Kyohei Tomita

Quantitative assessment of manual and robotic microcannulation for eye surgery using new eye model

Microcannulation, a surgical procedure for the eye that requires drug injection into a 60–90 µm retinal vein, is difficult to perform manually. Robotic assistance has been proposed; however, its effectiveness in comparison to manual operation has not been quantified.

Evaluation method of thermal conductivity of single carbon nanotube in liquid using quantum dot hydrogel sensor

In this paper, we propose new evaluation method for thermal conductivity measurement of single carbon nanotube (CNT) in liquid with hydrogel sensor containing quantum dot (Q-dot). Measurement of thermal property of single CNT in liquid is quite difficult because escape of the heat from measurement device. Therefore, novel evaluation method using the hydrogel sensors for both thermal input and temperature sensing was proposed. We can measure the local temperature by fluorescence intensity from the sensors. This sensor is also used for thermal input by absorption of near infrared (IR) laser to Q-dots. In our proposed model, two gel-sensors are adhered to both edges of the CNT. Heat is input to CNT through the gel-sensor. Heat transferred through the CNT is detected using the other sensor by measuring the temperature at the edge of the CNT. Sensitivity of the sensor is −1.1%/K and accuracy is ±0.5 K. The error of heat input is within 5%. Thermal conductivity was calculated from the proposed method. The estimated error of the thermal conductivity in our model is about 20%. We demonstrated the preliminary evaluation of the thermal conductivity of single CNT using the gel-sensors in liquid.

Temperature measurement by color analysis of fluorescent spectrum using cell investigation tool impregnated with quantum dot for cell measurement on a microfluidic chip

In this paper, we proposed cell investigation tool for measurement of physiological conditions of single cell. We developed a novel temperature measurement method using temperature dependence of the quantum dot. The cell investigation tool encapsulates the quantum dot and adheres to the cell membrane. These tools can be manipulated in a solution by optical tweezers. We proposed image processing of the tools using the color information for temperature measurement. We calibrated the temperature using the tool impregnated with quantum dot by several color spaces such as HSV and YCrCb (H: hue, S: saturation, V: values (brightness). Y: brightness, Cr: color difference of red, Cb: color difference of blue). Y and Cr represent the monotone decrease according to the temperature increase, while H and Cb do not represent monotone variation. Measurement value by Cr is stable rather than the values by Y and V information because the color difference is robust against brightness fluctuation. From these results, we confirmed temperature measurement using Cr information suitable for cell analysis. Sensitivity is −1.3 %/K and accuracy is 0.3 K.

Fabrication of 3D Capillary Vessel Models with Circulatory Connection Ports

Bionic microscopic vessel models can contribute to the development of vascular treatment skills and techniques for clinical training. Most microscopic vessel models are limited to two dimensions, but three-dimensional (3D) models are important for surgery, such as on retina microscopic vessels, for the observation of colon microvessels, for measuring the deformability of red blood cell (RBC), and so on. Therefore, bionic 3D blood vessel models are increasingly in demand. For this reason, it is necessary to establish 3D fabrication techniques for microchannels. In this study, we established two fabrication methods for 3D microfluidic devices for the development of microscopic vessel models. First, we employed an exposure method using photolithographic technology. Second, we employed a 3D method using femtosecond laser and mask hybrid exposure (FMEx). Both methods made it possible to fabricate a millimeter-scale 3D structure with a submicrometer resolution and achieve an easy injection of solution. This is because it was possible to fabricate typical microfluidic channels used for model inlet and outlet ports. Furthermore, in the FMEx method, we employed an acid-diffusion effect using a chemically amplified resist to form a circular channel cross-section. The acid-diffusion effect made it realizable to fabricate a smooth surface independent of the laser scanning line width. Thus, we succeeded in establishing two methods for the fabrication of bionic 3D microfluidic devices with microfluidic channels having diameters of 15–16 µm for mimicking capillary vessels.

