Development and first in‐human use of a Raman spectroscopy guidance system integrated with a brain biopsy needle

Navigation‐guided brain biopsies are the standard of care for diagnosis of several brain pathologies. However, imprecise targeting and tissue heterogeneity often hinder obtaining high‐quality tissue samples, resulting in poor diagnostic yield. We report the development and first clinical testing of a navigation‐guided fiberoptic Raman probe that allows surgeons to interrogate brain tissue in situ at the tip of the biopsy needle prior to tissue removal. The 900 μm diameter probe can detect high spectral quality Raman signals in both the fingerprint and high wavenumber spectral regions with minimal disruption to the neurosurgical workflow. The probe was tested in three brain tumor patients, and the acquired spectra in both normal brain and tumor tissue demonstrated the expected spectral features, indicating the quality of the data. As a proof‐of‐concept, we also demonstrate the consistency of the acquired Raman signal with different systems and experimental settings. Additional clinical development is planned to further evaluate the performance of the system and develop a statistical model for real‐time tissue classification during the biopsy procedure.      

Human calf microvascular compliance measured by near-infrared spectroscopy.

The purpose of this study is to develop a new method for the measurement in humans of the compliance of the microvascular superficial venous system of the lower limb by near-infrared spectroscopy (NIRS). This method is complementary to strain-gauge plethysmography, which does not allow compliance between deep and superficial venous or between venous and arterial compartments to be distinguished. In practice, hydrostatic pressure (P) changes were induced in a calf region of interest by head-up tilt of the subject from alpha = -10 to 75 degrees. For P < or = 24 mmHg, the measured compliance [0.086 +/- 0.005 (SD) ml. l(-1). mmHg(-1)] based on NIRS data of total, deoxygenated, and oxygenated hemoglobin, reflects essentially that of the superficial venous system. For P > or = 24 mmHg, no distinction can be made between arterial and venous volumes changes. However, by following the changes in oxy- and deoxyhemoglobin in the P range -16 to 100 mmHg, it appears to be possible to assess the characteristics of the vasomotor response of the arteriolar system.     

Relationships between kernel vitreousness and dry matter degradability for diverse corn germplasm: I. Development of near-infrared reflectance spectroscopy calibrations

Negative correlations between corn vitreousness and ruminal dry matter and starch degradabilities have been widely reported. To measure corn vitreousness and density more rapidly, Correa et al. [Correa, C.E.S., Shaver, R.D., Pereira, M.N., Lauer, J.G., Kohn, K., 2002. Relationship between corn vitreousness and ruminal in-situ starch degradability. J. Dairy Sci. 85, 3008–3012] initiated the development of near-infrared reflectance spectroscopy (NIRS) calibrations from 47 samples derived from 14 US and five Brazilian commercial hybrids. In this study, we generated more data to add to these NIRS calibrations with the objective of making them more robust. We also evaluated the potential of using Stenvert hardness measurements for NIR calibrations. Thirty-three diverse corn germplasm sources were grown at University of Wisconsin West Madison Research Station. These included a wide range of endosperm characteristics from opaque 2 (o2) types to densely packed flint types, and a number of intermediates. Harvest was at 1/2 milkline and black-layer maturity stages. Dried kernels from middle portions of ears from 12 selected inbreds, four each from low (0–30%), medium (30–70%), and high (70–100%) vitreousness classifications were used to determine vitreousness by manual dissection and density by water displacement using a pycnometer. Hardness was determined on all 33 inbreds on a 20 g sample using a Stenvert micro hammer-cutter mill with 2 mm screen size and 3600 rpm to measure time to collect ground sample to a set receptacle height (T); total column height (CH); and height ratio of coarse to fine (C/F) particles. The NIRS equations were selected on the basis of high R²-values (0.90, 0.92, 0.85, and 0.85) and low SEC (4.85, 0.01, 1.39, and 0.19) and SECV (6.04, 0.02, 1.79, and 0.25), for vitroueness, density, T and CH factors, respectively. Calibrations for vitreousness and density were regarded as the best prediction models compared to stenvert hardness measurements as determined by their RPD values (3.73 and 2.50, respectively). These results show that NIRS can be used as a screening tool in large-scale breeding trials to develop corn hybrids of desired endosperm properties for improved ruminal degradabilities.     

