Search

We used diffuse reflectance spectroscopy to quantify tissue absorption and scattering-based parameters in similarly sized tumors derived from a panel of four isogenic murine breast cancer cell lines (4T1, 4T07, 168FARN, 67NR) that are each capable of accomplishing different steps of the invasion-metastasis cascade. We found lower tissue scattering, increased hemoglobin concentration, and lower vascular oxygenation in indolent 67NR tumors incapable of metastasis compared with aggressive 4T1 tumors capable of metastasis. Supervised learning statistical approaches were able to accurately differentiate between tumor groups and classify tumors according to their ability to accomplish each step of the invasion-metastasis cascade. We investigated whether the inhibition of metastasis-promoting genes in the highly metastatic 4T1 tumors resulted in measurable optical changes that made these tumors similar to the indolent 67NR tumors. These results demonstrate the potential of diffuse reflectance spectroscopy to noninvasively evaluate tumor biology and discriminate between indolent and aggressive tumors., Competing Interests: The authors declare no potential conflicts of interest., (© 2023 Optica Publishing Group.)

Immune checkpoint inhibitors have revolutionized cancer treatment. However, there are currently no methods for noninvasively and nondestructively evaluating tumor response to immune checkpoint inhibitors. We used diffuse reflectance spectroscopy to monitor in vivo tumor microenvironmental changes in response to immune checkpoint inhibitors in a CT26 murine colorectal cancer model. Mice growing CT26 tumor xenografts were treated with either anti-PD-L1, anti-CTLA-4, a combination of both inhibitors, or isotype control on 3 separate days. Monotherapy with either anti-PD-L1 or anti-CTLA-4 led to a large increase in tumor vascular oxygenation within the first 6 days. Reoxygenation in anti-CTLA-4-treated tumors was due to a combination of increased oxygenated hemoglobin and decreased deoxygenated hemoglobin, pointing to a possible change in tumor oxygen consumption following treatment. Within the anti-PD-L1-treated tumors, reoxygenation was primarily due to an increase in oxygenated hemoglobin with the minimal change in deoxygenated hemoglobin, indicative of a likely increase in tumor perfusion. The tumors in the combined treatment group did not show any significant changes in tumor oxygenation following therapy. These studies demonstrate the sensitivity of diffuse reflectance spectroscopy to tumor microenvironmental changes following immunotherapy and the potential of such non-invasive techniques to determine early tumor response to immune checkpoint inhibitors., Competing Interests: The authors declare no potential conflicts of interest., (© 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.)

An improved technique for fractal characterization called the modified blanket method is introduced that can quantify surrounding fractal structures on a pixel by pixel basis without artifacts associated with scale-dependent image features such as object size. The method interprets images as topographical maps, obtaining information regarding the local surface area as a function of image resolution. Local fractal dimension (FD) can be quantified from the power law exponent derived from the surface area and image resolution relationship. We apply this technique on simulated cell images of known FD and compared the obtained values to power spectral density (PSD) analysis. Our method is sensitive to a wider FD range (2.0-4.5), having a mean error of 1.4% compared to 6% for PSD analysis. This increased sensitivity and an ability to compute regional FD properties enabled the discrimination of the differences in radiation resistant cancer cell responses that could not be detected using PSD analysis., Competing Interests: The authors declare that there are no conflicts of interest related to this article.

There is a critical need to identify patients with radiation-resistant tumors early after treatment commencement. In this study, we use diffuse reflectance spectroscopy (DRS) to investigate changes in vascular oxygenation and total hemoglobin concentration in A549 radiation-sensitive and resistant tumors treated with a clinically relevant dose fraction of 2 Gy. DRS spectra were acquired before, immediately after, 24, and 48 hours after radiation. Our data reveals a significantly higher reoxygenation (sO 2 ) in the radiation-resistant tumors 24 and 48h after treatment, and provides promising evidence that DRS can discern between the reoxygenation trends of radiation-sensitive and resistant tumors., Competing Interests: The authors declare that there are no conflicts of interest related to this article.

