Self-calibrating time-resolved near infrared spectroscopy

Time-resolved near infrared spectroscopy is considered to be a gold standard technique when measuring absolute values of tissue optical properties, as it provides separable and independent information about both tissue absorption and scattering. However, time-resolved instruments require an accurate characterization by measuring the instrument response function in order to decouple the contribution of the instrument itself from the measurement. In this work, a new approach to the methodology of analysing time-resolved data is presented where the influence of instrument response function is eliminated from the data and a self-calibrating analysis is proposed. The proposed methodology requires an instrument to provide at least two wavelengths and allows spectral parameters recovery (optical properties or constituents concentrations and reduced scatter amplitude and power). Phantom and in-vivo data from two different time-resolved systems are used to validate the accuracy of the proposed self-calibrating approach, demonstrating that parameters recovery compared to the conventional curve fitting approach is within 10% and benefits from introducing a spectral constraint to the reconstruction problem. It is shown that a multiwavelength time-resolved data can be used for parameters recovery directly without prior calibration (instrument response function measurement)

Eight-wavelength, dual detection channel instrument for near-infrared time-resolved diffuse optical spectroscopy

In this paper, we present an innovative instrument for near-infrared time-resolved spectroscopy. The system is based on eight custom-designed pulsed diode lasers emitting at different wavelengths in the near-infrared region (635-1050 nm), all exhibiting an average optical power higher than 1 mW at 40 MHz pulse repetition rate, two custom-made single-photon detectors based on wide-area silicon photomultipliers and two time-measurement units based on a custom time-to-digital converter with 10 ps timing resolution. The system instrument response function has a width narrower than 160 ps (fullwidth at half-maximum) and stability better than ±1% for several hours for all the wavelengths. All the components of the instrument were designed in order to be compact. The entire system will be hosted in a standard 19 inches, 5U rack case (size 48 × 38 × 20 cm3 ). The system communicates with the external computer through a USB 2.0 link and is designed to be employed in a clinical environment. The proposed instrument, thanks to the reduction of its cost and dimensions, paves the way to a wider diffusion of multiwavelengths near-infrared time-resolved spectroscopy systems

In vivo characterization of the optical and hemodynamic properties of the human sternocleidomastoid muscle through ultrasound-guided hybrid near-infrared spectroscopies

Objective. In this paper, we present a detailed in vivo characterization of the optical and hemodynamic properties of the human sternocleidomastoid muscle (SCM), obtained through ultrasound-guided near-infrared time-domain and diffuse correlation spectroscopies. Approach. A total of sixty-five subjects (forty-nine females, sixteen males) among healthy volunteers and thyroid nodule patients have been recruited for the study. Their SCM hemodynamic (oxy-, deoxy- and total hemoglobin concentrations, blood flow, blood oxygen saturation and metabolic rate of oxygen extraction) and optical properties (wavelength dependent absorption and reduced scattering coefficients) have been measured by the use of a novel hybrid device combining in a single unit time-domain near-infrared spectroscopy, diffuse correlation spectroscopy and simultaneous ultrasound imaging. Main results. We provide detailed tables of the results related to SCM baseline (i.e. muscle at rest) properties, and reveal significant differences on the measured parameters due to variables such as side of the neck, sex, age, body mass index, depth and thickness of the muscle, allowing future clinical studies to take into account such dependencies. Significance. The non-invasive monitoring of the hemodynamics and metabolism of the sternocleidomastoid muscle during respiration became a topic of increased interest partially due to the increased use of mechanical ventilation during the COVID-19 pandemic. Near-infrared diffuse optical spectroscopies were proposed as potential practical monitors of increased recruitment of SCM during respiratory distress. They can provide clinically relevant information on the degree of the patient's respiratory effort that is needed to maintain an optimal minute ventilation, with potential clinical application ranging from evaluating chronic pulmonary diseases to more acute settings, such as acute respiratory failure, or to determine the readiness to wean from invasive mechanical ventilation.</p

Multi-laboratory performance assessment of diffuse optics instruments: the BitMap exercise

SIGNIFICANCE: Multi-laboratory initiatives are essential in performance assessment and standardization-crucial for bringing biophotonics to mature clinical use-to establish protocols and develop reference tissue phantoms that all will allow universal instrument comparison. AIM: The largest multi-laboratory comparison of performance assessment in near-infrared diffuse optics is presented, involving 28 instruments and 12 institutions on a total of eight experiments based on three consolidated protocols (BIP, MEDPHOT, and NEUROPT) as implemented on three kits of tissue phantoms. A total of 20 synthetic indicators were extracted from the dataset, some of them defined here anew. APPROACH: The exercise stems from the Innovative Training Network BitMap funded by the European Commission and expanded to include other European laboratories. A large variety of diffuse optics instruments were considered, based on different approaches (time domain/frequency domain/continuous wave), at various stages of maturity and designed for different applications (e.g., oximetry, spectroscopy, and imaging). RESULTS: This study highlights a substantial difference in hardware performances (e.g., nine decades in responsivity, four decades in dark count rate, and one decade in temporal resolution). Agreement in the estimates of homogeneous optical properties was within 12% of the median value for half of the systems, with a temporal stability of <5  %   over 1 h, and day-to-day reproducibility of <3  %  . Other tests encompassed linearity, crosstalk, uncertainty, and detection of optical inhomogeneities. CONCLUSIONS: This extensive multi-laboratory exercise provides a detailed assessment of near-infrared Diffuse optical instruments and can be used for reference grading. The dataset-available soon in an open data repository-can be evaluated in multiple ways, for instance, to compare different analysis tools or study the impact of hardware implementations

