u/s beam to generate shear waves
-Uses doppler like technique to measure SW propagation
Is fibroscan or real time elastography integrated into conventional u/s?
Real time (incorporated into routine liver u/s exam)
What type of elastography is NOT limited by ascites?
Real time
Where is real time elastography typically used?
In medical imaging departments
Which type of elastography is commercially available by several u/s vendors?
Real time
What are the main differences b/w real time elastography + fibroscan?
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
SWE findings for focal liver lesions are ___?
Non-specific
(the overlap in values b/w benign + malignant make this technique unreliable for diagnosis)
What liver segments can we measure in?
7 or 8
Our SWE box must be ___ cm below liver capsule?
1-2cm
The middle of our SWE box must be ___ cm deep?
4-5cm
What must we avoid when using SWE?
Rib shadows, vessels + breathing
Can we increase our gain when using SWE?
NO! Do not change any image parameter setting
Up to ___ measurements can be taken?
12 (min of 3 obtained)
The measurement analysis circle must be at least ___cm in diameter?
1cm
The kPa + m/s measurements should be within what percentage for the IQR/Median to be accurate?
kPa: <30%
M/s: <15%
Can we overlap measurements?
No!
Can the measurement analysis circle extend outside of the SWE box?
Yes, does not affect measurements
How to know when our image is good enough to measure on?
-When >50% of the SWE box has color fill with default gain
-When box has uniform color fill
Is <5kPa normal?
Yes
Is >5kPa normal?
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