Human cortical perfusion and the arterial pulse: a near-infrared spectroscopy study

Background  

The pulsatile nature of the arterial pulse induces a pulsatile perfusion pattern which can be observed in human cerebral cortex with non-invasive near-infrared spectroscopy. The present study attempts to establish a quantitative relation between these two events, even in situations of very weak signal-to-noise ratio in the cortical perfusion signal. The arterial pulse pattern was extracted from the left middle finger by means of plethesmographic techniques. Changes in cortical perfusion were detected with a continuous-wave reflectance spectrophotometer on the scalp overlying the left prefrontal cortex. Cross-correlation analysis was performed to provide evidence for a causal relation between the arterial pulse and relative changes in cortical total hemoglobin. In addition, the determination of the statistical significance of this relation was established by the use of phase-randomized surrogates.     

Real time monitoring of a biogas digester with gas chromatography, near-infrared spectroscopy, and membrane-inlet mass spectrometry

Four methods of monitoring the anaerobic digestion process were studied at pilot scale. The methods employed were Micro Gas Chromatography (μ-GC) and Membrane Inlet Mass Spectrometry (MIMS) for measurements in the gas phase, Near Infrared Spectroscopy (NIRS) and pH in the liquid phase. Micro Gas Chromatography accurately measured H₂, CH₄, H₂S, N₂ and O₂ in the headspace whereas the MIMS accurately measured CH₄, CO₂, H₂S, reduced organic sulfur compounds and p-cresol, also in the headspace. In the liquid phase, NIRS was found to be suitable for estimating the concentrations of acetate, propionate and total volatile fatty acids (VFA) but the error of prediction was too large for accurate quantification. Both the μ-GC and NIRS were low maintenance methods whereas the MIMS required frequent cleaning and background measurements.     

High-pressure near-infrared Raman spectroscopy of bacteriorhodopsin light to dark adaptation.

Near-infrared (NIR) Raman spectroscopy is employed as an in situ probe of the chromophore conformation to study the light to dark-adaptation process in bacteriorhodopsin (bR) at variable pressure and temperature in the absence of undesired photoreactions. In dark-adapted bR deconvolution of the ethylenic mode into bands assigned to the all-trans (1526 cm-1) and 13-cis (1534 cm-1) isomers yields a 13-cis to all-trans ratio equal to 1 at ambient pressure (Schulte et al., 1995, Appl. Spectrosc. 49:80-83). Detailed spectroscopic evidence is presented that at high pressure the equilibrium is shifted toward the 13-cis isomers and that the light to dark adaptation kinetics is accelerated. The change in isomeric composition with temperature and pressure as well as the kinetics support a two-state model activation volumes of -16 ml/mol for the transition of 13-cis to all-trans and -22 ml/mol for the reverse process. These compare with a conformational volume difference of 6.6 ml/mol, which may be attributed to the ionization of one or two residues or the formation of three hydrogen bonds.     

At-line near-infrared spectroscopy for monitoring concentrations in temperature-triggered glutamate fermentation

Rapid development in the glutamate fermentation industry has dictated the need for effective fermentation monitoring by rapid and precise methods that provide real-time information for quality control of the end-product. In recent years, near-infrared (NIR) spectroscopy and multivariate calibration have been developed as fast, inexpensive, non-destructive and environmentally safe techniques for industrial applications. The purpose of this study was to develop models for monitoring glutamate, glucose, lactate and alanine concentrations in the temperature-triggered process of glutamate fermentation. NIR measurements of eight batches of samples were analyzed by partial least-squares regression with several spectral pre-processing methods. The coefficient of determination (R ²), model root-mean square error of calibration (RMSEC), root-mean square error of prediction (RMSEP) and residual predictive deviation (RPD) of the test calibration for the glutamate concentration were 0.997, 3.11 g/L, 2.56 g/L and 19.81, respectively. For the glucose concentration, R ², RMSEC, RMSEP and RPD were 0.989, 1.37 g/L, 1.29 g/L and 9.72, respectively. For the lactate concentration, R ², RMSEC, RMSEP and RPD were 0.975, 0.078 g/L, 0.062 g/L and 6.29, respectively. For the alanine concentration, R ², RMSEC, RMSEP and RPD were 0.964, 0.213 g/L, 0.243 g/L and 5.29, respectively. New batch fermentation as an external validation was used to check the models, and the results suggested that the predictive capacity of the models for the glutamate fermentation process was good.     

