In the treatment of acute cerebral infarction, it is important to remove the thrombus quickly without side effects such as intracranial hemorrhage. We have been developing a new therapy way of acute cerebral infraction using laser to solve some weaknesses of current devices and medicines. We use 532nm pulsed laser to remove clot without damage of vessel wall, but it is difficult to adjust position of the tip of catheter to a clot within an effective range. Then, we developed real time monitoring function to evaluate it. In a real-time monitoring function, we used 785nm CW laser added on 532nm pulsed laser, evaluated the 785nm laser which is reflected the tip of the optical fiber. A power of the reflected 785nm is based on the Fresnel equations, and time change levels of reflected 785nm reflects how bubbles generated by pulsed lasers disappear. In the result of evaluation of in vitro studies, it turned out that how its change is affected by the surrounding environment (e.g., hardness and viscosity around the catheter tip). If the area around the catheter tip is filled with liquid, the signal will disappear quickly and simply, and if there is a blood clot, it will be less likely to disappear and its shape is more complex and the key to these phenomena is how the shock generated by the pulsed laser propagates, and we hypothesize that it is a type of rebound due to cavitation.
Several types of the cuffless blood pressure (BP) devices have been developed to calculate BP values mainly from the heart rate (HR). But the cuffless devices suffer from low accuracy compared to the BP values directly measured using sphygmomanometer a with inflatable cuff. Since cuffless BP estimated by optical technology is affected not only by HR but also by vascular resistance, vascular resistance can cause inaccuracies. Vascular resistance is determined by the stiffness of the blood vessels and the air temperature. To examine how air temperature affects the fingertip BP, we prototyped a Fingertip BP device with a non-contact thermometer for measuring outside temperature. This presentation clarifies the findings during the trial production.
Solid homogeneous turbid phantoms can be employed to mimic the attenuation and angular distribution of light
emerging from tissue, e.g., to assess the responsivity of the detection system of diffuse optics instrumentation and to
support standardized performance tests of functional near-infrared spectroscopy devices. We present three methods to
quantify the wavelength-dependent diffuse transmittance, relying on (1) measurement of radiance exiting the phantom by
a detector far from the exit aperture, (2) simple recording of radiance by a power meter close to the exit aperture and
correction for the finite distance between phantom surface and detector, (3) determination of the reduced scattering and
absorption coefficients by time-resolved diffuse transmittance measurements and forward calculation of the time-integrated
diffuse transmittance based on the diffusion model. The implications of the different approximations related to
these approaches are discussed. The various methods were applied to characterize solid slab phantoms, and the results
were compared. Specifically, for an epoxy-resin based phantom having a thickness of 2 cm, a reduced scattering
coefficient of about 0.5/mm and an absorption coefficient of about 0.01/mm, the diffuse transmittance values obtained by
the three different methods were found to agree within about 10%.
Near-infrared spectroscopy (NIRS) is based on the modified-Lambert-Beer's law that changes in absorbance are
proportional to changes in hemoglobin parameters. Majority of the conventional measurement methods uses only two or
three wavelengths. In this research, basic examination of NIRS measurement was approached by acquiring wide range of
wavelength information. Arterial occlusion task was performed by using the blood pressure cuff around the upper arm.
Pressure of 200mmHg was then applied for about 3 minutes. During the arterial occlusion, the spectrum of the lower arm
muscles was measured every 15 seconds, within the range of 600 to 1100nm. The secondary derivative spectrum was
calculated from the measured spectrum. Arterial occlusion is a task which changes the oxygenation level of the tissue.
The change can be regarded as the change of the spectrum form, not as the change of the baseline. Furthermore, it was
found that other wavelength bands hold information correlating to this arterial occlusion task.
Near-infrared spectroscopy (NIRS) calculates hemoglobin parameters, such as oxygenated hemoglobin (oxyHb) and
deoxygenated hemoglobin (deoxyHb) using the near-infrared light around the wavelength of 800nm. This is based on
the modified-Lambert-Beer's law that changes in absorbance are proportional to changes in hemoglobin parameters.
Many conventional measurement methods uses only a few wavelengths, however, in this research, basic examination of
NIRS measurement was approached by acquiring wide range of wavelength information. Venous occlusion test was
performed by using the blood pressure cuff around the upper arm. Pressure of 100mmHg was then applied for about 3
minutes. During the venous occlusion, the spectrum of the lower arm muscles was measured every 15 seconds, within
the range of 600 to 1100nm. It was found that other wavelength bands hold information correlating to this venous
occlusion task. Technique of improving the performance of NIRS measurement using the Spectroscopic Method is very
important for Brain science.
