Background: Singlet oxygen (1O2) is a key therapeutic molecule in photodynamic therapy (PDT). Quantitation of 1O2 luminescence is important for monitoring and optimizing PDT process. Objective: The aim of this study was to evaluate a custom-built superconducting strip single photon detector (SSPD)-based time-resolved photon counting system for 1O2 luminescence detection. Materials and Methods: The wavelength responses of optical collection system were verified by a spectrum analyzer. A dual-channel signal generator simulates pulsed signals of different frequencies were used to verify the circuit system. 1O2 luminescence generated by the photoexcitation of Rose Bengal solution was examined. Results: The 1O2 detection system could transmit photons of 1270 nm and the time-resolved system showed the response down to the nanosecond range and was capable of converting the different time responses into a square wave signal. When 10 μM aqueous and methanolic RB solutions were excited with a 20 mW 532 nm laser the measured 1O2 lifetimes were 2.93±0.37 μs and 9.45±0.83 μs, respectively. At the same concentration, when the excitation power increased the number of singlet oxygen produced per unit of time also increased. Conclusions: The custom-built SSPD-based 1O2 detection system provides a reliable and sensitive means for the quantitation of 1O2 luminescence generated from PDT process.
Background: Superconducting strip photon detector (SSPD) have been applied to monitor singlet oxygen ( 1O2) luminescence produced during photodynamic therapy (PDT) due to its high detection efficiency, low dark count and fast detection speed. Objective: This study calibrate of the detection efficiency and dark counts of a new SSPD system for singlet oxygen luminescence detection. Materials and Method: The input photons that passing through the attenuator, polarization controller and optical fiber were carefully controlled so that the average photon arrival-time interval was much larger than the response time of SSPD detector. The electrical signals generated from SSPD detector were collected after passing through a low-noise amplifier and analyzed using data acquisition card. Bias current started at 10 μA and increased by 1 μA step until saturation. The electrical signal pulses were recorded. The detection efficiency was determined by the ratio of the electrical signal pulse count minus the dark count to the number of photons input to the detector. Dark counts were measured by adjusting the bias current with the light input channel completely closed and in a dark environment. The experimental temperature was controlled at 2.2 K. Result: The best detection efficiency was achieved when the bias current was 23 μA with the input photon power of -107.6 dBm. The detection efficiency was 88% and 90% for two tested detectors with the optimized polarization. The dark count rate was less than 100 cps. Conclusions: This study demonstrated that the optimization of attenuator, polarization controller and bias current can improve the detection efficiency of SSPD system for singlet oxygen detection.
In this study, three-channel microscopy was used to study the effect of lipid rafts disruption on LMP1 oligomerization by quantitative fluorescence resonance transfer method (E-FRET). We first verified four crosstalk and bleedthrough parameters and the system parameter G on our imaging system by ECFP-only and EYFP-only plasmids. Furtherly, two FRET-based probes associated with LMP1, were constructed to study oligomerization of oncoprotein LMP1 in nasopharyngeal carcinoma cell line (CNE1). Methyl-β-cyclodextrin (MβCD) was used to disrupt lipid rafts, quickly. The FRET images displayed that majority of LMP1 oligomer localized in internal perinuclear membranes of CNE1 and enhancement of LMP1 oligomerization caused by lipid rafts disruption. These findings provided some novel views for LMP1 and lipid rafts.
KEYWORDS: Fiber lasers, Temperature metrology, Sensors, Temperature sensors, Structured optical fibers, Single mode fibers, Sensing systems, Photonics, Water
A single mode fiber-tapered multi-core fiber-single mode fiber (SMFTMCF-SMF) structure for the temperature measurement with fiber ring cavity laser at 2 μm band is proposed and demonstrated. The sensor consists of a tapered MCF spliced between two single-mode fibers. By tapering the MCF, the modal fields of the different multi-cores run out and then couple with each other. Experimental results show that the proposed laser works stably at the resonant wavelength of 1979.2 nm at ambient temperature. A sensitivity of -4 pm/°C was obtained with the temperature changing from 70°C to 35°C.
The study of micro-motion amplification technology has been widely concerned. Eulerian Video Magnification is one of the methods of concern and affirmation. Ischemia refers to the lack of blood flowing in certain parts of the body, which can occur in the limb, heart, brain or other parts of the body. Ischemia is a serious disease, which can cause serious tissue damage or let limbs not move. In this paper, we use Eulerian Video Magnification to initially detect whether someone suffers from limb ischemia by amplifying the movement of limb blood.