LOS SILOS. SANTA BRÍGIDA [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201

Efficacy of a Cosmetic Treatment in Decreasing the Mild-to-Moderate Atopic Dermatitis in Babies, Children, and Adults: A Pilot Study

Atopic dermatitis (AD) is a chronic inflammatory and pruritic skin disease with a worldwide progressive increase in its incidence. In this clinical study, we studied the effect of a cosmetic treatment composed of a cleanser, and a body and face cream, on subjects (babies, children, and adults) suffering from mild-to-moderate AD. The product effect on AD clinical signs was investigated by SCORing Atopic Dermatitis (SCORAD) index, subjective evaluation, skin erythema index, and transepidermal water loss (TEWL) measurements. The products were shown to be effective in improving the AD scoring by SCORAD in all the groups, and a trend towards the decrease of the erythema index and the TEWL in the adult population. An improvement in itching sensation, skin redness, and skin dryness scoring was also reported by the subjects. Results from this study demonstrate the efficacy of the tested products in decreasing the overall AD severity through 28 days of treatment. Overall, the first results occurred within 14 days of treatment

Cerebral time domain-NIRS: Reproducibility analysis, optical properties, hemoglobin species and tissue oxygen saturation in a cohort of adult subjects

The reproducibility of cerebral time-domain near-infrared spectroscopy (TDNIRS) has not been investigated so far. Besides, reference intervals of cerebral optical properties, of absolute concentrations of deoxygenated-hemoglobin (HbR), oxygenatedhemoglobin (HbO), total hemoglobin (HbT) and tissue oxygen saturation (StO2) and their variability have not been reported. We have addressed these issues on a sample of 88 adult healthy subjects. TD-NIRS measurements at 690, 785, 830 nm were fitted with the diffusion model for semi-infinite homogenous media. Reproducibility, performed on 3 measurements at 5 minutes intervals, ranges from 1.8 to 6.9% for each of the hemoglobin species. The mean ± SD global values of HbR, HbO, HbT, StO2are respectively 24 ± 7 μM, 33.3 ± 9.5 μM, 57.4 ± 15.8 μM, 58 ± 4.2%. StO2displays the narrowest range of variability across brain regions

A novel approach to online Physics refresher courses at Politecnico di Milano

Among the challenges that universities are facing nowadays, one that deserves special attention is the increasing number of dropouts. Refresher courses for perspective freshmen have regularly been organised at Politecnico di Milano over the last years as a means to tackle this issue. Due to the Covid-19 pandemic, the present situation posed serious limitations to traditional teaching methods this year, especially for long (3-4 hours) lectures which may be difficult to follow online. In this paper we present a novel approach based on a blend of non-interactive conventional lectures in large groups and interactive lessons in smaller groups. The course was delivered online using the Microsoft Teams software according to the following structure: first, a live video of a 1-hour lecture was streamed by a single tutor for the whole pool of approximately 1000 students. During this streaming, the students were not allowed to interact with the tutor or with one another by any means. Afterwards, 8 teams of students were formed and assigned to different tutors for the following three hours of more interactive lectures. Each tutor presented examples and exercises of their own choice (mainly on the same topic as the streamed video) and delivered guided solutions while promoting the interaction among students. Furthermore, a common set of short problems was given to each team: this activity could be performed at any time during the second part of the block, as decided by each tutor. In order to span among different teaching styles, the student teams were assigned to a different tutor every day for the interactive part of the lesson. As an additional resource, an online forum was activated on a dedicated website, which allowed students to ask questions on the course topics in an asynchronous way. At the end of the course, every student was invited to fill in an anonymous survey to express their satisfaction with the course. The results of the survey indicate an overall degree of satisfaction with a mean rating over 75%

NIRS-EMG for Clinical Applications: A Systematic Review

In this review, we present an overview of the applications and computed parameters of electromyography (EMG) and near-infrared spectroscopy (NIRS) methods on patients in clinical practice. The eligible studies were those where both techniques were combined in order to assess muscle characteristics from the electrical and hemodynamic points of view. With this aim, a comprehensive screening of the literature based on related keywords in the most-used scientific data bases allowed us to identify 17 papers which met the research criteria. We also present a brief overview of the devices designed specifically for muscular applications with EMG and NIRS sensors (a total of eight papers). A critical analysis of the results of the review suggests that the combined use of EMG and NIRS on muscle has been only partially exploited for assessment and evaluation in clinical practice and, thus, this field shows promises for future developments

Time domain near infrared spectroscopy system for oxygen saturation assessment in stroke patients

In this work we present a medical device for non-invasive oxygen saturation assessment in stroke patients. The system based on time-resolved near infrared spectroscopy was fully characterized and tested on healthy volunteers