Presidential Greeting - American Society for Laser Medicine and ...

14 American Society for Laser Medicine and Surgery Abstracts
#41
IN VITRO TESTING OF DUAL-MODE THULIUM
MICROSURICAL LASER
Matthew Keller, James Stafford, Jonathon Wells
Lockheed Martin Aculight, Bothell, WA
Background: The Ho:YAG laser is commonly used for a variety
of surgical applications, especially in urology. Recently, thulium
(Tm) fiber lasers have been investigated for use in place of the
Ho:YAG because their 1.94 mm output is absorbed by tissue 5
times stronger than the 2.1 mm of the Ho:YAG. Lockheed Martin
Aculight has recently developed the first truly dual-mode Tm
laser, which can be operated in either CW or in pulsed mode
(rather than modulated) to produce high peak power. The goal of
this study was to assess the ablation performance and collateral
damage characteristics of this laser in vitro.
Study: The laser was operated with a 200 mm diameter spot in CW
and at both 10 and 1 kHz rep rates ( 150 nanoseconds pulse
width), with total energy delivered to the tissue (chicken muscle)
held constant for a given comparison. Ablation efficiencies for 5minute
exposures, crater size for 5-second exposures, and
collateral damage zones for both stationary and scanned laser
delivery for 5-second exposures were calculated for the different
pulse modes and a range of pulse energies (1.1–2.2 mJ).
Results: The most energy-efficient ablation (lowest J/g) occurred
for the 10 kHz pulsed mode operating just above ablation
threshold with 1.1 mJ pulses, while the highest mass removal rate
occurred in 10 kHz pulsed mode operating at max energy (2.2 mJ).
In histological sections from short exposures, 10 kHz pulsed
exposures created slightly larger craters and slightly smaller
thermal coagulation zones than matched CW exposures, while
1 kHz deliveries removed smaller volumes and also had smaller
thermal damage zones.
Conclusion: The dual-mode Tm laser can provide a variety of
ablation characteristics in generic soft tissue based on its mode of
operation and energy/power levels.
#42
HYPERTHERMIA ENHANCED IMAGE GUIDED
LASER-ICG THERAPY
Klressa Barnes, Gal Shafirstein, Wolfgang Baumler,
Ran Friedman, Leah Hennings,
Mustafa Sarimollaoglu, Jessica Webber,
Cassie Jackson, James Suen, Robert Griffin
University of Arkansas for Medical Sciences, Little Rock, AR;
Regensberg University, Regensberg, Germany
Background: Indocyanine green (ICG) dye effectively converts
near infrared (NIR) laser light into heat that can destroy
vasculature and kill tumor cells. However, the short half-life of the
ICG in the vascular system limits the treatment time and efficacy.
We postulate that hyperthermia prior to ICG administration and
near infrared (NIR) laser therapy can improve the efficacy of ICGlaser
treatment of solid tumors. To test this hypothesis, we
quantified the effect of local hyperthermia on ICG accumulation in
the tumor site prior to NIR laser therapy.
Study: Three groups of A/J mice were inoculated with mammary
adenocarcinoma cells. Tumor sizes ranged from 7 to 9 mm. The
first group received an intravenous saline injection prior to laser
treatment. The second received ICG prior to laser treatment. The
third was irradiated with a 808-nm NIR laser (5 mm, 0.2 seconds,
85 W) preceded by tail vein injection of ICG dye (4 mg/kg) and
60 minutes hyperthermia at 41.58C prior to ICG injection.
Epidermal cooling was accomplished by applying ultrasonic gel at
28C to the skin, 1 minute prior to laser irradiation, in all groups.
Tumor size was measured daily and animals were euthanized at
specific time points post treatment for histopathological
evaluation and ICG content measurements.
Results: We observed elevated temperatures of 308C or greater in
animals that received ICG above that of saline alone. In those
animals that received ICG administration prior to hyperthermia,
we saw an increase in the accrual of ICG in the tumor region. In
both groups that received ICG before irradiation, there was an
enhancement in anti-tumor effect compared to laser only.
Conclusion: Hyperthermia prior to intravenous administration
of 4 mg/kg ICG significantly enhanced accumulation of ICG in the
tumor region and, in turn, enhanced the efficacy of thermal
ablation during a single NIR laser irradiation session.
#43
FIBEROPTIC MICRONEEDLES FOR
MICROSCALE INTERSTITIAL DELIVERY OF
THERAPEUTIC LIGHT
Mehmet Kosoglu, Robert Hood, Christopher
Rylander
Virginia Tech, Blacksburg, VA
Background: Light-based cosmetic procedures such as hair
removal and skin rejuvenation are limited due to the poor
penetration depth of light in skin. Novel fiberoptic microneedles
provide a means for mechanically penetrating tissue several
millimeters to deliver light directly into a target area. Our goal is
to develop novel fiberoptic microneedles for minimally invasive
interstitial delivery of diffuse therapeutic light into epithelial
tissues.
Study: A novel manufacturing technique which utilizes angle
polishing and hydrofluoric acid etching of optical fibers was
developed to control diffuse light delivery from the microneedle
surface. The light delivery and the resulting temperature
distribution for two new microneedle designs and a flat-cleaved
fiber control were determined. The light delivery on white paper
was evaluated using microscopic imaging and thermal
distribution was measured by IR thermography. These microoptical
diffusers were also used to liquefy ex vivo porcine fat.
Results: Acid etching removed the fiber cladding, exposing a
greater length of the fiber core, which allowed the circumferential
delivery of light along a 3 mm length. Distribution of light
intensity correlated closely with the resulting temperature map.
The microneedle design with a double-thinning etched taper
generated a more homogenous light distribution and lower
temperatures compared to the other more uniformly etched
microneedle and the flat cleaved fiber control. In addition, no
carbonization of the tissue was observed during lipolysis
experiments for the double-thinned microneedle design while
delivering 3 W of laser power (1,064 nm wavelength, CW). In
comparison, the flat-cleaved fiber carbonized the fat tissue sample
while delivering 1 W of power.
Conclusion: These novel fiberoptic microneedles avoided
carbonization of the tissue and thermal damage to the
microneedle while providing a greater homogeneous light
distribution than any existing optical diffuser at this scale.
Promising new modality for the treatment of acne scars in skin of
color.