Liquid-assisted hard tissue ablation has been paid more and more attentions in recent years and its enhancement mechanism has not yet been fully understood. In the present paper, the dynamic process of cavitation bubble and microjet generation induced by Ho:YAG laser, as well as their effects on hard dental tissue ablation were monitored by a high-speed camera. The results showed that the maximum size of the cavitation bubble increases with the increase of laser energy, and the collapse time of cavitation bubbles is also extended accordingly.
Nonlinear optical spectroscopy has wide applications in the medical field with special advantages. Through combining nonlinear optical spectroscopy with membrane electrophoresis, we endeavored to develop a novel method for blood serum analysis for cancer detection applications. In this method, albumin and globin are isolated from blood serum by membrane electrophoresis to perform two-photon excitation fluorescences (TPEF) spectral analysis. The obtained spectra present rich signatures of the biochemical constituents of whole proteins. We evaluated the utility of this method by analyzing albumin and globin samples of blood serum from esophageal cancer patients and healthy volunteers. Twophoton excitation fluorescences revealed that esophageal cancer group can be unambiguously discriminated from the normal group, and I457/I639, I511/I639, and I543/I639 ratios can be used as indicators to diagnose early esophageal cancer. These results are very promising for developing a label-free, non-invasive clinical tool for early cancer detection and screening.
Liquid-assisted hard biotissue ablation with the pulsed lasers takes advantages in precision and compatibility than mechanical tools in traditional surgery. The objective of this study was to monitor the dynamic process of the cavitation bubble evolution induced by Ho:YAG laser under water and identify the opening time of channel formation between the fiber tip to the target tissue surface. A free-running Ho:YAG laser was used in the experiment. The wavelength was 2.1 μm with a pulse duration of 350 us and pulse energy varied from 500 mJ to 2000 mJ. The high-speed camera (PCO. dimax, Germany, PCO) applied to monitor the whole ablation process was setting at a frame rate of 52000 frames/s. The results showed that the cavitation bubble induced by laser energy experienced an oscillation process including occurrence, expansion, contraction and subsequent collapse. A channel connected the fiber tip and target tissue surface was formed during the dynamic process which allowed the following pulse energy transmitted through the channel with a relative low absorption and directly interacted with the target tissue. The beginning time of channel formation, as well as the duration of channel opening, as functions of incident laser energy were also presented. A micro-explosion was observed near the tissue surface during the bubble collapse, which may contribute to produce a clean cut, reduce the thermal injury and improve the morphology of ablation crater.
The goal of this study was to evaluate the dynamic process of water-mediated hard dental tissue ablation induced by Ho:YAG laser with high-speed camera. Human molars in vitro of yellow race were cut into tooth sections and irradiated with pulsed Ho:YAG laser with a wavelength of 2.08μm. The pulse repetition rate was 3 Hz and laser energy ranged from 300 to 2000 mJ. The frame rate of high-speed camera used in the experiment was 50525 fps. Based on the observation by high-speed camera, the dynamic process of the oscillating cavitation bubble and water-mediated ablation induced by Ho:YAG laser was efficiently recorded and graphically described. The pulsation period, the maximum length and width of vapor channel increased with laser energy. The results showed that the external water played multiple roles in laser ablation of hard dental tissue, not only acting as a channel to transmit laser energy, but also helping to improve the regularity of the ablation shape.
Liquid-assisted laser ablation has been investigated in laser surface cleaning, laser osteotomy, and dental tissue ablation.
However, the actual mechanism of liquid-assisted ablation is not clear yet. The purpose of this study was to investigate
the influence of liquid medium with different absorption and the liquid thickness on laser ablation efficiency. A pulsed
CO2 laser was employed to ablate bovine bone tibia under liquid layer which varied from 0.6 mm to 2 mm. The applied
pulse power level was set at 5 w and each crater was produced with six laser pulses. The results showed that the ablation
cross-section area produced with various levels of pure water thickness (0.6, 0.8, 1 and 2 mm)were lower than under ink,
and the ablation depth gradually decreased as the water layer becoming thicker. The biggest cross-section area in liquid
thickness of ink was 0.8mm, but as the layer thicker than 0.8 mm the ablation depth decreased suddenly. There was
thermal damage seen on samples in all of the groups, but less in pure water.
