Ikuo Konishi

Cortical mapping of gait in humans: a near-infrared spectroscopic topography study.

While we have a fair understanding of how and where forelimb-hand manipulative movements are controlled by the neocortex, due to functional imaging studies, we know little about the control of bipedal movements such as walking because of technical difficulties. We succeeded in visualizing cortical activation patterns of human gait by measuring relative changes in local hemoglobin oxygenation using a recently developed near-infrared spectroscopic (NIRS) topography technique. Walking activities were bilaterally associated with increased levels of oxygenated and total hemoglobin in the medial primary sensorimotor cortices and the supplementary motor areas. Alternating foot movements activated similar but less broad regions. Gait imagery increased activities caudally located in the supplementary motor areas. These findings provide new insight into cortical control of human locomotion. NIRS topography might be also useful for evaluating cerebral activation patterns during pathological gait and rehabilitative intervention.

Prefrontal and premotor cortices are involved in adapting walking and running speed on the treadmill: an optical imaging study

We investigated changes of regional activation in the frontal cortices as assessed by changes of hemoglobin oxygenation during walking at 3 and 5 km/h and running at 9 km/h on a treadmill using a near-infrared spectroscopic (NIRS) imaging technique. During the acceleration periods immediately preceded reaching the steady walking or running speed, the levels of oxygenated hemoglobin (oxyHb) increased, but those of deoxygenated hemoglobin (deoxyHb) did not in the frontal cortices. The changes were greater at the higher locomotor speed in the bilateral prefrontal cortex and the premotor cortex, but there were less speed-associated changes in the sensorimotor cortices. The medial prefrontal activation was most prominent during the running task. These results indicate that the prefrontal and premotor cortices are involved in adapting to locomotor speed on the treadmill. These areas might predominantly participate in the control of running rather than walking.

Multimodal assessment of cortical activation during apple peeling by NIRS and fMRI

An intriguing application of neuroimaging is directly measuring actual human brain activities during daily living. To this end, we investigated cortical activation patterns during apple peeling. We first conducted a pilot study to assess the activation pattern of the whole lateral cortical surface during apple peeling by multichannel near-infrared spectroscopy (NIRS) and detected substantial activation in the prefrontal region in addition to expected activations extending over the motor, premotor and supplementary motor areas. We next examined cortical activation during mock apple peeling by simultaneous measurement using multichannel NIRS and functional magnetic resonance imaging (fMRI) in four subjects. We detected activations extending over the motor, premotor and supplementary motor areas, but not in the prefrontal cortex. Thus, we finally focused on the prefrontal cortex and examined its activation during apple peeling in 12 subjects using a multichannel NIRS. We subsequently found that regional concentrations of oxygenated hemoglobin significantly increased in the measured region, which encompassed portions of the dorsolateral, ventrolateral and frontopolar areas of the prefrontal cortex. The current study demonstrated that apple peeling as practiced in daily life recruited the prefrontal cortex but that such activation might not be detected for less laborious mock apple peeling that can be performed in an fMRI environment. We suggest the importance of cortical study of an everyday task as it is but not as a simplified form; we also suggest the validity of NIRS for this purpose. Studies on everyday tasks may serve as stepping stone toward understanding human activities in terms of cortical activations.

Premotor cortex is involved in restoration of gait in stroke

Cortical activation during hemiplegic gait was assessed in six nonambulatory patients with severe stroke (four men, two women; four with right and two with left hemiplegia; 57 years old and 3 months after stroke on average), using a near‐infrared spectroscopic imaging system. Each patient performed tasks of treadmill walking (0.2km/hr), alternated with rest every 30 seconds for four repetitions, under partial body weight support, either with mechanical assistance in swinging the paretic leg control (CON) or with a facilitation technique that enhanced swinging of the paretic leg (FT), provided by physical therapists. Gait performance was associated with increased oxygenated hemoglobin levels in the medial primary sensorimotor cortex in the unaffected hemisphere greater than in the affected hemisphere. Both cortical mappings and quantitative data showed that the premotor activation in the affected hemisphere was enhanced during hemiplegic gait. There was also a prominent activation in the presupplementary motor area. Overall cortical activations and gait performance were greater in walking with FT than with CON. These indicate that multiple motor areas including the premotor cortex and presupplementary motor area might play important roles in restoration of gait in patients with severe stroke.

