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Fu C, Wang D, Wang L, Zhu L, Li Z, Chen T, Feng H, Li F. Diffuse optical detection of global cerebral ischemia in an adult porcine model. JOURNAL OF BIOPHOTONICS 2023; 16:e202200168. [PMID: 36397661 DOI: 10.1002/jbio.202200168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2022] [Revised: 11/13/2022] [Accepted: 11/14/2022] [Indexed: 06/16/2023]
Abstract
Rapid screening for ischemic strokes in prehospital settings may improve patient outcomes by allowing early deployment of vascular recanalization therapies. However, there are no low-cost and convenient methods that can assess ischemic strokes in such a setting. Diffuse correlation spectroscopy (DCS) is a promising method for continuous, noninvasive transcranial monitoring of cerebral blood flow. In this study, we used a DCS system to detect cerebral hemodynamics before and after acute ischemic stroke in pigs. Seven adult porcines were chosen to establish ischemic stroke models via bilateral common carotid artery ligation (n = 5) or air emboli (n = 2). The results showed a significant difference in blood flow index (BFI) between the normal and ischemic groups. Relative blood flow index (rBFI) exhibited excellent results. Therefore, the diffuse optical method can assess the hemodynamic changes in acute cerebral ischemic stroke onset in pigs, and rBFI may be a promising biomarker for identifying cerebral ischemic stroke.
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Affiliation(s)
- Chuhua Fu
- Department of Neurosurgery of Southwest Hospital, Army Medical University, Chong Qing, People's Republic of China
- Department of Neurosurgery, Xiangyang No.1 People's Hospital, Hubei University of Medicine, Xiangyang, People's Republic of China
| | - Detian Wang
- Department of Neurosurgery of Southwest Hospital, Army Medical University, Chong Qing, People's Republic of China
- Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan, People's Republic of China
| | - Long Wang
- Department of Neurosurgery of Southwest Hospital, Army Medical University, Chong Qing, People's Republic of China
| | - Liguo Zhu
- Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan, People's Republic of China
| | - Zeren Li
- Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan, People's Republic of China
| | - Tunan Chen
- Department of Neurosurgery of Southwest Hospital, Army Medical University, Chong Qing, People's Republic of China
| | - Hua Feng
- Department of Neurosurgery of Southwest Hospital, Army Medical University, Chong Qing, People's Republic of China
| | - Fei Li
- Department of Neurosurgery of Southwest Hospital, Army Medical University, Chong Qing, People's Republic of China
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2
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Refaat A, Yap ML, Pietersz G, Walsh APG, Zeller J, Del Rosal B, Wang X, Peter K. In vivo fluorescence imaging: success in preclinical imaging paves the way for clinical applications. J Nanobiotechnology 2022; 20:450. [PMID: 36243718 PMCID: PMC9571426 DOI: 10.1186/s12951-022-01648-7] [Citation(s) in RCA: 53] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2022] [Accepted: 09/23/2022] [Indexed: 11/10/2022] Open
Abstract
Advances in diagnostic imaging have provided unprecedented opportunities to detect diseases at early stages and with high reliability. Diagnostic imaging is also crucial to monitoring the progress or remission of disease and thus is often the central basis of therapeutic decision-making. Currently, several diagnostic imaging modalities (computed tomography, magnetic resonance imaging, and positron emission tomography, among others) are routinely used in clinics and present their own advantages and limitations. In vivo near-infrared (NIR) fluorescence imaging has recently emerged as an attractive imaging modality combining low cost, high sensitivity, and relative safety. As a preclinical tool, it can be used to investigate disease mechanisms and for testing novel diagnostics and therapeutics prior to their clinical use. However, the limited depth of tissue penetration is a major challenge to efficient clinical use. Therefore, the current clinical use of fluorescence imaging is limited to a few applications such as image-guided surgery on tumors and retinal angiography, using FDA-approved dyes. Progress in fluorophore development and NIR imaging technologies holds promise to extend their clinical application to oncology, cardiovascular diseases, plastic surgery, and brain imaging, among others. Nanotechnology is expected to revolutionize diagnostic in vivo fluorescence imaging through targeted delivery of NIR fluorescent probes using antibody conjugation. In this review, we discuss the latest advances in in vivo fluorescence imaging technologies, NIR fluorescent probes, and current and future clinical applications.
