Toshiaki Nagakura

Auto-regulated osmotic pump for insulin therapy by sensing glucose concentration without energy supply

We designed an osmotic pump, using a semipermeable membrane which changes its volume according to the concentration of an outside solution. No energy supply or regulation system are required. This pump directly converts chemical potential to mechanical action without an intermediary like an electrical apparatus, called a mechanochemical actuator. This mechanism was applied to an insulin pump that works by changing the glucose concentration. We demonstrated that this pump may possibly be used in the treatment of diabetes mellitus patients.

The study of three-dimensional measurement from an endoscopic images with stereo matching method

In these days, an endoscope is applied to therapy as well as a diagnosis. Especially, the early gastric cancer can be treated by ether endoscopic mucosa resection (EMR) or endoscopic submucosal dissection (ESD). So a pathological information of a depth direction of mucosal tissue is important. For a precise endoscopic diagnosis of a depth direction of mucosal tissue is used by ultrasound endoscope. And optical coherence tomography (OCT) and confocal endoscope will be used in the future. However the development of an image sensor is very fast, it could measure the depths of mucosa with a conventional endoscope to some extent. We studied that a probability of three dimensional measurement with a conventional endoscope.

Functional Analysis of Internal Moving Organs Using Super-Resolution Echography

We have developed super-resolution echography to visualize instantaneous velocity and acceleration of internal organs from time-series echograms recorded by a high-frame-rate echograph. The algorithm for this method involves subtraction of two echograms, dividing the difference by the brightness gradient of the first echogram, and normalization of that result by the time interval between the two echograms. Velocity or acceleration is classified into some suitable colors and superimposed on the original B-mode image. Functional diagnosis of moving organs can be made by visualizing instantaneous velocity. In the case of the heart, hypokinesis can be distinguished from a normal heart by the value and the variation of colored parts representing instantaneous velocity. This can also be applied to the liver to observe pulsatile motion. By visualizing instantaneous acceleration, increase or decrease of velocity can be detected. Throb timing and the location of arrhythmia in a heart can be observed. This method has the possibility of contributing to noninvasive functional and characteristic evaluation.

Dynamic Pressure Measurement Using Two-Frequency Ultrasound

To perform non-invasive pressure measurement by ultrasound, we examined the acoustic characteristics of microcapsules which are dependent on the surrounding pressure. The linear amplitude change of frequency spectrum by pressure was used to develop a fast pressure measurement method. To determine the correspondence of the spectrum amplitude with pressure, we defined a twin frequency attenuation ratio (TAR) as a new pressure parameter measured by two-frequency ultrasound. Dynamic change of pressure was experimentally detected by TAR, whose sensitivity for ultrasonic pressure measurement was thus indicated.

Gastric Contraction Imaging System Using a 3-D Endoscope

This paper presents a gastric contraction imaging system for assessment of gastric motility using a 3-D endoscope. Gastrointestinal diseases are mainly based on morphological abnormalities. However, gastrointestinal symptoms are sometimes apparent without visible abnormalities. One of the major factors for these diseases is abnormal gastrointestinal motility. For assessment of gastric motility, a gastric motility imaging system is needed. To assess the dynamic motility of the stomach, the proposed system measures 3-D gastric contractions derived from a 3-D profile of the stomach wall obtained with a developed 3-D endoscope. After obtaining contraction waves, their frequency, amplitude, and speed of propagation can be calculated using a Gaussian function. The proposed system was evaluated for 3-D measurements of several objects with known geometries. The results showed that the surface profiles could be obtained with an error of <;10% of the distance between two different points on images. Subsequently, we evaluated the validity of a prototype system using a wave simulated model. In the experiment, the amplitude and position of waves could be measured with 1-mm accuracy. The present results suggest that the proposed system can measure the speed and amplitude of contractions. This system has low invasiveness and can assess the motility of the stomach wall directly in a 3-D manner. Our method can be used for examination of gastric morphological and functional abnormalities.

