Endovenous laser ablation (EVLA) is popular as a less invasive treatment for varicose veins. To reduce undesired side effects, such as postoperative pain and subcutaneous hemorrhage, a semiconductor laser device with a wavelength of 1,470 nm and the ELVeS Radial 2ring^TM fiber (CeramOptec, Germany) have been developed. To obtain regulatory approval for such new medical devices in a short period of time and with minimal clinical trials, it is necessary to establish an objective technique for evaluating efficacy and safety in a manner that is not influenced by the operator’s skill. The purpose of this study was to develop a computer simulation model for estimating the intravascular temperature during EVLA and to evaluate the efficacy and safety of the new devices. The simulation was performed under the same irradiation conditions as an ex vivo experiment of EVLA, and validated by comparing the measured and calculated temperatures. When the output power was 7.0 W, the measured peak temperatures were about 90°C and coincided well with the calculated temperatures. On the other hand, when the output power was 10.0 W, the calculated temperatures exceeded 100°C and were higher than the experimental values by 13°C or more. We speculate that the overestimation of the temperature was caused by the latent heat, because vacuolation was observed in the histological images of the venous walls after laser irradiation. Therefore, the results of this simulation are comparable to the measured values. This simulation model should be useful for determining the optimal irradiation condition, and the method of quantitative analysis developed in this study will play a key role in theoretical interpretation of thermal effects during EVLA.

To evaluate the electrical potential decrease in an in vivo animal myocardial model by oxidation induced by an extracellular photosensitization reaction using talaporfin sodium, the authors studied an in vitro myocardial cell model that has an irrigation system that improves the oxygen supply. To perform this evaluation, the authors compared the in vivo and in vitro models using a new metric to measure the electrophysiological effect on the myocardium/myocardial cells by a photosensitization reaction. The electrical potential in the myocardium on the inside surface of a canine superior vena cava of the in vivo model was measured by a multielectrode ring catheter. In the in vitro model, the spontaneous action potential waveforms were measured using a voltage-sensitive dye. The model used a flowing talaporfin sodium solution—at a rate of approximately three replacements per second—to improve the oxygen supply in the area of the photosensitization reaction. A new metric—the radiant exposure required to decrease the electrophysiological signal to 1/e of its initial value—was used to compare the electrophysiological effects on myocardium/myocardial cells due to the induced oxidation derived from the photosensitization reaction. Based on the agreement between the in vivo and in vitro models regarding the order of magnitude of the defined radiant exposure, the authors believe that the in vitro model with the improved oxygen supply could be useful for investigating in vivo situations with respect to the electrophysiological effects by an extracellular photosensitization reaction on myocardial cells using this new metric.

Functional diagnosis possibility of photoacoustic imaging has been attracted much attention especially in clinical field. Among them, a system using compact and low priced LED light source which visualize real time image has appeared. Compared to solid state laser, the pulse energy of LED was extremely small, so it had been thought that imaging was so difficult, but by adding pre-amplifier, real time photoacoustic imaging became possible. However the SNR and the amplifier gain needed for making real time imaging possible are not clear. In this work, we have clarified using the phantom and human fingers that SNR > 4 and amplifier gain > 80 dB were found to be needed and why making image without a pre-amplifier had been difficult.

Terahertz (THz) waves lie in the frequency range between 300 GHz and 30 THz, known as undeveloped electromagnetic waves. In recent years much attention has been paid in this field because a variety of applications have been expected. Among them, sensing application in the field of medical, pharmaceutical, and bioscience is especially important and promising owing to the expected large market. This reviews the prospect of THz science and technology in such field and introduces some of recent topics.

Biosensing with terahertz (THz) waves is receiving a lot of attentions due to the potential for extracting the important information on the vital function without any fluorescent labels. However, due to the diffraction limit of THz waves and the strong absorption into water, it is challenging to develop compact chip sensors that capable of quantitative and high-sensitive measurement of ultra-trace amount of solution. To overcome these difficulties, here, we present a nonlinear optical crystal-based THz microfluidic chip with a few arrays of split ring resonators and investigate possibility of ultra-trace biosensing with THz waves.

Metallic mesh is optical element which creates a localized electric field within and around openings in the mesh when incident light interacts with the openings. Using such a structure, samples do not need to be labelled and changes in the transmission property of the mesh when dielectric samples are present in the localized electric field, and it can be easily used as a sensor to detect biomolecules. For detection of minute biomolecules, such as allergens, sensitivity can be improved by actively immobilizing the sample within the localized electric field. To demonstrate the relationship between object immobilization and sensitivity, a metallic mesh prototype was developed with openings filled by an porous polymer, which has high transmission property in the Terahertz region: the light range used in this experiment. This porous polymer coating was modified to contain components which can bind a specific to biomolecule, such as streptavidin and ovalbumin. The metallic mesh demonstrated larger sensitivity when the target was immobilized on the porous polymer within and around openings of the metallic mesh.

We have developed various types of terahertz sensing systems for evaluation of bio-related materials. Here, we describe a terahertz chemical microscopy that we have invented and demonstrate a label-free immune assay and evaluation of penetration speed of cosmetic liquid, each of which was realized using different way of use of the terahertz chemical microscopy.