Applicability of near-infrared spectroscopy for process monitoring in bioethanol production

The applicability of near-infrared (NIR) spectroscopy to bioethanol production is investigated. The NIR technique can provide assistance for rapid process monitoring, because organic compounds absorb radiation in the wavelength range 1100–2300 nm. For quantification of a sample's chemical composition, a calibration model is required that relates the measured spectral NIR absorbances to concentrations. For calibration, the concentrations in g/l are determined by the analytical reference method high performance liquid chromatography (HPLC). The calibration models are built and validated for moisture, protein, and starch in the feedstock material, and for glucose, ethanol, glycerol, lactic acid, acetic acid, maltose, fructose, and arabinose in the processed broths. These broths are prepared in laboratory experiments: The ground cereal samples are fermented to alcoholic broths (‘mash’), which are divided into an ethanol fraction and the residual fraction ‘stillage’ by distillation. The NIR technology together with chemometrics proved itself beneficial for fast monitoring of the current state of the bioethanol process, primarily for higher concentrated substances (>1 g/l).     

Interpretation of near-infrared spectroscopy signals: a study with a newly developed perfused rat brain model.

Using a newly developed perfused rat brain model, we examined direct effects of each change in cerebral blood flow (CBF) and oxygen metabolic rate on cerebral hemoglobin oxygenation to interpret near-infrared spectroscopy signals. Changes in CBF and total hemoglobin (tHb) were in parallel, although tHb showed no change when changes in CBF were small (< or =10%). Increasing CBF caused an increase in oxygenated hemoglobin (HbO(2)) and a decrease in deoxygenated hemoglobin (deoxy-Hb). Decreasing CBF was accompanied by a decrease in HbO(2), whereas changes in direction of deoxy-Hb were various. Cerebral blood congestion caused increases in HbO(2), deoxy-Hb, and tHb. Administration of pentylenetetrazole without increasing the flow rate caused increases in HbO(2) and tHb with a decrease in deoxy-Hb. There were no significant differences in venous oxygen saturation before vs. during seizure. These results suggest that, in activation studies with near-infrared spectroscopy, HbO(2) is the most sensitive indicator of changes in CBF, and the direction of changes in deoxy-Hb is determined by the degree of changes in venous blood oxygenation and volume.     

Human respiratory muscle blood flow measured by near-infrared spectroscopy and indocyanine green.

Measurement of respiratory muscle blood flow (RMBF) in humans has important implications for understanding patterns of blood flow distribution during exercise in healthy individuals and those with chronic disease. Previous studies examining RMBF in humans have required invasive methods on anesthetized subjects. To assess RMBF in awake subjects, we applied an indicator-dilution method using near-infrared spectroscopy (NIRS) and the light-absorbing tracer indocyanine green dye (ICG). NIRS optodes were placed on the left seventh intercostal space at the apposition of the costal diaphragm and on an inactive control muscle (vastus lateralis). The primary respiratory muscles within view of the NIRS optodes include the internal and external intercostals. Intravenous bolus injection of ICG allowed for cardiac output (by the conventional dye-dilution method with arterial sampling), RMBF, and vastus lateralis blood flow to be quantified simultaneously. Esophageal and gastric pressures were also measured to calculate the work of breathing and transdiaphragmatic pressure. Measurements were obtained in five conscious humans during both resting breathing and three separate 5-min bouts of constant isocapnic hyperpnea at 27.1 +/- 3.2, 56.0 +/- 6.1, and 75.9 +/- 5.7% of maximum minute ventilation as determined on a previous maximal exercise test. RMBF progressively increased (9.9 +/- 0.6, 14.8 +/- 2.7, 29.9 +/- 5.8, and 50.1 +/- 12.5 ml 100 ml(-1) min(-1), respectively) with increasing levels of ventilation while blood flow to the inactive control muscle remained constant (10.4 +/- 1.4, 8.7 +/- 0.7, 12.9 +/- 1.7, and 12.2 +/- 1.8 ml 100 ml(-1) min(-1), respectively). As ventilation rose, RMBF was closely and significantly correlated with 1) cardiac output (r = 0.994, P = 0.006), 2) the work of breathing (r = 0.995, P = 0.005), and 3) transdiaphragmatic pressure (r = 0.998, P = 0.002). These data suggest that the NIRS-ICG technique provides a feasible and sensitive index of RMBF at different levels of ventilation in humans.     

