10 Virtual Touch Applications
Instructions for Use 10 - 3
Acoustic Radiation Force Impulse Technology
WARNING: To prevent the possibility of inadvertently heating tissue, avoid repeated image
acquisitions near the interface of bone and tissue within a short period of time.
The following features use acoustic radiation force impulse (ARFI) technology to obtain
qualitative visualizations or quantitative measurements of tissue stiffness:
 Virtual Touch Imaging
 Virtual Touch Quantification
 Virtual Touch IQ
ARFI technology uses a time-controlled sequence of "push pulses" from the transducer, rather
than manual compression or palpation cycles, to induce a small displacement of tissue. The
image qualitatively depicts the relative stiffness of tissue within a selected region of interest
compared to surrounding tissue. The system can also provide a quantitative measurement of
shear velocity (Vs) or elasticity (E) at a specific anatomical location.
During acquisition, ARFI technology combines a period of pulse sequences with a temporary
freeze period of no transmit power. A timer indicates the remaining time in seconds until the
transducer is available for imaging. This duration is typically a few seconds depending on the
transducer and imaging conditions. The cooling timer prevents possible heating of the
transducer surface from the momentary shear wave generation pulses.
Cooling 5
Example of Virtual Touch timer.
The system uses an optimization algorithm to ensure acceptable levels for the I
SPTA.3
, the
Mechanical Index (MI), and the Thermal Index (TI) during use. When imaging is activated, you
cannot adjust imaging parameters that affect the transmit power output until the acquisition is
complete.
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