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Ndabakuranye JP, Belcourt J, Sharma D, O'Connell CD, Mondal V, Srivastava SK, Stacey A, Long S, Fleiss B, Ahnood A. Miniature fluorescence sensor for quantitative detection of brain tumour. LAB ON A CHIP 2024; 24:946-954. [PMID: 38275166 DOI: 10.1039/d3lc00982c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2024]
Abstract
Fluorescence-guided surgery has emerged as a vital tool for tumour resection procedures. As well as intraoperative tumour visualisation, 5-ALA-induced PpIX provides an avenue for quantitative tumour identification based on ratiometric fluorescence measurement. To this end, fluorescence imaging and fibre-based probes have enabled more precise demarcation between the cancerous and healthy tissues. These sensing approaches, which rely on collecting the fluorescence light from the tumour resection site and its "remote" spectral sensing, introduce challenges associated with optical losses. In this work, we demonstrate the viability of tumour detection at the resection site using a miniature fluorescence measurement system. Unlike the current bulky systems, which necessitate remote measurement, we have adopted a millimetre-sized spectral sensor chip for quantitative fluorescence measurements. A reliable measurement at the resection site requires a stable optical window between the tissue and the optoelectronic system. This is achieved using an antifouling diamond window, which provides stable optical transparency. The system achieved a sensitivity of 92.3% and specificity of 98.3% in detecting a surrogate tumour at a resolution of 1 × 1 mm2. As well as addressing losses associated with collecting and coupling fluorescence light in the current 'remote' sensing approaches, the small size of the system introduced in this work paves the way for its direct integration with the tumour resection tools with the aim of more accurate interoperative tumour identification.
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Affiliation(s)
| | | | - Deepak Sharma
- School of Engineering, RMIT University, VIC 3000, Australia.
- Photovoltaic Metrology Section, Advanced Materials and Device Metrology Division, CSIR-National Physical Laboratory, New Delhi, 110012, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
| | - Cathal D O'Connell
- School of Engineering, RMIT University, VIC 3000, Australia.
- Aikenhead Centre for Medical Discovery, St Vincent's Hospital Melbourne, VIC 3065, Australia
| | - Victor Mondal
- School of Health and Biomedical Sciences, RMIT University, VIC 3000, Australia
| | - Sanjay K Srivastava
- Photovoltaic Metrology Section, Advanced Materials and Device Metrology Division, CSIR-National Physical Laboratory, New Delhi, 110012, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
| | - Alastair Stacey
- School of Science, RMIT University, VIC 3000, Australia
- Princeton Plasma Physics Laboratory, Princeton University, Princeton, 08540 New Jersey, USA
| | - Sam Long
- Veterinary Referral Hospital, Victoria, Australia
| | - Bobbi Fleiss
- School of Health and Biomedical Sciences, RMIT University, VIC 3000, Australia
| | - Arman Ahnood
- School of Engineering, RMIT University, VIC 3000, Australia.
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Gautheron A, Bernstock JD, Picart T, Guyotat J, Valdés PA, Montcel B. 5-ALA induced PpIX fluorescence spectroscopy in neurosurgery: a review. Front Neurosci 2024; 18:1310282. [PMID: 38348134 PMCID: PMC10859467 DOI: 10.3389/fnins.2024.1310282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 01/02/2024] [Indexed: 02/15/2024] Open
Abstract
The review begins with an overview of the fundamental principles/physics underlying light, fluorescence, and other light-matter interactions in biological tissues. It then focuses on 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PpIX) fluorescence spectroscopy methods used in neurosurgery (e.g., intensity, time-resolved) and in so doing, describe their specific features (e.g., hardware requirements, main processing methods) as well as their strengths and limitations. Finally, we review current clinical applications and future directions of 5-ALA-induced protoporphyrin IX (PpIX) fluorescence spectroscopy in neurosurgery.