Measurement of cerebral blood volume using near-infrared spectroscopy and indocyanine green elimination.

Methods for measuring cerebral blood volume (CBV) have traditionally used radioisotopes. More recently, near-infrared spectroscopy (NIRS) has been used to measure CBV by using a technique involving O(2) desaturation of cerebral tissue, where the observed change in the concentration of oxygenated hemoglobin is a marker of the volume of blood contained within the brain. A new integration method employing NIRS is described by using indocyanine green (ICG) as the intravascular marker. After bolus injection, concentration-time integrals of cerebral tissue ICG concentration ([ICG](tissue)) measured by NIRS are compared with corresponding integrals of the cerebral blood ICG concentrations ([ICG](blood)) estimated by high-performance liquid chromatography of peripheral blood samples with allowance for cerebral-to-large-vessel hematocrit ratio. It is shown that CBV = integral [ICG]tissue/[ICG]blood. Measurements in 10 adult volunteers gave a mean value of 1.1 +/- 0.39 (SD) ml/100 g illuminated tissue. This result, although lower than previous NIRS estimations, is consistent with the long extracerebral path of light in the adult head. Scaling of results is required to take into account this component of the optical pathlength.     

At-line monitoring of a submerged filamentous bacterial cultivation using near-infrared spectroscopy

The use of near infra-red spectroscopy (NIRS) to monitor a submerged filamentous bacterial bioprocess was investigated. An industrial strain of the filamentous bacterium Streptomyces fradiae was cultured in a 12 litre stirred tank reactor (STR) using a complex medium. This mycelial 4 phase (oil, water, gas and solid) system produced highly complex and variable matrices, therefore monitoring such a complex fluid with NIRS represented a considerable challenge. Nevertheless, successful models for four key analytes (methyl oleate, glucose, glutamate and ammonium) were built at-line (rapid off-line) using NIRS. In the present study, the methods used to formulate, select and validate the models for the key analytes are discussed, with particular emphasis on how the model performance can be critically evaluated. Since previous reports on NIRS in monitoring bioprocesses have either involved simpler matrices, or, in filamentous systems, have not discussed how NIRS models can be critically assessed, the emphasis in the present study on providing an insight into the modelling process in such a complex matrix, may be particularly important to the applicability of NIRS to such industrial bioprocesses.     

Visible near-infrared reflectance spectroscopy as a predictive indicator of soil properties

It is becoming increasingly important to improve spatial resolutions of soil maps as a fundamental information layer for studying ecological processes and to tackle land degradation. There is growing interest in the use of remote sensing technologies to assist the identification and delineation of spatial variation in soils. This paper investigates whether selected properties of extensively weathered, low fertility soils can be predicted using high-resolution reflectance spectra over the range 400–2500 nm. Clay content, carbonate concentration, organic carbon content and iron oxide content were analysed for 300 soil samples collected from the Jamestown, Belalie district, South Australia. The paper also examines the efficacy of this soil analysis methodology to supplement or replace traditional soil sampling in soil survey to increase sampling density and improve the spatial resolution of soil maps.Reflectance spectra were obtained from air-dried samples under controlled laboratory conditions using an ASD FieldSpec Pro spectroradiometer. Partial least squares regression was used to examine relationships between soil mineralogy, clay content and organic carbon and the reflectance spectra and identify the wavelengths contributing to prediction of these soil properties. Results show that it is possible to predict clay content, soil organic carbon, iron oxide content and carbonate content. Cross-validation R² values for all analyses were above 0.5 and the residual prediction difference (RPD) was acceptable for all soil properties. Carbonate and clay content were more accurately predicted than iron oxide and organic carbon. All samples were collected from the same geographical area such that they represented physical properties over a naturally occurring range and provide a prediction that could be related to subsequent image analysis or be used to carry out local scale soil survey. A rapid and reliable form of soil mapping could be developed from this methodology.     