The development of prognostic indicators of breast cancer metastatic risk could reduce the number of patients receiving chemotherapy for tumors with low metastatic potential. Recent evidence points to a critical role for cell metabolism in driving breast cancer metastasis. Endogenous fluorescence intensity of nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) can provide a label-free method for assessing cell metabolism. We report the optical redox ratio of FAD/(FAD + NADH) of four isogenic triple-negative breast cancer cell lines with varying metastatic potential. Under normoxic conditions, the redox ratio increases with increasing metastatic potential (168FARN>4T07>4T1), indicating a shift to more oxidative metabolism in cells capable of metastasis. Reoxygenation following acute hypoxia increased the redox ratio by 43 ± 9% and 33 ± 4% in the 4T1 and 4T07 cells, respectively; in contrast, the redox ratio decreased 14 ± 7% in the non-metastatic 67NR cell line. These results demonstrate that the optical redox ratio is sensitive to the metabolic adaptability of breast cancer cells with high metastatic potential and could potentially be used to measure dynamic functional changes that are indicative of invasive or metastatic potential.

Early detection of structural or functional changes in dysplastic epithelia may be crucial for improving long-term patient care. Recent work has explored myriad non-invasive or minimally invasive "optical biopsy" techniques for diagnosing early dysplasia, such as high-resolution microendoscopy, a method to resolve sub-cellular features of apical epithelia, as well as broadband sub-diffuse reflectance spectroscopy, a method that evaluates bulk health of a small volume of tissue. We present a multimodal fiber-based microendoscopy technique that combines high-resolution microendoscopy, broadband (450-750 nm) sub-diffuse reflectance spectroscopy (sDRS) at two discrete source-detector separations (374 and 730 μm), and sub-diffuse reflectance intensity mapping (sDRIM) using a 635 nm laser. Spatial resolution, magnification, field-of-view, and sampling frequency were determined. Additionally, the ability of the sDRS modality to extract optical properties over a range of depths is reported. Following this, proof-of-concept experiments were performed on tissue-simulating phantoms made with poly(dimethysiloxane) as a substrate material with cultured MDA-MB-468 cells. Then, all modalities were demonstrated on a human melanocytic nevus from a healthy volunteer and on resected colonic tissue from a murine model. Qualitative in vivo image data is correlated with reduced scattering and absorption coefficients.

Diffuse reflectance spectroscopy (DRS) has been extensively applied for the characterization of biological tissue, especially for dysplasia and cancer detection, by determination of the tissue optical properties. A major challenge in performing routine clinical diagnosis lies in the extraction of the relevant parameters, especially at high absorption levels typically observed in cancerous tissue. Here, we present a new least-squares support vector machine (LS-SVM) based regression algorithm for rapid and accurate determination of the absorption and scattering properties. Using physical tissue models, we demonstrate that the proposed method can be implemented more than two orders of magnitude faster than the state-of-the-art approaches while providing better prediction accuracy. Our results show that the proposed regression method has great potential for clinical applications including in tissue scanners for cancer margin assessment, where rapid quantification of optical properties is critical to the performance.

We report a probe-based portable and clinically compatible instrument for the spectral diagnosis of melanoma and nonmelanoma skin cancers. The instrument combines two modalities--diffuse reflectance and intrinsic fluorescence spectroscopy--to provide complementary information regarding tissue morphology, function, and biochemical composition. The instrument provides a good signal-to-noise ratio for the collected reflectance and laser-induced fluorescence spectra. Validation experiments on tissue phantoms over a physiologically relevant range of albedos (0.35-0.99) demonstrate an accuracy of close to 10% in determining scattering, absorption and fluorescence characteristics. We also demonstrate the ability of our instrument to collect in vivo diffuse reflectance and fluorescence measurements from clinically normal skin, dysplastic nevus, and malignant nonmelanoma skin cancer.