Several studies have demonstrated that laser-induced hard tissue ablation effects can be enhanced by applying an additional water-layer on tissue surface. However, the related mechanism has not yet been presented clearly. In this paper, the influence of static pressure on dynamic characteristics of cavitation induced by pulse laser in liquid and its effect on bovine shank bone ablation were investigated. The laser source is fiber-guided free-running Ho:YAG laser with wavelength of 2080 nm, pulse duration of 350 μs and energy of 1600 mJ. The tissue samples were immerged in pure water at different depths of 11, 16, 21, 26 and 31 mm. The working distance between the fiber tip and tissue surface was fixed at 1 mm for all studies. The dynamic interaction between laser, water and tissue were recorded by high-speed camera, and the morphological changes of bone tissue were assessed by stereomicroscope and OCT. The results showed that many times expansion and collapse of bubble were observed, more than four pulsation periods were accurately achieved with the most energy deposited in the first period and the bubble became more and more irregular in shape. The longitudinal length (7.49--6.74 mm) and transverse width (6.69--6.08 mm) of bubble were slowly decreased while volume (0.0586--0.0124 mm3) of ablation craters were drastically reduced, with static pressure increasing. The results also presented that the water-layer on hard-tissue surface can not only reduce thermal injury but also improve lubricity of craters, although the water-layer reduced ablation efficiency.
The goal of this study was to evaluate the demineralization status at different acid-etch time based on fluorescence spectrum. Human molars in vitro of yellow race were cut into tooth sections and then they were immersed in 0.3% citric acid to simulate the oral natural demineralization. According to the acid-etch time, samples were randomly divided into three groups: I:20 min, II:40 min, and III:60 min. The normal untreated specimen was set as control group. The fluorescence spectra before and after treatment were measured and analyzed. The result showed that fluorescence spectrum could be efficiently used to monitor the demineralization status of human dental tissue. The relative fluorescence intensities of dental tissue excited respectively with 260, 330 and 400 nm decreased with the increase of acid-etch time, though there was no new constituent formed after demineralization.
In clinical practice, laser ablation usually works under liquid environment such as water, blood or their
mixture. Laser-induced vapor bubble or bubble formation and its consequent dynamics were believed to have
important influence on tissue ablation. In the paper, the dynamic process of vapor bubble formation and
consequently collapse induced by pulsed Ho:YAG laser in static water was investigated by using high-speed
camera. The results showed that vapor channel / bubble can be produced with pulsed Ho:YAG laser, and the
whole dynamic process of vapor bubble formation, pulsation and consequently collapse can be monitored by
using high-speed camera. The dynamic characteristics of vapor bubble, such as pulsation period, the
maximum depth and width were determined. The dependence of above dynamic parameters on incident
radiant exposure was also presented. Based on which, the influence of vapor bubble on hard tissue ablation
was discussed.
To examine the temperature changes in the pulp chamber during cavity preparation in dentin with the Er:YAG laser
(2940 nm), a total 20 intact premolars teeth were divided into 4 groups for dentin ablation with different radiant
exposures at 4Hz and 8Hz with and without water spray. A K-type thermocouple was used to monitor the temperature
changes in pulp chamber during laser treatment. The total time of irradiation was 70 sec. the water spray rate was 3
mL/min. It showed that maximum temperature rise increases with the increasing of radiant exposure and pulse
repetition rate and the additional water cooling during laser ablation can significantly reduce the temperature rise in
pulp chamber which will benefit to avoid or reduce thermal damage to tooth structure and dental pulp. The highest
rise of temperature in the pulp was achieved with 20 J/cm2 and 8 Hz (19.83°C ). For all sample without water spray, the
rise of temperature was exceed 5 °C . In contrast, with water spray, the temperature rise in the pulp can be firmly
controlled under 1°C. The results also indicated that ablation rate and efficiency can be enhanced by increasing the
incident radiant exposure and pulse repetition rate, which simultaneously producing more heat accumulation in
dental tissue and causing thermal damage to dental tissue. By applying an additional water spray, thermal damage
can be significantly reduced in clinical application.
The aim of this study is to evaluate the demineralization process in human dentine using Raman spectroscopy (RS). Nine
human molars from Chinese subjects were cut into twelve tooth sections. The sections were painted with an acidresistant
varnish leaving one dentine surface exposed and then immersed into 0.3% citric acid to simulate the oral natural
demineralization. According to the acid-etch time, specimens were randomly divided into four groups: Ⅰ5 min, Ⅱ 10
min, Ⅲ 20 min and Ⅳ 40 min. Raman spectra were measured before and after each treatment. The result showed that no
new bands, bands shifts, or disappearance of bands occurred in the whole process. However, the peak intensities of
inorganic constituents decreased with the increase of acid-etch time, while the trends of organic constituents were
opposite. In conclusion, RS could be able to efficiently monitor the demineralization status of human dentine.
