Optimizing Excitation Light for Accurate Rapid Bacterial Species Identification with Autofluorescence.

Rapid identification of bacterial species in patient samples is essential for the treatment of infectious diseases and the economics of health care. In this study, we investigated an algorithm to improve the accuracy of bacterial species identification with fluorescence spectroscopy based on autofluorescence from bacteria, and excitation wavelengths suitable for identification. The diagnostic accuracy of each algorithm for ten bacterial species was verified in a machine learning classifier algorithm. The three machine learning algorithms with the highest diagnostic accuracy, extra tree (ET), logistic regression (LR), and multilayer perceptron (MLP), were used to determine the number and wavelength of excitation wavelengths suitable for the diagnosis of bacterial species. The key excitation wavelengths for the diagnosis of bacterial species were 280 nm, 300 nm, 380 nm, and 480 nm, with 280 nm being the most important. The median diagnostic accuracy was equivalent to that of 200 excitation wavelengths when two excitation wavelengths were used for ET and LR, and three excitation wavelengths for MLP. These results demonstrate that there is an optimum wavelength range of excitation wavelengths required for spectroscopic measurement of bacterial autofluorescence for bacterial species identification, and that measurement of only a few wavelengths in this range is sufficient to achieve sufficient accuracy for diagnosis of bacterial species.

Feasibility study of a LED light irradiation device for the treatment of chronic neck with shoulder muscle pain/stiffness.

Neck with shoulder muscle stiffness/pain is a common disorder. Commonly used physical therapy, pharmacotherapy, acupuncture, and moxibustion only temporarily alleviate the disorder in most cases, thus the disorder often recurs. Low power laser therapy is often used for neck and shoulder stiffness/pain and has been effective in clinical trials. In this study, we evaluated the safety and effectiveness of a newly developed self-care device for disorders including neck with shoulder muscle stiffness/pain. The device incorporates light-emitting diodes (LEDs), which are safer than lasers, as its light source. Ten adults with neck with shoulder muscle stiffness/pain were subject to LED irradiation (wavelength 780 nm ± 15 nm, output 750 mW, power density 3.8 W/cm2, energy density 5.7×102 J/cm2) for 3 minutes on the affected shoulder at a standard acupuncture point (GB21, Jianjing). Immediately after irradiation, the subjective symptoms of the neck with shoulder muscle stiffness and pain evaluated by a visual analog scale were improved from 58.3 mm ± 18.7 mm to 45.5 mm ± 21.5 mm and from 45.8 mm ± 23.3 mm to 39.4 mm ± 21.8 mm, respectively. The symptoms further improved after 15 minutes of irradiation. The skin temperature at the irradiated point increased from 34.3°C ± 1.1°C to 41.0°C ± 0.7°C. The increase in skin temperature was observed within approximately 5 cm of the irradiated area. There was no effect on the heart rate variability, a measure of the autonomic nervous system; however, the baroreflex sensitivity was slightly increased. No irradiation-related adverse skin events were observed. Our LED irradiation device was found to be safe, and it improved the subjective symptoms of muscle stiff neck with shoulders.

The Effect of Motion Artifacts on Near-Infrared Spectroscopy (NIRS) Data and Proposal of a Video-NIRS System.

AIMS: The aims of this study were (1) to investigate the influence of physical movement on near-infrared spectroscopy (NIRS) data, (2) to establish a video-NIRS system which simultaneously records NIRS data and the subject's movement, and (3) to measure the oxygenated hemoglobin (oxy-Hb) concentration change (Δoxy-Hb) during a word fluency (WF) task. EXPERIMENT 1: In 5 healthy volunteers, we measured the oxy-Hb and deoxygenated hemoglobin (deoxy-Hb) concentrations during 11 kinds of facial, head, and extremity movements. The probes were set in the bilateral frontal regions. The deoxy-Hb concentration was increased in 85% of the measurements. EXPERIMENT 2: Using a pillow on the backrest of the chair, we established the video-NIRS system with data acquisition and video capture software. One hundred and seventy-six elderly people performed the WF task. The deoxy-Hb concentration was decreased in 167 subjects (95%). EXPERIMENT 3: Using the video-NIRS system, we measured the Δoxy-Hb, and compared it with the results of the WF task. Δoxy-Hb was significantly correlated with the number of words. CONCLUSION: Like the blood oxygen level-dependent imaging effect in functional MRI, the deoxy-Hb concentration will decrease if the data correctly reflect the change in neural activity. The video-NIRS system might be useful to collect NIRS data by recording the waveforms and the subject's appearance simultaneously.

