Yoshitoshi Ito

Spatial and temporal analysis of human motor activity using noninvasive NIR topography

The effect of motor activity on the left fronto-central region of the human brain was analyzed spatially and temporally by using noninvasive near-infrared light (NIR) topography. The changes in oxygenation states caused by motor activity were measured using intensity-modulated NIR spectroscopy at ten measurement positions on the head surface. The subject randomly performed unilateral finger opposition for 30 s as motor stimulation. When the subject performed contralateral (right) finger movement, significant increases in both oxygenated hemoglobin (oxy-Hb) and total hemoglobin (total-Hb) and decreases in deoxygenated hemoglobin (deoxy-Hb) were observed in a particular area. By mapping the static topograms of the changes of each Hb and comparing them with an anatomical image of MRI, it was found that the particular area was located on the motor cortex along the central sulcus. By mapping the dynamic topograms of the changes of total-Hb, which reflect the cerebral blood volume, and analyzing the spatiotemporal hemodynamic changes associated with the brain activity, it was found that the regional change in cerebral blood volume in the primary motor area overlaps the global change around the motor cortex. These results demonstrate that NIR topography can be used to effectively observe the human brain activity.

Non-invasive functional mapping with multi-channel near infra-red spectroscopic topography in humans

Near-infrared spectroscopy (NIRS) is a new technique for non-invasive monitoring of tissue oxygenation and its kinetics. Up to this date, it has been used solely in research for the global hemodynamic change of the brain and for rough regional activation after stimulating the brain physiologically. This paper describes functional brain mapping using multi channel (ten channel) NIRS by applying the motor stimulation in humans. Our results demonstrate that the regional hemodynamic change was detected in a small area around the motor cortex with a time resolution of 1-2 s. NIRS technique offers considerable potential for research and clinical applications with no invasion.

Higher-Order Brain Function Analysis by Trans-Cranial Dynamic Near-Infrared Spectroscopy Imaging

Near-infrared spectroscopy is discussed from the viewpoint of human higher-order brain function analysis. Pioneering work in this field is reviewed; then we describe our concept of noninvasive trans-cranial dynamic optical topography and its instrumentation. Also, the validity of its functional images is assessed from both physical and physiological viewpoints. After confirming the validity of this method, we have applied it to a wide variety of fields such as clinical medicine, cognitive science, and linguistics in collaboration with researchers at several other institutes. Further application possibilities and the future of trans-cranial dynamic optical topography are also discussed.

Noninvasive near-infrared topography of human brain activity using intensity modulation spectroscopy

Yuichi YamashitaAtsushi MakiYoshitoshi ItoHitachi Ltd.Central Research LaboratoryKokubunji, Tokyo 185, JapanE-mail: yu-yama@crl.hitachi.co.jpEiju WatanabeYoshiaki MayanagiTokyo Metropolitan Police HospitalDepartment of NeurosurgeryTokyo 102, JapanHideaki KoizumiHitachi Ltd.Central Research LaboratoryKokubunji, Tokyo 185, JapanAbstract. We describe the functional topography of human brain activitydue to motor stimulation by using near-infrared spectroscopy. Finger mo-tion by each hand was used as the motor stimulation, and activity in theleft fronto-central region of the brain was measured. A greater change inoxyhemoglobin concentration due to brain activity during the stimulationwas obtained for the right hand than for the left hand. Localization of theactivity was obtained by topographically mapping the measured changesfor ten positions within the region.

Assessment of heating effects in skin during continuous wave near infrared spectroscopy

Near infrared spectroscopy is an increasingly important tool for the investigation of human brain function, however, to date there have been few systematic evaluations of accompanying thermal effects due to absorption. We have measured the spatial distribution of temperature changes during near infrared irradiation (789 nm) as a function of laser power, in both excised tissue (chicken meat and skin) and in the forearm of an awake human volunteer. Light was applied using a 1 mm optical fiber which is characteristic of the topographic system. The temperature of excised chicken tissue increased linearly with power level as 0.097 and 0.042 degrees C/mW at depths of 0 and 1 mm, respectively. Human forearm studies yielded temperature changes of 0.101, 0.038, and 0.030 degrees C/mW at depths of 0.5, 1.0, and 1.5 mm, respectively. Due to direct irradiation of the thermocouple all measurements represent the maximum temperature increase from the laser. In all cases the estimated heating effects from continuous wave optical topography systems were small and well below levels which would endanger tissue cells. The close similarity between ex vivo and in vivo measurements suggests negligible contributions from blood flow in the skin which was further supported by measurements during cuff ischemia. Heating effects decreased sharply with both depth and lateral position; thus, for optode spacings greater than a few millimeters, fibers can be treated independently. Finite element analysis confirms that the experimental results are consistent with a simple heat conduction model.