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Affiliation(s)
- Ahmed Refaat
- Atherothrombosis and Vascular Biology Laboratory, Baker Heart and Diabetes Institute, Melbourne, VIC, Australia.,Molecular Imaging and Theranostics Laboratory, Baker Heart and Diabetes Institute, Melbourne, VIC, Australia.,Department of Engineering Technologies, Swinburne University of Technology, Melbourne, VIC, Australia.,Pharmaceutics Department, Faculty of Pharmacy, Alexandria University, Alexandria, Egypt
| | - May Lin Yap
- Atherothrombosis and Vascular Biology Laboratory, Baker Heart and Diabetes Institute, Melbourne, VIC, Australia
| | - Geoffrey Pietersz
- Atherothrombosis and Vascular Biology Laboratory, Baker Heart and Diabetes Institute, Melbourne, VIC, Australia.,Burnet Institute, Melbourne, VIC, Australia.,Department of Cardiometabolic Health, University of Melbourne, Melbourne, VIC, Australia
| | - Aidan Patrick Garing Walsh
- Atherothrombosis and Vascular Biology Laboratory, Baker Heart and Diabetes Institute, Melbourne, VIC, Australia.,Molecular Imaging and Theranostics Laboratory, Baker Heart and Diabetes Institute, Melbourne, VIC, Australia.,Department of Medicine, Monash University, Melbourne, VIC, Australia
| | - Johannes Zeller
- Atherothrombosis and Vascular Biology Laboratory, Baker Heart and Diabetes Institute, Melbourne, VIC, Australia.,Department of Plastic and Hand Surgery, University of Freiburg Medical Center, Freiburg, Germany
| | | | - Xiaowei Wang
- Atherothrombosis and Vascular Biology Laboratory, Baker Heart and Diabetes Institute, Melbourne, VIC, Australia. .,Molecular Imaging and Theranostics Laboratory, Baker Heart and Diabetes Institute, Melbourne, VIC, Australia. .,Department of Cardiometabolic Health, University of Melbourne, Melbourne, VIC, Australia. .,Department of Medicine, Monash University, Melbourne, VIC, Australia. .,Baker Department of Cardiovascular Research, Translation and Implementation, La Trobe University, Melbourne, VIC, Australia.
| | - Karlheinz Peter
- Atherothrombosis and Vascular Biology Laboratory, Baker Heart and Diabetes Institute, Melbourne, VIC, Australia. .,Department of Cardiometabolic Health, University of Melbourne, Melbourne, VIC, Australia. .,Department of Medicine, Monash University, Melbourne, VIC, Australia. .,Baker Department of Cardiovascular Research, Translation and Implementation, La Trobe University, Melbourne, VIC, Australia.
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3
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Forcione M, Yakoub KM, Chiarelli AM, Perpetuini D, Merla A, Sun R, Sawosz P, Belli A, Davies DJ. Dynamic contrast-enhanced near-infrared spectroscopy using indocyanine green on moderate and severe traumatic brain injury: a prospective observational study. Quant Imaging Med Surg 2020; 10:2085-2097. [PMID: 33139989 PMCID: PMC7547258 DOI: 10.21037/qims-20-742] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 07/08/2020] [Indexed: 12/11/2022]
Abstract
BACKGROUND The care given to moderate and severe traumatic brain injury (TBI) patients may be hampered by the inability to tailor their treatments according to their neurological status. Contrast-enhanced near-infrared spectroscopy (NIRS) with indocyanine green (ICG) could be a suitable neuromonitoring tool. METHODS Monitoring the effective attenuation coefficients (EAC), we compared the ICG kinetics between five TBI and five extracranial trauma patients, following a venous-injection of 5 mL of 1 mg/mL ICG, using two commercially available NIRS devices. RESULTS A significantly slower passage of the dye through the brain of the TBI group was observed in two parameters related to the first ICG inflow into the brain (P=0.04; P=0.01). This is likely related to the reduction of cerebral perfusion following TBI. Significant changes in ICG optical properties minutes after injection (P=0.04) were registered. The acquisition of valid optical data in a clinical environment was challenging. CONCLUSIONS Future research should analyze abnormalities in the ICG kinetic following brain trauma, test how these values can enhance care in TBI, and adapt the current optical devices to clinical settings. Also, studies on the pattern in changes of ICG optical properties after venous injection can improve the accuracy of the values detected.