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Affiliation(s)
- A. Gautheron
- Université Jean Monnet Saint-Etienne, CNRS, Institut d Optique Graduate School, Laboratoire Hubert Curien UMR 5516, Saint-Étienne, France
- Univ Lyon, INSA-Lyon, Université Claude Bernard Lyon 1, UJM-Saint Etienne, CNRS, Inserm, CREATIS UMR 5220, U1294, Lyon, France
| | - J. D. Bernstock
- Department of Neurosurgery, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, United States
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - T. Picart
- Department of Neurosurgical Oncology and Vascular Neurosurgery, Pierre Wertheimer Neurological and Neurosurgical Hospital, Hospices Civils de Lyon, Lyon, France
- Université Lyon 1, INSERM 1052, CNRS 5286, Lyon, France
| | - J. Guyotat
- Department of Neurosurgical Oncology and Vascular Neurosurgery, Pierre Wertheimer Neurological and Neurosurgical Hospital, Hospices Civils de Lyon, Lyon, France
| | - P. A. Valdés
- Department of Neurosurgery, University of Texas Medical Branch, Galveston, TX, United States
- Department of Neurobiology, University of Texas Medical Branch, Galveston, TX, United States
- Department of Electrical and Computer Engineering, Rice University, Houston, TX, United States
| | - B. Montcel
- Univ Lyon, INSA-Lyon, Université Claude Bernard Lyon 1, UJM-Saint Etienne, CNRS, Inserm, CREATIS UMR 5220, U1294, Lyon, France
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Kumar P, Rathod S, Pradhan A. Detection of oral mucosal lesions by the fluorescence spectroscopy and classification of cancerous stages by support vector machine. Lasers Med Sci 2024; 39:42. [PMID: 38240832 DOI: 10.1007/s10103-024-03995-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Accepted: 01/12/2024] [Indexed: 01/23/2024]
Abstract
Detection of oral mucosal lesions has been performed by an in-house developed fluorescence-based portable device in the present study. A laser diode of 405 nm wavelength and a UV-visible spectrometer are utilized in the portable device as excitation and detection sources. At the 405 nm excitation wavelength, the flavin adenine dinucleotide (FAD) band at 500 nm and three porphyrin bands at 634, 676, and 703 nm are observed in the fluorescence spectrum of the oral cavity tissue. We have conducted this clinical study on a total of 189 tissue sites of 36 oral squamous cell carcinoma (OSCC) patients, 18 dysplastic (precancerous) patients, and 34 volunteers. Analysis of the fluorescence data has been performed by using the principal component analysis (PCA) method and support vector machine (SVM) classifier. PCA is applied first in the spectral data to reduce the dimension, and then classification among the three groups has been executed by employing the SVM. The SVM classifier includes linear, radial basis function (RBF), polynomial, and sigmoid kernels, and their classification efficacies are computed. Linear and RBF kernels on the testing data sets differentiated OSCC and dysplasia to normal with an accuracy of 100% and OSCC to dysplasia with an accuracy of 95% and 97%, respectively. Polynomial and sigmoid kernels showed less accuracy values among the groups ranging from 48 to 88% and 51 to 100%, respectively. The result indicates that fluorescence spectroscopy and the SVM classifier can help to identify early oral mucosal lesions with significant high accuracy.
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Affiliation(s)
- Pavan Kumar
- Faculty of Engineering and Technology (FEAT), Datta Meghe Institute of Higher Education and Research (DMIHER), Wardha, 442001, India.
- Department of Physics, Indian Institute of Technology Kanpur (IITK), Kanpur, 208016, India.
| | - Shashikant Rathod
- Faculty of Engineering and Technology (FEAT), Datta Meghe Institute of Higher Education and Research (DMIHER), Wardha, 442001, India
- Department of Instrumentation and Control Engineering, COEP Technological University, Pune, 445001, India
| | - Asima Pradhan
- Department of Physics, Indian Institute of Technology Kanpur (IITK), Kanpur, 208016, India
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García MJ, Kamaid A, Malacrida L. Label-free fluorescence microscopy: revisiting the opportunities with autofluorescent molecules and harmonic generations as biosensors and biomarkers for quantitative biology. Biophys Rev 2023; 15:709-719. [PMID: 37681086 PMCID: PMC10480099 DOI: 10.1007/s12551-023-01083-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Accepted: 06/19/2023] [Indexed: 09/09/2023] Open
Abstract
Over the past decade, the utilization of advanced fluorescence microscopy technologies has presented numerous opportunities to study or re-investigate autofluorescent molecules and harmonic generation signals as molecular biomarkers and biosensors for in vivo cell and tissue studies. The label-free approaches benefit from the endogenous fluorescent molecules within the cell and take advantage of their spectroscopy properties to address biological questions. Harmonic generation can be used as a tool to identify the occurrence of fibrillar or lipid deposits in tissues, by using second and third-harmonic generation microscopy. Combining autofluorescence with novel techniques and tools such as fluorescence lifetime imaging microscopy (FLIM) and hyperspectral imaging (HSI) with model-free analysis of phasor plots has revolutionized the understanding of molecular processes such as cellular metabolism. These tools provide quantitative information that is often hidden under classical intensity-based microscopy. In this short review, we aim to illustrate how some of these technologies and techniques may enable investigation without the need to add a foreign fluorescence molecule that can modify or affect the results. We address some of the most important autofluorescence molecules and their spectroscopic properties to illustrate the potential of these combined tools. We discuss using them as biomarkers and biosensors and, under the lens of this new technology, identify some of the challenges and potentials for future advances in the field.
