Trial Information

Application of Novel, High Resolution, and Freehand Ultrasound Elasticity Imaging in Liver Surgery

Study Procedures This is a prospective cohort study. Data will be collected from patients
who have signed an informed consent form and are undergoing open, laparoscopic, or
percutaneous RFA or MWA as their treatment for liver tumors. Their images will be assembled
and correlated according to their IOUS characteristics plus processed strain images. Below
is the description of how each aim will be accomplished.

Aim-1: Ultrasound Elasticity Imaging Acquisition. USEI data (both raw US data and B-mode
data) will be recorded during standard operative ultrasound imaging used to guide thermal
ablative therapy in the operating room. Images will be acquired before, during, and after
RFA or MWA therapy. Raw data acquisition will be conducted using a Siemens Antares US
scanner (Siemens Medical Solutions USA, Inc. Ultrasound Division, Issaquah, WA) with an
ultrasound research interface (URI) to access raw US data. A Siemens VF 10-5 linear array
will be used to acquire data using manual handling. Typically, the ultrasound probe is
tracked and spatially registered with the coordinate frame of the of the CT images, so the
pixels of the B-mode images are known in the coordinate frame of the CT volume. Thus if one
localizes the target anatomy in the B-mode images, then the position of the target is
automatically known with respect to the CT volume for validation of the performance of the
elastography. The tracking beams are standard B-mode pulses (6.67 MHz center frequency,
F/1.5 focal configuration, apodized, pulse repetition frequency (PRF) of 10.6 KHz, with a
pulse length of 0.3μs). This US device is one of the standard machines available for
clinical US.

We will track the ultrasound probe with an Electro-Magnetic (EM) tracker. The tracker has
small sensors that can be attached to the ultrasound probe under the sterile cover of the
ultrasound probe, and therefore the sensor is not exposed. Also, the tracker has a
'transmitter' that is flat and is placed underneath the patient below a soft cushion. The
sensor is attached to the ultrasound probe prior to the surgery and hencethe probe will
remain sterile. The transmitter is flat and will be placed under a soft cushion so that it
does not cause any pressure effects on patient.

In both cases (raw data and B-mode), the freehand acquisition should allow for palpation
(manual compression within few millimeters). Risks and discomforts are negligible:
Interventional ultrasound is FDA-approved, and we will use only the data resulting from
standard of care use of clinically certified equipment. The maximum length of a data
recording session will be 1-2 minutes during standard ultrasound acquisition. We will
acquire cine sequences for five defined periods: 1) tumor imaging before probe placement; 2)
immediately after probe placement; 3) near completion during ablation; 4) two minutes
following ablation with probe in place; and 5) after removing the ablator probe.