Method for Quantitative Broadband Diffuse Optical Spectroscopy of Tumor-Like Inclusions

Vasudevan, Sandhya; Forghani, Farnoush; Campbell, Chris A.; Bedford, Savannah; O’Sullivan, Thomas D.

doi:10.3390/app10041419

Cited by 10 publications

(3 citation statements)

References 45 publications

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“…Additionally, despite FD typically being implemented at discrete λ, methods exist to achieve broadband µ a measurement. This may be done by combining measurements at discrete λs in FD (or TD) with measurements at broadband λs with Continuous-Wave (CW) [25][26][27], implemented with SC and a method dubbed Dual-Slope (DS), respectively, [28][29][30]. This leverages the fact that SC and DS both rely on a difference type measurement which is capable of subtracting away instrumental confounds.…”

Section: Introductionmentioning

confidence: 99%

Method for Measuring Absolute Optical Properties of Turbid Samples in a Standard Cuvette

2022

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Many applications seek to measure a sample’s absorption coefficient spectrum to retrieve the chemical makeup. Many real-world samples are optically turbid, causing scattering confounds which many commercial spectrometers cannot address. R1C1Using diffusion theory and considering absorption and reduced scattering coefficients on the order of 0.01/mm and 1/mm, respectively, we develop a method which utilizes frequency-domain to measure absolute optical properties of turbid samples in a standard cuvette ( 45x10x10mm). Inspired by the self-calibrating method, which removes instrumental confounds, the method uses measurements of the diffuse complex transmittance at two sets of two different source-detector distances. We find: this works best for highly scattering samples (reduced scattering coefficient above 1/mm); higher relative error in the absorption coefficient compared to the reduced scattering coefficient; accuracy is tied to knowledge of the sample’s index of refraction. Noise simulations with 0.1 amplitude and 0.1=1.7mrad phase uncertainty find errors in absorption and reduced scattering coefficients of 4 and 1 , respectively. We expect that higher error in the absorption coefficient can be alleviated with highly scattering samples and that boundary condition confounds may be suppressed by designing a cuvette with high index of refraction. Further work will investigate implementation and reproducibility.

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Section: Introductionmentioning

confidence: 99%

Method for Measuring Absolute Optical Properties of Turbid Samples in a Standard Cuvette

2022

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“…NIRS diffuse optical tomography (NIRS-DOT) uses spectroscopy and tomographic method. NIRS-DOT key strength lies in its ability to non-invasively probe biological tissues with depth and detail [5,6]. By leveraging near-infrared light, NIRS-DOT enables the assessment of internal tissue composition and functional characteristics, offering a comprehensive view of anatomical structures and physiological processes.…”

Section: Introduction To Nirs Imagingmentioning

confidence: 99%

Near-infrared Spectroscopy for Brain and Breast Imaging

Buckley

2023

Preprint

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Near-infrared spectroscopy (NIRS) has become a key modality in medical imaging, finding application in both brain and breast imaging. This paper discusses the current trends in NIRS for brain and breast imaging, exploring advances in multi-modal integration with modalities such as functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). Challenges related to spatial resolution, depth sensitivity, and the impact of extracerebral tissues on signal specificity are examined. In addition, ongoing efforts to enhance hemodynamic measurements’ quantitative accuracy. Challenges, including limited spatial resolution and tissue heterogeneity, are discussed. The discussion extends to diffuse optical tomography and ongoing instrumentation development, clinical trials and studies validating NIRS diagnostic efficacy in breast imaging. The paper emphasizes the need for standardization, integration into routine clinical practice, and motivates for future work.

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“…Therefore, CW broadband DRS (CW-bDRS) has the advantage of collecting data over many wavelengths but the disadvantage that absorption and scattering are coupled and inseparable due to the use of CW illumination. A solution that has become more and more common is to combine a time-resolved NIRS instrument at few wavelengths with a CW-bDRS system [29][30][31][32][33][34]. Such a technique allows extrapolation of scattering from few to many wavelengths, by assuming a power law decay of the reduced scattering coefficient with wavelength [2], as well as decoupling of absorption from scattering in the CW-bDRS data.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2021

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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.

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Method for Quantitative Broadband Diffuse Optical Spectroscopy of Tumor-Like Inclusions

Cited by 10 publications

References 45 publications

Method for Measuring Absolute Optical Properties of Turbid Samples in a Standard Cuvette

Method for Measuring Absolute Optical Properties of Turbid Samples in a Standard Cuvette

Near-infrared Spectroscopy for Brain and Breast Imaging

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

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