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Konugolu Venkata Sekar S, Beh JS, Farina A, Dalla Mora A, Pifferi A, Taroni P. Broadband diffuse optical characterization of elastin for biomedical applications. Biophys Chem 2017; 229:130-134. [PMID: 28733103 DOI: 10.1016/j.bpc.2017.07.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 07/06/2017] [Accepted: 07/11/2017] [Indexed: 12/21/2022]
Abstract
Elastin is a key structural protein of dynamic connective tissues widely found in the extracellular matrix of skin, arteries, lungs and ligaments. It is responsible for a range of diseases related to aging of biological tissues. The optical characterization of elastin can open new opportunities for its investigation in biomedical studies. In this work, we present the absorption spectra of elastin using a broadband (550-1350nm) diffuse optical spectrometer. Distortions caused by fluorescence and finite bandwidth of the laser source on estimated absorption were effectively accounted for in measurements and data analysis and compensated. A comprehensive summary and comparison between collagen and elastin is presented, highlighting distinct features for its accurate quantification in biological applications.
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Affiliation(s)
| | - Joo Sin Beh
- Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Andrea Farina
- Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Alberto Dalla Mora
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Antonio Pifferi
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy; Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Paola Taroni
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy; Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
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Bergauer B, Knipfer C, Amann A, Rohde M, Tangermann-Gerk K, Adler W, Schmidt M, Nkenke E, Stelzle F. Does Laser Surgery Interfere with Optical Nerve Identification in Maxillofacial Hard and Soft Tissue?--An Experimental Ex Vivo Study. SENSORS 2015; 15:25416-32. [PMID: 26437416 PMCID: PMC4634421 DOI: 10.3390/s151025416] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 09/09/2015] [Accepted: 09/28/2015] [Indexed: 11/16/2022]
Abstract
The protection of sensitive structures (e.g., nerves) from iatrogenic damage is of major importance when performing laser surgical procedures. Especially in the head and neck area both function and esthetics can be affected to a great extent. Despite its many benefits, the surgical utilization of a laser is therefore still limited to superficial tissue ablation. A remote feedback system which guides the laser in a tissue-specific way would provide a remedy. In this context, it has been shown that nerval structures can be specifically recognized by their optical diffuse reflectance spectra both before and after laser ablation. However, for a translation of these findings to the actual laser ablation process, a nerve protection within the laser pulse is of utmost significance. Thus, it was the aim of the study to evaluate, if the process of Er:YAG laser surgery--which comes with spray water cooling, angulation of the probe (60°) and optical process emissions--interferes with optical tissue differentiation. For the first time, no stable conditions but the ongoing process of laser tissue ablation was examined. Therefore, six different tissue types (nerve, skin, muscle, fat, cortical and cancellous bone) were acquired from 15 pig heads. Measurements were performed during Er:YAG laser ablation. Diffuse reflectance spectra (4500, wavelength range: 350-650 nm) where acquired. Principal component analysis (PCA) and quadratic discriminant analysis (QDA) were calculated for classification purposes. The clinical highly relevant differentiation between nerve and bone was performed correctly with an AUC of 95.3% (cortial bone) respectively 92.4% (cancellous bone). The identification of nerve tissue against the biological very similar fat tissue yielded good results with an AUC value of 83.4% (sensitivity: 72.3%, specificity: of 82.3%). This clearly demonstrates that nerve identification by diffuse reflectance spectroscopy works reliably in the ongoing process of laser ablation in spite of the laser beam, spray water cooling and the tissue alterations entailed by tissue laser ablation. This is an essential step towards a clinical utilization.
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Affiliation(s)
- Bastian Bergauer
- Department of Oral and Maxillofacial Surgery, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany.
| | - Christian Knipfer
- Department of Oral and Maxillofacial Surgery, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany.
| | - Andreas Amann
- Department of Oral and Maxillofacial Surgery, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany.
| | - Maximilian Rohde
- Department of Oral and Maxillofacial Surgery, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany.
| | - Katja Tangermann-Gerk
- Bavarian Laser Center GmbH (blz), Erlangen 91054, Germany.
- SAOT-Graduate School in Advanced Optical Technologies, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany.
| | - Werner Adler
- Department of Medical Informatics, Biometry and Epidemiology, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany.
| | - Michael Schmidt
- Bavarian Laser Center GmbH (blz), Erlangen 91054, Germany.
- SAOT-Graduate School in Advanced Optical Technologies, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany.
- Chair of Photonic Technologies, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany.
| | - Emeka Nkenke
- Department of Oral and Maxillofacial Surgery, Medical University of Vienna, Vienna 1090, Austria.
| | - Florian Stelzle
- Department of Oral and Maxillofacial Surgery, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany.
- SAOT-Graduate School in Advanced Optical Technologies, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany.
