Yuko Fukami

Gelatin ablation wavelength dependency in the range of 5.6–6.7 μm using a mid-infrared Free Electron Laser

Abstract Efficient and precise ablation of soft tissue is needed for non-invasive dermatological and corneal surgeries. Previous research has revealed that smooth and efficient cutting of certain soft tissues and gelatin is possible using a Free Electron Laser (FEL) with a wavelength of λ = 6.45 µm, tuned to the amide-II band of protein. Gelatin ablation experiments have been carried out using a mid-infrared FEL within the waveband λ = 5.6–6.7 µm by changing the primary absorbers such as water (λ = 6.1 µm) and protein (λ = 6.45 µm). The gelatin with 80 wt% water was efficiently ablated by FEL irradiation with the waveband λ= ∼5.95–6.19 µm. On the other hand, using irradiation within λ = ∼6.4–6.6 µm, many small bubbles were observed in the irradiated volume, and the gelatin was not ablated but significantly melted. Thus, it was found that the most effective wavelength was ∼6.1 µm, not ∼6.45 µm, in order to cut soft tissue with a high water concentration at the expense of surface smoothness.© 2003 Elsevire Scienec B.V. All righst reserved.PACS: 42.62.Be

Microwave dielectric properties of textured BaLa4Ti4O15 ceramics with layered perovskite structure

Textured ceramics of BaLa4Ti4O15 (BaLT) with layered perovskite structure have been investigated by characterizing their dielectric properties at MHz and GHz frequencies. The highly grain-oriented ceramics were obtained by a templated grain growth technique. Hexagonal {001}-platelet BaLT particles prepared in molten salt were used as the template. The sintered ceramics containing template powders of 10 wt % exhibited a degree of -orientation of 80% for the casting plane, whereas the plane perpendicular to the casting direction showed a degree of -orientation of 76%. The effect of grain orientation on the dielectric properties was observed as an anisotropy between the directions of parallel and perpendicular to the c-axis. As a result of the anisotropy, enhanced microwave dielectric properties (er=53, Qf=41,400 GHz and τf=-1 ppm/°C) compared with those of a randomly oriented ceramics were obtained in the TE011 mode for a cylindrical specimen with a {001} grain-orientation in the circular plane.

Selective removal of cholesteryl oleate through collagen films by MIR FEL

Abstract In this paper, two layers tissue model were proposed to evaluate the removal effect. The sample was made of cholesteryl oleate as a model of atherosclerotic legions and collagen as a model of endothelial cells and was exposed to the 5.75xa0μm FEL. As results, it was found that the amount of the light which transmitted gelatin layer was enough to remove cholesteryl oleate, and that the cholesteryl oleate under the gelatin layer can be removed by the FEL about 15% without structure damage of the gelatin layer as a model of normal endothelial cells.

Evaluation of an attenuation system for an infrared free-electron laser

This study concerns the attenuation of the incident power from a free-electron laser (FEL) in steps of up to two orders of magnitude, while maintaining optical beam geometry. We have developed and evaluated the properties of a FEL attenuation filter system, which can be attached and detached, with the position of the focusing lens and the target sample fixed. As a result, we have established that our FEL attenuation filter system enables two orders of magnitude of power control for infrared wavelengths between 5.5 and 6.5 μm. We conclude that the attenuation system is extremely useful for various FEL applications.

The thermal dissociation of cholesterol esters using a 5.75-μm free-electron laser

In order to estimate the optimum laser conditions for efficient dissociation of cholesterol ester in an arteriosclerotic region of blood vessels, we have invstigated the relationship between laser wavelength and power density on cholesterol ester dissociation using a mid infrared free electron laser (MIR-FEL). In this study, cholesteryl oleate, which is a typical cholesterol ester found in arteriosclerotic regions, was irradited with 5.75-μm-FELs, which cause vibration of ester bonds. Two results were obtained. (1) Ester dissociated depending on the absorption coefficient, and the macropulse duration was shorter than the thermal relaxation time, showing that ester bonds dissociated into carboxylic acid and cholesterol by macropulse-induced thermal effects without accompanying thermal diffusion, (2) Using a wavelength of 5.75-μm the maximum ester dissociation ratio was achieved under the optimum laser conditions of a macropulse energy density of 0.4-1.0 J/cm2. We conclude that MIR pulsed-lasers with a wavelegnth of 5.75 μm can be useful for removal of cholesteryl lester in an arteriosclerotic region of blood vessels.

