Optical Topography System Research Articles

Impact of Escalating Cognitive Workload and Temporal Demands on Surgeons Cognitive Function

Impact of Escalating Cognitive Workload and Temporal Demands on Surgeons Cognitive Function

Altered cortical brain activity in end stage liver disease assessed by multi-channel near-infrared spectroscopy: Associations with delirium

Delirium is a common and serious psychiatric syndrome caused by an underlying medical condition. It is associated with significant mortality and increased healthcare resource utilization. There are few biological markers of delirium, perhaps related to the etiologic heterogeneity of the syndrome. Functional near-infrared spectroscopy (fNIRS) is an optical topography system to measure changes in the concentration of oxygenated hemoglobin ([oxy-Hb]) in the cerebral cortex. We examined whether altered cortical brain activity in delirious patients with end stage liver disease (ESLD) is detected by fNIRS. We found that the [oxy-Hb] change during the verbal fluency task (VFT) was reduced in patients with ESLD compared with healthy controls (HC) in the prefrontal and bi-temporal regions. The [oxy-Hb] change during the sustained attention task (SAT) was elevated in patients with ESLD compared to HC in the prefrontal and left temporal regions. Notably, [oxy-Hb] change in the left dorsolateral prefrontal cortex during SAT showed a positive correlation with the severity of delirium. Our results suggest that [oxy-Hb] change in the prefrontal cortex during the sustained attention task measured with fNIRS might serve as a biological marker associated with delirium in ESLD patients.

PASAT時の前頭葉脳血流動態に関する検討

In this report, we compare the hemodynamic change at frontal lobe by ingestion of glucose. The brain activity is evaluated by the form of oxidized hemoglobin concentration, measured by wearable optical topography system. The data are measured during Paced Auditory Serial Addition Test (PASAT) which is known for its usefulness in the area of attentional dysfunction in cognitive rehabilitation. Properties of blood flow change are estimated by transition of time-series data or principal components analysis as well as the relation between blood sugar level and activation in frontal lobe.

IS-008 Shedding Light On The Neonatal Brain

Brain injury in the newborn remains a major cause of death and serious lifelong disability, with alterations in cerebral perfusion and oxygenation implicated in the pathophysiology of injury in both preterm and term infants. Near-infrared light shows a strong absorption dependency on oxygenation state and provides a safe, non-invasive means of monitoring cerebral function at the cotside. Improved continuous quantification in newer generation instruments are an important step in developing clinically useful monitors. Multi-channel systems allow images of the haemodynamic response to functional activation to be reconstructed. A collaborative group, neoLAB , has been created between Cambridge and University College London (UCL) with the aim of developing and refining optical systems to study the development of haemodynamic activity in the developing brain. A frequency multiplexed optical topography system, designed and built at UCL, has been used to study novel haemodynamic events associated with seizures in the newborn. Work is currently being undertaken to look at the development of functional resting state cortical networks. The UCL group has also developed the first 3D optical imaging system. The optical tomography system uses time-correlated single photon counting (TCSPC) technology to measure the flight times of photons as they are transmitted between points on the surface in order to generate 3D images of regional blood volume and oxygenation. The latest generation of this system has a significantly improved time resolution designed to capture dynamic changes in regional blood flow associated with functional activation.

Effects of Preterm Birth on Intrinsic Fluctuations in Neonatal Cerebral Activity Examined Using Optical Imaging

Medical advancements in neonatology have significantly increased the number of high-risk preterm survivors. However, recent long-term follow-up studies have suggested that preterm infants are at risk for behavioral, educational, and emotional problems. Although clear relationships have been demonstrated between preterm infants and developmental problems during childhood and adolescence, less is known about the early indications of these problems. Recently, numerous studies on resting-state functional connectivity (RSFC) have demonstrated temporal correlations of activity between spatially remote cortical regions not only in healthy adults but also in neuropathological disorders and early childhood development. In order to compare RSFC of the cerebral cortex between preterm infants at term-equivalent ages and full-term neonates without any anatomical abnormality risk during natural sleep, we used an optical topography system, which is a recently developed extension of near-infrared spectroscopy. We clarified the presence of RSFC in both preterm infants and full-term neonates and showed differences between these groups. The principal differences were that on comparison of RSFC between the bilateral temporal regions, and bilateral parietal regions, RSFC was enhanced in preterm infants compared with full-term neonates; whereas on comparison of RSFC between the left temporal and left parietal regions, RSFC was enhanced in full-term neonates compared with preterm infants. We also demonstrated a difference between the groups in developmental changes of RSFC related to postmenstrual age. Most importantly, these findings suggested that preterm infants and full-term neonates follow different developmental trajectories during the perinatal period because of differences in perinatal experiences and physiological and structural development.