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Wu M, Jansen K, van der Steen AFW, van Soest G. Specific imaging of atherosclerotic plaque lipids with two-wavelength intravascular photoacoustics. BIOMEDICAL OPTICS EXPRESS 2015; 6:3276-86. [PMID: 26417500 PMCID: PMC4574656 DOI: 10.1364/boe.6.003276] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 07/02/2015] [Accepted: 07/03/2015] [Indexed: 05/11/2023]
Abstract
The lipid content in plaques is an important marker for identifying atherosclerotic lesions and disease states. Intravascular photoacoustic (IVPA) imaging can be used to visualize lipids in the artery. In this study, we further investigated lipid detection in the 1.7-µm spectral range. By exploiting the relative difference between the IVPA signal strengths at 1718 and 1734 nm, we could successfully detect and differentiate between the plaque lipids and peri-adventitial fat in human coronary arteries ex vivo. Our study demonstrates that IVPA imaging can positively identify atherosclerotic plaques using only two wavelengths, which could enable rapid data acquisition in vivo.
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Affiliation(s)
- Min Wu
- Department of Biomedical Engineering, Thorax Center, Erasmus University Medical Center, PO Box 2040, 3000 CA Rotterdam, The Netherlands
| | - Krista Jansen
- Department of Biomedical Engineering, Thorax Center, Erasmus University Medical Center, PO Box 2040, 3000 CA Rotterdam, The Netherlands
- Interuniversity Cardiology Institute of The Netherlands–Netherlands Heart Institute, PO Box 19258, 3501 DG Utrecht, The Netherlands
- Section Audiology, Department of Otolaryngology–Head and Neck Surgery, and EMGO Institute of Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands
| | - Antonius F. W. van der Steen
- Department of Biomedical Engineering, Thorax Center, Erasmus University Medical Center, PO Box 2040, 3000 CA Rotterdam, The Netherlands
- Interuniversity Cardiology Institute of The Netherlands–Netherlands Heart Institute, PO Box 19258, 3501 DG Utrecht, The Netherlands
- Department of Imaging Science and Technology, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
- Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, 518055 Shenzhen, China
| | - Gijs van Soest
- Department of Biomedical Engineering, Thorax Center, Erasmus University Medical Center, PO Box 2040, 3000 CA Rotterdam, The Netherlands
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Jansen K, Wu M, van der Steen AF, van Soest G. Photoacoustic imaging of human coronary atherosclerosis in two spectral bands. PHOTOACOUSTICS 2014; 2:12-20. [PMID: 25302152 PMCID: PMC4182816 DOI: 10.1016/j.pacs.2013.11.003] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 10/29/2013] [Accepted: 11/16/2013] [Indexed: 05/03/2023]
Abstract
Spectroscopic intravascular photoacoustic imaging (sIVPA) has shown promise to detect and distinguish lipids in atherosclerotic plaques. sIVPA generally utilizes one of the two high absorption bands in the lipid absorption spectrum at 1.2 μm and 1.7 μm. Specific absorption signatures of various lipid compounds within the bands in either wavelength range can potentially be used to differentiate between plaque lipids and peri-adventitial lipids. With the aim to quantify any differences between the two bands, we performed combined sIVPA imaging in both absorption bands on a vessel phantom and an atherosclerotic human coronary artery ex vivo. Lipid detection in a human atherosclerotic lesion with sIVPA required lower pulse energy at 1.7 μm than at 1.2 μm (0.4 mJ versus 1.2 mJ). The imaging depth was twice as large at 1.2 μm compared to 1.7 μm. Adequate differentiation between plaque and peri-adventitial lipids was achieved at 1.2 μm only.
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Affiliation(s)
- Krista Jansen
- Department of Biomedical Engineering, Erasmus MC, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands
- Interuniversity Cardiology Institute of The Netherlands – Netherlands Heart Institute, P.O. Box 19258, 3501 DG Utrecht, The Netherlands
| | - Min Wu
- Department of Biomedical Engineering, Erasmus MC, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands
| | - Antonius F.W. van der Steen
- Department of Biomedical Engineering, Erasmus MC, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands
- Interuniversity Cardiology Institute of The Netherlands – Netherlands Heart Institute, P.O. Box 19258, 3501 DG Utrecht, The Netherlands
- Department of Imaging Science and Technology, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Gijs van Soest
- Department of Biomedical Engineering, Erasmus MC, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands
- Corresponding author. Tel.: +31 10 70 44638; fax: +31 10 70 44720.
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Allen TJ, Hall A, Dhillon AP, Owen JS, Beard PC. Spectroscopic photoacoustic imaging of lipid-rich plaques in the human aorta in the 740 to 1400 nm wavelength range. JOURNAL OF BIOMEDICAL OPTICS 2012; 17:061209. [PMID: 22734739 DOI: 10.1117/1.jbo.17.6.061209] [Citation(s) in RCA: 135] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Spectroscopic photoacoustic imaging has the potential to discriminate between normal and lipid-rich atheromatous areas of arterial tissue by exploiting the differences in the absorption spectra of lipids and normal arterial tissue in the 740 to 1400 nm wavelength range. Identification of regions of high lipid concentration would be useful to identify plaques that are likely to rupture (vulnerable plaques). To demonstrate the feasibility of visualizing lipid-rich plaques, samples of human aortas were imaged in forward mode, at wavelengths of 970 and 1210 nm. It was shown that the structure of the arterial wall and the boundaries of lipid-rich plaques obtained from the photoacoustic images were in good agreement with histology. The presence of lipids was also confirmed by comparing the photoacoustic spectra (740 to 1400 nm) obtained in a region within the plaque to the spectral signature of lipids. Furthermore, a lipid-rich plaque was successfully imaged while illuminating the sample through 2.8 mm of blood demonstrating the possibility of implementing the photoacoustic technique in vivo.
