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Diffuse reflectance spectroscopy of liver tissue
Abstract
Results Conclusion • there is a need for intraoperative quantification and staging of liver damage induced by preoperative chemotherapy to assess the physiological state of the liver before liver tumour resection, • it is possible to aquire reproducible DRS spectra from highly pigmen-ted liver and to identify known characteristic absorption peaks and spectral shapes.
... We have recently developed a novel DRS system that combines 2 spectrometers (VIS-NIR and NIR-SWIR) to visualize an extendedwavelength spectrum, revealing optical properties of the tissue between 450 and 1550 nm, which we call the extended-wavelength DRS technique (EWDRS). 18,19 This technique provides a broader view of the molecular composition of the skin, since melanin and hemoglobin primarily absorb light in the VIS-NIR range, while water, lipids, and collagen primarily absorb light in the NIR-SWIR range. 20 EWDRS has recently proven to be able to accurately differentiate between healthy and metastatic human liver tissue, 19,21 and to differentiate between different skin and tissue types 22 and to monitor perfusion in flaps. ...
... 18,19 This technique provides a broader view of the molecular composition of the skin, since melanin and hemoglobin primarily absorb light in the VIS-NIR range, while water, lipids, and collagen primarily absorb light in the NIR-SWIR range. 20 EWDRS has recently proven to be able to accurately differentiate between healthy and metastatic human liver tissue, 19,21 and to differentiate between different skin and tissue types 22 and to monitor perfusion in flaps. 18 It is our intention to develop EWDRS into a useful tool for non-invasive skin tumor margin delineation. ...
Objective
A novel extended‐wavelength diffuse reflectance spectroscopy (EWDRS) technique is being developed for future clinical non‐invasive tumor margin delineation. In this study, the ability of EWDRS to identify the margins of pigmented skin lesions in an in vivo pig model was evaluated.
Materials and methods
Extended‐wavelength diffuse reflectance spectroscopy recordings (350‐1550 nm) were made on 13 pigmented skin lesions and non‐pigmented skin, as a reference. The hand‐held probe was swept toward the pigmented area until the signal changed, thus indicating that the margin had been identified. A needle was inserted as a marker, and tissue samples were sent for histological analysis. The distance between the EWDRS‐defined border and the histological border was measured by 3 independent examiners.
Results
The median difference between the EWDRS‐defined border and the histological border was 70 μm toward the pigmented tissue (range: −579 to 538 μm). A Pearson correlation coefficient of .95 was obtained for the examiners.
Conclusions
Extended‐wavelength diffuse reflectance spectroscopy can be used in vivo to delineate the border of pigmented skin lesions in a porcine model with high accuracy, indicating that it may be a useful tool for non‐invasive tumor margin delineation in the future.
... Hyperspectral images can typically contain as many as tens of continuous spectral bands 16 . Due to the strong light absorption of hemoglobin and other tissue components in the visible near infra-red (Vis-NIR) region, DRS and MSI imaging offer great value for classification and analysis of tissue samples [17][18][19] . ...
... Over the past decade, DRS and MSI have emerged as promising clinically viable tools for disease diagnosis and monitoring [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] . In DRS, tissue characterization can be realized after illuminating it with light in a specific spectral band and detecting the diffuse reflected light. ...
Adipose (fat) tissue is a complex metabolic organ that is highly active and essential. In contrast to white adipose tissue (WAT), brown adipose tissue (BAT) is deemed metabolically beneficial because of its ability to burn calories through heat production. The conversion of WAT-resident adipocytes to " beige " or " brown-like " adipocytes has recently attracted attention. However, it typically takes a few days to analyze and confirm this browning of WAT through conventional molecular, biochemical, or histological methods. Moreover, accurate quantification of the overall browning process is not possible by any of these methods. In this context, we report the novel application of diffuse reflectance spectroscopy (DRS) and multispectral imaging (MSI) to detect and quantify the browning process in mice. We successfully demonstrated the time-dependent increase in browning of WAT, following its induction through β-adrenergic agonist injections. The results from these optical techniques were confirmed with those of standard molecular and biochemical assays, which measure gene and protein expression levels of UCP1 and PGC-1α, as well as with histological examinations. We envision that the reported optical methods can be developed into a fast, real time, cost effective and easy to implement imaging approach for quantification of the browning process in adipose tissue.
