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

SURGICAL APPLICATIONS
INTERSTITIAL LASER
THERAPY
#181
USE OF GOLD-BASED NANOPARTICLES TO
DIRECT LASER INTERSTITIAL PHOTOTHERMAL
CANCER THERAPY
Jon Schwartz, Glenn Goodrich, Kelly Gill-Sharp,
J. Donald Payne
Nanospectra Biosciences, Inc., Houston, TX
Background: Laser-delivered thermal energy, if it can be
adequately targeted and calibrated holds the possibility for
treatment of tumors that are otherwise non-resectable due either
to their proximity to critical structures which limit radiation and
surgical options, or due to accumulated multi-drug resistance. We
have investigated nanoparticles as a means of directing
photothermal treatment to cancer by determining that: (1)
nanoparticles accumulate passively in tumors, (2) there exists
appropriate laser dosimetries that ablate target tissue and
simultaneously minimize thermal damage to neighboring healthy
tissue, and (3) particle infusion and selective laser ablation may be
combined therapeutically.
Study: Nanoparticle specificity for tumor was determined by
infusing nanoparticles into a variety of murine (CT26.wt) and
canine (cTVT, J3T) tumor lines and sampling tissues at necropsy.
Elemental analysis was used to quantify nanoparticle
accumulation in various tumor types and organs. Laser doses at
various power levels and temporal durations were tested in vitro
and in vivo to derive a laser dosimetry that is sub-ablative in
native tissue, but which results in thermal ablation lesions if
nanoparticles are present. Finally, in a set of pre-clinical studies,
we ablated tumors in which therapeutic nanoparticles had been
either directly injected or accumulated passively.
Results: Gold-based nanoparticles circulate in the bloodstream
with half-lives of 2–4 hours, passively accumulate in the
fenestrations of tumor capillaries, and are cleared by the reticuloendothelial
system (RES). Near-infrared laser energy, delivered
percutaneously using an optical fiber system with an isotropic
diffuser was used to deliver 3–7 W into native brain and prostate
(canine) and muscle (murine and canine) and the power adjusted
to arrive at a threshold for ablation in vivo.
Conclusion: Based on in vitro and in vivo studies we have shown
that solid tumors may be treated with 1–3 mm thermal damage
margins using directly injected or systemically delivered
nanoparticles combined with NIR laser irradiation.
#182
American Society for Laser Medicine and Surgery Abstracts 53
MR-GUIDED LASER ABLATION OF LIVER AND
KIDNEY TUMORS
Ashok Gowda, Eric Walser
Visualase, Inc., Houston, TX; Mayo Clinic, Jacksonville, FL
Background: MR-Guided Laser Ablation may offer advantages
in minimizing tumor recurrence and enhancing safety near
critical structures during ablation of tumors in the liver and
kidney. The goal of this work was to perform pilot clinical work in
patients suitable to thermal ablation and evaluate the safety and
preliminary efficacy of MR-guided laser interstitial therapy
(MRgLITT) with real-time MR temperature monitoring in
patients with liver and kidney tumors.
Study: Six patients (three kidney and three hepatic) were treated
using the Visualase Thermal Therapy System (Visualase, Inc.).
All procedures were completed with patients under general
anesthesia positioned within a 1.5 T MRI system. A 14 Ga catheter
with MR-compatible titanium stylet was placed percutaneously
into target masses under MR-guidance. Once positioning, the
stylet was replaced with a cooled laser applicator (600-mm core
diameter with 1.5 cm diffusing tip and 1.85 mm OD cooling
catheter). Under continuous thermal imaging, a single laser
applicator in two cases and two applicators in three cases were
used to create 2–4 ablation zones per tumor using 30 W of 980 nm
laser power for between 90 and 120. Post-treatment contrast
images were compared to estimated treatment zones.
Results: There were no complications in any procedures and
thermal imaging was performed successfully during short
breath holds, and in some cases during normal breathing. In all
cases, the user could appreciate the area of ablation in near
real-time within the tissue which was estimated from a damage
model and overlaid on corresponding real-time magnitude images.
In three patients at 3 months post-ablation, there is no evidence of
recurrent or residual tumor by MR examination. One patient went
on to liver transplant and pathology confirmed complete necrosis
of the treated area. Two patients are pending initial follow-up
imaging.
Conclusion: MRgLITT of liver and kidney tumors is safe and
feasible, and thus far has been performed without complications
or side effects.
#183
LASER INTERSTITIAL THERMOTHERAPY FOR
PROSTATE CANCER: ANIMAL MODEL AND
NUMERICAL SIMULATION OF TEMPERATURE
AND DAMAGE DISTRIBUTION
Mohamad-Feras Marqa, Pierre Colin,
Pierre Nevoux, Serge Mordon, Nacim Betrouni
INSERM U703, Lille, France
Background: Laser interstitial thermo therapy (LITT) ablation
of low volume prostate cancer is feasible. However, conformation
of the treated area within the tumor remains a major issue. One of
the effective methods to perform pre-treatment planning is the
simulation.
Study: We used Dunning R3327-AT2 prostate adenocarcinoma
implanted in the flank of Copenhagen rat. Ten rats were used. The
laser was a diode system emitting at 980 nm. The device was
equipped with cylindrical diffusing fiber (CDF) of 10 mm length
with a 500 mm core diameter. The CDF was inserted into the
center of the tumor; the power provided was 5 W with energy
fluence of 1,145 J/cm 2 . The irradiance duration was 75 seconds.
Thermal camera was used to measure temperature at the tip end
of fiber. MR acquisition was performed at t þ 48 hours. The
images were used to estimate the thermal damage volume. The
heat elevation in prostate tissues and thermal damage was
modeled using COMSOL MultiphysicsV4.0. Transient analysis of
the Bioheat equation application mode was used to describe the
thermal process. Damage inside the irradiated tissue was
estimated by solving the Arrhenius integral. Validation of the
model was performed by comparing the results of the bioheat
equation with results of the MR images.