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Affiliation(s)
- Thomas J Allen
- University College London, Department of Medical Physics and Bioengineering, Gower Street, WC1E 6BT London, United Kingdom.
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Stelzle F, Adler W, Zam A, Tangermann-Gerk K, Knipfer C, Douplik A, Schmidt M, Nkenke E. In vivo optical tissue differentiation by diffuse reflectance spectroscopy: preliminary results for tissue-specific laser surgery. Surg Innov 2012; 19:385-93. [PMID: 22344924 DOI: 10.1177/1553350611429692] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
OBJECTIVES Laser surgery requires feedback to avoid the accidental destruction of critically important tissues. It was the aim of the authors to identify different tissue types in vivo by diffuse reflectance spectroscopy to set the basis for tissue-specific control of laser surgery. METHODS Tissue differentiation was performed on in vivo tissue of rats (skin, fat, muscle, and nerve) by diffuse reflectance spectroscopy between 350 and 650 nm. Data analysis was done using principal components analysis, followed by linear discriminant analysis (LDA). The differentiation performance was evaluated by receiver operating characteristic (ROC) analysis. RESULTS ROC analysis showed a tissue differentiation of 100%, with a high sensitivity of more than 99%. Only the tissue pair skin/fat showed a reduced differentiation performance and specificity. CONCLUSION The results show the general viability of in vivo optical tissue differentiation and create a basis for the further development of a control system for tissue-specific laser surgery.
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Affiliation(s)
- Florian Stelzle
- Department of Oral and Maxillofacial Surgery, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany.
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Venius J, Bagdonas S, Zurauskas E, Rotomskis R. Visualization of human heart conduction system by means of fluorescence spectroscopy. JOURNAL OF BIOMEDICAL OPTICS 2011; 16:107001. [PMID: 22029363 DOI: 10.1117/1.3631786] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The conduction system of the heart is a specific muscular tissue, where a heartbeat signal originates and initiates the depolarization of the ventricles. The muscular origin makes it complicated to distinguish the conduction system from the surrounding tissues. A surgical intervention can lead to the accidental harm of the conduction system, which may eventually result in a dangerous obstruction of the heart functionality. Therefore, there is an immense necessity for developing a helpful method to visualize the conduction system during the operation time. The specimens for the spectroscopic studies were taken from nine diverse human hearts. The localization of distinct types of the tissue was preliminary marked by the pathologist and approved histologically after the spectral measurements. Variations in intensity, as well as in shape, were detected in autofluorescence spectra of different heart tissues. The most distinct differences were observed between the heart conduction system and the surrounding tissues under 330 and 380 nm excitation. The spectral region around 460 nm appeared to be the most suitable for an unambiguous differentiation of the human conduction system avoiding the absorption peak of blood. The visualization method, based on the intensity ratios calculated for two excitation wavelengths, was also demonstrated.
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Affiliation(s)
- Jonas Venius
- Vilnius University Institute of Oncology, Laboratory of Biomedical Physics, Baublio 3A, Vilnius, LT- 08406, Lithuania.
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Stelzle F, Zam A, Adler W, Tangermann-Gerk K, Douplik A, Nkenke E, Schmidt M. Optical nerve detection by diffuse reflectance spectroscopy for feedback controlled oral and maxillofacial laser surgery. J Transl Med 2011; 9:20. [PMID: 21310023 PMCID: PMC3042403 DOI: 10.1186/1479-5876-9-20] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Accepted: 02/10/2011] [Indexed: 11/29/2022] Open
Abstract
Background Laser surgery lacks haptic feedback, which is accompanied by the risk of iatrogenic nerve damage. It was the aim of this study to investigate diffuse reflectance spectroscopy for tissue differentiation as the base of a feedback control system to enhance nerve preservation in oral and maxillofacial laser surgery. Methods Diffuse reflectance spectra of nerve tissue, salivary gland and bone (8640 spectra) of the mid-facial region of ex vivo domestic pigs were acquired in the wavelength range of 350-650 nm. Tissue differentiation was performed using principal component (PC) analysis followed by linear discriminant analysis (LDA). Specificity and sensitivity were calculated using receiver operating characteristic (ROC) analysis and the area under curve (AUC). Results Five PCs were found to be adequate for tissue differentiation with diffuse reflectance spectra using LDA. Nerve tissue could be differed from bone as well as from salivary gland with AUC results of greater than 88%, sensitivity of greater than 83% and specificity in excess of 78%. Conclusions Diffuse reflectance spectroscopy is an adequate technique for nerve identification in the vicinity of bone and salivary gland. The results set the basis for a feedback system to prevent iatrogenic nerve damage when performing oral and maxillofacial laser surgery.
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Affiliation(s)
- Florian Stelzle
- Department of Oral and Maxillofacial Surgery, Erlangen University Hospital, Erlangen, Germany.
