Michinosuke Takada

Multichannel time-resolved optical tomographic imaging system

A time-resolved optical imaging system using near-infrared light has been developed. The system had three pulsed light sources and total 64 channels of detection, working simultaneously for acquisition of the time-resolved data of the pulsed light transmitted through scattering media like biological tissues. The light sources were provided by high power picosecond pulsed diode lasers, and optical switches directed one of the light sources to the object through an optical fiber. The light signals reemitted from the surface of the object were collected by optical fibers, and transmitted to a time-resolved detecting system. Each of the detecting channels consisted of an optical attenuator, a fast photomultiplier, and a time-correlated single photon counting circuit which contained a miniaturized constant fraction discriminator/time-to-amplitude converter module, and a signal acquisition unit with an A/D converter. The performance and potentiality of the imaging system have been examined by the image reconstr...

New instrument for monitoring hemoglobin oxygenation.

A new compact high-performance instrument for monitoring the oxygenation state of the human newborn are developed. First we applied this instrument to the rat head, and next to the human arm. We could confirm that the volume of Oxy-Hb, Deoxy-Hb and total blood volume were well monitored by using our instrument. Now we started to apply this technique to the human newborn. Furthermore, we started the experiments of the near-infrared tomography for the small animals on the basis of this technique.

Noninvasive hemoglobin oxygenation monitor and computed tomography by NIR spectrophotometry

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.

Optical tomography by the temporally extrapolated absorbance method.

The concept of the temporally extrapolated absorbance method (TEAM) for optical tomography of turbid media has been verified by fundamental experiments and image reconstruction. The TEAM uses the time-resolved spectroscopic data of the reference and object to provide projection data that are processed by conventional backprojection. Optical tomography images of a phantom consisting of axisymmetric double cylinders were experimentally obtained with the TEAM and time-gating and continuous-wave (CW) methods. The reconstructed TEAM images are compared with those obtained with the time-gating and CW methods and are found to have better spatial resolution.

Non-Invasive Near-Infrared Measurements of Human Arm Tissues in Vivo

Near-infrared spectroscopy has been used for the measurement of tissue oxygenation in animals (Jobsis, 1977; Gianni et al., 1982; Kariman and Burkhart, 1985). To extend this technique for clinical use, we have tried to measure the haemoglobin oxygenation state in human muscle tissues under various conditions.

Absorbance Profile of Red Blood Cell Suspension in Vitro and in Situ

In order to achieve non-invasive monitoring of the oxygenation state of hemoglobin, there are many problems that must be solved. (e.g. selection of appropriate measuring wavelengths, establishment of the calibration curve etc.)

Image reconstruction in optical CT using TEAM (temporally extrapolated absorbance method)

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.

Optical CT using the temporally extrapolated absorbance method (TEAM)

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.

Supersonic jet absorption spectrometry utilizing a xenon flashlamp and a monochromator equipped with a photodiode array

Abstract A multichannel spectrometric system is constructed for measurements of an absorption spectrum for a sample in a supersonic jet. The system consists of a xenon flashlamp and a monochromator equipped with a photodiode array. This instrument covers 18.5 nm with 512 diode arrays, and the data are accumulated during 32 min to improve the signal-to-noise ratio. The absorption spectrum is obtained simply by subtracting the sample signal (I) from the reference signal (I0). The spectrum is measured for benzene and its analogs in spectral regions of 254–312 nm. The typical signal intensities are 0.5%, the noise level being reduced to 0.005% by averaging 9600 data. The amount of sample required for recording a spectrum is ca. 100 mg for aniline.