Differentiating tobacco budworm and corn earworm using near-infrared spectroscopy

Near-infrared spectroscopy (NIRS) was used to develop a simple and quick technique to differentiate two economically important species, the tobacco budworm, Heliothis cirescens (F.), and corn earworm, Helicoverpa zea (Boddie), which are major pests of cotton, Gossypium hirsutum L., in the southern United States. In practice, it is difficult to distinguish the two species during their immature stages using morphological characteristics unless expensive microscopy equipment or trained technicians are available. The current studies demonstrated that the two species could be quickly and readily differentiated during early developmental stages, including egg and young larval (younger than third instar) stages, by using NIRS technology with up to 95% accuracy. NIRS technology could significantly improve pest diagnosis in cotton pest management.     

Temperature-pressure phase diagram of a heterogeneous anionic model biomembrane system: results from a combined calorimetry, spectroscopy and microscopy study

By using Fourier transform infrared (FT-IR) spectroscopy in combination with differential scanning calorimetry (DSC) coupled with pressure perturbation calorimetry (PPC), ultrasound velocimetry, Laurdan fluorescence spectroscopy, fluorescence microscopy and atomic force microscopy (AFM), the temperature and pressure dependent phase behavior of the five-component anionic model raft lipid mixture DOPC/DOPG/DPPC/DPPG/cholesterol (20:5:45:5:25 mol%) was investigated. A temperature range from 5 to 65 °C and a pressure range up to 16 kbar were covered to establish the temperature-pressure phase diagram of this heterogeneous model biomembrane system. Incorporation of 10-20 mol% PG still leads to liquid-ordered (l(o))-liquid-disordered (l(d)) phase coexistence regions over a wide range of temperatures and pressures. Compared to the corresponding neutral model raft mixture (DOPC/DPPC/Chol 25:50:25 mol%), the p,T-phase diagram is - as expected and in accordance with the Gibbs phase rule - more complex, the phase sequence as a function of temperature and pressure is largely similar, however. This anionic heterogeneous model membrane system will serve as a more realistic model biomembrane system to study protein interactions with anionic lipid bilayers displaying liquid-disordered/liquid-ordered domain coexistence over a wide range of the temperature-pressure plane, thus allowing also studies of biologically relevant systems encountered under extreme environmental conditions.     

Assessment of in-line near-infrared spectroscopy for continuous monitoring of fermentation processes

The application of NIR in-line to monitor and control fermentation processes was investigated. Determination of biomass, glucose, and lactic and acetic acids during fermentations of Staphylococcus xylosus ES13 was performed by an interactance fiber optic probe immersed into the culture broth and connected to a NIR instrument. Partial least squares regression (PLSR) calibration models of second derivative NIR spectra in the 700-1800 nm region gave satisfactory predictive models for all parameters of interest: biomass, glucose, and lactic and acetic acids. Batch, repeated batch, and continuous fermentations were monitored and automatically controlled by interfacing the NIR to the bioreactor control unit. The high frequency of data collection permitted an accurate study of the kinetics, supplying lots of data that describe the cultural broth composition and strengthen statistical analysis. Comparison of spectra collected throughout fermentation runs of S. xylosus ES13, Lactobacillus fermentum ES15, and Streptococcus thermophylus ES17 demonstrated the successful extension of a unique calibration model, developed for S. xylosus ES13, to other strains that were differently shaped but growing in the same medium and fermentation conditions. NIR in-line was so versatile as to measure several biochemical parameters of different bacteria by means of slightly adapted models, avoiding a separate calibration for each strain.     

A new evaluation method for +Gz tolerance with loratadine by using a near-infrared spectroscopy

Background

Loratadine (Claritin^®), an over the counter antihistamine in U.S. and UK, is acceptable for use without adverse side effects by aircrew with mild or moderate allergic or other situations requiring an antihistamine. Although +Gz (head to foot direction) tolerance testing for aircrew with loratadine has not been documented in the published literature, it is commonly accepted that loratadine dose not effect +Gz tolerance. The purpose of this study was to offer and validate a new evaluation method for +Gz tolerance testing with loratadine by using a near-infrared spectroscopy (NIRS).