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Stelzle F, Tangermann-Gerk K, Adler W, Zam A, Schmidt M, Douplik A, Nkenke E. Diffuse reflectance spectroscopy for optical soft tissue differentiation as remote feedback control for tissue-specific laser surgery. Lasers Surg Med 2010; 42:319-25. [PMID: 20432281 DOI: 10.1002/lsm.20909] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
BACKGROUND AND OBJECTIVE Laser surgery does not provide haptic feedback for operating layer-by-layer and thereby preserving vulnerable anatomical structures like nerve tissue or blood vessels. Diffuse reflectance spectra can facilitate remote optical tissue differentiation. It is the aim of the study to use this technique on soft tissue samples, to set a technological basis for a remote optical feedback system for tissue-specific laser surgery. MATERIALS AND METHODS Diffuse reflectance spectra (wavelength range: 350-650 nm) of ex vivo types of soft tissue (a total of 10,800 spectra) of the midfacial region of domestic pigs were remotely measured under reduced environmental light conditions and analyzed in order to differentiate between skin, mucosa, muscle, subcutaneous fat, and nerve tissue. We performed a principal components (PC) analysis (PCA) to reduce the number of variables. Linear discriminant analysis (LDA) was utilized for classification. For the tissue differentiation, we calculated the specificity and sensitivity by receiver operating characteristic (ROC) analysis and the area under curve (AUC). RESULTS Six PCs were found to be adequate for tissue differentiation with diffuse reflectance spectra using LDA. All of the types of soft tissue could be differentiated with high specificity and sensitivity. Only the tissue pairs nervous tissue/fatty tissue and nervous tissue/mucosa showed a decline of differentiation due to bio-structural similarity. However, both of these tissue pairs could still be differentiated with a specificity and sensitivity of more than 90%. CONCLUSIONS Analyzing diffuse reflectance spectroscopy with PCA and LDA allows for remote differentiation of biological tissue. Considering the limitations of the ex vivo conditions, the obtained results are promising and set a basis for the further development of a feedback system for tissue-specific laser surgery.
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Affiliation(s)
- Florian Stelzle
- Department of Oral and Maxillofacial Surgery, University Hospital Erlangen, Erlangen, Germany.
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Brown CP, Bowden JC, Rintoul L, Meder R, Oloyede A, Crawford RW. Diffuse reflectance near infrared spectroscopy can distinguish normal from enzymatically digested cartilage. Phys Med Biol 2009; 54:5579-94. [DOI: 10.1088/0031-9155/54/18/015] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Bagdonas S, Zurauskas E, Streckyte G, Rotomskis R. Spectroscopic studies of the human heart conduction system ex vivo: implication for optical visualization. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2008; 92:128-34. [PMID: 18590965 DOI: 10.1016/j.jphotobiol.2008.05.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2007] [Revised: 04/19/2008] [Accepted: 05/22/2008] [Indexed: 11/27/2022]
Abstract
Fluorescence excitation and emission spectra of the heart tissues specimens have been measured ex vivo with the aim of finding out the optical differences characteristic for the human heart conduction system (the His bundle) and ventricular myocardium. The optimal conditions enhancing the spectral differences between the His bundle and myocardium were found by recording the fluorescence signal in the range from 420 nm to 465 nm under the excitation at wavelengths starting from 320 nm to 370 nm. In addition, the spectral differences between the His bundle and the connective tissue, which is often present in the heart, could be displayed by comparing the ratios of fluorescence intensities being measured at above 460 nm under the preferred excitation of elastin and collagen. The left and right branches of the His bundle were visualized ex vivo in the interventricular septum of the human heart under illumination at 366 nm.
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Affiliation(s)
- S Bagdonas
- Vilnius University Laser Research Centre, Sauletekio 9, Building 3, LT-10222 Vilnius, Lithuania
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Rodríguez-Casado A, Alvarez I, Toledano A, de Miguel E, Carmona P. Amphetamine effects on brain protein structure and oxidative stress as revealed by FTIR microspectroscopy. Biopolymers 2007; 86:437-46. [PMID: 17480001 DOI: 10.1002/bip.20753] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Amphetamines are psychostimulants abused by man, that eventually leads to drug dependence. Amphetamine administration to rodents has been shown to provoke significant neurotoxicity involving dopaminergic nerve terminal degeneration. However, little information related to the effect of amphetamines on reactive oxygen species (ROS) production and neurotoxicity in brain is currently available. Herein we report the biochemical alterations of lipids and proteins in brain sections from amphetamine-treated rodents using infrared microspectroscopy, immunohistochemistry, and immunoblotting. The spectroscopic changes reveal for the first time the formation of beta-sheet-rich proteins in the cortex, but no significant protein alterations are visible in hippocampus region where hydroperoxide concentration is found to be lower relative to cortex. These result suggest that ROS generated by amphetamine-mediated oxidative stress induce formation beta-sheet-rich proteins which can be of amyloid beta-like character.