Simultaneous measurement of size and refractive index of a fine particle in flowing liquid

A new technique is developed for the rapid, simultaneous determination of diameter d and refractive index n of a spherical particle in flowing liquid. Scattered light intensities at two wavelengths (441.6 and 632.8 nm) from a particle are measured in forward and sideways directions. To rapidly determine the values of d and n of the particle, the inverse problem of Mie scattering is solved using these data by referring to a precalculated table (scattering intensities against d and n). The method is verified by measuring d and n distributions of standard particles (for polystyrene, d=0.8 and 1.1 mu m, n=1.59) in water. Experimental errors are 18% for d and 3% for n. Particles in milk are also measured and the results are consistent with conventional microscopic measurements.

Concentration measurements of a light absorber localized in a scattering medium

Using a time-resolved technique, we have studied two methods of quantifying the concentration of a light absorber localized in a scattering medium. Because some of the transmitted photons pass through the absorber region many times because of complicated photon propagation in the scattering medium, we used the following methods. First, early-arriving photons passing through the absorber approximately once were selected. Using these photons, we quantified the concentration of the absorber by an ordinary spectroscopic method based on the Beer-Lambert law. Second, for later-arriving photons, after empirically determining the distribution of the number of passes through the absorber as a function of detection time, we obtained the concentration by applying this function to the Beer-Lambert law.

SU‐E‐T‐561: Development of Depth Dose Measurement Technique Using the Multilayer Ionization Chamber for Spot Scanning Method

PURPOSE To develop a measurement technique which suppresses the difference between profiles obtained with a multilayer ionization chamber (MLIC) and with a water phantom. METHODS The developed technique multiplies the raw MLIC data by a correction factor that depends on the initial beam range and water equivalent depth. The correction factor is derived based on a Bragg curve calculation formula considering range straggling and fluence loss caused by nuclear reactions. Furthermore, the correction factor is adjusted based on several integrated depth doses measured with a water phantom and the MLIC. The measured depth dose profiles along the central axis of the proton field with a nominal field size of 10 by 10 cm were compared between the MLIC using the new technique and the water phantom. The spread out Bragg peak was 20 cm for fields with a range of 30.6 cm and 6.9 cm. Raw MLIC data were obtained with each energy layer, and integrated after multiplying by the correction factor. The measurements were performed by a spot scanning nozzle at Nagoya Proton Therapy Center, Japan. RESULTS The profile measured with the MLIC using the new technique is consistent with that of the water phantom. Moreover, 97% of the points passed the 1% dose /1mm distance agreement criterion of the gamma index. CONCLUSION We have demonstrated that the new technique suppresses the difference between profiles obtained with the MLIC and with the water phantom. It was concluded that this technique is useful for depth dose measurement in proton spot scanning method.

Development of noninvasive measurement techniques for the human brain

This paper proposes optical topography using near-infrared light as a new noninvasive measurement method for higher brain function. The brain activity accompanying human finger movement is measured by the proposed method. By static optical topography, the activation, of the primary motor area in connection with contralateral finger movement side is observed, which is consistent with established knowledge, and indicates the validity of the proposed method. By using dynamic optical topography, the hemodynamic changes accompanying the activation of the brain function are temporally and spatially analyzed. As a result, the change of the blood volume in the neighborhood of the motor area as a whole is observed at the start and immediately after the movement, as a characteristic event in common to both ipsilateral and contralateral finger movements. The increase of the local blood volume in the primary motor area is observed in the movement period as a characteristic event of the finger movement on the contralateral side. Near-infrared optical topography is a practical noninvasive method of measurement for the higher brain function, which has high portability and can be used in various environments.