Analysis of nonlinear relation for skin hemoglobin imaging.

This paper discusses the accuracy of the optical determination of the oxygenated and deoxygenated hemoglobin content of human skin under the influence of a melanin layer for a multi-wavelengths imager. The relation between the nonlinear results by Monte Carlo simulation (MCS) and the modified Lambert Beers law (MLB) is also clarified, emphasizing the importance of the absolute values of skin pigments and their influence on the mean path-length used in MLB. The fitting procedure of the MCS data to the actual skin spectra is shown to obtain the absolute values. It is also shown that once the proper mean path-lengths have been determined, MLB can be used fairly well within an accuracy of 80% compared with MCS. Images of oxygenated hemoglobin with a newly-developed fourwavelength camera are presented to demonstrate the advantages of a multiwavelength system.

Measurement of hydrogen content in diamond like carbon thin films by ERDA

Abstract The hydrogen content in diamond like carbon (DLC) thin films has been determined by elastic recoil detection analysis (ERDA) using a 2.7 MeV He 2+ beam. The DLC films were prepared by an electron cyclotron resonance (ECR) microwave plasma chemical vapor deposition (CVD) system. Analysis of the spectra obtained reveals a uniform 29% concentration of hydrogen in the sub-surface region. Increasing the substrate temperature from room temperature to 250°C resulted in a decrease to 23% of the hydrogen concentration, accompanied by a 2.4 times increase of the films Knoop hardness. This clearly demonstrates the usefulness of the hydrogen concentration measurement in monitoring changes in the film properties. We also discuss other factors during deposition such as bias voltage, microwave power, etc., which influences the hydrogen contents in the DLC film.

Near-infrared optical imager for cerebral blood flow and oxygenation detection

This paper describes the theory and the apparatus on our newly developed 64 channel optical imager that enables imaging of three components, indocyanine green (ICG), oxyHb and deoxyHb. Knowledge on blood flow is obtainable using ICG as a blood flow indicator that is to be introduced via injection. ICG has a strong absorption at 805nm, therefore the changes in ICG is detectable with NIR spectroscopy separating from oxyHb and deoxyHb using proper three wavelengths. In addition to the system description, it describes an animal experiment and a phantom test for the validation study. It discusses independence features of ICG on Hb values. Using a simple quasi Lambert Beers law, it proved the excellent separation of the three components. It also discusses the factors that affect the performance of signal separation.

Strong X-ray emission due to electrification

Abstract Peisach and his co-workers reported in 1993 an enhancement effect of PIXE (particle-induced X-ray emission) spectra for fluorides. We have measured Ni Kα X-ray emission spectra under various experimental conditions, and again observed the enhancement effect for electrified NiF2. The enhancement factors were 22 for the Ni Kα peak and 55 for the total counts including continuum X-rays for 600 keV proton bombardment. This is the same effect which Terasawa reported in 1968.

Estimation of regional cerebral blood flow distribution in infants by multichannel near-infrared spectroscopy with indocyanine green

This is the report on the use of multichannel near-infrared spectroscopy (MNIRS) with indocyanine green (ICG) to determine regional cerebral blood flow (rCBF) distribution disturbance in infants. We measured rCBF in an infant with subdural hemorrhage after surgical removal of a subdural hematoma. A probe consisting of 12 optical fibers, 6 for transmission and 6 for detection, was set on the right and then left temporal regions of the head of the infant, and 16 measuring points were determined. Changes in ICG concentration were recorded using MNIRS (near infrared optical imaging system, OMM-2000, Shimadzu Corp., Japan).

An RFQ accelerator system for MeV ion implantation

Abstract A 4-vane-type Radio-Frequency Quadrupole (RFQ) accelerator system for MeV ion implantation has been constructed and ion beams of boron and nitrogen have been accelerated successfully up to an energy of 1.01 and 1.22 MeV, respectively. The acceleration of phosphorus is now ongoing. The design was performed with two computer codes called SUPERFISH and PARMTEQ. The energy of the accelerated ions was measured by Rutherford backscattering spectroscopy. The obtained values agreed well with the designed ones. Thus we have confirmed the validity of our design and have found the possibility that the present RFQ will break through the production-use difficulty of MeV ion implantation.