Near-infrared spectroscopy in studies of brain oxygenation.

Near-infrared spectroscopy (NIRS) is widely used in studies of brain activity. In this article I explain the principles and theoretical limits of NIRS. I also discuss the need for the development of portable NIRS.

Development of a new rehabilitation system based on a brain-computer interface using near-infrared spectroscopy.

We describe the set-up for an electrical muscle stimulation device based on near-infrared spectroscopy (NIRS), designed for use as a brain-computer interface (BCI). Employing multi-channel NIRS, we measured evoked cerebral blood oxygenation (CBO) responses during real motor tasks and motor-imagery tasks. When a supra-threshold increase in oxyhemoglobin concentration was detected, electrical stimulation (50 Hz) of the biceps brachii muscle was applied to the side contralateral to the hand grasping task or ipsilateral to the motor-imagery task. We observed relatively stable and reproducible CBO responses during real motor tasks with an average accuracy of 100%, and during motor imagery tasks with an average accuracy of 61.5%. Flexion movement of the arm was evoked in all volunteers in association with electrical muscle stimulation and no adverse effects were noted. These findings suggest that application of the electrical muscle stimulation system based on a NIRS-BCI is non-invasive and safe, and may be useful for the physical training of disabled patients.

Circulatory basis of fMRI signals: relationship between changes in the hemodynamic parameters and BOLD signal intensity.

Blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-fMRI) is widely used as a tool for functional brain mapping. During brain activation, increases in the regional blood flow lead to an increase in blood oxygenation and a decrease in paramagnetic deoxygenated hemoglobin (deoxy-Hb), causing an increase in the MR signal intensity at the site of brain activation. However, not a few studies using fMRI have failed to detect activation of areas that ought to have been activated. We assigned BOLD-positive (an increase in the signal intensity), BOLD-negative (a decrease in the signal intensity), and BOLD-silent (no change) brain activation to respective circulatory conditions through a description of fMRI signals as a function of the concentration of oxygenated Hb (oxy-Hb) and deoxy-Hb obtained with near-infrared optical imaging (NIOI). Using this model, we explain the sensory motor paradox in terms of BOLD-positive, BOLD-negative, and BOLD-silent brain activation.

Absorber's effect projected directly above improves spatial resolution in near infrared backscattered imaging.

The spatial resolution of near infrared spectroscopic imaging in brain function mapping studies needs to be improved. Most near infrared spectroscopic imaging systems use optical fibers that are arranged like a lattice. The light source and the detector have one-on-one correspondence at intervals of about 3 cm. In this study, we apply several detectors against one source to improve spatial resolution. We assume that a local absorber within a strong scattering medium is a model for local cerebral activation. When we calculate absorbance, which is used to spectroscopically calculate hemoglobin concentration, the peak position shifts away from above the position where an absorber is located. As far as absorbance is calculated, we cannot obtain spatial information about the absorber even if many detectors are used against one source. When we calculate the difference between detected light intensities, however, we demonstrate that an absorber projected onto the measuring surface has an influence directly above it. We predict this property from a light diffusion equation and also prove it experimentally through measurements of a uniform resinous phantom with an absorber. This is one of the basic principles supporting the achievement of higher spatial resolutions with near infrared spectroscopic imaging.

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.