Laser tissue soldering of the gastrointestinal tract: A systematic review LTS of the gastrointestinal tract.

Background: Laser Tissue Soldering (LTS) is a promising tissue bonding technique in which a solder is applied between the tissues and then irradiated by laser, causing it to solidify and form links with the tissue. Methods: A comprehensive systematic review summarizing the state of research of LTS in the gastrointestinal tract. Results: Most studies were conducted on large animal tissues, using liquid proteinaceous solder, and irradiated by a continuous wave laser at 808 nm. LTS can provide better sealing and burst pressure than conventional methods. The application of LTS on top of or in addition to sutures showed an impressive increase in burst pressures. LTS may decrease the inflammatory and foreign body reaction caused by sutures. Conclusions: LTS has strong potential to be applied in a clinical setting in leak prevention and in closure of gastrointestinal structures as an adjunct or additional anastomotic technology, decreasing leak rates, morbidity, and mortality.

Technical Note: Noninvasive mid-IR fiber-optic evanescent wave spectroscopy (FEWS) for early detection of skin cancers.

PURPOSE: Melanoma is the most lethal of the three primary skin cancers, including also basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), which are less lethal. The accepted diagnosis process involves manually observing a suspicious lesion through a Dermascope (i.e., a magnifying glass), followed by a biopsy. This process relies on the skill and the experience of a dermatologist. However, to the best of our knowledge, there is no accepted automatic, noninvasive, and rapid method for the early detection of the three types of skin cancer, distinguishing between them and noncancerous lesions, and identifying each of them. It is our aim to develop such a system. METHODS: We developed a fiber-optic evanescent wave spectroscopy (FEWS) system based on middle infrared (mid-IR) transmitting AgClBr fibers and a Fourier-transform infrared spectrometer (FTIR). We used the system to perform mid-IR spectral measurements on suspicious lesions in 90 patients, before biopsy, in situ, and in real time. The lesions were then biopsied and sent for pathology. The spectra were analyzed and the differences between pathological and healthy tissues were found and correlated. RESULTS: Five of the lesions measured were identified as melanomas, seven as BCC, and three as SCC. Using mathematical analyses of the spectra of these lesions we were able to tell that all were skin cancers and we found specific and easily identifiable differences between them. CONCLUSIONS: This FEWS method lends itself to rapid, automatic and noninvasive early detection and characterization of skin cancers. It will be easily implemented in community clinics and has the potential to greatly simplify the diagnosis process.

Strong bonding of corneal incisions using a noncontact fiber-optic laser soldering method.

Suturing of corneal incisions requires significant skill. We demonstrate a noncontact method that will simplify the bonding process. 5-mm-long penetrating vertical and slanted incisions were made in corneas of eyes, extracted from dead piglets. A fiber-optic laser system was used for laser soldering of the incisions, under close temperature control, using albumin solder. The burst-pressure PB immediately after the soldering was found to be PB ≈ 92 and 875 mmHg, for vertical and slanted incisions, respectively. PB = 875 mmHg is an exceptionally high figure, ≈10 times the clinically acceptable value for sutured incisions. Laser soldering was then performed on penetrating incisions made in the corneas of live healthy piglets, of weight ≈10 Kg. After a healing period, the eyes were extracted, and the corneas were examined by histopathology and by optical coherence tomography. Our method immediately generated watertight and strong bonding without noticeable corneal shape distortion. These results would be beneficial for cataract surgery and for corneal transplantations. The fiber-optic system makes it much easier to bond corneal incisions. In the future, laser soldering could be automated and efficiently used by less experienced surgeons, thereby reducing the workload on the experienced ones.

Toward the Required Detection Limits for Volatile Organic Constituents in Marine Environments with Infrared Evanescent Field Chemical Sensors.