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Affiliation(s)
- Mario Forcione
- University Hospitals Birmingham NHS Foundation Trust, National Institute for Health Research Surgical Reconstruction and Microbiology Research Centre (NIHR-SRMRC), Mindelsohn Way, Birmingham, UK
- University of Birmingham, Neuroscience & Ophthalmology Research Group, Institute of Inflammation & Ageing, College of Medical and Dental Sciences, Edgbaston, Birmingham, UK
| | - Kamal Makram Yakoub
- University Hospitals Birmingham NHS Foundation Trust, National Institute for Health Research Surgical Reconstruction and Microbiology Research Centre (NIHR-SRMRC), Mindelsohn Way, Birmingham, UK
| | - Antonio Maria Chiarelli
- University G. D’Annunzio of Chieti-Pescara, Institute for Advanced Biomedical Technologies, Department of Neuroscience, Imaging and Clinical Sciences, Chieti, Italy
| | - David Perpetuini
- University G. D’Annunzio of Chieti-Pescara, Institute for Advanced Biomedical Technologies, Department of Neuroscience, Imaging and Clinical Sciences, Chieti, Italy
| | - Arcangelo Merla
- University G. D’Annunzio of Chieti-Pescara, Institute for Advanced Biomedical Technologies, Department of Neuroscience, Imaging and Clinical Sciences, Chieti, Italy
| | - Rosa Sun
- University Hospitals Birmingham NHS Foundation Trust, National Institute for Health Research Surgical Reconstruction and Microbiology Research Centre (NIHR-SRMRC), Mindelsohn Way, Birmingham, UK
| | - Piotr Sawosz
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Trojdena 4, Warsaw, Poland
| | - Antonio Belli
- University Hospitals Birmingham NHS Foundation Trust, National Institute for Health Research Surgical Reconstruction and Microbiology Research Centre (NIHR-SRMRC), Mindelsohn Way, Birmingham, UK
- University of Birmingham, Neuroscience & Ophthalmology Research Group, Institute of Inflammation & Ageing, College of Medical and Dental Sciences, Edgbaston, Birmingham, UK
| | - David James Davies
- University Hospitals Birmingham NHS Foundation Trust, National Institute for Health Research Surgical Reconstruction and Microbiology Research Centre (NIHR-SRMRC), Mindelsohn Way, Birmingham, UK
- University of Birmingham, Neuroscience & Ophthalmology Research Group, Institute of Inflammation & Ageing, College of Medical and Dental Sciences, Edgbaston, Birmingham, UK
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4
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Forcione M, Chiarelli AM, Davies DJ, Perpetuini D, Sawosz P, Merla A, Belli A. Cerebral perfusion and blood-brain barrier assessment in brain trauma using contrast-enhanced near-infrared spectroscopy with indocyanine green: A review. J Cereb Blood Flow Metab 2020; 40:1586-1598. [PMID: 32345103 PMCID: PMC7370372 DOI: 10.1177/0271678x20921973] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Contrast-enhanced near-infrared spectroscopy (NIRS) with indocyanine green (ICG) can be a valid non-invasive, continuous, bedside neuromonitoring tool. However, its usage in moderate and severe traumatic brain injury (TBI) patients can be unprecise due to their clinical status. This review is targeted at researchers and clinicians involved in the development and application of contrast-enhanced NIRS for the care of TBI patients and can be used to design future studies. This review describes the methods developed to monitor the brain perfusion and the blood-brain barrier integrity using the changes of diffuse reflectance during the ICG passage and the results on studies in animals and humans. The limitations in accuracy of these methods when applied on TBI patients and the proposed solutions to overcome them are discussed. Finally, the analysis of relative parameters is proposed as a valid alternative over absolute values to address some current clinical needs in brain trauma care. In conclusion, care should be taken in the translation of the optical signal into absolute physiological parameters of TBI patients, as their clinical status must be taken into consideration. Discussion on where and how future studies should be directed to effectively incorporate contrast-enhanced NIRS into brain trauma care is given.