Wavelength dependency of the optical properties of water in the bending vibrational band with photo-acoustic measurement

Laser-induced acoustic waves have been successfully used for the measurements of dynamic optical properties. We estimated the optical properties of water in the O-H bending vibrational band using the acoustic waves emitted from water irradiated by a tunable mid-infrared Free Electron Laser (MIR-FEL). From these observations, the following results were obtained. (1) The absorption spectrum of water from photo-acoustic measurements was in agreement with that obtained by the FT-IR measurement at room temperature. (2) There was a slight trend in the absorption spectrum below ~6.1 µm to shift toward longer wavelengths, which is consistent with the previous report on the dynamic optical properties. This technique using longer MIR pulsed-lasers can be used to elucidate the dynamic optical properties of the tissues that depend on the temperature and composition during laser irradiation.

Dissociation of cholesterol ester induced by the thermal effect of mid-infrared free electron laser

Cholesteryl ester is a compound of cholesterol and fatty acid, and is highly accumulated in arteriosclerosis regions and gallstones. We have studied irradiation effects of mid-infrared free electron laser (MIR-FEL) on cholesterol ester. In order to search optimum laser conditions for efficient removal of cholesterol ester, we tuned the FEL wavelengths to 5.75 (ester bond) and 6.82 µm (methylene bond), and irradiated cholesteryl oleate, a kind of cholesterol esters. The average power density was varied in the range of 1-10 W/cm2. Each irradiated sample was analyzed using a mass spectrometer to examine products after irradiation and obtain efficiencies of ester dissociation. The results indicate that (1) ester bond of cholesteryl oleate was dissociated to generate cholesterol and oleic acid, (2) irradiation products and dissociation efficiency of ester bond were similar regardless of the vibration modes which absorbs irradiated wavelength of MIR-FEL, and (3) the laser induced effects were considered to be thermal effects without accompanying thermal diffusion.

Design of micropulse-picking system with acoustic-optic modulators in mid-infrared region FEL

A micropulse-picking system attached to a free electron laser (FEL) opens a broad range of potential applications of ultrafast phenomena in medicine and biology. This paper reports the micropulse-picking system of a mid-infrared (IR) FEL at iFEL, Osaka University. We have designed the system with a germanium acousto-optic modulator (Ge-AOM), which can effectively deflect the direction of the FEL propagation due to Bragg diffraction of the FEL and radio frequency (RF) waves. The system includes a reducing optics for the FEL beam, a focusing optics onto the Ge- AOM and a micropulse-picking device (including the Ge-AOM and the RF driver). The system, which is independent on wavelength in the mid-IR region, can be realized by using the following technique: the RF frequency is carefully controlled to satisfy the Bragg angle matching over the mid-IR region. As a result, the micropulse-picking system can supply single and/or some FEL micropulses at an arbitrary repetition rate over the mid-IR region (equals 2 - 12 micrometers ) and can control the resulting peak power and average power in the ranges of approximately 1 - 2 MW and approximately 50 (mu) W - 20 mW, respectively.

Usefulness of indocyanine green as an infrared marker

Indocyanide green (ICG) is widely used as a tracer for the non-invasive estimation of liver function. ICG has properties of binding with plasma protein, and has a large absorption peak at 805 nm. There were no reports, however, about the IR absorption peak of ICG at 7.1 micrometers , which absorption coefficient amounts to approximately 13000cm-1. In this study, ICG was exposed to free electron lasers (FELs) with wavelength of 7.1 micrometers and usefulness of ICG as an IR-marker was discussed. ICG film sample was formed on IR-transparent BaF2 crystal substrate and exposed to FELs with the wavelength of 7.1micrometers . After exposure the sample was analyzed by FT-IR and film thickness measurements. As results, ICG ablated with the FEL of the power density of more than 5 W/cm2(equalsPdth), and that the molecular structure of ICG was still stable for the power density of less than Pdth, 3 W/cm2. Therefore, ICG can be considered as a novel infrared marker (IR marker) to the living tissue which absorbs FEL photon energy without changing the IR absorption peak.