Robust servoing method for renal stones/tumors for the non-invasive ultrasound theragnostic system

The main problem on HIFU (High Intensity Focused Ultrasound) therapy is the difficulty to locate HIFU focus precisely onto the focal lesion, which is located in the moving organ such as livers/kidneys, due to the deformation and rotation, which is caused by respiration. Furthermore, rib bones frequently block the acoustic path to the lesion. The acoustic shadow, which is generated by the rib bone, is observed in the ultrasound images and the lesion is hidden in the shadow. To cope with this problem, we have developed a novel method to track, follow, and monitor the lesion by utilizing the contour information of the organ, which incorporate the lesion under those difficult conditions. As for the tracking method, the contour of the organ, which is deformed and rotated in accordance with respiration, is extracted automatically in 2-D ultrasound images. The missing contour information in the acoustic shadow area is estimated and compensated by the surrounding contours, which are successfully extracted. To con...

Liver tracking system utilizing template matching and energy function in high intensity focused ultrasound/radio frequency ablation therapy

Monitoring and evaluating the therapeutic effects, in ultrasound images during HIFU (High Intensity Focused Ultrasound) and RFA (Radio Frequency Ablation) therapies, are important. However, the common problem is the difficulty to monitor the progress and identify the positions of the focal lesion precisely in accordance with the progress of the treatment. This problem is caused by the movement of organs and the change of the textures information in ultrasound images. To overcome those problems, we have developed a novel method to track, follow, and monitor the focal lesion by the combination of the energy function method and the template matching method. The template matching method uses the characteristic texture information of the organ near the focal lesion. The energy function is implemented in order to reinforce the robustness of the tracking performance of the template matching method. Particularly, we evaluate the existing probability of the focal lesion considering the continuity of the movement a...

An ultrasound guided monitoring system for high intensity focused ultrasound and radio frequency ablation therapies

In accordance with the progress of the HIFU (High Intensity Focused Ultrasound) and RFA (Radio Frequency Ablation) treatments, the intensity of the focal lesion and the surrounding marginal area changes little by little. Here, it should be noted that the human eyes are very weak when the image takes a long time to change even if the image change from the start of the ablation treatment is large. To cope with those problems, we propose an ultrasound guided monitoring system to evaluate the progress of the ablation therapy quantitatively in order to secure the certain level of the monitoring during the HIFU and RFA therapies by reinforcing the lack of experience of medical doctors. Particularly, we propose a system to monitor and evaluate the intensity of the focal lesion and the intensity of the surrounding marginal area by tracking the position of the characteristic texture area near the focal lesion, which moves in accordance with the respiration. Our method to overlay the focal lesion and the surroundin...

3D capillary vessel and arteriole simulator fabricated by using femtosecond laser and mask hybrid exposure

Blood vessel simulators can contribute to development of endovascular treatment techniques. However, most of the blood vessel model, whose diameter is smaller than 500 µm, of conventional simulators is fabricated by using mask exposure, and the microfluidic network is limited in the two dimensional plane. Here, we propose fabrication method of arbitral three-dimensional (3D) vessel simulators whose diameter is smaller than 500 µm. We employ 3D exposure method using femtosecond laser and mask hybrid exposure(FMEx). FMEx makes it possible to fabricate a millimeter-sized large structure with submicrometer resolution in three dimensions. In this paper, we fabricated 3D capillary vessel and arteriole simulator with two branches by using FMEx.

Fabrication of 3D capillary vessel simulator using femtosecond laser and mask hybrid exposure

Circulation-type blood vessel model can contribute to evaluation of drag delivery systems and the alternative systems for animal test. The shape of conventional models fabricated by photolithography is limited to two dimensions (2D). Therefore, we needed to fabricate three-dimensional (3D) blood vessel models for simulating real blood vessel shapes. For this purpose, we propose a novel 3D exposure method as femtosecond laser and mask hybrid exposure: FMEx. FMEx is integrated two-photon absorption exposure method by using femtosecond laser and photolithography method by using mask aligner. We report the results of fabricated 3D capillary vessel model by using FMEx.