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

9:00
5aBBa5. Image-guided high intensity focused ultrasound annular
array for hemostasis and tumor treatment. Vesna Zderic, Robert
Held, Thuc Nguyen, and Shahram Vaezy Appl. Phys. Lab. and
Bioengineering, Univ. of Washington, 1013 NE 40th St., Seattle, WA
98105, vesna@u.washington.edu
To develop and characterize an ultrasound-guided high intensity focused
ultrasound HIFU array, an 11-element annular phased array aperture
of 3.56.0 cm, focal depth of 3.0–6.0 cm, frequency of 3 MHz was
coupled to an imaging probe C9-5, Philips. LabView software was developed
to control driving electronics and image guidance. Radiation force
balance measurements, Schlieren imaging, and hydrophone field mapping
were performed. Lesions were produced in gel phantoms, and ex vivo
porcine liver and human cancerous uterus. The lesions were formed beginning
at a focal depth of 6.0 cm and moving by 0.5 cm increments to 3.0
cm, and vice versa, with the overall treatment time of 2 min. The transducer
had efficiency of 38%, with intensities of up to 6200 W/cm 2 at the
natural focus of 5 cm, in water. The 6 dB focal area varied from 0.4 mm 2
at3cm to 1.5 mm 2 at6cm. The 3 to 6 cm tissue lesions were 2.7
0.5 cm in length, compared to 4.10.3 cm for the 6 to 3 cm lesions.
The average lesion width was 1 cm. Image-guided HIFU array may enable
treatment of large tumor volumes and hemorrhage control at different
depths inside the body.
9:15
5aBBa6. Image guided acoustic hemostasis. Sean Burgess Dept. of
Bioengineering, Univ. of Washington, Box 355640, 1013 NE 40th St.,
Seattle, WA 98105, sburgess@u.washington.edu, Vesna Zderic Univ. of
Washington, and Shahram Vaezy Univ. of Washington
Previous studies have shown that high intensity focused ultrasound
HIFU can successfully control visible bleeding from solid organ injuries.
This study investigates the ability of ultrasound image-guided HIFU to
arrest occult hemorrhaging in the posterior liver parenchyma using a pig
model. The image-guided HIFU device consisted of an intraoperative imaging
probe and a spherically-curved HIFU transducer with focal length of
3.5 cm, frequency of 3.23 MHz, and focal acoustic intensity of
2350 W/cm 2 . A total of 19 incisions 14 HIFU-treated and 5 control incisions
were made in five pig livers. The incisions were 30 mm long and 7
mm deep with HIFU application occurring within 20 s of making an
incision. Hemostasis was achieved in all treated incisions after a mean
SD of 6515 s of HIFU application. The mean blood loss rate of the
control incisions initially and after seven minutes was 0.268 and 0.231
mL/s, respectively. Subsequent histological analysis showed coagulative
necrosis of liver tissue around the incision which appeared to be responsible
for hemostasis. Ultrasound image-guided HIFU offers a promising
method for achieving hemostasis in surgical settings in which the hemorrhage
site is not accessible.
9:30
5aBBa7. Ultrasound-guided high frequency focused ultrasound
neurolysis of peripheral nerves to treat spasticity and pain. Jessica L.
Foley, Frank L. StarrIII, Carie Frantz, Shahram Vaezy Ctr. for Industrial
and Medical Ultrasound, Univ. of Washington, 1013 NE 40th St., Seattle,
WA 98105, jlf2@u.washington.edu, Jessica L. Foley, Shahram Vaezy
Univ. of Washington, Seattle, WA 98195, and James W. Little Univ. of
Washington, Seattle, WA 98195
Spasticity, a complication of central nervous system disorders, signified
by uncontrollable muscle contractions, is difficult to treat effectively.
The use of ultrasound image-guided high-intensity focused ultrasound
HIFU to target and suppress the function of the sciatic nerve of rabbits in
vivo, as a possible treatment of spasticity and pain, will be presented. The
image-guided HIFU device included a 3.2-MHz spherically-curved transducer
and an intraoperative imaging probe. A focal intensity of
14801850 W/cm 2 was effective in achieving complete conduction block
in 100% of 22 nerves with HIFU treatment times of 3614 s (mean
SD). Gross examination showed blanching of the nerve at the treatment
site and lesion volumes of 2.81.4 cm 3 encompassing the nerve. Histological
examination indicated axonal demyelination and necrosis of
Schwann cells as probable mechanisms of nerve block. Long-term studies
showed that HIFU intensity of 1930 W/cm 2 , applied to 12 nerves for an
average time of 10.54.9 s, enabled nerve blocks that remained for at
least 7–14 days after HIFU treatment. Histological examination showed
degeneration of axons distal to the HIFU treatment site. With accurate
localization and targeting of peripheral nerves using ultrasound imaging,
HIFU could become a promising tool for the suppression of spasticity and
pain.
9:45
5aBBa8. Percutaneous high intensity focused ultrasound on pigs.
Herman du Plessis Surgery, 1 Military Hospital, Thaba Tshwane 0143,
South Africa and Shahram Vaezy Univ. of Washington, Seattle, WA
98195
Two types of HIFU Handpieces were tested on pigs under general
anesthesia. The direct applicator focal distance 4 cm was adequate to
control bleeding from a liver injury, although direct pressure was effective
in a shorter time. The percutaneous application did not work at all, as the
fixed focal distance 6 cm was too deep for the size pigs available, and
the diagnostic modality was difficult to integrate with the therapeutic window.
We were able to create necrotic lesions in the liver substance, but not
in the areas where the injury was situated. More development is needed to
build a better, user-friendly application device before HIFU can be used in
the clinical situation for control of hemorrhage.
5a FRI. AM
2585 J. Acoust. Soc. Am., Vol. 117, No. 4, Pt. 2, April 2005 149th Meeting: Acoustical Society of America 2585