A portable sensor system for the simultaneous detection of multiple environmentally relevant volatile organic compounds (VOCs) in real seawater based on Fourier transform infrared fiber-optic evanescent wave spectroscopy (FT-IR-FEWS) was developed. A cylindrical silver halide (AgX) fiber with an ethylene/propylene copolymer (E/P-co) coated flattened segment was used as an active optical transducer. The polymer membrane enriches the hydrophobic analytes, while water is effectively excluded from the penetration depth of the evanescent field. Determination of multicomponent mixtures (i.e., 10 VOCs in real-world seawater samples) collected in Arcachon Bay, France revealed a high accuracy and reproducibility with detection limits down to 560 ppb. The measurement showed no significant influence from changing water conditions (e.g., salinity, turbidity, and temperature or other interfering substances). The time constants for 90% saturation of the polymer ranged from 20 to 60 min. The sensor system is capable of being transported for on-site monitoring of environmental pollutants in aqueous matrices with efficient long-term stability, thus showing great potential to be utilized as an early warning system.

Mid-IR evanescent-field fiber sensor with enhanced sensitivity for volatile organic compounds.

The increasing awareness of the harsh environmental and health risks associated with air pollution has placed volatile organic compounds (VOCs) sensor technologies in elevated demand. While the currently available VOC-monitoring technologies are either bulky and expensive, or only capable of measuring a total VOC concentration, the selective detection of VOCs in the gas-phase remains a challenge. To overcome this, a novel method and device based on mid-IR evanescent-wave fiber-optic spectroscopy, which enables enhanced detection of VOCs, is hereby proposed. This is achieved by increasing the number of analyte molecules in the proximity of the evanescent field via capillary condensation inside nano-porous microparticles coated on the fiber surface. The nano-porous structure of the coating allows the VOC analytes to rapidly diffuse into the pores and become concentrated at the surface of the fiber, thereby allowing the utilization of highly sensitive evanescent-wave spectroscopy. To ascertain the effectiveness and performance of the sensor, different VOCs are measured, and the enhanced sensitivity is analyzed using a custom-built gas cell. According to the results presented here, our VOC sensor shows a significantly increased sensitivity compared to that of an uncoated fiber.

Laser Soldering of Cartilage Graft Interposed Into a Tracheal Incision in a Porcine Model.

OBJECTIVES/HYPOTHESIS: Investigate the feasibility of soldering a free cartilage graft into a tracheal defect by laser heating and assessing the resulting burst pressure and thermal damage to the cartilage. STUDY DESIGN: Animal study. METHODS: A 20 × 8 mm defect was created in fresh cadaveric pig tracheas, a cartilage graft of the same size was harvested from the thyroid ala cartilage, and the graft was fitted into the defect. The soldering process involved covering the edges with liquid albumin and using a fiber-laser system for heating the edges to temperature T under temperature control. This was done for groups of grafts at various temperatures T = 60°C to 90°C. The tracheas were sealed, for each group the burst pressure was measured, and a histologic examination of the soldered incisions was performed. RESULTS: The burst pressures were in the range of 66 to 409 mm Hg. The median burst pressure was 78, 157, 231, and 146 mm Hg, respectively, for T = 60°C, 70°C, 80°C, and 90°C. Statistical analysis revealed significant differences in burst pressures between the T = 60°C group and the T = 80°C and T = 90°C groups (P < .05). The highest burst pressure was measured in the T = 80°C group. Histologic examination revealed no thermal damage to the cartilage at this temperature. CONCLUSIONS: Performing a sutureless laser soldering of a free cartilage graft to a tracheal defect, achieving an immediate watertight bond, is feasible. At T = 80°C the highest burst pressures were achieved. No histologic damage was observed. In vivo studies are needed before implementation of this technique in laryngotracheopasty. LEVEL OF EVIDENCE: NA Laryngoscope, 129:58-62, 2019.

Robot-assisted laser tissue soldering system.

Fast and reliable incision closure is critical in any surgical intervention. Common solutions are sutures and clips or adhesives, but they all present difficulties. These difficulties are especially pronounced in classical and robot-assisted minimally-invasive interventions. Laser soldering methods present a promising alternative, but their reproducibility is limited. We present a system that combines a previously reported laser soldering system with a robotic system, and demonstrate its feasibility on the incision-closure of ex-vivo mice skins. In this demonstration, we measured tearing forces of ~2.5N, 73% of the tearing force of a mouse skin without an incision. This robot-assisted laser soldering technique has the potential to make laser tissue soldering more reproducible and revolutionize surgical tissue bonding.

