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.

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.

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

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.

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.

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

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.

- 2D conventional US (a) and virtual touch tissue imaging (VTI, b).

Tumor mass is markedly darker (stiffer) than adjacent hepatic

parenchyma on VTI.

• 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

- 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

- 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.

FibroadenomaDuke university

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

2D conventional US (a) and virtual touch tissue imaging (VTI, b)

showing a dark color nodule (stiff nodule)

Papillary thyroid carcinoma.

VTQ in thyroid lesions

The median velocity in benign thyroid

lesions are 2.06 m/sec and 3.0 m/sec in

malignant lesions.

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).

MINI QUIZ

Right lobe thyroid nodule by B mode and ARFI------

Benign or malignant ?

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

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

• 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)

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.

Pancreas

Breast

Shear waves