Ultrasound ImageGuided Acoustic Hemostasis of Occult Liver Hemorrhage

1
Ultrasound Image-Guided Acoustic Hemostasis of
Occult Liver Hemorrhage
Sean Burgess, Vesna Zderic, Frank L. Starr
III, Shahram Vaezy
Department of Bioengineering, University of
Washington, Seattle, WA, USACenter for
Industrial and Medical Ultrasound, Applied
Physics Laboratory, University of Washington
Uncontrolled hemorrhage from high grade hepatic
injuries is highly lethal. 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 (US)
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/cm2. A total
of 24 incisions (17 HIFU-treated and 7 control
incisions) were made in 5 pig livers. The
incisions, 30 mm long and 7 mm deep, resulted in
a mean blood loss rate of 0.336 mL/s and 0.268
mL/s in the treated and control incisions
respectively. HIFU was applied within 20 seconds
of making an incision. Hemostasis was achieved
in all treated incisions after a mean ? SD of 65
? 15 seconds of HIFU application. After 7
minutes the control incisions had a mean blood
loss rate of 0.231 mL/s. Ultrasound image-guided
HIFU offers a promising method of hemostasis in
surgical settings in which the hemorrhage site is
not accessible.

• 5 female pigs weighing approximately 30-35 kg
  each were used
• Animals were anesthetized and administered
  heparin to place in a coagulative state
• Abdomen was opened allowing access to the liver
• Incisions were made on the posterior side of
  liver lobe, 30 mm long, 8mm deep, and 5 mm wide
  creating a wedge of tissue which was then removed
  
• Blood was collected using gauze pads for blood
  loss rate determination
• Liver lobe was placed on a bed of gauze
  concealing the incision
• Image-guided HIFU device placed on anterior side
  of liver lobe
• Incision was located and targeted using B-mode
  ultrasound
• HIFU of 2350 W/cm2 was applied for 10-15 seconds
  while scanning at approximately 0.5 mm/s
• Liver lobe was lifted from gauze bed and incision
  inspected for hemostasis
• Incision targeting and HIFU treatment continued
  until hemostasis achieved
• Control incisions were made using same procedure
  except that HIFU was not applied and blood was
  collected immediately after making the incision
  and after 7 minutes

• The liver has a soft parenchyma which is highly
  vascularized and thinly protected by a fibrous
  capsule which makes it susceptible to injury
  during blunt and penetrating abdominal trauma.
• Severe liver injury is the most common cause of
  hemorrhagic death after abdominal trauma.
• Previous studies have shown that HIFU can
  successfully control visible bleeding from solid
  organ. injuries

• HIFU is an acoustic therapy modality that
  utilizes high power, focused ultrasound waves to
  induce a biological effect.
• Ultrasound waves can propagate through tissue and
  deposit energy within a millimeter sized focus
  without damaging intervening tissue.
• Bioeffects are achieved via thermal and
  mechanical mechanisms resulting in coagulative
  necrosis.
• Thermal effects can result in rapid rise in
  tissue temperature in excess of 70C.
• Therapeutic uses of HIFU currently under
  investigation include tumor treatment and
  hemostasis.

• Hemostasis was achieved in all treated incisions
  (n17)
• Mean ? standard deviation HIFU treatment time was
  66 ? 19 seconds
• Blood loss rate immediately following making an
  incision was 0.327 ? 0.179 mL/s for the treated
  incisions
• Blood loss rates for the control incisions were
  0.344 ? 0.284 and 0.274 ? 0.132 mL/s at t0 and
  t7 minutes respectively
• Control incisions (n7) had a reduction in
  bleeding rate after 7 minutes but were not
  hemostatic
• Thermal and mechanical effects of HIFU probable
  mechanism of hemostasis

a. Liver section showing normal hepatic
architecture taken from region closest to the
image-guided HIFU device b. Liver section
surrounding treatment site showing sinusoids
congested with red blood cells (arrow) c.
Transition from congested sinusoids towards the
treatment site d. Treated liver having distorted
hepatic structure consistant with coagulative
necrosis (dark smudged nuclei (arrow),
detached individual hepatocytes

• Ultrasound image-guided HIFU allows targeting and
  treatment below the tissue surface
• HIFU and ultrasound transducers are mechanically
  coupled such that HIFU focus lies within the
  ultrasound image plane
• HIFU and ultrasound imaging are electronically
  synchronized producing a visualization window
• HIFU is powered using a 75 duty cycle,
  ultrasound imaging occurs during HIFU off-time
• Circulating water pillow provides coupling
  between HIFU transducer and tissue as well as
  cooling to HIFU transducer

• Image guided HIFU can provide hemostasis of
  occult liver hemorrhage
• Image-guided acoustic hemostasis may have
  considerable potential in advanced trauma care of
  solid organ injuries
• Additional studies are needed to improve bleeding
  site targeting to minimize tissue damage during
  HIFU hemostasis

Acknowledgments This work was supported by the
US Army Remote Acoustic Hemostasis Grant and NIH
Organ Hemostasis Grant. Contact
sburgess_at_u.washington.edu

• HIFU Transducer Frequency 3.23 MHz Focal
  Length 35 mm

• Imaging Transducer Philips HDI-1000
  Linear Array Bandwidth 5-10 MHz