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Affiliation(s)
- María José García
- Departamento de Fisiopatología, Hospital de Clínicas, Facultad de Medicina, Universidad de La República, Montevideo, Uruguay
- Advanced Bioimaging Unit, Institut Pasteur de Montevideo & Universidad de la República, Montevideo, Uruguay
| | - Andrés Kamaid
- Advanced Bioimaging Unit, Institut Pasteur de Montevideo & Universidad de la República, Montevideo, Uruguay
| | - Leonel Malacrida
- Departamento de Fisiopatología, Hospital de Clínicas, Facultad de Medicina, Universidad de La República, Montevideo, Uruguay
- Advanced Bioimaging Unit, Institut Pasteur de Montevideo & Universidad de la República, Montevideo, Uruguay
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Reichert D, Wadiura LI, Erkkilae MT, Gesperger J, Lang A, Roetzer-Pejrimovsky T, Makolli J, Woehrer A, Wilzbach M, Hauger C, Kiesel B, Andreana M, Unterhuber A, Drexler W, Widhalm G, Leitgeb RA. Flavin fluorescence lifetime and autofluorescence optical redox ratio for improved visualization and classification of brain tumors. Front Oncol 2023; 13:1105648. [PMID: 36890834 PMCID: PMC9986542 DOI: 10.3389/fonc.2023.1105648] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Accepted: 02/07/2023] [Indexed: 02/22/2023] Open
Abstract
Purpose Modern techniques for improved tumor visualization have the aim to maximize the extent of resection during brain tumor surgery and thus improve patient prognosis. Optical imaging of autofluorescence is a powerful and non-invasive tool to monitor metabolic changes and transformation in brain tumors. Cellular redox ratios can be retrieved from fluorescence emitted by the coenzymes reduced nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) and flavin adenine dinucleotide (FAD). Recent studies point out that the influence of flavin mononucleotide (FMN) has been underestimated. Experimental design Fluorescence lifetime imaging and fluorescence spectroscopy were performed through a modified surgical microscope. We acquired 361 flavin fluorescence lifetime (500-580 nm) and fluorescence spectra (430-740 nm) data points on freshly excised different brain tumors: low-grade gliomas (N=17), high-grade gliomas (N=42), meningiomas (N=23), metastases (N=26) and specimens from the non-tumorous brain (N=3). Results Protein-bound FMN fluorescence in brain tumors did increase with a shift toward a more glycolytic metabolism (R=-0.87). This increased the average flavin fluorescence lifetime in tumor entities with respect to the non-tumorous brain. Further, these metrics were characteristic for the different tumor entities and showed promise for machine learning based brain tumor classification. Conclusions Our results shed light on FMN fluorescence in metabolic imaging and outline the potential for supporting the neurosurgeon in visualizing and classifying brain tumor tissue during surgery.