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Affiliation(s)
- Mario Forcione
- National Institute for Health Research Surgical Reconstruction and Microbiology Research Centre (NIHR-SRMRC), University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK.,Neuroscience & Ophthalmology Research Group, Institute of Inflammation & Ageing, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Antonio M Chiarelli
- Department of Neuroscience Imaging and Clinical Science, Institute for Advanced Biomedical Technologies, University G. D'Annunzio of Chieti-Pescara, Chieti, Italy
| | - David J Davies
- National Institute for Health Research Surgical Reconstruction and Microbiology Research Centre (NIHR-SRMRC), University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK.,Neuroscience & Ophthalmology Research Group, Institute of Inflammation & Ageing, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - David Perpetuini
- Department of Neuroscience Imaging and Clinical Science, Institute for Advanced Biomedical Technologies, University G. D'Annunzio of Chieti-Pescara, Chieti, Italy
| | - Piotr Sawosz
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland
| | - Arcangelo Merla
- Department of Neuroscience Imaging and Clinical Science, Institute for Advanced Biomedical Technologies, University G. D'Annunzio of Chieti-Pescara, Chieti, Italy
| | - Antonio Belli
- National Institute for Health Research Surgical Reconstruction and Microbiology Research Centre (NIHR-SRMRC), University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK.,Neuroscience & Ophthalmology Research Group, Institute of Inflammation & Ageing, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
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5
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Wabnitz H, Contini D, Spinelli L, Torricelli A, Liebert A. Depth-selective data analysis for time-domain fNIRS: moments vs. time windows. BIOMEDICAL OPTICS EXPRESS 2020; 11:4224-4243. [PMID: 32923038 PMCID: PMC7449728 DOI: 10.1364/boe.396585] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 06/20/2020] [Accepted: 06/22/2020] [Indexed: 05/10/2023]
Abstract
Time-domain measurements facilitate the elimination of the influence of extracerebral, systemic effects, a key problem in functional near-infrared spectroscopy (fNIRS) of the adult human brain. The analysis of measured time-of-flight distributions of photons often relies on moments or time windows. However, a systematic and quantitative characterization of the performance of these measurands is still lacking. Based on perturbation simulations for small localized absorption changes, we compared spatial sensitivity profiles and depth selectivity for moments (integral, mean time of flight and variance), photon counts in time windows and their ratios for different time windows. The influence of the instrument response function (IRF) was investigated for all measurands and for various source-detector separations. Variance exhibits the highest depth selectivity among the moments. Ratios of photon counts in different late time windows can achieve even higher selectivity. An advantage of moments is their robustness against the shape of the IRF and instrumental drifts.