Water plays an important role in laser ablation. There are two main interpretations of laser-water interaction:
hydrokinetic effect and vapor phenomenon. The two explanations are reasonable in some way, but they can’t explain the
mechanism of laser-water interaction completely. In this study, the dynamic process of vapor channel formation induced
by pulsed CO2 laser in static water layer was monitored by high-speed camera. The wavelength of pulsed CO2 laser is
10.64 um, and pulse repetition rate is 60 Hz. The laser power ranged from 1 to 7 W with a step of 0.5 W. The frame rate
of high-speed camera used in the experiment was 80025 fps. Based on high-speed camera pictures, the dynamic process
of vapor channel formation was examined, and the threshold of vapor channel formation, pulsation period, the volume,
the maximum depth and corresponding width of vapor channel were determined. The results showed that the threshold of
vapor channel formation was about 2.5 W. Moreover, pulsation period, the maximum depth and corresponding width of
vapor channel increased with the increasing of the laser power.
The theory of hard tissue ablation reported for IR lasers is based on a process of thermomechanical interaction, which is explained by the absorption of the radiation in the water component of the tissue. The microexplosion of the water is the cause of tissue fragments being blasted from hard tissue. The aim of this study is to evaluate the influence of the interdependence of water layer thickness and incident radiant exposure on ablation performance. A total of 282 specimens of bovine shank bone were irradiated with a pulse CO2 laser. Irradiation was carried out in groups: without a water layer and with a static water layer of thickness ranging from 0.2 to 1.2 mm. Each group was subdivided into five subgroups for different radiant exposures ranging from 18 to 84 J/cm2, respectively. The incision geometry, surface morphology, and microstructure of the cut walls as well as thermal injury were examined as a function of the water layer thickness at different radiant exposures. Our results demonstrate that the additional water layer is actually a mediator of laser-tissue interaction. There exists a critical thickness of water layer for a given radiant exposure, at which the additional water layer plays multiple roles, not only acting as a cleaner to produce a clean cut but also as a coolant to prevent bone heating and reduce thermal injury, but also helping to improve the regularity of the cut shape, smooth the cut surface, and enhance ablation rate and efficiency. The results suggest that desired ablation results depend on optimal selection of both water layer thickness and radiant exposure.
The purpose of this study was to evaluate the shear bond strength of a self-etch adhesive to caries-affected dentin after
caries removal by erbium: yttrium, aluminum garnet (Er:YAG) laser and analyze the resin-dentin interface. The caries-infected
dentin of human molars were removed by Er:YAG laser with energy density of 20 J/cm2 and pulse repetition
rate of 20 Hz. The conventional bur was used as control group. After bonding procedures, specimens were subjected to
shear bond strength test and the adhesive interface was examined by laser confocal scanning microscope (LCSM). The
result showed that Er:YAG laser could effectively remove dentin caries. There was no statistical difference in shear bond
strength between two groups and the adhesive interface created on laser-irradiated dentin surface presented similar
feature to that on bur-ground surface.
The objective of this study was to investigate the influence of an applied water film on bone hard tissue ablation by pulse
CO2 laser. Fresh bovine shank bone in vitro used in the experiment were put on a PC-controlled motorized linear drive
stage and moved repeatedly through focused beam of laser without and with a water film of 0.4 mm and 1 mm on target
tissue. The wavelength of pulse CO2 laser was 10.64 μm, pulse repetition rate was 60 Hz, the energy density was 18-84
J/cm2 and the beam diameter of about 400 μm. The moving speed of stage was 12 mm/s, scanning times was 5. The
surface morphology and microstructure of ablation grooves were examined by stereomicroscope and scanning electron
microscope (SEM) respectively. The geometry of the groove was measured with optical coherence tomography (OCT),
and the thermal injury was examined by histology. It shows that water film on the target tissue surface plays an
important role during the ablation process. A proper thickness of water film applied to target tissue surface could
improve the regular of cut shape, smooth the cut surface, produce the same or even larger ablation rate and efficiency,
and reduce the thermal injury around the groove by compared with dry ablation condition. Moreover, the addition of
water could alter the microstructure of bone sample.