Background and Objective
Due to the existing prevalence of nonalcoholic fatty liver disease (NAFLD) and its relation to the epidemic of obesity in the general population, it is imperative to develop detection and evaluation methods of the early stages of the disease with improved efficacy over the current diagnostic approaches. We aimed to obtain an improved diagnosis, combining methods of optical spectroscopy -diffuse reflectance and fluorescence- with statistical data analysis applied to detect early stages of NAFLD.
Methods
Statistical analysis scheme based on quadratic discriminant analysis followed by canonical discriminant analysis were applied to the diffuse reflectance data combined with endogenous fluorescence spectral data excited at one of these wavelengths: 330, 365, 385, 405 or 415 nm. The statistical scheme was also applied to the combinations of fluorescence spectrum (405 nm) with each one of the other fluorescence spectra. Details of the developed software, including the application of machine learning algorithms to the combination of spectral data followed by classification statistical schemes, are discussed.
Results
Steatosis progression was differentiated with little classification error (≤1.3%) by using diffuse reflectance and endogenous fluorescence at different wavelengths. Similar results were obtained using fluorescence at 405 nm and one of the other fluorescence spectra (classification error ≤1.0%). Adding the corresponding areas under the curves to the above combinations of spectra diminished errors to 0.6% and 0.3% or less, respectively. The best results for the compounded reflectance-plus-fluorescence spectra were obtained with fluorescence spectra excited at 415 nm with a total classification error of 0.2%; for the combination of the 405nm-excited fluorescence spectrum with another fluorescence spectrum, the best results were achieved for 385 nm, for which total relative classification error amounted 0.4%. The consideration of the area under the spectral curves further improved both classifiers, reducing the error to 0.0% in both cases.
Conclusion
Spectrometric techniques combined with statistical processing are a promising tool to improve steatosis classification through a label free approach. However, statistical schemes here applied, might result complex for the everyday medical practice, the designed software including machine learning algorithms is able to render automatic classification of samples according to their steatosis grade with low error.
Intramedullary nailing is a routine orthopedic procedure used for treating fractures of femoral or tibial shafts. A critical part of this procedure involves the drilling of pilot holes in both ends of the bone for the placement of the screws that will secure the IM rod to sections of the fractured bone. This step introduces a risk of soft tissue damage because the drill bit, if not stopped in time, can transverse the bone-tissue boundary into the overlying muscle, causing unnecessary injury and prolonging healing time due to periosteum damage. In this respect, detecting the bone-tissue boundary before break-through can reduce the risks and complications associated with intramedullary nailing. Hence, in the present study, a two-wavelength diffuse reflectance spectroscopy technique was integrated into a surgical drill to optically detect bone-tissue boundary and automatically trigger the drill to stop. Furthermore, Monte-Carlo simulations were used to estimate the maximum distance from within the bone at which the bone-tissue boundary could be detected using DRS. The simulation results estimated that the detection distance, termed the “look-ahead-distance” was ∼1.5 mm for 1.3 mm source-detector fiber separation. Experimental measurements with 1.3 mm source-detector fiber separation showed that the look-ahead-distance was in the order of 250 µm in experiments with set drill rate and in the range of 1 mm in experiments where the holes were drilled by hand. Despite this difference, the automated DRS enhanced drill successfully detected the approaching bone tissue boundary when tested on samples of bovine femur and muscle tissue.
Objective:
This study investigates the hypoperfusion effects of epinephrine in local anesthesia in eyelid surgery. A novel form of extended-wavelength diffuse reflectance spectroscopy was evaluated.