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Affiliation(s)
- Heidrun Wabnitz
- Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin, Germany
| | - Davide Contini
- Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milan, Italy
| | - Lorenzo Spinelli
- Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Piazza Leonardo da Vinci 32, 20133 Milan, Italy
| | - Alessandro Torricelli
- Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milan, Italy
- Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Piazza Leonardo da Vinci 32, 20133 Milan, Italy
| | - Adam Liebert
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Trojdena 4, 02-109 Warsaw, Poland
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6
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Milej D, He L, Abdalmalak A, Baker WB, Anazodo UC, Diop M, Dolui S, Kavuri VC, Pavlosky W, Wang L, Balu R, Detre JA, Amendolia O, Quattrone F, Kofke WA, Yodh AG, St Lawrence K. Quantification of cerebral blood flow in adults by contrast-enhanced near-infrared spectroscopy: Validation against MRI. J Cereb Blood Flow Metab 2020; 40:1672-1684. [PMID: 31500522 PMCID: PMC7370369 DOI: 10.1177/0271678x19872564] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2019] [Accepted: 07/29/2019] [Indexed: 12/11/2022]
Abstract
The purpose of this study was to assess the accuracy of absolute cerebral blood flow (CBF) measurements obtained by dynamic contrast-enhanced (DCE) near-infrared spectroscopy (NIRS) using indocyanine green as a perfusion contrast agent. For validation, CBF was measured independently using the MRI perfusion method arterial spin labeling (ASL). Data were acquired at two sites and under two flow conditions (normocapnia and hypercapnia). Depth sensitivity was enhanced using time-resolved detection, which was demonstrated in a separate set of experiments using a tourniquet to temporally impede scalp blood flow. A strong correlation between CBF measurements from ASL and DCE-NIRS was observed (slope = 0.99 ± 0.08, y-intercept = -1.7 ± 7.4 mL/100 g/min, and R2 = 0.88). Mean difference between the two techniques was 1.9 mL/100 g/min (95% confidence interval ranged from -15 to 19 mL/100g/min and the mean ASL CBF was 75.4 mL/100 g/min). Error analysis showed that structural information and baseline absorption coefficient were needed for optimal CBF reconstruction with DCE-NIRS. This study demonstrated that DCE-NIRS is sensitive to blood flow in the adult brain and can provide accurate CBF measurements with the appropriate modeling techniques.
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Affiliation(s)
- Daniel Milej
- Department of Medical Biophysics, Western University, London, ON, Canada
- Imaging Division, Lawson Health Research Institute, London, ON, Canada
| | - Lian He
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA, USA
| | - Androu Abdalmalak
- Department of Medical Biophysics, Western University, London, ON, Canada
- Imaging Division, Lawson Health Research Institute, London, ON, Canada
| | - Wesley B Baker
- Department of Anesthesiology and Critical Care, University of Pennsylvania, Philadelphia, PA, USA
| | - Udunna C Anazodo
- Department of Medical Biophysics, Western University, London, ON, Canada
- Imaging Division, Lawson Health Research Institute, London, ON, Canada
| | - Mamadou Diop
- Department of Medical Biophysics, Western University, London, ON, Canada
- Imaging Division, Lawson Health Research Institute, London, ON, Canada
| | - Sudipto Dolui
- Department of Neurology, University of Pennsylvania, Philadelphia, PA, USA
| | - Venkaiah C Kavuri
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA, USA
| | - William Pavlosky
- Imaging Division, Lawson Health Research Institute, London, ON, Canada
| | - Lin Wang
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA, USA
| | - Ramani Balu
- Department of Neurology, University of Pennsylvania, Philadelphia, PA, USA
| | - John A Detre
- Department of Neurology, University of Pennsylvania, Philadelphia, PA, USA
| | - Olivia Amendolia
- Department of Neurosurgery, University of Pennsylvania, Philadelphia, PA, USA
| | - Francis Quattrone