Methods

A double-blind, placebo-controlled, randomized, crossover protocol was used to administer 10 mg of loratadine or placebo in nine healthy subjects. The subjects didn't wear anti-G suit. The +Gz exposure profiles consisted of, in series, a gradual onset ran (0.1 G·sec^-1) to the subject's visual end-point (peripheral light loss) or loss of consciousness (GLOC), and rapid onset run (1.0 G·sec^-1) to the subject's same end-point. In this study, G-level tolerance was defined as the +Gz level at visual end-point and/or at GLOC. As a subject's G-duration tolerance, we measured the total time (seconds) during rapid onset run. Otherwise, to confirm the effect of loratadine on +Gz tolerance, we measured the cerebral NIRS variables (hemoglobin concentration changes and tissue oxygenation index) as a new quantitative method for +Gz tolerance during a centrifuge experiments.

Results

No significant differences were observed in +Gz tolerance (+Gz level, duration time and NIRS variables) between subjects taking loratadine and placebo.

Conclusion

Our results demonstrate that loratadine has no detectable effect on +Gz tolerance by using a new method with cerebral NIRS variables and the traditional method with +Gz level and duration time. This study represents the first use of a quantitative parameter such as cerebral NIRS variables to assess the effects of a drug on acceleration tolerance.

     

Detection of ventilatory thresholds using near-infrared spectroscopy with a polynomial regression model

Whether near-infrared spectroscopy (NIRS) is a convenient and accurate method of determining first and second ventilatory thresholds (VT₁ and VT₂) using raw data remains unknown. This study investigated the reliability and validity of VT₁ and VT₂ determined by NIRS skeletal muscle hemodynamic raw data via a polynomial regression model. A total of 100 male students were recruited and performed maximal cycling exercises while their cardiopulmonary and NIRS muscle hemodynamic data were measured. The criterion validity of VT_1VET and VT_2VET were determined using a traditional V-slope and ventilatory efficiency. Statistical significance was set at α = . 05. There was high reproducibility of VT_1NIRS and VT_2NIRS determined by a NIRS polynomial regression model during exercise (VT_1NIRS, r = 0.94; VT_2NIRS, r = 0.93). There were high correlations of VT_1VET vs VT_1NIRS (r = 0.93, p < .05) and VT_2VET vs VT_2NIRS (r = 0.94, p < .05). The oxygen consumption (VO₂) between VT_1VET and VT_1NIRS or VT_2VET and VT_2NIRS was not significantly different. NIRS raw data are reliable and valid for determining VT₁ and VT₂ in healthy males using a polynomial regression model. Skeletal muscle raw oxygenation and deoxygenation status reflects more realistic causes and timing of VT₁ and VT₂.     

Quantification of cerebral oxygenation by full-spectrum near-infrared spectroscopy using a two-point method

The aim of this study was to quantify the relative concentrations of oxyhemoglobin and deoxyhemoglobin within the light path of the brain and to estimate cerebral hemoglobin (Hb) oxygen saturation using full-spectrum near-infrared spectroscopy (fsNIRS). For this purpose, we developed a novel exponential correction equation as well as a two-point spectroscopy method to estimate the relative concentrations of Hb and Hb oxygen saturation in biological tissues. The results of evaluation of measurements using an in vitro model indicated that our fsNIRS method enables accurate and non-invasive measurements of Hb content and saturation in a highly scattered medium such as the human brain. According to the results of analysis using a hypoxic piglet model, the mean cerebral Hb oxygen saturation (SbO(2)) of newborn piglets at an inspired oxygen gas concentration of 0.21 was estimated to be 63+/-4% (mean+/-S.D.). Umbilical arterial and left internal jugular venous Hb oxygen saturation were simultaneously estimated to be 96+/-2% and 52+/-11%, respectively. SbO(2) and arterial Hb oxygen saturation values had a linear relationship. The average oxygenation state of cerebral tissue is comparable with that of the cerebral vein. The results of this study showed that our method can be used to monitor Hb oxygen saturation in the neonatal brain at the bedside in an intensive care unit.