scholarly journals Dual-Slope Diffuse Reflectance Instrument for Calibration-Free Broadband Spectroscopy

2021 ◽  
Vol 11 (4) ◽  
pp. 1757
Author(s):  
Giles Blaney ◽  
Ryan Donaldson ◽  
Samee Mushtak ◽  
Han Nguyen ◽  
Lydia Vignale ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Frequency Domain ◽  
Diffuse Reflectance ◽  
Continuous Wave ◽  
Diffuse Reflectance Spectroscopy ◽  
Spectral Features ◽  
Water Phantom ◽  
India Ink ◽  
Measured Absorption ◽  
Calibration Free

This work presents the design and validation of an instrument for dual-slope broadband diffuse reflectance spectroscopy. This instrument affords calibration-free, continuous-wave measurements of broadband absorbance of optically diffusive media, which may be translated into absolute absorption spectra by adding frequency-domain measurements of scattering at two wavelengths. An experiment on a strongly scattering liquid phantom (milk, water, dyes) confirms the instrument’s ability to correctly identify spectral features and measure absolute absorption. This is done by sequentially adding three dyes, each featuring a distinct spectral absorption, to the milk/water phantom. After each dye addition, the absorption spectrum is measured, and it is found to reproduce the spectral features of the added dye. Additionally, the absorption spectrum is compared to the absorption values measured with a commercial frequency-domain instrument at two wavelengths. The measured absorption of the milk/water phantom quantitatively agrees with the known water absorption spectrum (R2=0.98), and the measured absorption of the milk/water/dyes phantom quantitatively agrees with the absorption measured with the frequency-domain instrument in six of eight cases. Additionally, the measured absorption spectrum correctly recovers the concentration of one dye, black India ink, for which we could accurately determine the extinction spectrum (i.e., the specific absorption per unit concentration). The instrumental methods presented in this work can find applications in quantitative spectroscopy of optically diffusive media, and particularly in near-infrared spectroscopy of biological tissue.

The role of optical spectroscopy in epilepsy surgery in children

2008 ◽  
Vol 25 (3) ◽  
pp. E24 ◽  
Author(s):  
Sanjiv Bhatia ◽  
John Ragheb ◽  
Mahlon Johnson ◽  
Sanghoon Oh ◽  
David I. Sandberg ◽  
...  
Keyword(s):  
Epilepsy Surgery ◽  
Diffuse Reflectance ◽  
Pediatric Patients ◽  
Diffuse Reflectance Spectroscopy ◽  
Reflectance Spectroscopy ◽  
Preoperative Imaging ◽  
Spectral Features ◽  
Histological Features ◽  
The Brain

Object Surgery is an important therapeutic modality for pediatric patients with intractable epilepsy. However, existing imaging and diagnostic technologies such as MR imaging and electrocochleography (ECoG) do not always effectively delineate the true resection margin of an epileptic cortical lesion because of limitations in their sensitivity. Optical spectroscopic techniques such as fluorescence and diffuse reflectance spectroscopy provide a nondestructive means of gauging the physiological features of the brain in vivo, including hemodynamics and metabolism. In this study, the authors investigate the feasibility of using combined fluorescence and diffuse reflectance spectroscopy to assist epilepsy surgery in children. Methods In vivo static fluorescence and diffuse reflectance spectra were acquired from the brain in children undergoing epilepsy surgery. Spectral measurements were obtained using a portable spectroscopic system in conjunction with a fiber optic probe. The optical investigations were conducted at the normal and abnormal cortex as defined by intraoperative ECoG and preoperative imaging studies. Biopsy samples were taken from the investigated sites located within the zone of resection. The optical spectra were classified into multiple subsets in accordance with the ECoG and histological study results. The authors used statistical comparisons between 2 given data subsets to identify unique spectral features. Empirical discrimination algorithms were developed using the identified spectral features to determine if the objective of the study was achieved. Results Fifteen pediatric patients were enrolled in this pilot study. Elevated diffuse reflectance signals between 500 and 600 nm and/or between 650 and 850 nm were observed commonly in the investigated sites with abnormal ECoG and/or histological features in 10 patients. The appearance of a fluorescent peak at 400 nm was observed in both normal and abnormal cortex of 5 patients. These spectral alterations were attributed to changes in morphological and/or biochemical characteristics of the epileptic cortex. The sensitivities and specificities of the empirical discrimination algorithms, which were constructed using the identified spectral features, were all > 90%. Conclusions The results of this study demonstrate the feasibility of using static fluorescence and diffuse reflectance spectroscopy to differentiate normal from abnormal cortex on the basis of intraoperative assessment of ECoG and histological features. It is therefore possible to use fluorescence and diffuse reflectance spectroscopy as an aid in epilepsy surgery.

