Acoustic radiation force impulse (ARFI) is a sonographic technique that uses acoustic beams to mechanically excite tissue and monitor the displacement response to assess tissue stiffness without external compression. It provides qualitative images (Virtual Touch Tissue Imaging) and quantitative stiffness measurements (Virtual Touch Tissue Quantification) by tracking tissue displacement over time. Stiffer tissues like malignancies display as darker on images and have higher shear wave velocities measured in m/s. ARFI can help characterize and differentiate liver masses, breast and thyroid nodules, prostate cancer, and more.

2. Acoustic radiation force impulse (ARFI)
Acoustic Radiation Force Impulse (ARFI)
 A new sonographic technology that allow assessment of the
tissue stiffness.
 ARFI employs high intensity acoustic beam in order to
mechanically excite tissue, and monitor the tissue displacement
response.
 No need for an external compression.

3. Acoustic radiation force impulse (ARFI)
 The generated wave scan from the
transducer provides qualitative
(imaging) and quantitative (wave
velocity values, measured in m/s)
responses, by Virtual Touch Tissue
Imaging and Virtual Touch Tissue
Quantification, respectively.

4. Virtual Touch Tissue
Imaging (VTI):
- Series of acoustic push
pulse/detection pulse sequences:
- Acoustic push pulse is transmitted
to compress tissue then detection
pulses are used to track the amount
of displacement on axis to the push
pulse within the ROI.
-The relative tissue displacements
are mapped to the image
ECR 2012 / C-1477

5. Virtual Touch Tissue Imaging (VTI)
 The degree of displacement is interpreted into degree
of lightness and darkness in the regions of interest
 The more light color = the more compliant tissue =
benign lesion.
 The darker color = the more hard tissue = malignant
lesion.

6. The left image shows thyroid nodule by B mode.
The right one :- VTI shows that the nodule appear dark
in color = hard in consistency= malignancy.

7. Virtual Touch Tissue Quantification(VTQ)
 Push pulse (orange) generates
shear waves (blue) (mechanical
waves propagates transversely in
tissues) through a region of
interest.
 Detection pulses (green) track
the degree of displacement vs.
time .
 The speed of the wave is
computed.
 The speed of shear wave
propagation is related to tissue
stiffness.
ECR 2012 / C-1477

8. Clinical applications---characterize tissue stiffness
 Liver:-
 Can estimate liver stiffness diagnosing cirrhosis.
 A safe and non-invasive alternative to liver biopsy.
 Differentiate benign from malignant liver masses,
 Breast :
 Diagnosis of breast masses.
 Prostate:-
 Help targeting prostate biopsy.
 Providing image guidance during focal therapy procedures.
 Monitor disease progression and response to treatment noninvasively.
 Thyroid ---Differentiation of thyroid nodules.

9. - 2D conventional US (a) and virtual touch tissue imaging (VTI, b).
Tumor mass is markedly darker (stiffer) than adjacent hepatic
parenchyma on VTI.

10. • VTQ for liver fibrosis
- Mean normal values range is about 0.8-1.22 m/s
- Values predicting different stages of liver fibrosis
were:
F1 - 1.24 m/s
F2 – 1.48 m/s
F3 – 1.61 m/s
F4 – 1.75 m/s

11. - The left image shows breast mass in B mode.
- The right one :- VTI shows that the mass appear dark in color
= hard in consistency= malignant.
Invasive ductal carcinoma
Duke university

12. - The left image shows breast mass in B mode.
- The right one :- VTI shows that the mass appear light in
color = soft in consistency= benign.
Fibroadenoma
Duke university

13. ARFI imaging can clearly portray zonal anatomy and some
cancerous lesions in the prostate.
ARFI shows that the lesion is stiffer than the back ground
material.
ARFI and B-mode image volumes of the prostate
Duke university

14. 2D conventional US (a) and virtual touch tissue imaging (VTI, b)
showing a dark color nodule (stiff nodule)
Papillary thyroid carcinoma.

15. VTQ in thyroid lesions
 The median velocity in benign thyroid
lesions are 2.06 m/sec and 3.0 m/sec in
malignant lesions.

18.  The mean shear wave velocity (SWVs) in normal adult kidneys were 2.24-
2.37 m/sec.
 SWVs of 1.75 m/sec in children normal kidneys.
 SWVs increased in high-grade hydronephrotic kidneys (image B).

19. MINI QUIZ
 Right lobe thyroid nodule by B mode and ARFI------
Benign or malignant ?

20. Mean shear wave velocity values
1. HCC -----------------------------2.17 ml/s
2. Hemangioma ------------------2.30 ml/s
3. Adenoma ----------------------1.25 ml/s
4. Metastasis ---------------------2.87 ml/s
5. FNH ----------------------------=2.75 ml/s

21.  A Qualitative implementation called
virtual touch tissue quantification
gives an objective numerical
evaluation of the tissue stiffness.
 The calculation of the shear wave
velocity mainly reflects the elasticity
and viscosity of the target tissue.
 The harder the tissue the faster the
velocity.
Virtual touch tissue quantification

22. • Elastography in predicting
Lymph Node Malignancy
 The Elastographic pattern will findings will be
classified into the following 4 patterns:
 Pattern 1: >80% of the color is red-green.
 pattern 2 50-80% of the color is red-green
 Pattern 3 (50-80% of the color is blue)
 Pattern 4 (>80% of the color is blue)

23. Thyroid nodules
Four different patterns have been described
including :-
"patterns 3 and 4" that suggest malignancy
While "patterns 1 and 2" indicate thyroid
nodule benignity.

24. Pancreas

25. Breast

27. Shear waves