- Department of Neurosurgery, University of Pennsylvania, Philadelphia, PA, USA
| | - W Andrew Kofke
- Department of Anesthesiology and Critical Care, University of Pennsylvania, Philadelphia, PA, USA
- Department of Neurosurgery, University of Pennsylvania, Philadelphia, PA, USA
| | - Arjun G Yodh
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA, USA
| | - Keith St Lawrence
- Department of Medical Biophysics, Western University, London, ON, Canada
- Imaging Division, Lawson Health Research Institute, London, ON, Canada
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7
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Novi SL, Roberts E, Spagnuolo D, Spilsbury BM, Price DC, Imbalzano CA, Forero E, Yodh AG, Tellis GM, Tellis CM, Mesquita RC. Functional near-infrared spectroscopy for speech protocols: characterization of motion artifacts and guidelines for improving data analysis. NEUROPHOTONICS 2020; 7:015001. [PMID: 31956662 PMCID: PMC6953699 DOI: 10.1117/1.nph.7.1.015001] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Accepted: 12/19/2019] [Indexed: 05/02/2023]
Abstract
Monitoring speech tasks with functional near-infrared spectroscopy (fNIRS) enables investigation of speech production mechanisms and informs treatment strategies for speech-related disorders such as stuttering. Unfortunately, due to movement of the temporalis muscle, speech production can induce relative movement between probe optodes and skin. These movements generate motion artifacts during speech tasks. In practice, spurious hemodynamic responses in functional activation signals arise from lack of information about the consequences of speech-related motion artifacts, as well as from lack of standardized processing procedures for fNIRS signals during speech tasks. To this end, we characterize the effects of speech production on fNIRS signals, and we introduce a systematic analysis to ameliorate motion artifacts. The study measured 50 healthy subjects performing jaw movement (JM) tasks and found that JM produces two different patterns of motion artifacts in fNIRS. To remove these unwanted contributions, we validate a hybrid motion-correction algorithm based sequentially on spline interpolation and then wavelet filtering. We compared performance of the hybrid algorithm with standard algorithms based on spline interpolation only and wavelet decomposition only. The hybrid algorithm corrected 94% of the artifacts produced by JM, and it did not lead to spurious responses in the data. We also validated the hybrid algorithm during a reading task performed under two different conditions: reading aloud and reading silently. For both conditions, we observed significant cortical activation in brain regions related to reading. Moreover, when comparing the two conditions, good agreement of spatial and temporal activation patterns was found only when data were analyzed using the hybrid approach. Overall, the study demonstrates a standardized processing scheme for fNIRS data during speech protocols. The scheme decreases spurious responses and intersubject variability due to motion artifacts.
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Affiliation(s)
- Sergio L. Novi
- University of Campinas, Institute of Physics, Campinas, São Paulo, Brazil
- Brazilian Institute of Neuroscience and Neurotechnology, Campinas, São Paulo, Brazil
| | - Erin Roberts
- Misericordia University, Department of Speech-Language Pathology, Dallas, Pennsylvania, United States
| | - Danielle Spagnuolo
- Misericordia University, Department of Speech-Language Pathology, Dallas, Pennsylvania, United States
| | - Brianna M. Spilsbury
- Misericordia University, Department of Speech-Language Pathology, Dallas, Pennsylvania, United States
| | - D’manda C. Price
- Misericordia University, Department of Speech-Language Pathology, Dallas, Pennsylvania, United States
| | - Cara A. Imbalzano
- Misericordia University, Department of Speech-Language Pathology, Dallas, Pennsylvania, United States
| | - Edwin Forero
- University of Campinas, Institute of Physics, Campinas, São Paulo, Brazil
- Brazilian Institute of Neuroscience and Neurotechnology, Campinas, São Paulo, Brazil