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Affiliation(s)
- A Rodríguez-Casado
- Instituto de Estructura de la Materia (CSIC), Serrano 121, Madrid, Spain
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Wang L, Chapman J, Palmer RA, van Ramm O, Mizaikoff B. Classification of atherosclerotic rabbit aorta samples by mid-infrared spectroscopy using multivariate data analysis. JOURNAL OF BIOMEDICAL OPTICS 2007; 12:024006. [PMID: 17477721 DOI: 10.1117/1.2714030] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Atherosclerotic and normal rabbit aorta samples show a marked difference in chemical composition governed by the water, lipid, and protein content. The strongly overlapping infrared absorption features of the different constituents, and the complexity of the tissue matrix, render tissue classification by direct evaluation of molecular spectroscopic characteristics obtained from IR reflectance or attenuated total reflectance (ATR) measurements virtually impossible. We apply multivariate analysis and classification techniques based on partial least squares regression (PLS) and linear discriminant analysis to IR spectroscopic data obtained by IR-ATR measurements and reflectance IR microscopy with high predictive accuracy during blind testing. Training data are collected from atherosclerotic and normal rabbit aorta samples. These results demonstrate the potential of IR spectroscopy combined with multivariate classification strategies for the in-vitro identification of normal and atherosclerotic aorta tissue. The prospect for future in-vivo measurement concepts is also discussed.
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Affiliation(s)
- Liqun Wang
- Georgia Institute of Technology, School of Chemistry and Biochemistry, Atlanta, Georgia 30332, USA
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Wang L, Chapman J, Palmer RA, Alter TM, Hooper BA, van Ramm O, Mizaikoff B. Classification of atherosclerotic rabbit aorta samples with an infrared attenuated total reflection catheter and multivariate data analysis. APPLIED SPECTROSCOPY 2006; 60:1121-6. [PMID: 17059663 DOI: 10.1366/000370206778664608] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The strongly overlapping infrared absorption features of atherosclerotic and normal rabbit aorta samples as governed by their water, lipid, and protein content render the direct evaluation of molecular characteristics obtained from infrared (IR) spectroscopic measurements challenging for classification. We have successfully applied multivariate data analysis and classification techniques based on partial least squares regression (PLS), linear discriminant analysis (LDA), and principal component regression (PCR) to IR spectroscopic data obtained by using a recently developed infrared attenuated total reflectance (IR-ATR) catheter prototype for future in vivo diagnostic applications. Training data were collected ex vivo from atherosclerotic and normal rabbit aorta samples. The successful classification results on atherosclerotic and normal aorta samples utilizing the developed data evaluation routines reveals the potential of spectroscopy combined with multivariate classification strategies for the identification of normal and atherosclerotic aorta tissue for in vitro and, in the future, in vivo applications.
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Affiliation(s)
- Liqun Wang
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA
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15
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Bonnier F, Rubin S, Ventéo L, Krishna CM, Pluot M, Baehrel B, Manfait M, Sockalingum GD. In-vitro analysis of normal and aneurismal human ascending aortic tissues using FT-IR microspectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:968-73. [PMID: 16904629 DOI: 10.1016/j.bbamem.2006.05.018] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2006] [Revised: 05/19/2006] [Accepted: 05/19/2006] [Indexed: 11/26/2022]
Abstract
FTIR microspectroscopy has shown to be a proven tool in the investigation of many tissue types. We have used this spectroscopic approach to analyse structural differences between normal and aneurismal aortic tissues and also aortas from patients with congenital anomalies like aortic bicuspid valves. Spectral analysis showed important variations in amide I and II regions, related to changes in alpha-helix and beta-sheet secondary structure of proteins that seem to be correlated to structural modifications of collagen and elastin. These proteins are the major constituents of the aortic wall associated to smooth muscular cells. The amide regions have thus been identified as a marker of structural modifications related to these proteins whose modifications can be associated to a given aortic pathological situation. Both univariate (total absorbance image and band ratio) and multivariate (principal components analysis) analyses of the spectral information contained in the infrared images have been performed. Differences between tissues have been identified by these two approaches and allowed to separate each group of aortic tissues. However, with univariate band ratio analysis, the pathological group was found to be composed of samples from aneurismal aortas associated or not with an aortic bicuspid valve. In contrast, PCA was able to separate these two types of aortic pathologies. For other groups, PCA and band ratio analysis can differentiate between normal, aneurismal, and none dilated aortas from patients with a bicuspid aortic valve.
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Affiliation(s)
- F Bonnier
- Unité MéDIAN, CNRS UMR 6142, UFR de Pharmacie, IFR 53, Université de Reims Champagne-Ardenne, 51 rue Cognacq-Jay, 51096 Reims cedex, France
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Lilledahl MB, Haugen OA, Barkost M, Svaasand LO. Reflection spectroscopy of atherosclerotic plaque. JOURNAL OF BIOMEDICAL OPTICS 2006; 11:021005. [PMID: 16674180 DOI: 10.1117/1.2186332] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Heart disease is the primary cause of death in the western world. Many of these deaths are caused by the rupture of vulnerable plaque. Vulnerable plaques are characterized by a large lipid core covered by a thin fibrous cap. One method for detecting these plaques is reflection spectroscopy. Several studies have investigated this method using statistical methods. A more analytic and quantitative study might yield more insight into the sensitivity of this detection modality. This is the approach taken in this work. Reflectance spectra in the spectral region from 400 to 1700 nm are collected from 77 measurement points from 23 human aortas. A measure of lipid content in a plaque based on reflection spectra is presented. The measure of lipid content is compared with the thickness of the lipid core, determined from histology. Defining vulnerable plaque as having a lipid core >500 microm and fibrous cap <500 microm, vulnerable plaques are detected with a sensitivity of 88% and a specificity of 94%. Although the method can detect lipid content, it is not very sensitive to the thickness of the fibrous cap. Another detection modality is necessary to detect this feature.