Using Attenuated Total Reflection-Fourier Transform Infra-Red (ATR-FTIR) spectroscopy to distinguish between melanoma cells with a different metastatic potential.

The vast majority of cancer related deaths are caused by metastatic tumors. Therefore, identifying the metastatic potential of cancer cells is of great importance both for prognosis and for determining the correct treatment. Infrared (IR) spectroscopy of biological cells is an evolving research area, whose main aim is to find the spectral differences between diseased and healthy cells. In the present study, we demonstrate that Attenuated Total Reflection Fourier Transform IR (ATR-FTIR) spectroscopy may be used to determine the metastatic potential of cancer cells. Using the ATR-FTIR spectroscopy, we can identify spectral alterations that are a result of hydration or molecular changes. We examined two murine melanoma cells with a common genetic background but a different metastatic level, and similarly, two human melanoma cells. Our findings revealed that higher metastatic potential correlates with membrane hydration level. Measuring the spectral properties of the cells allows us to determine the membrane hydration levels. Thus, ATR-FTIR spectroscopy has the potential to help in cancer metastasis prognosis.

Fourier transform infrared spectroscopy on external perturbations inducing secondary structure changes of hemoglobin.

The secondary structure of proteins and their conformation are intimately related to their biological functions. In this study, heat-induced changes in the secondary structure and conformation of hemoglobin were investigated via infrared attenuated total reflection (IR-ATR) spectroscopy. The secondary structure changes of hemoglobin were derived from IR-ATR spectra using second derivatives and curve fitting. Thereby, the thermal denaturation temperature ranges and the secondary structure changes with temperature were revealed. More detailed information on the secondary structure and conformation was elucidated via two-dimensional infrared correlation spectroscopy. This study deciphers the detailed conformational behavior of hemoglobin molecular changes along with temperature, and creates a general methodological framework for analyzing the heat-induced behavior of biomacromolecules.

Coherent beam combining in atmospheric channels using gated backscatter.

This paper introduces the concept of atmospheric channels and describes a possible approach for the coherent beam combining of lasers of an optical phased array (OPA) in a turbulent atmosphere. By using the recently introduced sparse spectrum harmonic augmentation method, a comprehensive simulative investigation was performed and the exceptional properties of the atmospheric channels were numerically demonstrated. Among the interesting properties are the ability to guide light in a confined manner in a refractive channel, the ability to gather different sources to the same channel, and the ability to maintain a constant relative phase within the channel between several sources. The newly introduced guiding properties combined with a suggested method for channel probing and phase measurement by aerosol backscattered radiation allows coherence improvement of the phased array's elements and energy refocusing at the location of the channel in order to increase power in the bucket without feedback from the target. The method relies on the electronic focusing, electronic scanning, and time gating of the OPA, combined with elements of the relative phase measurements.

High-sensitivity infrared attenuated total reflectance sensors for in situ multicomponent detection of volatile organic compounds in water.

In situ detection of volatile organic compounds (VOCs) in aqueous environments is imperative for ensuring the quality and safety of water supplies, yet it remains a challenging analytical task. We present a high-sensitivity method for in situ analysis of multicomponent VOCs at low concentrations based on the use of infrared attenuated total reflection (IR-ATR) spectroscopy. This protocol uses a unique ATR waveguide, which comprises a planar silver halide (AgCl(x)Br(1-x)) fiber with cylindrical extensions at both ends to increase the number of internal reflections, and a polymer coating that traps VOCs and excludes water molecules. Depending on the type of VOC and measurement scenario, IR spectra with specific frequency windows, scan times and spectral resolutions are obtained, from which concentration information is derived. This protocol allows simultaneous detection of multiple VOCs at concentrations around 10 p.p.b., and it enables accurate quantification via a single measurement within 5 min without the need for sample collection or sample pretreatment. This IR-ATR sensor technology will be useful for other applications; we have included a procedure for the analysis of protein conformation changes in Supplementary Methods as an example.

Corneal cut closure using temperature-controlled CO2 laser soldering system.