Note: Wearable near-infrared spectroscopy imager for haired region

A wearable optical topography system was developed that is based on near-infrared spectroscopy (NIRS) for observing brain activity noninvasively including in regions covered by hair. An avalanche photo diode, high voltage dc-dc converter, and preamplifier were placed in an electrically shielded case to be safely mounted on the head. Rubber teeth and a glass rod were prepared to clear away hair and reach the scalp. These devices realized for the first time a wearable NIRS imager for any region of the cortex. The activity in the motor cortex during finger tapping was successfully observed.

Noncontact Optical Brain Activity Measurement System Using Phosphor Placed on Skin

A noncontact brain activity measurement system using phosphor [Li(Nd0.9Yb0.1)P4O12] which is excited by and emits near-infrared light was developed. To optimize and validate this system, first, the influence of fluorescence lifetime on the amplitude of lock-in detection was investigated to determine the optimal frequency of the light source's intensity modulation. Second, the sensitivity of the system to the internal absorbance change was estimated using a phantom measurement. Third, to clearly show that this system can detect the absorbance changes in the cerebral blood instead of those in the superficial regions, the hemoglobin changes in the same area of the prefrontal cortex were measured during a working memory task by simultaneously using this system and a conventional contact optical topography system. Finally, the precision of the system was evaluated. The results verified that this system was as effective as a conventional system in detecting human brain activity.

Noninvasive imaging of prefrontal activation during attention-demanding tasks performed while walking using a wearable optical topography system

Optical topography (OT) based on near-infrared spectroscopy is a noninvasive technique for mapping the relative concentration changes in oxygenated and deoxygenated hemoglobin (oxy- and deoxy-Hb, respectively) in the human cerebral cortex. In our previous study, we developed a small and light wearable optical topography (WOT) system that covers the entire forehead for monitoring prefrontal activation. In the present study, we examine whether the WOT system is applicable to OT measurement while walking, which has been difficult with conventional OT systems. We conduct OT measurements while subjects perform an attention-demanding (AD) task of balancing a ping-pong ball on a small card while walking. The measured time course and power spectra of the relative concentration changes in oxy- and deoxy-Hb show that the step-related changes in the oxy- and deoxy-Hb signals are negligible compared to the task-related changes. Statistical assessment of the task-related changes in the oxy-Hb signals show that the dorsolateral prefrontal cortex and rostral prefrontal area are significantly activated during the AD task. These results suggest that our functional imaging technique with the WOT system is applicable to OT measurement while walking, and will be a powerful tool for evaluating brain activation in a natural environment.

Use of fNIRS to assess resting state functional connectivity

Recently, resting state functional connectivity (RSFC) studies based on fMRI and EEG/MEG have provided valuable insight into the intrinsic functional architecture of the human brain. However, whether functional near infrared spectroscopy (fNIRS), a suitable imaging method for infant and patient populations, can be used to examine RSFC remains elusive. Using an ETG-4000 Optical Topography System, the present study measured 29 adult subjects (14 females) over the sensorimotor and auditory cortexes during a resting session and a motor-localizer task session. The RSFC maps were computed by seed-based correlation analysis and data-driven cluster analysis. The results from both analyses showed robust RSFC maps, which were not only consistent with the localizer task-related activation results, but also those of previous fMRI findings. Moreover, the strong consistency between the seed-based correlation analysis and the data-driven cluster analysis further validated the use of fNIRS to assess RSFC. The potential influence of a specific low-frequency filtering range (0.04–0.15 Hz and 0.01–0.08 Hz) and three fNIRS parameters (oxy-Hb, deoxy-Hb, and total-Hb) on RSFC results were also examined.

A quantitative assessment of the depth sensitivity of an optical topography system using a solid dynamic tissue-phantom

A solid dynamic phantom with tissue-like optical properties is presented, which contains seven discrete targets impregnated with thermochromic pigment located at different depths from the surface. Changes in absorption are obtained in response to localized heating of the targets, simulating haemodynamic changes occurring in the brain and other tissues. The depth sensitivity of a continuous wave optical topography system was assessed successfully using the phantom. Images of the targets have been reconstructed using a spatially variant regularization, and the determined spatial localization in the depth direction is shown to be accurate within an uncertainty of about 3 mm down to a depth of about 30 mm.

