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

10 American Society for Laser Medicine and Surgery Abstracts
we have tested a hypothesis where signal of a fluorescein dye may
vary based on the location of the dye either by the presence of
natural occurring fluorophores of the eye tissue or the dye itself.
In this study, we have identified a unique phenomenon in signal
variation of fluorescence emission spectra based on the variation
of the location.
Study: We have developed a fluorescence spectrophotometer (FS)
system to identify the emission spectra at 520 nm from the 10% Na
fluorescein USP sterile dye. The FS system consists of four main
components: (i) a tungsten halogen lamp to shine white light (LS-
1, Ocean Optics), (ii) a low pass filter with transmission between
390 and 480 nm with cutoff at 505 15 nm wavelength (FD1B, an
additive dichroic color filter, blue, Thorlabs, Inc., Newton, NJ,
USA) (iii) a custom-designed fiber-optic probe (core
diameter ¼ 200 mm; NA ¼ 0.22; FiberTech Optica), and (iv) a
spectrometer (USB4000, Ocean Optics). The fiber-optic probe
consists of two individual fibers with core-to-core separation of
370 mm that are terminated with SMA connectors. For both in
vitro and in vivo experiments we have injected 0.01 ml dye in
either the anterior or posterior chamber (not both) of an
enucleated pig (n ¼ 4) and in vivo rabbit eye (n ¼ 2), respectively.
Then, fluorescence emission spectra are collected every 2 minutes
up to 10 minutes using the FS system. However, for the in vivo
experiment the emission spectra is only collected after the pupil is
dilated using three drops of 1% tropicamide every 11 2 minutes for
5 minutes and the dilation completes within 10 minutes.
Results: Preliminary results showed signal variation between the
anterior and posterior chambers of the eye. The emission peak of
the fluorescence signal from the posterior chamber slightly blue
shifted about 28 nm unlike the anterior chamber. Also, the line
shape of the emission signal was distinctive for the posterior
chamber. We eliminated the possibility of this signal difference
(by further experiment) due to the constituents of the aqueous and
vitreous humors from the anterior and posterior chambers,
respectively. Thus, the most likely reason for this blue shift to the
shorter wavelength may be due to the presence of intrinsic
fluorescence of protein in the crystalline lens of the enucleated pig
and in vivo rabbit eyes. The aromatic amino acid residue
tryptophan (Trp) can cause such a distinct emission shapes.
Conclusion: These results clearly identify the variability in
fluorescence emission spectra of the 10% Na fluorescein dye based
on the location of the dye in the eye. This unique phenomenon
could help determine the location of a fluorescently tagged
molecule within the eye and deserves further investigation.
#30
IS EXTERNAL SKIN TEMPERATURE AN
ADEQUATE MODALITY TO SAFELY MONITOR
PATIENTS DURING LASER LIPOLYSIS?
Kenneth Rothaus
New York Presbyterian Hospital Weill Cornell, New York, NY
Background: Currently, most laser lipolysis systems use
external skin temperature as a guide to assess adequacy of
treatment. Reports of complications or unsatisfactory results may
reflect poor assessments of the effects of laser energy on target
tissue using external skin temperature as an end point of
treatment. The purpose of this study is to determine if the change
in the external skin temperature accurately reflects the change in
internal temperature during laser lipolysis.
Study: A 24 W 924/975 nm laser (Palomar Medical Technologies)
was used to perform laser lipolysis. Treatments were performed
using local tumescent anesthesia. External and internal skin
temperatures were recorded at intervals throughout the
treatment using a non-contact infrared radiometer (Raytek
Mini-Temp) for external temperature and a internal probe and
Ebro thermometer for internal temperature. Laser energies were
delivered until an internal temperature of 45–508C was achieved.
All internal and external temperature measurements were
conducted simultaneously and immediately after the cessation of
lasing. Following the laser lipolysis, the patients underwent
traditional liposuction using 1.7–2.5 mm cobra cannulae. The
patients have been followed for up to 1 year post-op for
complications, results and patient satisfaction.
Results: Dual data points (585) of internal and external
temperature were collected from 227 treatment sites in 50
patients. Statistical analysis revealed low correlation between
internal and external skin temperatures (correlation ¼ 0.27,
P < 0.0001). For every degree rise in internal temperature, the
external temperature rose 0.158. There were no complications.
Patients reported a high degree of satisfaction with the results.
Conclusion: Monitoring of the internal temperature during laser
lipolysis appears to be a more accurate means of assessing the
desired effects on target tissue. Relying on external temperature
alone may result in over-treatment or under-treatment of skin
and adipose tissue and result in either increased complications or
unsatisfactory results.
#31
PREDICTION OF THE MAXIMAL SAFE LASER
RADIANT EXPOSURE ON AN INDIVIDUAL
PATIENT BASIS BASED ON PHOTOTHERMAL
TEMPERATURE PROFILING IN HUMAN SKIN
Boris Majaron, Matija Milanic, Wangcun Jia,
J. Stuart Nelson, Luka Vidovic
Jozef Stefan Institute, Ljubljana, Slovenia, Beckman Laser
Institute and Medical Clinic, University of California, Irvine, CA
Background: Despite the application of dynamic cooling, the
efficacy and safety of cutaneous laser treatments are often
compromised by nonselective absorption in epidermal melanin,
which limits the light fluence delivered to the subsurface target
site (e.g., blood vessel, hair follicle, tattoo granule) and induces a
risk of permanent side effects, such as scarring or
dyspigmentation, due to overheating of the basal layer. Our aim is
to determine the potential of pulsed photothermal radiometric
(PPTR) temperature depth profiling for prediction of maximal safe
radiant exposure (Hmax) for human skin on an individual basis.
Study: Diagnostic PPTR measurements were performed on 326
distinct spots on the extremities of 13 healthy volunteers using
3 milliseconds laser pulses at 755 nm and 6 J/cm 2 . From these
radiometric signals, the respective laser-induced temperature
depth profiles in skin were reconstructed using a custom iterative
algorithm with adaptive regularization. The same test spots were
irradiated with the same laser at radiant exposures from 10 to
90 J/cm 2 with application of cryogen spray precooling at constant
settings. The resulting adverse effects were quantified by blind
scoring and correlated with various characteristics of the
corresponding PPTR temperature profiles.
Results: The area under the epidermal part of the reconstructed
temperature profiles (representing the surface density of the laser
energy deposited in the epidermis) enables a rather robust
prediction of individual epidermal damage threshold across a wide
range of tested skin phototypes (I–IV).
Conclusion: PPTR depth profiling appears promising for
prediction of the maximal safe radiant exposure on an individual