Lithotripsy with a Holmium laser is painless using an optical fiber catheter in the urinary tract with a minimally invasive surgical procedure. A video clip of the lithotripsy of the urinary stone phantom was obtained using a high-speed camera, and the lithotripsy results were visually evaluated. This result shows that precise lithotripsy is possible by multiple laser pulses by using the developed Holmium medical laser system.
In the case of the medical lasers used for skin diseases and skin beauty, picosecond lasers with pulse durations of hundreds of picoseconds are mainly used. The picosecond laser breaks the pigment of the lesion into small pieces, enabling effective treatment without damaging the surrounding tissue. In the case, the beam profile is important because the laser must be uniformly irradiated to the desired area. In this paper, in order to obtain a uniform beam profile, the size of Nd:YAG Rod, which is a laser gain medium for each amplification stages, is different, and cap is used for the pre amplification stage. In addition, a beam shape compensator with an aspherical lens at the front of the handpiece was designed to realize a uniform beam in all handpieces.
High-energy ultrashort pulse lasers have been developed in a variety of applications such as medical treatment, defense, semiconductor and manufacturing. In terms of aesthetic dermatology, Alexandrite (Cr3+:BeAl2O4) lasers have an attractive and useful wavelength band (700 nm to approximately 800 nm). Therefore, Alexandrite lasers with shorter pulses and higher energy are required in the medical device market. Since alexandrite medium has a low energy gain at room temperature, it is not easy to make a flash-pumped picosecond alexandrite laser that produces sufficiently high output energy. To generate high-power picosecond laser pulses, we used self-injection and ultra short pulse generation techniques including Q-switching, mode-locking and cavity dumping. We have developed picosecond 755 nm alexandrite laser which can be operated at pulse width in the range from 600 to 2000 ps. A maximum average output energy of 400 mJ was achieved in the picosecond regime.
We report on the design and construction of a goggle-type eye tracker using a low-cost and high-speed lensless camera for monitoring eye movements in neurodegenerative diseases. A Rolling Shutter image sensor combined with lensless computational imaging allows for the reconstruction of a time sequence of images from a single snapshot, effectively improving the framerate of the camera. We constructed and demonstrated the prototype device using a commercial-grade CMOS image sensor and achieved the improvement of framerate from 15 to 480Hz, with the tracking results for 28 clinical measured data. Our device can potentially measure microsaccadic eye movements in a wearable camera format, allowing routine monitoring of abnormal eye movements for the early diagnosis and tracking of Alzheimer’s and Parkinson’s disease.
We developed a photoacoustic imaging (PAI) system based on a solid-state dye laser. Using the system, PA images of a tube filled with methylene blue (MB) below 3.9 cm chicken tissue were successfully obtained. After injecting MB into a rat, MB dyed sentinel lymph node (SLN) under chicken tissue was well described. In addition, it was confirmed the change in PA amplitude of the SLN over time in the PA images. Additionally, lymph vessels, SLN, and blood vessels were also successfully identified in multispectral PA images. These results demonstrate the clinical potential of the system in SLN detection.
Liposuction is one of the most common plastic surgery. Recently developed, a variety of technologies for lipolysis have been introduced to replace conventional liposuction. We have developed two types of laser lipolysis systems, which are non-invasive 1060 nm diode laser and minimally invasive laser system with 1980 nm and 2300 nm wavelengths. The developed laser lipolysis systems were used for preclinical experiments for a mini-pig. The thickness of the subcutaneous fat layer was measured by micro-CT, ultrasound and histopathology analysis. Our preclinical results showed that fat reduction was the most noticeable when using both non-invasive and invasive laser irradiation with combined all three laser wavelengths.
We have developed a lipolysis laser system that can be commercialized using wavelengths of 1980 nm and 2300 nm with excellent absorption in fat and water. An 808 nm laser diode and Nd:YVO4 were used to generate a 1064 nm wavelength light source, which is used as pumping light for nonlinear crystals. The oven was designed and fabricated to precisely control the temperature of the nonlinear crystal and applied to the mid-infrared lipolysis laser system. The characteristics of the developed laser were validated by measuring the change of the wavelength depending on the temperature and the output according to the wavelength. We analyzed fat reduction efficacy appears for two selected wavelengths.
OCT is a non-invasive imaging technique that can be applied to diagnose various skin disease. Since its introduction in 1997, dermatology has used OCT technology to obtain high quality images of human skin.
Recently, in order to accurately diagnose skin diseases, it is essential to develop OCT equipment that can obtain high quality images. Therefore, we developed the system that can obtain a high quality image by using a 1300 nm light source with a wide bandwidth and deep penetration depth, high-resolution image, and a camera capable of high sensitivity and high speed processing.
We introduce the performance of the developed system and the clinical application data.
We report optical amplification in a bismuth-doped silica glass and fiber at 1300 nm region. The optical gain was obtained in a bismuth-doped silica glass at five different wavelengths between 1260 and 1360 nm and the amplification bandwidth was greater than 75 nm. This new gain medium is expected to be useful for application in ultra-wide broadband optical communication. A 5.8 dB gain was observed at 1308 nm in an 8.0 cm bismuth-doped silica fiber. A launched pump power of 152 mW was obtained using an 810-nm laser diode. Simultaneous amplification of two signals from a dual-wavelength near 1300 nm region, the closest to the important telecommunications window, was also achieved. This technique can be used for wavelength division multiplexing optical amplifiers at 1300 nm, which is the range of zero-dispersion for silica fibers.
A new center position detecting algorithm of the spot image for the Shack-Hartmann wavefront sensor was developed. The new algorithm is a modified center of weight algorithm, which uses some power of the grey level intensity of the spot images instead of thr grey level intensity itself of the spot images. From experiments, the repeatability and accuracy of the center position detection of the spot images of the Shack-Hartmann wavefrond sensor which used the new algorithm were improved compared with the conventional center position detection algorithm using the center of weight. Applications of the algorithm to measurement of the displacement of the spot images and the Shack-Hartmann wavefront sensor for measuring wavefornt distortion and the experimental results of closed-loop wavefront correction are described in this paper.
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