FRIDAY MORNING, 20 MAY 2005 REGENCY E, 8:30 A.M. TO 12:00 ...

FRIDAY MORNING, 20 MAY 2005
REGENCY A, 8:00 TO 10:00 A.M.
Session 5aBBa
Biomedical UltrasoundÕBioresponse to Vibration: Hemostatis and Bleeding Detection
Tyrone M. Porter, Chair
Univ. of Cincinnati, Biomedical Engineering, 231 Albert Sabin Way, Cincinnati, OH 45267-0761
Contributed Papers
8:00
5aBBa1. Vector-Doppler ultrasound for the detection of internal
bleeding. Bryan W. Cunitz, Peter J. Kaczkowski, and Andrew A.
Brayman Ctr. for Industrial and Med. Ultrasound, Appl. Phys. Lab.,
Univ. of Washington, 1013 NE 40th St., Seattle, WA 98105
A vector Doppler VDop ultrasound system uses a transmitter and a
spatially separated pair of receivers to measure bistatic scattering from
blood. VDop has two principal advantages over color-flow Doppler in
identifying internal bleeding: 1 measures flow direction, and thus absolute
magnitude of flow velocity 2 does not require special orientation to
detect and measure flow, thus can measure flows perpendicular to the
transmitter. Our hypothesis is that real-time flow direction and magnitude
can be used to detect and characterize internal bleeding. A real-time vector
Doppler system has been built and tested in vitro. The system is capable of
measuring flow magnitude and direction up to 145 cm/s at a depth of 3.6
cm at a processing rate of 10 Hz. Accuracy was measured using a calibrated
moving string phantom and the system performs well within a
useful range. A blood flow phantom was developed to mimic arterial flow
into an open cavity as well as into tissue and replicate both pulsatile flow
as well as the energy storage due to vascular elasticity. Flow signature data
is gathered under conditions of normal branching flow, and vessel breach.
The talk will describe the VDop system and the flow phantom and summarize
results.
8:30
5aBBa3. A pulsatile flow phantom for image-guided high-intensity
focused ultrasound studies on blood vessels. Robyn Greaby and
Shahram Vaezy Ctr. for Medical and Industrial Ultrasound, APL, Univ.
of Washington, 1013 NE 40th St., Seattle, WA 98105-6698,
rgreaby@u.washington.edu
A pulsatile flow phantom has been developed for controlled studies of
acoustic hemostasis and high intensity focused ultrasound HIFU effects
on blood vessels. The flow phantom consists of an excised carotid artery
attached to a pulsatile pump and embedded in an optically and acoustically
transparent gel to create an ex vivo model of a human artery. The artery
was punctured with a needle to simulate percutaneous vascular injury. A
HIFU transducer with a focal distance of 6 cm and a frequency of 3.33
MHz was used to treat the puncture. B-mode and power-Doppler ultrasound
were used to locate the site of the puncture, target the HIFU focus,
and monitor treatment. Also, the effects of vascular flow on HIFU lesions
were studied by treating vessels in the phantom for different times at a
variety of flows. In both studies, histology was done on the artery. In nine
trials, HIFU was able to provide complete hemostasis in 55 31 s. It is
feasible to use the flow phantom to study acoustic hemostasis of blood
vessels. Histology shows that the flow in the phantom appears to diminish
the vascular damage from HIFU.
8:15
5aBBa2. Color-Doppler guided high intensity focused ultrasound for
hemorrhage control. Vesna Zderic, Brian Rabkin, Lawrence Crum, and
Shahram Vaezy Appl. Phys. Lab. and Bioengineering, Univ. of
Washington, 1013 NE 40th St, Seattle, WA 98105,
vesna@u.washington.edu
To determine efficacy of high intensity focused ultrasound HIFU in
occlusion of pelvic vessels a 3.2 MHz HIFU transducer was synchronized
with color-Doppler ultrasound imaging for real-time visualization of flow
within blood vessels during HIFU therapy. HIFU was applied to pig and
rabbit pelvic vessels in vivo, both transcutaneously and with skin removed.
The in situ focal intensity was 4000 W/cm 2 on average. Vessel occlusion
was confirmed by color or audio Doppler, and gross and histological observations.
In rabbits, five out of 10 femoral arteries diameter of 2 mm
were occluded after 30–60 s of HIFU application. The average blood flow
reduction of 40% was observed in the remaining arteries. In pigs, out of 7
treated superficial femoral arteries 2 mm in diameter, 4 were occluded,
one had 80% blood flow reduction, and 2 were patent. In addition, 3 out of
4 superficial femoral arteries, punctured with 18 gauge needle, were occluded
after 60–90 s of HIFU application. Larger vessels diameter of 4
mm were patent after HIFU treatment. Doppler-guided HIFU has potential
application in occlusion of injured pelvic vessels similar to angiographic
embolization.
8:45
5aBBa4. High throughput high intensity focused ultrasound „HIFU…
treatment for tissue necrosis. Vesna Zderic, Jessica Foley, Sean
Burgess, and Shahram Vaezy Appl. Phys. Lab. and Bioengineering,
Univ. of Washington, 1013 NE 40th St., Seattle WA 98105,
vesna@u.washington.edu
To increase HIFU throughput, a HIFU transducer diameter of 7 cm,
focal length of 6 cm, operating frequency of 3.4 MHz, coupled to an
imaging probe ICT 7-4, Sonosite, was driven by 100 W driving unit with
500 W amplifier. A water pillow connected to a circulation pump with
degassed water provided transducer coupling and cooling. Input electrical
power was 400 W, corresponding to focal intensity of 51 300 W/cm 2 in
water. HIFU was applied transcutaneously in porcine thigh muscle in
vivo, and intraoperatively in liver hilum, for 30–60 s. After 30 s of treatment,
muscle lesions had diameter of 2.10.4 cm and length of 2.0
0.4 cm. After 60 s of treatment, muscle lesions had diameter of 3.1
0.9 cm and length of 3.11.0 cm. In few cases of severe skin burns, the
lesions were formed immediately under the skin and were shallow
(1 cm). Liver lesions had diameter of 2.10.3 cm and length of 2.3
0.6 cm. In comparison, after the 30 s treatment with our standard HIFU
device focal intensity of 27 000 W/cm 2 , in water the muscle lesions had
diameter of 1.30.6 cm and length of 1.10.6 cm. High power HIFU
device can quickly coagulate large tissue volumes.
2584 J. Acoust. Soc. Am., Vol. 117, No. 4, Pt. 2, April 2005 149th Meeting: Acoustical Society of America 2584