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Affiliation(s)
- David Reichert
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Christian Doppler Laboratory for Innovative Optical Imaging and its Translation to Medicine (OPTRAMED), Medical University of Vienna, Vienna, Austria
| | - Lisa I Wadiura
- Department of Neurosurgery, General Hospital and Medical University of Vienna, Vienna, Austria
| | - Mikael T Erkkilae
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
| | - Johanna Gesperger
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Alexandra Lang
- Department of Neurosurgery, General Hospital and Medical University of Vienna, Vienna, Austria
| | - Thomas Roetzer-Pejrimovsky
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Jessica Makolli
- Department of Neurosurgery, General Hospital and Medical University of Vienna, Vienna, Austria
| | - Adelheid Woehrer
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Marco Wilzbach
- Advanced Development Microsurgery, Carl Zeiss Meditec AG, Oberkochen, Germany
| | - Christoph Hauger
- Advanced Development Microsurgery, Carl Zeiss Meditec AG, Oberkochen, Germany
| | - Barbara Kiesel
- Department of Neurosurgery, General Hospital and Medical University of Vienna, Vienna, Austria
| | - Marco Andreana
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
| | - Angelika Unterhuber
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
| | - Wolfgang Drexler
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
| | - Georg Widhalm
- Department of Neurosurgery, General Hospital and Medical University of Vienna, Vienna, Austria
| | - Rainer A Leitgeb
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Christian Doppler Laboratory for Innovative Optical Imaging and its Translation to Medicine (OPTRAMED), Medical University of Vienna, Vienna, Austria
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Harada Y, Murayama Y, Takamatsu T, Otsuji E, Tanaka H. 5-Aminolevulinic Acid-Induced Protoporphyrin IX Fluorescence Imaging for Tumor Detection: Recent Advances and Challenges. Int J Mol Sci 2022; 23:ijms23126478. [PMID: 35742921 PMCID: PMC9223645 DOI: 10.3390/ijms23126478] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 06/02/2022] [Accepted: 06/07/2022] [Indexed: 12/18/2022] Open
Abstract
5-Aminolevulinic acid (5-ALA) is a natural amino acid and a precursor of heme and chlorophyll. Exogenously administered 5-ALA is metabolized into protoporphyrin IX (PpIX). PpIX accumulates in cancer cells because of the low activity of ferrochelatase, an enzyme that metabolizes PpIX to heme. High expression of 5-ALA influx transporters, such as peptide transporters 1/2, in cancer cells also enhances PpIX production. Because PpIX radiates red fluorescence when excited with blue/violet light, 5-ALA has been used for the visualization of various tumors. 5-ALA photodynamic diagnosis (PDD) has been shown to improve the tumor removal rate in high-grade gliomas and non-muscular invasive bladder cancers. However, 5-ALA PDD remains a challenge as a diagnostic method because tissue autofluorescence interferes with PpIX signals in cases where tumors emit only weak signals, and non-tumorous lesions, such as inflammatory sites, tend to emit PpIX fluorescence. Here, we review the current outline of 5-ALA PDD and strategies for improving its diagnostic applicability for tumor detection, focusing on optical techniques and 5-ALA metabolic pathways in both viable and necrotic tumor tissues.
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Affiliation(s)
- Yoshinori Harada
- Department of Pathology and Cell Regulation, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, 465 Kajii-cho Kamigyo-ku, Kyoto 602-8566, Japan;
- Correspondence: ; Tel.: +81-75-251-5322
| | - Yasutoshi Murayama
- Division of Digestive Surgery, Department of Surgery, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, 465 Kajii-cho Kamigyo-ku, Kyoto 602-8566, Japan; (Y.M.); (E.O.)
| | - Tetsuro Takamatsu
- Department of Medical Photonics, Kyoto Prefectural University of Medicine, 465 Kajii-cho Kamigyo-ku, Kyoto 602-8566, Japan;
| | - Eigo Otsuji
- Division of Digestive Surgery, Department of Surgery, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, 465 Kajii-cho Kamigyo-ku, Kyoto 602-8566, Japan; (Y.M.); (E.O.)
| | - Hideo Tanaka
- Department of Pathology and Cell Regulation, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, 465 Kajii-cho Kamigyo-ku, Kyoto 602-8566, Japan;
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Does pigmentation, hemosiderin and blood affect visible 5-ALA fluorescence in cerebral melanoma metastasis? Photodiagnosis Photodyn Ther 2022; 39:102864. [DOI: 10.1016/j.pdpdt.2022.102864] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 04/10/2022] [Accepted: 04/12/2022] [Indexed: 11/23/2022]
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Alfonso-García A, Zhou X, Bec J, Anbunesan SN, Fereidouni F, Jin LW, Lee HS, Bloch O, Marcu L. First in patient assessment of brain tumor infiltrative margins using simultaneous time-resolved measurements of 5-ALA-induced PpIX fluorescence and tissue autofluorescence. JOURNAL OF BIOMEDICAL OPTICS 2022; 27:020501. [PMID: 35112514 PMCID: PMC8809358 DOI: 10.1117/1.jbo.27.2.020501] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 01/11/2022] [Indexed: 06/14/2023]
Abstract