We aimed to evaluate the effectiveness of temperature-controlled laser soldering for repair of large perforated corneas in a porcine model. Eight Yorkshire pigs aged 6 months underwent 6-mm-deep 180° crescent-shaped trephination of the central corneas. Right corneal injuries were repaired by placement of 47 % bovine albumin along the cut followed by CO2 laser soldering (power density 16 W/cm(2)) to a target temperature of 65(°). Left corneal injuries were repaired with 10/0 nylon sutures. The groups were compared for operative time, leakage, and histopathological findings. Mean tissue temperature was 63 ± 4 °C. Mean operative time was 31.57 ± 2.8 min in laser-soldered eyes and 41.38 ± 2.3 min in controls (p < 0.0001, unpaired Student's t test). Compared to controls, the soldered corneas had less neovascularization, complete re-epithelization, and mild stromal inflammation. There was no leakage in either group. Combined CO2 laser and radiometer is effective for the in vivo repair of corneal cuts. These results have important implications for modern corneal surgery. Further studies are needed in the clinical setting.

Temperature-controlled laser-soldering system and its clinical application for bonding skin incisions.

Laser tissue soldering is a method of repairing incisions. It involves the application of a biological solder to the approximated edges of the incision and heating it with a laser beam. A pilot clinical study was carried out on 10 patients who underwent laparoscopic cholecystectomy. Of the four abdominal incisions in each patient, two were sutured and two were laser soldered. Cicatrization, esthetical appearance, degree of pain, and pruritus in the incisions were examined on postoperative days 1, 7, and 30. The soldered wounds were watertight and healed well, with no discharge from these wounds or infection. The total closure time was equal in both methods, but the net soldering time was much shorter than suturing. There was no difference between the two types of wound closure with respect to the pain and pruritus on a follow-up of one month. Esthetically, the soldered incisions were estimated as good as the sutured ones. The present study confirmed that temperature-controlled laser soldering of human skin incisions is clinically feasible, and the results obtained were at least equivalent to those of standard suturing.

Probing the secondary structure of bovine serum albumin during heat-induced denaturation using mid-infrared fiberoptic sensors.

Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy using a special waveguide based on a silver halide fiber was used for probing the heat-induced secondary structure and conformation changes of bovine serum albumin (BSA). From the secondary derivative and the curve fitting of the obtained ATR-FTIR spectra, the changes of the BSA secondary structure with temperature were clearly identified. Two different thermal denaturation temperature ranges (i.e., 50-52 and 80-82 °C, at which a change of the protein structure occurred) were determined, while only one denaturation temperature was previously identified via classical FTIR measurements. Additionally, taking advantage of two-dimensional correlation spectroscopy more detailed information on changes of the protein secondary structure was revealed. The developed method facilitates in situ, sensitive, and more in-depth probing of protein secondary structures, which represents a significant advancement compared to conventional characterization methods.

Perfectly correlated phase screen realization using sparse spectrum harmonic augmentation.

The split-step Fourier method is commonly used to simulate the propagation of radiation in a turbulent atmosphere using two-dimensional phase screens that have the desired spatial spectral content given by the atmospheric power spectrum. Using existing methodologies, isotropy of the structure function can never be achieved, mainly along the axis of propagation, for several reasons. In this paper, we introduce the sparse spectrum harmonic augmentation method that will address the lack of isotropy along the propagation axis, the limited achievable frequencies, and the limited time development possible using known approaches. Following the methodology described will produce phase screens that are transversely endless, perfectly correlated along the propagation axis, and contain the desired spectral content, including the low frequencies that even though they contain most of the energy, are usually neglected. The methodology presented can be used for many aspects of wave propagation in random media, such as atmospheric propagation, underwater acoustics, radio wave propagation in the ionosphere, and more.

CO2 laser welding of corneal cuts with albumin solder using radiometric temperature control.