Methods:
Blood perfusion in porcine eyelid flaps was measured using laser Doppler velocimetry and laser speckle contrast imaging, whereas the tissue response was measured using diffuse reflectance spectroscopy with a broad spectrum (450-1550 nm). Epinephrine was either injected cumulatively, 0.1 (1:10,000,000), 1.0 (1:1,000,000), 10 (1:100 000), and 100 μg/ml (1:10 000), to determine the dose-response relation, or given as a single dose (10 μg/ml). Control experiments were performed with saline or lidocaine.
Results:
Increasing concentrations of epinephrine resulted in a gradual decrease in tissue perfusion, measured by laser Doppler velocimetry and laser speckle contrast imaging, approaching a minimum after the injection of 10 μg/ml. Similar tissue response was observed with diffuse reflectance spectroscopy. The time from the injection of epinephrine (10 μg/ml) to the stabilization of hypoperfusion was 75 seconds. After administration of 10 μg/ml epinephrine, about 20% of the blood perfusion remained, supporting the use of epinephrine in eyelid flaps with a narrow pedicle.
Conclusions:
10 μg/ml epinephrine appears to be adequate for vasoconstriction before oculoplastic surgery. Incisions need only be delayed for about 1 minute. Extended-wavelength diffuse reflectance spectroscopy appears to be a promising technique for monitoring the tissue response following changes in blood perfusion in plastic surgery reconstructions. However, more rigorous validation of the technique is required before it can be implemented in clinical practice.
Epidural injection is commonly used to provide intraoperative anesthesia, postoperative and obstetric analgesia, and to treat acute radicular pain. Identification of the epidural space is typically carried out using the loss of resistance (LOR) technique, but the usefulness of this technique is limited by false LOR and the inability to reliably detect intravascular or subarachnoid needle placement. In this study, we present a novel epidural needle that allows for the acquisition of optical reflectance spectra from tissue close to the beveled surface. This needle has optical fibers embedded in the cannula that deliver and receive light. With two spectrometers, light received from tissue is resolved across the wavelength range of 500 to 1600 nm. To determine the feasibility of optical tissue differentiation, spectra were acquired from porcine tissues during a post mortem laminectomy. The spectra were processed with an algorithm that derives estimates of the hemoglobin and lipid concentrations. The results of this study suggest that the optical epidural needle has the potential to improve the accuracy of epidural space identification.
Background: Surgical resection is the most effective treatment for colorectal liver metastases but only a minority of patients are candidates for a potentially curative resection. Our experience with neoadjuvant chemotherapy followed by resection and five years survival analysis of the patients treated is presented. Methods: Between February of 1988 and September of 1996, 701 patients with unresectable colorectal liver metastases were treated with neoadjuvant chemotherapy. Four categories of nonresectable disease were defined: large size, ill location, multinodularity, and extrahepatic disease. Liver resection was performed in those patients whose disease became resectable. After resection, the patients were followed up every 3 months. A 5-year survival analysis by the different categories described was performed. Results: Ninety-five patients (13.5%) were found to be resectable on reevaluation and underwent a potentially curative resection. There was no perioperative mortality, and the complication rate was 23%. As of December of 1999, 87 patients have completed 5 years of follow-up. The overall 5-year survival is 35% from the time of resection and 39% from the onset of chemotherapy. Respective 5-year survival rates are 60% for large tumors, 49% for ill-located lesions, 34% for multinodular disease, and 18% for liver metastases with extrahepatic disease. In this latter category, however, a 35% 5-year survival was found when all the patients with extrahepatic disease were analyzed rather than only those for whom extrahepatic disease was the main cause of nonresectability. Conclusions: Neoadjuvant chemotherapy enables liver resection in some patients with initially unresectable colorectal metastases. Long-term survival is similar to that reported for a priori surgical candidates.
- T M Bydlon
Bydlon, T.M., et al., Journal of Biophotonics, 2015.
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- M.-Y Chen
Chen, M.-Y., et al., Hepatobiliary & Pancreatic Diseases
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Cugmas, B., et al., Journal of Biomedical Optics, 2014.
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