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Affiliation(s)
- Magnus B Lilledahl
- Norwegian University of Science and Technology, Department of Electronics and Telecommunications, O.S. Bragstads plass 2A, Trondheim 7491, Norway.
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Emmelkamp J, Wolbers F, Andersson H, Dacosta RS, Wilson BC, Vermes I, van den Berg A. The potential of autofluorescence for the detection of single living cells for label-free cell sorting in microfluidic systems. Electrophoresis 2005; 25:3740-5. [PMID: 15565697 DOI: 10.1002/elps.200406070] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A novel method for studying unlabeled living mammalian cells based on their autofluorescence (AF) signal in a prototype microfluidic device is presented. When combined, cellular AF detection and microfluidic devices have the potential to facilitate high-throughput analysis of different cell populations. To demonstrate this, unlabeled cultured cells in microfluidic devices were excited with a 488 nm excitation light and the AF emission (> 505 nm) was detected using a confocal fluorescence microscope (CFM). For example, a simple microfluidic three-port glass microstructure was used together with conventional electroosmotic flow (EOF) to switch the direction of the fluid flow. As a means to test the potential of AF-based cell sorting in this microfluidic device, granulocytes were successfully differentiated from human red blood cells (RBCs) based on differences in AF. This study demonstrated the use of a simple microfabricated device to perform high-throughput live cell detection and differentiation without the need for cell-specific fluorescent labeling dyes and thereby reducing the sample preparation time. Hence, the combined use of microfluidic devices and cell AF may have many applications in single-cell analysis.
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Affiliation(s)
- Jurjen Emmelkamp
- Mesa+ Institute, Lab-on-a-Chip group, University of Twente, Enschede, The Netherlands.
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18
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Laiho LH, Pelet S, Hancewicz TM, Kaplan PD, So PTC. Two-photon 3-D mapping of ex vivo human skin endogenous fluorescence species based on fluorescence emission spectra. JOURNAL OF BIOMEDICAL OPTICS 2005; 10:024016. [PMID: 15910090 DOI: 10.1117/1.1891370] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Spectral resolved tissue imaging has a broad range of biomedical applications such as the minimally invasive diagnosis of diseases and the study of wound healing and tissue engineering processes. Two-photon microscopy imaging of endogenous fluorescence has been shown to be a powerful method for the quantification of tissue structure and biochemistry. While two-photon excited autofluorescence is observed ubiquitously, the identities and distributions of endogenous fluorophores have not been completely characterized in most tissues. We develop an image-guided spectral analysis method to analyze the distribution of fluorophores in human skin from 3-D resolved two-photon images. We identify five factors that contribute to most of the luminescence signals from human skin. Luminescence species identified include tryptophan, NAD(P)H, melanin, and elastin, which are autofluorescent, and collagen that contributes to a second harmonic signal.
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Affiliation(s)
- Lily H Laiho
- Massachusetts Institute of Technology, Department of Mechanical Engineering, 77 Massachusetts Avenue, NE47-276, Cambridge, Massachusetts 02139, USA.
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20
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Hooper BA, Maheshwari A, Curry AC, Alter TM. Catheter for diagnosis and therapy with infrared evanescent waves. APPLIED OPTICS 2003; 42:3205-3214. [PMID: 12790471 DOI: 10.1364/ao.42.003205] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We have developed an optical delivery device (catheter) capable of transmitting broadband infrared light (IR wavelengths from 2 to 10 microm) for both diagnostic and therapeutic applications. The catheter is 1.68 mm in outer diameter and 1 m in length. It consists of two hollow glass waveguides coupled to a high-refractive-index optic tip. The IR light interacts with the tissue at the optic-tissue interface to measure the spectral signatures and perform therapy on the tissue at this interface. Fourier-transform IR spectrophotometer light is used to obtain the spectral signatures, and an IR free-electron laser (FEL) is used to study the therapeutic interaction of evanescent waves with the tissue. We present our catheter design; preliminary IR spectroscopy of aorta, blood, fatty tissue, and muscle; and IR FEL therapy on atheroslerotic aorta.
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Affiliation(s)
- Brett A Hooper
- Department of Biomedical Engineering and the Center for Emerging Cardiovascular Technologies, Duke University, Durham, North Carolina 27708-0319, USA.
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21
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Inayama K, Ito S, Muguruma N, Kusaka Y, Bando T, Tadatsu Y, Tadatsu M, Ii K, Shibamura S, Takesako K. Basic study of an agent for reinforcement of near-infrared fluorescence on tumor tissue. Dig Liver Dis 2003; 35:88-93. [PMID: 12747626 DOI: 10.1016/s1590-8658(03)00005-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND AND AIMS An indocyanine green derivative (ICG-sulfo-OSu) and agents for reinforcement of infrared fluorescence, which can be used as an infrared fluorescent labeling substance suitable for detection of microlesions by an IR fluorescence endoscope, have been developed. The study aims were to confirm the ability of a reinforcement agent, as well as imaging processing, to intensify fluorescence from the labeled antibody on immunohistochemical staining. SUBJECTS AND METHODS ICG-sulfo-OSu-labeled MUC1 antibody and an IR fluorescence imaging system were employed in the present study. Paraffin sections of gastric cancer were stained with anti-MUC1 antibody by the avidin-biotinylated peroxidase complex method. Among the positive specimens, three cases were used for IR imaging analysis. Octylglucoside was used as a reinforcement agent. RESULTS The incubation of paraffin sections with ICG-sulfo-OSu-labeled MUC1 antibody resulted in positive staining of the tumor sites by an IR fluorescence imaging system, and the intensity of fluorescence was increased depending on the concentration of octylglucoside and grade of imaging processing. CONCLUSION A reinforcement agent, and image processing, intensify a labeled antibody excitable by infrared fluorescence in tumor sections and can generate a strong enough fluorescent signal to detect small cancers when examined with an infrared fluorescence endoscope.