Auto-regulated medical pump without energy supply

The authors fabricated an osmotic pump using semipermeable membrane which changes its volume according to outside concentration of solution without any energy supply and regulation system. This pump directly converts chemical potential to mechanical action without an intermediary like an electrical apparatus: it is is called a mechanochemical actuator. The authors applied this mechanism for an insulin pump driven by changing glucose concentration. It was demonstrated that this pump has the possibility of being applied to treat diabetes mellitus patients.

Development of three dimensional endoscope by compound optics

The three dimensional endoscope by compound optics is presented. The system consists of a micro-lens array, a signal separator and a photo-detector array. Digital processing of the captured multiple images is used to extract the surface profile. Preliminary experiments were executed on an evaluation system to verify the principles of the system and to clarify the issues related to its implementation.

Gastrointestinal tract volume measurement method using a compound eye type endoscope

We propose an intestine volume measurement method using a compound eye type endoscope. This method aims at assessment of the gastrointestinal function. Gastrointestinal diseases are mainly based on morphological abnormalities. However, gastrointestinal symptoms are sometimes apparent without visible abnormalities. Such diseases are called functional gastrointestinal disorder, for example, functional dyspepsia, and irritable bowel syndrome. One of the major factors for these diseases is abnormal gastrointestinal motility. For the diagnosis of the gastrointestinal tract, both aspects of organic and functional assessment is important. While endoscopic diagnosis is essential for assessment of organic abnormalities, three-dimensional information is required for assessment of the functional abnormalities. Thus, we proposed the three dimensional endoscope system using compound eye. In this study, we forces on the volume of gastrointestinal tract. The volume of the gastrointestinal tract is thought to related its function. In our system, we use a compound eye type endoscope system to obtain three-dimensional information of the tract. The volume can be calculated by integrating the slice data of the intestine tract shape using the obtained three-dimensional information. First, we evaluate the proposed method by known-shape tube. Then, we confirm that the proposed method can measure the tract volume using the tract simulated model. Our system can assess the wall of gastrointestinal tract directly in a three-dimensional manner. Our system can be used for examination of gastric morphological and functional abnormalities.

Feasibility study of paper-based surface enhanced Raman spectroscopy of tear fluids for onsite therapeutic drug monitoring

This paper discuss drug concentration measurement based on Raman spectroscopy of tear fluids with paper substrates for on-site therapeutic drug monitoring (TDM). We focus on tear fluids as alternative specimens to blood for minimally-invasive TDM. By using paper substrates, specimen collection and measurement based on surface enhanced Raman spectroscopy will be performed easily and inexpensively. In experiment, we fabricated paper-based substrate for surface enhanced Raman spectroscopy (SERS) of tear fluids and evaluated its surface. Scanning electron microscope images of them showed that gold nano-rods were adsorbed on the surface uniformly. This result implies that analysis of tear fluids with paper substrates would be realized with high sensitivity by SERS.

Evaluation of the three-dimensional endoscope system for assessing the gastrointestinal motility

This paper described evaluation of the three-dimensional endoscope system for assessing the gastrointestinal motility. Gastrointestinal diseases are mainly based on the morphological or anatomical abnormity. However, sometimes the gastrointestinal symptoms are apparent without visible abnormalities. Such diseases are called functional gastrointestinal disorder, for example, functional dyspepsia, and irritable bowel syndrome. One of the major factors of these diseases is the gastrointestinal dysmotility. Assessment procedures for motor function are either invasive, or indirect. We thus propose a three-dimensional endoscope system for assessing the gastrointestinal motility. To assess the dynamic motility of the stomach, three-dimensional endoscopic imaging of stomach lining is performed. Propagating contraction waves are detected by subtracting estimated stomach geometry without contraction waves from one with contraction waves. After detecting constriction waves, their frequency, amplitude, and speed of propagation can be calculated. In this study, we evaluate the proposed system. First, we evaluate the developed three-dimensional endoscope system by a flat plane. This system can measure the geometry of the flat plane with an error of less than 10 percent of the distance between endoscope tip and the object. Then we confirm the validity of a prototype system by a wave simulated model. The detected wave is approximated by a Gaussian function. In the experiment, the amplitude and position of the wave can be measure with 1 mm accuracy. These results suggest that the proposed system can measure the speed and amplitude of contraction. In the future, we evaluate the proposed system in vivo experiments.