| | - Arjun G. Yodh
- University of Pennsylvania, Department of Physics and Astronomy, Philadelphia, Pennsylvania, United States
| | - Glen M. Tellis
- Misericordia University, Department of Speech-Language Pathology, Dallas, Pennsylvania, United States
| | - Cari M. Tellis
- Misericordia University, Department of Speech-Language Pathology, Dallas, Pennsylvania, United States
| | - Rickson C. Mesquita
- University of Campinas, Institute of Physics, Campinas, São Paulo, Brazil
- Brazilian Institute of Neuroscience and Neurotechnology, Campinas, São Paulo, Brazil
- Address all correspondence to: Rickson C. Mesquita, E-mail:
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8
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Grosenick D, Wabnitz H, Macdonald R. Diffuse near-infrared imaging of tissue with picosecond time resolution. ACTA ACUST UNITED AC 2019; 63:511-518. [PMID: 29494335 DOI: 10.1515/bmt-2017-0067] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 12/04/2017] [Indexed: 02/02/2023]
Abstract
Optical imaging of biological tissue in vivo at multiple wavelengths in the near-infrared (NIR) spectral range can be achieved with picosecond time resolution at high sensitivity by time-correlated single photon counting. Measuring and analyzing the distribution of times of flight of photons randomly propagated through the tissue has been applied for diffuse optical imaging and spectroscopy, e.g. of human breast tissue and of the brain. In this article, we review the main features and the potential of NIR multispectral imaging with picosecond time resolution and illustrate them by exemplar applications in these fields. In particular, we discuss the experimental methods developed at the Physikalisch-Technische Bundesanstalt (PTB) to record optical mammograms and to quantify the absorption and scattering properties from which hemoglobin concentration and oxygen saturation of healthy and diseased breast tissue have been derived by combining picosecond time-domain and spectral information. Furthermore, optical images of functional brain activation were obtained by a non-contact scanning device exploiting the null source-detector separation approach which takes advantage of the picosecond time resolution as well. The recorded time traces of changes in the oxy- and deoxyhemoglobin concentrations during a motor stimulation investigation show a localized response from the brain.
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Affiliation(s)
- Dirk Grosenick
- Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin, Germany, Phone: +49 30 3481-7302, Fax: +49 30 3481-7505
| | - Heidrun Wabnitz
- Physikalisch-Technische Bundesanstalt (PTB), 10587 Berlin, Germany
| | - Rainer Macdonald
- Physikalisch-Technische Bundesanstalt (PTB), 10587 Berlin, Germany
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9
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Kacprzak M, Sawosz P, Weigl W, Milej D, Gerega A, Liebert A. Frequency analysis of oscillations in cerebral hemodynamics measured by time domain near infrared spectroscopy. BIOMEDICAL OPTICS EXPRESS 2019; 10:761-771. [PMID: 30800513 PMCID: PMC6377883 DOI: 10.1364/boe.10.000761] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 12/23/2018] [Accepted: 12/23/2018] [Indexed: 05/21/2023]
Abstract
In this paper, we propose the application of time-domain near-infrared spectroscopy to the assessment of oscillations in cerebral hemodynamics. These oscillations were observed in the statistical moments of the distributions of time of flight of photons (DTOFs) measured on the head. We analyzed the zeroth and second centralized moments of DTOFs (total number of photons and variance) to obtain their spectra to provide parameters for the frequency components of microcirculation, which differ between the extracerebral and intracerebral layers of the head. Analysis of these moments revealed statistically significant differences between a control group of healthy subjects and a group of patients with severe neurovascular disorders, which is a promising result for the assessment of cerebral microcirculation and cerebral autoregulation mechanisms.