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Affiliation(s)
- K Inayama
- Second Department of Internal Medicine, University of Tokushima School of Medicine, 3-18-15 Kuramoto-cho, Tokushima City 770-803, Japan
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Plesnila N, Putz C, Rinecker M, Wiezorrek J, Schleinkofer L, Goetz AE, Kuebler WM. Measurement of absolute values of hemoglobin oxygenation in the brain of small rodents by near infrared reflection spectrophotometry. J Neurosci Methods 2002; 114:107-17. [PMID: 11856562 DOI: 10.1016/s0165-0270(01)00487-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Reflection near infrared spectroscopy (reNIRS) has been proposed as a novel technique for the measurement of absolute values of total hemoglobin (tHb), oxygenated hemoglobin (oxHb), hemoglobin saturation (SO2), and cytochrome aa3 oxidation status (oxCyt aa3) in living tissue. In this study, we evaluated reNIRS during physiological cerebral blood flow conditions in rats (n=6) and during the induction of global cerebral ischemia in gerbils (n=6). ReNIRS parameters were assessed over the exposed cerebral cortex and compared to regional cerebral blood flow (rCBF) data obtained by laser Doppler flowmetry. Under physiological conditions, reNIRS measurements reflected the large intra- and interindividual variability of oxHb and tHb in the brain. The absolute values obtained by reNIRS for tHb (6.3 +/- 1.7 mg/ml), oxHb (3.7 +/- 1.1 mg/ml), and SO2 (61 +/- 5%) matched expected values. In contrast, measurements of oxCyt aa3 were unstable and results unreliable. reNIRS reliably detected cerebral ischemia, verified by a reduction of rCBF to 11% of baseline. tHb dropped to 74 +/- 7% of baseline (P<0.001), reflecting ischemic microvascular vasoconstriction. oxHb and SO2 dropped to expected near-zero values (2 +/- 4 and 3 +/- 5% of baseline, respectively; P<0.001). We conclude that reNIRS provides reliable and reproducible absolute values for brain tissue tHb, oxHb, and SO2 in small rodents. Determination of physiological values requires measurements at multiple locations, while cerebral ischemia is reliably detected by continuous recordings at a single location.
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Affiliation(s)
- Nikolaus Plesnila
- Institute for Surgical Research, Klinikum Grosshadern, Ludwig-Maximilians University, Marchioninistr. 27, 81377, Munich, Germany.
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Rovithakis GA, Maniadakis M, Zervakis M, Filippidis G, Zacharakis G, Katsamouris AN, Papazoglou TG. Artificial neural networks for discriminating pathologic from normal peripheral vascular tissue. IEEE Trans Biomed Eng 2001; 48:1088-97. [PMID: 11585032 DOI: 10.1109/10.951511] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The identification of the state of human peripheral vascular tissue by using artificial neural networks is discussed in this paper. Two different laser emission lines (He-Cd, Ar+) are used to excite the chromophores of tissue samples. The fluorescence spectrum obtained, is passed through a nonlinear filter based on a high-order (HO) neural network neural network (NN) [HONN] whose weights are updated by stable learning laws, to perform feature extraction. The values of the feature vector reveal information regarding the tissue state. Then a classical multilayer perceptron is employed to serve as a classifier of the feature vector, giving 100% successful results for the specific data set considered. Our method achieves not only the discrimination between normal and pathologic human tissue, but also the successful discrimination between the different types of pathologic tissue (fibrous, calcified). Furthermore, the small time needed to acquire and analyze the fluorescence spectra together with the high rates of success, proves our method very attractive for real-time applications.
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Affiliation(s)
- G A Rovithakis
- Department of Electronic and Computer Engineering, Technical University of Crete, Greece.
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Kochiadakis GE, Chrysostomakis SI, Kalebubas MD, Filippidis GM, Zacharakis IG, Papazoglou TG, Vardas PE. The role of laser-induced fluorescence in myocardial tissue characterization: an experimental in vitro study. Chest 2001; 120:233-9. [PMID: 11451844 DOI: 10.1378/chest.120.1.233] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
OBJECTIVE The fluorescence of tissue when stimulated by a laser beam is a well-known phenomenon. The resulting emission spectra depend on the biochemical and structural composition of the tissue. In this study, we examined the spectra of laser-induced fluorescence emitted by myocardial tissue. METHODS We used an argon-ion laser to stimulate the myocardium of 20 intact sheep hearts. For each spectral emission, we calculated the intensity in specific regions in order to characterize the spectra and to reveal intercavitary and intracavitary morphologic differences. RESULTS The statistical analysis showed significant differences in the emission spectra intensity between atria and ventricles. The intensity was higher in the atria than in the ventricles (p < 0.001). The atrial emission spectra were morphologically different from those of the ventricles. There was no difference in the intensity or morphology of emission spectra within each chamber. All measurements showed good reproducibility after a short period of time. CONCLUSIONS Laser-induced fluorescence of myocardial tissue seems to have the characteristics necessary for tissue recognition. This might prove useful in identifying cardiomyopathies and transplant rejection, as well as for myocardial mapping, assisting electrophysiologists in discovering fibrotic arrhythmogenic foci.