PURPOSE: To examine the efficacy and reproducibility of CO2 laser soldering of corneal cuts using real-time infrared fiber-optic radiometric control of tissue temperature in bovine eyes (in vitro) and to evaluate the duration of this procedure in rabbit eyes (in vivo). METHODS: In vitro experiment: a 6-mm central perforating cut was induced in 40 fresh bovine eyes and sealed with a CO2 laser, with or without albumin soldering, following placement of a single approximating nylon suture. A fiber-optic radiometric temperature control system for the CO2 laser was used. Leaking pressure and histological findings were analyzed and compared between groups. In vivo experiment: following creation of a central perforation, 6 rabbit eyes were treated with a CO2 laser with albumin solder and 6 rabbit eyes were treated with 10-0 nylon sutures. The amount of time needed for completion of the procedures was compared. RESULTS: In vitro experiment: effective sealing was achieved by CO2 laser soldering. Mean (± SD) leaking pressure was 109 ± 30 mm Hg in the bovine corneas treated by the laser with albumin solder compared to 51 ± 7 mm Hg in the sutured control eyes (n = 10 each; p < 0.001). Mean leaking pressures were much lower in the corneal cuts sealed only with the laser without albumin solder (48 ± 12 mm Hg) and in the cuts sealed only with albumin without laser welding (6.3 ± 4 mm Hg) than in the cuts treated with laser welding and albumin solder. In vivo experiment: mean surgical time was 140 ± 17 s in the laser-treated rabbits compared to 330 ± 30 s in the sutured controls (n = 6; p < 0.001). A histopathological study of the rabbit corneas 1 day after laser soldering revealed sealed corneal edges with a small gap bridged by coagulated albumin. The inflammatory reaction was minimal in contrast to the sutured controls. No thermal damage was detected at the wound edges. CONCLUSIONS: CO2 laser soldering combined with the fiber-optic radiometer is an effective, reliable, and rapid tool for the closure of corneal wounds, and holds advantages over conventional suturing in terms of leaking pressure and surgical time.

Mid-infrared planar silver halide waveguides with integrated grating couplers.

Grating couplers for planar silver halide waveguides were designed and fabricated by using focused ion beam (FIB) milling technology, facilitating coupling of mid-infrared radiation from quantum cascade lasers into thin-film waveguide structures. An optimized rectangular grating structure for an emitted wavelength of 10.4 µm, with a grating constant of 16.4 µm was integrated into a silver halide waveguide substrate via an optimized FIB fabrication procedure. Efficient incoupling and radiation propagation through the waveguide was confirmed by analyzing droplets of acetic acid at different concentrations, deposited at the waveguide surface via evanescent field absorption spectroscopy.

Bonding surgical incisions using a temperature-controlled laser system based on a single infrared fiber.

ABSTRACT. Although there has been great interest in laser heating for bonding of surgical incisions in tissues, it has not gained wide acceptance by surgeons. We argue that the main obstacle has been the lack of temperature control, which may lead to a weak bonding. We previously developed a laser bonding system based on two infrared transmitting AgBrCl fibers, one for laser heating and one for temperature control. In view of the inherent limitations of such systems observed in many animal experiments, we developed an improved system based on a single infrared fiber. Besides the decreased dimensions, this system offers many advantages over the two-fiber system. It is less sensitive to accuracy of height and tilt of the fiber distal tip above the tissue, ensuring more accurate heating that can potentially lead to stronger bonding with minimal thermal damage. The system is successfully tested in the soldering of 15 corneal incisions, ex vivo. Histopathology shows little thermal damage and good wound apposition. The average burst pressure is 100±30 mm Hg. These findings indicate the usefulness of the system for ophthalmic surgery as well as other surgical procedures, including endoscopic and robotic surgery.

Determination of chlorinated hydrocarbons in water using highly sensitive mid-infrared sensor technology.

Chlorinated aliphatic hydrocarbons and chlorinated aromatic hydrocarbons (CHCs) are toxic and carcinogenic contaminants commonly found in environmental samples, and efficient online detection of these contaminants is still challenging at the present stage. Here, we report an advanced Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) sensor for in-situ and simultaneous detection of multiple CHCs, including monochlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, trichloroethylene, perchloroethylene, and chloroform. The polycrystalline silver halide sensor fiber had a unique integrated planar-cylindric geometry, and was coated with an ethylene/propylene copolymer membrane to act as a solid phase extractor, which greatly amplified the analytical signal and contributed to a higher detection sensitivity compared to the previously reported sensors. This system exhibited a high detection sensitivity towards the CHCs mixture at a wide concentration range of 5~700 ppb. The FTIR-ATR sensor described in this study has a high potential to be utilized as a trace-sensitive on-line device for water contamination monitoring.