Internal refractive index changes affect light transport in tissue

Brooksby, Ben; Dehghani, Hamid; Vishwanath, Karthik; Pogue, Brian W.; Paulsen, Keith D.

doi:10.1117/12.477365

Cited by 3 publications

(4 citation statements)

References 31 publications

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“…Measurements on the colonic mucosa, submucosa and serosa layers of the normal state, as well as the surface of the different adenomatous histological types, were conducted within no more than 2 hours after removal. Our refractive index data may be exploited by models of light transport in tissue and assist the solution of various boundary problems, like those appearing in an interface between a biological sample and an optical fiber . Such calculations are important for optimizing the therapeutic effect of light delivery to tissue (in the “forward” direction), as well as for the improvement of contrast and resolution of optical diagnostic and tomographic methods (in the “reverse” direction) .…”

Section: Introductionmentioning

confidence: 99%

Complex refractive index of normal and malignant human colorectal tissue in the visible and near‐infrared

Giannios

Koutsoumpos

Toutouzas

et al. 2016

Journal of Biophotonics

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A multi-wavelength prism coupling refractometer is utilized to measure the angular reflectance of freshly excised human intestinal tissue specimens. Based on reflectance data, the real and imaginary part of the refractive index is calculated via Fresnel analysis for three visible (blue, green, red) and two near-infrared (963 nm and 1551 nm) wavelengths. Averaged values of the complex refractive index and corresponding Cauchy dispersion fits are given for the mucosa, submucosa and serosa layers of the colorectal wall at the normal state. The refractive constants of tumorous and normal mucosa are then cross-compared for the indicative cases of one patient diagnosed with a benign polyp and three patients diagnosed with adenocarcinomas of different phenotype. Significant index contrast exists between the normal and diseased states, indicating the potential use of refractive index as a marker of colorectal dysplasia.

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Section: Introductionmentioning

confidence: 99%

Complex refractive index of normal and malignant human colorectal tissue in the visible and near‐infrared

Giannios

Koutsoumpos

Toutouzas

et al. 2016

Journal of Biophotonics

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“…11 Specifically, we defined an internal boundary condition that allows for discontinuous internal variations of RI between regions of contrast (or slowly varying) optical properties. This approach provided a good match between three-dimensional finite-element model results and Monte Carlo simulations, as well as controlled experimental measurements, 14 suggesting that the technique is a valid approximation.…”

Section: Introductionmentioning

confidence: 74%

“…Estimates are difficult to obtain accurately in vivo, but some data have been reported for various tissue types. 14,15 Although adipose tissue (fatty layer) has been measured to be 1.455, to the best of our knowledge no results exist for fibroglandular tissue. Nonetheless, the RI of glandular tissue is believed to be lower than that of adipose (e.g., values of 1.4 have been assumed 15,16 ).…”

Section: Introductionmentioning

confidence: 97%

Effects of refractive index on near-infrared tomography of the breast

et al. 2005

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Near infrared (NIR) optical tomography is an imaging technique in which internal images of optical properties are reconstructed with the boundary measurements of light propagation through the medium. Recent advances in instrumentation and theory have led to the use of this method for the detection and characterization of tumors within the female breast tissue. Most image reconstruction approaches have used the diffusion approximation and have assumed that the refractive index of the breast is constant, with a bulk value of approximately 1.4. We have applied a previously reported modified diffusion approximation, in which the refractive index for different tissues can be modeled. The model was used to generate NIR data from a realistic breast geometry containing a localized anomaly. Using this simulated data, we have reconstructed optical images, both with and without correct knowledge of the refractive-index distribution to show that the modified diffusion approximation can accurately recover the anomaly given a priori knowledge of refractive index. But using a reconstruction algorithm without the use of correct a priori information regarding the refractive-index distribution is shown as recovering the anomaly but with a degraded quality, depending on the degree of refractive index mismatch. The results suggest that provided the refractive index of breast tissue is approximately 1.3-1.4, their exclusion will have minimal effect on the reconstructed images.

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“…However, the region of increase does not span the full area expected, and heterogeneity is visible (especially around the perimeter of the image. The second algorithm assumes homogeneous optical properties for each tissue type, and utilizes parameter reduction 20 , which leads to a 'fitting' for four values: Uaadipose^O.OOS, |j. s adi P ose=0.93, Ua g ianduiar=0'.006, M s / g ianduiar=1.12 ( Figure 7(d)).…”

Section: -V-z)(r)v$(rö))+ U(r) + -Mrco) = S(rco)mentioning

confidence: 99%

Three Dimensional Reconstruction Algorithm for Imaging Pathophysiological Signal within Breast Tissue Using Near Infrared Light

Dehghani¹

2004

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and AUTHOR(S)Hamid Dehghani, Ph.D. FUNDING NUMBERSDAMD17-03-1-0405 PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)Dartmouth ABSTRACT (Maximum 200 Words)Optical tomography is a non-invasive imaging technique that can image properties of biological tissue. Measurements of light propagation through tissue can be used to calculate and reconstruct images of internal optical properties. Since the absorption and scattering of light in the tissue is a function its physiological state, the aim is to calculate maps of physiological parameters, which can be early markers of tumor development. Specifically the aim is to image total hemoglobin, oxygen saturation, water and lipid concentrations, as well as potentionally molecular concentrations when used with fluorescent markers. Cancerous regions within the breast have shown to be physiologically different from normal tissue. These include a higher amount of angiogenesis and higher metabolic rate as compared to normal tissue. These differences will result in a change in optical attenuation and scatter of light due to hemoglobin changes, which will cause a change in the measured tomographic boundary data. Light transport modeling of propagation in tissue can be used to calculate maps of optical changes within the breast, and therefore physiological maps of total hemoglobin and oxygen saturation. SUBJECT TERMS Breast Cancer Body 4Key Research Accomplishments 4Reportable Outcomes 4 Conclusions 8References 8Appendices 8Introduction In this work, a novel imaging technique is explored that uses non-harmful application of near infrared light to determine the properties of tissue. Using this technique, known as near infrared (NIR) tomography, an optical fiber placed on the surface of the region of interest, the breast, delivers an input signal while other optical fibers placed at different locations on the same surface detect the outcoming photons, which have propagated through the volume under investigation. The intensity and path-length distributions of the exiting light provide information about the optical properties of the transilluminated tissue using a model-based interpretation where photon propagation is simulated by the diffusion theory. Through iterative solution to match the theory to the real measurements, images of internal absorption and scattering coefficient distribution can be reconstructed. Tissue optical properties have shown to be a function of their structure and more import...

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Internal refractive index changes affect light transport in tissue

Cited by 3 publications

References 31 publications

Complex refractive index of normal and malignant human colorectal tissue in the visible and near‐infrared

Complex refractive index of normal and malignant human colorectal tissue in the visible and near‐infrared

Effects of refractive index on near-infrared tomography of the breast

Three Dimensional Reconstruction Algorithm for Imaging Pathophysiological Signal within Breast Tissue Using Near Infrared Light

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