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Affiliation(s)
- G E Kochiadakis
- Cardiology Department, University Hospital of Crete, Heraklion Crete, Greece
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Eker C, Rydell R, Svanberg K, Andersson-Engels S. Multivariate analysis of laryngeal fluorescence spectra recorded in vivo. Lasers Surg Med 2001; 28:259-66. [PMID: 11295762 DOI: 10.1002/lsm.1048] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND AND OBJECTIVE The potential of using various multivariate analysis methods for classification of fluorescence spectra acquired in vivo from laryngeal tissues in Patients was investigated. STUDY DESIGN/MATERIALS AND METHODS Autofluorescence spectra were measured on 29 normal tissue sites and 25 laryngeal lesions using 337-nm excitation. Four different multivariate analysis schemes were applied. Laryngeal fluorescence spectra from patients who had been administered delta-aminolevulinic acid (ALA) were obtained using 405-nm excitation and were classified using partial least squares discriminant analysis (PLS-DA). RESULTS For autofluorescence spectra, logistic regression based on principal component analysis (PCA) or PLS, or PLS-DA all resulted in sensitivities and specificities around 90% for lesion vs. normal. Using ALA and 405-nm excitation gave a sensitivity of 100% and a specificity of 69%. CONCLUSION Multivariate analysis of fluorescence spectra could allow classification of laryngeal lesions in vivo with high sensitivity and specificity. PLS performs at least as well as PCA, and PLS-DA performs as well as logistic regression techniques on these data.
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Affiliation(s)
- C Eker
- Department of Physics, Lund Institute of Technology, SE-221 00 Lund, Sweden
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Filippidis G, Zacharakis G, Katsamouris A, Giannoukas A, Papazoglou TG. Single and double wavelength excitation of laser-induced fluorescence of normal and atherosclerotic peripheral vascular tissue. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2000; 56:163-71. [PMID: 11079477 DOI: 10.1016/s1011-1344(00)00073-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Laser-induced fluorescence spectra were recorded from the exposure of peripheral vascular tissue to both helium-cadmium and argon-ion laser radiation. Spectral analysis was based on simple algebraic expressions constructed using the intensity difference of the various spectral regions. The above methods were developed in order to determine the degree of atherosclerosis according to the laser-induced fluorescence signal. Similar results with single wavelength excitation were observed during in vivo irradiation of peripheral vessels.
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Affiliation(s)
- G Filippidis
- Foundation for Research and Technology-Hellas, Institute of Electronic Structure and Laser, Laser and Applications Division, Crete, Greece.
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Morgan DC, Wilson JE, MacAulay CE, MacKinnon NB, Kenyon JA, Gerla PS, Dong C, Zeng H, Whitehead PD, Thompson CR, McManus BM. New method for detection of heart allograft rejection: validation of sensitivity and reliability in a rat heterotopic allograft model. Circulation 1999; 100:1236-41. [PMID: 10484546 DOI: 10.1161/01.cir.100.11.1236] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Patients with inflammatory heart muscle diseases would benefit from a safe, convenient, rapidly performed diagnostic technique with real-time results not involving tissue removal. We have performed a detailed evaluation of detection of heart allograft rejection by autofluorescence in a heterotopic abdominal rat heart allograft model ex vivo. METHODS AND RESULTS Recipient rats with allograft (Lewis to Fisher 344; n=71) and isograft (Lewis to Lewis; n=33) hearts, treated with cyclosporine or untreated, were killed at days 2, 4, 7, 14, 21, 28, and 56 after transplant. Nontransplant controls with (n=24) or without (n=24) immunosuppressive therapy were also studied. When the rats were killed, autofluorescence spectra were acquired under blue-light excitation from midtransverse ventricular sections of native and transplanted hearts. Corresponding sections were then evaluated pathologically by a modified International Society for Heart and Lung Transplantation (ISHLT) grading schema. The spectral differences between rejecting and nonrejecting hearts were quantified by linear discriminant functions, producing scores that decreased progressively with increasing severity of tissue rejection. Mean+/-SD discriminant function scores were 2.9+/-1.6, 1.8+/-2.2, -0.1+/-2.8, -1.2+/-2.3, and -2.3+/-3.0 for isografts and allograft ISHLT grades 0, I, II, and III, respectively (Spearman rank-order correlation -0.6; P<0.001, test for trend). Cyclosporine had no detectable effect on the spectra. CONCLUSIONS The correlation between changes in autofluorescence spectra and ISHLT rejection grade strongly supports the possibility of catheter-based, fluorescence-guided surveillance of rejection.
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