SIGNIFICANCE 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PpIX) fluorescence is currently used for image-guided glioma resection. Typically, this widefield imaging method highlights the bulk of high-grade gliomas, but it underperforms at the infiltrating edge where PpIX fluorescence is not visible to the eyes. Fluorescence lifetime imaging (FLIm) has the potential to detect PpIX fluorescence below the visible detection threshold. Moreover, simultaneous acquisition of time-resolved nicotinamide adenine (phosphate) dinucleotide [NAD(P)H] fluorescence may provide metabolic information from the tumor environment to further improve overall tumor detection. AIM We investigate the ability of pulse sampling, fiber-based FLIm to simultaneously image PpIX and NAD(P)H fluorescence of glioma infiltrative margins in patients. APPROACH A mesoscopic fiber-based point-scanning FLIm device (355 nm pulses) was used to simultaneously resolve the fluorescence decay of PpIX (629/53 nm) and NAD(P)H (470/28 nm). The FLIm device enabled data acquisition at room light and rapid (<33 ms) augmentation of FLIm parameters on the surgical field-of-view. FLIm measurements from superficial tumors and tissue areas around the resection margins were performed on three glioblastoma patients in vivo following inspection of PpIX visible fluorescence with a conventional neurosurgical microscope. Microbiopsies were collected from FLIm imaged areas for histopathological evaluation. RESULTS The average lifetime from PpIX and NAD(P)H fluorescence distinguished between tumor and surrounding tissue. FLIm measurements of resection margins presented a range of PpIX and NAD(P)H lifetime values (τPpIX ∼ 3 to 14 ns, τNAD(P)H = 3 to 6 ns) associated with unaffected tissue and areas of low-density tumor infiltration. CONCLUSIONS Intraoperative FLIm could simultaneously detect the emission of PpIX and NAD(P)H from patients in vivo during craniotomy procedures. This approach doubles as a clinical tool to identify tumor areas while performing tissue resection and as a research tool to study tumor microenvironmental changes in vivo. Intraoperative FLIm of 5-ALA-induced PpIX and tissue autofluorescence makes a promising surgical adjunct to guide tumor resection surgery.
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Affiliation(s)
- Alba Alfonso-García
- University of California Davis, Department of Biomedical Engineering, Davis, California, United States
| | - Xiangnan Zhou
- University of California Davis, Department of Biomedical Engineering, Davis, California, United States
| | - Julien Bec
- University of California Davis, Department of Biomedical Engineering, Davis, California, United States
| | - Silvia N. Anbunesan
- University of California Davis, Department of Biomedical Engineering, Davis, California, United States
| | - Farzad Fereidouni
- University of California Davis, Department of Biomedical Engineering, Davis, California, United States
- University of California Davis, Department of Pathology and Laboratory Medicine, Sacramento, California, United States
| | - Lee-Way Jin
- University of California Davis, Department of Pathology and Laboratory Medicine, Sacramento, California, United States
| | - Han S. Lee
- University of California Davis, Department of Pathology and Laboratory Medicine, Sacramento, California, United States
| | - Orin Bloch
- University of California Davis, Department of Neurological Surgery, Sacramento, California, United States
| | - Laura Marcu
- University of California Davis, Department of Biomedical Engineering, Davis, California, United States
- University of California Davis, Department of Neurological Surgery, Sacramento, California, United States
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Improved Protoporphyrin IX-Guided Neurosurgical Tumor Detection with Frequency-Domain Fluorescence Lifetime Imaging. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12031002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Precise intraoperative brain tumor visualization supports surgeons in achieving maximal safe resection. In this sense, improved prognosis in patients with high-grade gliomas undergoing protoporphyrin IX fluorescence-guided surgery has been demonstrated. Phase fluorescence lifetime imaging in the frequency-domain has shown promise to distinguish weak protoporphyrin IX fluorescence from competing endogenous tissue fluorophores, thus allowing for brain tumor detection with high sensitivity. In this work, we show that this technique can be further improved by minimizing the crosstalk of autofluorescence signal contributions when only detecting the fluorescence emission above 615 nm. Combining fluorescence lifetime and spectroscopic measurements on a set of 130 ex vivo brain tumor specimens (14 low- and 56 high-grade gliomas, 39 meningiomas and 21 metastases) coherently substantiated the resulting increase of the fluorescence lifetime with respect to the detection band employed in previous work. This is of major interest for obtaining a clear-cut distinction from the autofluorescence background of the physiological brain. In particular, the median fluorescence lifetime of low- and high-grade glioma specimens lacking visual fluorescence during surgical resection was increased from 4.7 ns to 5.4 ns and 2.9 ns to 3.3 ns, respectively. While more data are needed to create statistical evidence, the coherence of what was observed throughout all tumor groups emphasized that this optimization should be taken into account for future studies.
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