Over the past decade, the application of results from brain science research to education research has been a
controversial topic. A NIRS imaging system shows images of Hb parameters in the brain. Measurements using NIRS are
safe, easy and the equipment is portable, allowing subjects to tolerate longer research periods. The purpose of this
research is to examine the characteristics of Hb using NIRS at the moment of understanding. We measured Hb in the
prefrontal cortex of children while they were solving mathematical problems (tangram puzzles). As a result of the
experiment, we were able to classify the children into three groups based on their solution methods. Hb continually
increased in a group which could not develop a problem solving strategy for the tangram puzzles. Hb declined steadily
for a group which was able to develop a strategy for the tangram puzzles. Hb was steady for a certain group that had
already developed a strategy before solving the problems. Our experiments showed that the brain data from NIRS
enables the visualization of children's mathematical solution processes.
This study examines differences in concentration changes of hemoglobin in the brain while finding algebraic solutions
versus geometrical solutions. We use Near Infrared Spectroscopy imaging system to measure the hemoglobin changes
while subjects are solving algebraic task and geometrical task. NIRS imaging system can measure changes in the
concentration of hemoglobin. This brain activity data shows a difference between the two different experimental tasks
which helps us to identify the characteristics of thinking processes.
We discuss the possibility of Near Infrared Spectroscopy (NIRS) application to the educational research. NIRS system
was used for prefrontal cortex measurement of children, when they were solving Mushi-kuizan problems. The Mushi-kuizan
task is one of the mathematical puzzles. Subjects were four children in fifth grade. Hemoglobin parameters such
as oxygenated hemoglobin and deoxygenated hemoglobin were calculated during Mushi-kuizan problems. The
parameters were compared with the performance data of each subject. Changes Hb parameters described how children
use their brain. NIRS evaluated the thinking process of mathematics task. It is very useful for mathematics teachers to
catch the children's thinking process dynamically because they can consider the way of teaching for each child. It was
shown that NIRS may be able to apply to education.
Near infrared (NIR) light has become a powerful tool for non-invasive imaging of human brain activity. Many systems have been developed to capture the changes in regional brain blood flow and hemoglobin oxygenation, which occur in the human cortex in response to neural activity. We have developed a multi-channel reflectance imaging system, which can be used as a `mapping device' and also as a `multi-channel spectrophotometer'. In the present study, we visualized changes in the hemodynamics of the human occipital region in multiple ways. (1) Stimulating left and right primary visual cortex independently by showing sector shaped checkerboards sequentially over the contralateral visual field, resulted in corresponding changes in the hemodynamics observed by `mapping' measurement. (2) Simultaneous measurement of functional-MRI and NIR (changes in total hemoglobin) during visual stimulation showed good spatial and temporal correlation with each other. (3) Placing multiple channels densely over the occipital region demonstrated spatial patterns more precisely, and depth information was also acquired by placing each pair of illumination and detection fibers at various distances. These results indicate that optical method can provide data for 3D analysis of human brain functions.
Reconstructed images in optical CT by using temporally extrapolated absorbance method (TEAM) are presented. In order to evaluate the system we made optical phantoms with absorbing material, scattering material, and solvents. We reconstructed images by FBP with the new concept on the optical density by the TEAM. TEAM was superior to other methods in S/N ratio and spatial resolution.
KEYWORDS: Scattering, Absorption, Diffusion, Reflectivity, Solids, Picosecond phenomena, Information operations, Head, Transmittance, Monte Carlo methods
This paper describes a convenient and quick method to determine the reduced scattering coefficient (mu) s' and absorption coefficient (mu) a by fitting a theoretical equation to a measured profile Rm(t). It is based on two new principles; one is to adjust (mu) s' so as to make a new function f(t) be linear and the other is to use a special function (alpha) t + (beta) + (gamma) /t for quick determination of (mu) s1. Test results of the new method are given for several samples.
In this paper, we describe the experimental evaluation of the temporally extrapolated absorbance method (TEAM) in turbid media. The TEAM is the method utilizing the extrapolated absorbance, obtained by temporally extrapolating the time-resolved absorbance difference between an object and a reference to the shortest photon flight time. Using the TEAM, we reconstructed the CT image of an absorber-containing cylinder in a strong scattering media and compared it with those obtained with the time gating and cw methods based on the same data. Among the three methods, the TEAM presented best spatial resolution in the reconstructed CT images.
Using a near infrared (NIR) spectrophotometry, a compact instrument for monitoring the hemoglobin (Hb) oxygenation state in human brain was developed. Brian oxygen metabolism was non-invasively studied by simultaneous measurement of oxygenated Hb, deoxygnated Hb and total Hb content in rat and human head. After evaluating our method using anesthetized and artificially ventilated rats, this instrument was applied for clinical use, and was useful for the management of clinical patients. The same method was applied to develope the NIR computed tomography (CT). Human X-ray CT was modified for NIR-CT, and CT images were obtained using the back-projection (BP) method. NIR-CT could measure the oxygenation map of the tissues of anesthetized rats.
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