The purpose of this study was to determine the shear bond strength of a self-etch adhesive to Er:YAG laser-prepared
dentin and evaluate the resin-dentin interface. Extracted sound human molars were sectioned and wet-ground to expose
flat dentin surfaces. These surfaces were subsequently irradiated by an Er:YAG laser with a wavelength of 2.94 μm and
pulse repetition rate of 20 Hz. Energy density was set at 20 J/cm2 and spot size was 2 mm. The conventional bur was
used as a control group. After surface treatments, a self-etch adhesive was bonded to the irradiated dentin surface and
then a resin composite was applied to the dentin surface. Specimens were subjected to shear bond strength test after 24 h
of storage in water. The bonding interface was examined by laser confocal scanning microscope (LCSM) after specimens
were serially sectioned into multiple slices. The results revealed that Er:YAG laser irradiation did not present advantages
compared to the conventional bur.
To evaluate the feasibility of middle ear bone ablation in-vivo with pulse CO2 laser. Healthy male New Zealand rabbits
were used in the experiment. Middle ear mastoid bone of animal model was completely exposed by surgeon with
conventional method, and then Pulse CO2 laser with a wavelength of 10.6μm and pulse lengths of about 10ms was used
to carry out the opening surgery. Laser fluence was 8.3 J/cm2 with a repetition rates of 60 Hz, the beam diameter was 1.0
mm. After opening surgery, whole middle ear mastoid bone was obtained and processed with traditional histological
method, the morphology changes and thermal damage around the opening window were examined by light microscope.
Total operation time and light irradiation time were recorded. It showed that pulse CO2 laser is suitable for the
fenestration operation in middle ear bone, and this no-touch technique not only can obtain the similar outcome as
traditional methods, but also present a lot of advantages compared to the traditional methods. With the development of
laser technology and the appearance of relative instruments, especially when the thermal damage was efficiently
controlled, fenestration operation in ear with laser systems will be possible in near future.
The goal of this study was an in vitro evaluation of one dimension dynamic ablation of hard bone tissue with pulse CO2 laser. The tissue model was bovine shank bone which was put on a PC-controlled motorized linear drive stage and move repeatedly through the focused beam. Pulse CO2 laser wavelength 10.6μm was focused down to a spot size of 510μm on the tissue sample surface. radiant exposure ranged from 5J/cm2 to 45J/cm2, repetition rates was 60Hz. After irradiation, the groove morphology produced by laser ablation were examined by optical coherent tomography (OCT) and light microscope following standard histological processing. Quantitative measurement of geometry and thermal damage of ablation groove was presented. It was shown that the width and depth of ablation groove and the zone of collateral thermal damage created in hard bone sample increased steadily with laser fluence. The results suggest that pulse CO2 laser can be a suitable candidate to cut hard bone tissue, and laser radiant exposure has an important effect on ablation rate and collateral thermal damage.
Second harmonic generation (SHG) is a well-known physical phenomenon of important in nonlinear optics, which has
been widely used in tissue morphology and pathology. In this thesis, the influences on backward SHG intensity were
studied. A two-photon laser scanning confocal microscope coupled with a mode-locked femtosecond Ti: sapphire laser
was used to carry out the experiments. Rat-tails were used as experimental objects, there were 40 slices including
transverse and longitudinal. All slices were un-dyed. The changes of backward SHG intensities of rat-tails versus the
excited wavelengths, excited powers, exploring-depths and so on were obtained. It was clear that different irradiation
conditions had evident influences on backward SHG intensity. Subsequently, the backward SHG imaging and
two-photon excited fluorescence (TPEF) imaging through two independent channels were also compared preliminarily.
This study demonstrates that SHG is a promising tool for more accurate information in biomedicine fields.
Because of the unique properties with regard to the absorption in organic tissue, pulsed Er:YAG laser has found most
interest for various application in medicine, such as dermatology, dentistry, and cosmetic surgery. However, consensus
regarding the optimal parameters for clinical use of this tool has not been reached. In this paper, the laser ablation
characteristics of soft tissue by Er:YAG laser irradiation was studied. Porcine skin tissue in vitro was used in the
experiment. Laser fluences ranged from 25mJ/mm2 to 200mJ/mm2, repetition rates was 5Hz, spot sizes on the tissue surface was 2mm. The ablation effects were assessed by the means of optical microscope, ablation diameters and depths
were measured with reading microscope. It was shown that the ablation of soft biotissue by pulsed Er:YAG laser was a
threshold process. With appropriate choice of irradiation parameters, high quality ablation with clean, sharp cuts
following closely the spatial contour of the incident beam can be achieved. The curves of ablation crater diameter and
depth versus laser fluence were obtained, then the ablation threshold and ablation yield were calculated subsequently, and the influence of the number of pulses fired into a crater on ablation crater depth was also discussed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.