scholarly journals Nondestructive Evaluation of Apple Fruit Quality by Frequency-Domain Diffuse Reflectance Spectroscopy: Variations in Apple Skin and Flesh

2019 ◽  
Vol 9 (11) ◽  
pp. 2355 ◽  
Author(s):  
Nan-Yu Cheng ◽  
Chien-Chih Chen ◽  
Bo-Jian Liang ◽  
Sheng-Hao Tseng
Keyword(s):  
Optical Properties ◽  
Nondestructive Evaluation ◽  
Frequency Domain ◽  
Diffuse Reflectance ◽  
Diffuse Reflectance Spectroscopy ◽  
Biological Tissues ◽  
Reflectance Spectroscopy ◽  
Apple Fruit ◽  
Scattering Coefficients

The optical properties of fruits, such as light absorption and scattering characteristics, change with biochemical activities during storage. Diffuse reflectance spectroscopy (DRS) systems have been widely applied for noninvasively observing biological tissues. In this study, we used a frequency-domain DRS system to measure the optical properties of apples. Results showed that variations in the chlorophyll, water, and flesh-texture of apples could be noninvasively monitored over time. We also observed substantial differences in the absorption and reduced scattering coefficients between injured and normal apples. The DRS techniques could be used for apple grading, and, by extension, for monitoring the quality of other fruits.

scholarly journals Single-Fiber Diffuse Reflectance Spectroscopy and Spatial Frequency Domain Imaging in Surgery Guidance: A Study on Optical Phantoms

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7502
Author(s):  
Polina S. Tseregorodtseva ◽  
Kirill E. Buiankin ◽  
Boris P. Yakimov ◽  
Armais A. Kamalov ◽  
Gleb S. Budylin ◽  
...  
Keyword(s):  
Spatial Frequency ◽  
Frequency Domain ◽  
Diffuse Reflectance ◽  
Diffuse Reflectance Spectroscopy ◽  
Reflectance Spectroscopy ◽  
Optical Techniques ◽  
Tumor Margin ◽  
Spatial Frequency Domain Imaging ◽  
Margin Detection ◽  
Spatial Frequency Domain

Diffuse reflectance spectroscopy (DRS) and imaging are increasingly being used in surgical guidance for tumor margin detection during endoscopic operations. However, the accuracy of the boundary detection with optical techniques may depend on the acquisition parameters, and its evaluation is in high demand. In this work, using optical phantoms with homogeneous and heterogeneous distribution of chromophores mimicking normal and pathological bladder tissues, the accuracy of tumor margin detection using single-fiber diffuse reflectance spectroscopy and spatial frequency domain imaging was evaluated. We also showed how the diffuse reflectance response obtained at different spatial frequencies with the spatial frequency domain imaging technique could be used not only to quantitatively map absorption and scattering coefficients of normal tissues and tumor-like heterogeneities but also to estimate the tumor depth localization. The demonstrated results could be helpful for proper analysis of the DRS data measured in vivo and for translation of optical techniques for tumor margin detection to clinics.

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