Development of wearable optical topography system for mapping the prefrontal cortex activation

Optical topography (OT) based on near infrared spectroscopy is effective for measuring changes in the concentrations of oxygenated hemoglobin (oxy-Hb) and deoxygenated hemoglobin (deoxy-Hb) in the brain. It can be used to investigate brain functions of subjects of all ages because it is noninvasive and less constraining for subjects. Conventional OT systems use optical fibers to irradiate the scalp and detect light transmitted through the tissue in the human head, but optical fibers limit the subject's head position, so some small systems have been developed without using optical fibers. These systems, however, have a small number of measurement channels. We developed a prototype of a small, light, and wearable OT system that covers the entire forehead. We measured changes in the concentrations of oxy-Hb and deoxy-Hb in the prefrontal cortex while a subject performed a word fluency task. The results show typical changes in oxy-Hb and deoxy-Hb during the task and suggest that the prototype of our system can be used to investigate functions in the prefrontal cortex.

An electrically-activated dynamic tissue-equivalent phantom for assessment of diffuse optical imaging systems

A novel design of solid dynamic phantom with tissue-like optical properties is presented, which contains variable regions of contrast which are activated electrically. Reversible changes in absorption are produced by localized heating of targets impregnated with thermochromic pigment. A portable, battery-operated prototype has been constructed, and its optical and temporal characteristics have been investigated. The phantom has been developed as a means of assessing the performance of diffuse optical imaging systems, such as those used to monitor haemodynamic changes in the brain and other tissues. Images of the phantom have been reconstructed using data acquired with a continuous wave optical topography system.

0949 光トポグラフィ装置を用いた運動状態の評価(S05-4 生体のシミュレーション・モデリング・計測(4),S05 生体のシミュレーション・モデリング・計測)

0949 光トポグラフィ装置を用いた運動状態の評価(S05-4 生体のシミュレーション・モデリング・計測(4),S05 生体のシミュレーション・モデリング・計測)

Prefrontal cerebral blood volume patterns while playing video games—A near-infrared spectroscopy study

Video game playing is an attractive form of entertainment among school-age children. Although this activity reportedly has many adverse effects on child development, these effects remain controversial. To investigate the effect of video game playing on regional cerebral blood volume, we measured cerebral hemoglobin concentrations using near-infrared spectroscopy in 12 normal volunteers consisting of six children and six adults. A Hitachi Optical Topography system was used to measure hemoglobin changes. For all subjects, the video game Donkey Kong ® was played on a Game Boy ® device. After spectroscopic probes were positioned on the scalp near the target brain regions, the participants were asked to play the game for nine periods of 15 s each, with 15-s rest intervals between these task periods. Significant increases in bilateral prefrontal total-hemoglobin concentrations were observed in four of the adults during video game playing. On the other hand, significant decreases in bilateral prefrontal total-hemoglobin concentrations were seen in two of the children. A significant positive correlation between mean oxy-hemoglobin changes in the prefrontal region and those in the bilateral motor cortex area was seen in adults. Playing video games gave rise to dynamic changes in cerebral blood volume in both age groups, while the difference in the prefrontal oxygenation patterns suggested an age-dependent utilization of different neural circuits during video game tasks.

A frequency multiplexed near-infrared topography system for imaging functional activation in the brain

We have developed a novel near-infrared optical topography system that can acquire images of functional activation in the human brain at 10 frames per second using 32 detectors. The image acquisition rate is inversely proportional to the number of detectors, so the maximum acquisition rate using four detectors is 80Hz. 16 laser diode sources (8 at 785 and 8 at 850nm) are illuminated simultaneously, and each of 8 avalanche photodiode detectors records light from several sources at the same time. The contribution from each source is demultiplexed in software using fast Fourier transforms. This allows for a more flexible, smaller, and less complex system than is achievable using traditional hardware demodulation techniques, such as lock-in amplifiers. The system will eventually incorporate a total of 64 sources and 32 detectors, enabling the entire adult cortex to be imaged. The system is designed to be as flexible as possible, and to be applicable to a wide variety of experimental and clinical needs. To this end, it can operate in two distinct modes: As a frequency multiplexed system and as a time multiplexed system. We describe phantom and in vivo investigations that have been undertaken using the new instrument in its frequency multiplexed operating mode.

Functional brain imaging of optical topography.

Hitachi medical corporation developed and produced a new modality called Optical Topography System "ETG-100". This system uses near infrared light as in spectroscopy. ETG-100 measures the oxy hemoglobin, deoxy hemoglobin and total hemoglobin volume changes in cerebral cortex. This optical topography system has various features, i.e., displaying the hemoglobin volume change in 2 dimensional images, non-invasiveness, compactness, low cost and less patient restraint. This system is now being used for the research of higher-order brain functions, for example language function, language recognition. Research of brain function disease of new born babies, cerebral blood flow infarction detection are expected.