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Affiliation(s)
- Michal Kacprzak
- Nalecz Institute of Biocybernetics and Biomedical Engineering Polish Academy of Sciences Trojdena 4, 02-109 Warsaw, Poland
| | - Piotr Sawosz
- Nalecz Institute of Biocybernetics and Biomedical Engineering Polish Academy of Sciences Trojdena 4, 02-109 Warsaw, Poland
| | - Wojciech Weigl
- Anesthesiology and Intensive Care, Department of Surgical Sciences, Uppsala University, Akademiska Hospital, 751 85 Uppsala, Sweden
| | - Daniel Milej
- Nalecz Institute of Biocybernetics and Biomedical Engineering Polish Academy of Sciences Trojdena 4, 02-109 Warsaw, Poland
- Department of Medical Biophysics, Western University, London, Ontario N6A 5C1, Canada
- Imaging Division, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
| | - Anna Gerega
- Nalecz Institute of Biocybernetics and Biomedical Engineering Polish Academy of Sciences Trojdena 4, 02-109 Warsaw, Poland
| | - Adam Liebert
- Nalecz Institute of Biocybernetics and Biomedical Engineering Polish Academy of Sciences Trojdena 4, 02-109 Warsaw, Poland
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10
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He L, Baker WB, Milej D, Kavuri VC, Mesquita RC, Busch DR, Abramson K, Jiang JY, Diop M, St. Lawrence K, Amendolia O, Quattrone F, Balu R, Kofke WA, Yodh AG. Noninvasive continuous optical monitoring of absolute cerebral blood flow in critically ill adults. NEUROPHOTONICS 2018; 5:045006. [PMID: 30480039 PMCID: PMC6251207 DOI: 10.1117/1.nph.5.4.045006] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2018] [Accepted: 10/29/2018] [Indexed: 05/18/2023]
Abstract
We investigate a scheme for noninvasive continuous monitoring of absolute cerebral blood flow (CBF) in adult human patients based on a combination of time-resolved dynamic contrast-enhanced near-infrared spectroscopy (DCE-NIRS) and diffuse correlation spectroscopy (DCS) with semi-infinite head model of photon propogation. Continuous CBF is obtained via calibration of the DCS blood flow index (BFI) with absolute CBF obtained by intermittent intravenous injections of the optical contrast agent indocyanine green. A calibration coefficient ( γ ) for the CBF is thus determined, permitting conversion of DCS BFI to absolute blood flow units at all other times. A study of patients with acute brain injury ( N = 7 ) is carried out to ascertain the stability of γ . The patient-averaged DCS calibration coefficient across multiple monitoring days and multiple patients was determined, and good agreement between the two calibration coefficients measured at different times during single monitoring days was found. The patient-averaged calibration coefficient of 1.24 × 10 9 ( mL / 100 g / min ) / ( cm 2 / s ) was applied to previously measured DCS BFI from similar brain-injured patients; in this case, absolute CBF was underestimated compared with XeCT, an effect we show is primarily due to use of semi-infinite homogeneous models of the head.
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Affiliation(s)
- Lian He
- University of Pennsylvania, Department of Physics and Astronomy, Philadelphia, Pennsylvania, United States
- Address all correspondence to: Lian He, E-mail:
| | - Wesley B. Baker
- University of Pennsylvania, Department of Physics and Astronomy, Philadelphia, Pennsylvania, United States
- University of Pennsylvania, Department of Anesthesiology and Critical Care, Perelman School of Medicine, Philadelphia, Pennsylvania, United States
| | - Daniel Milej
- Western University, Department of Medical Biophysics, London, Ontario, Canada
- Lawson Health Research Institute, Imaging Division, London, Ontario, Canada
| | - Venkaiah C. Kavuri
- University of Pennsylvania, Department of Physics and Astronomy, Philadelphia, Pennsylvania, United States
| | | | - David R. Busch
- University of Texas Southwestern, Department of Neurology and Neurotherapeutics, Dallas, Texas, United States
- University of Texas Southwestern, Department of Anesthesiology and Pain Management, Dallas, Texas, United States
| | - Kenneth Abramson
- University of Pennsylvania, Department of Physics and Astronomy, Philadelphia, Pennsylvania, United States
| | - Jane Y. Jiang
- University of Pennsylvania, Department of Physics and Astronomy, Philadelphia, Pennsylvania, United States
| | - Mamadou Diop
- Western University, Department of Medical Biophysics, London, Ontario, Canada
- Lawson Health Research Institute, Imaging Division, London, Ontario, Canada
| | - Keith St. Lawrence
- Western University, Department of Medical Biophysics, London, Ontario, Canada
- Lawson Health Research Institute, Imaging Division, London, Ontario, Canada
| | - Olivia Amendolia
- University of Pennsylvania, Department of Neurosurgery, Perelman School of Medicine, Philadelphia, Pennsylvania, United States
| | - Francis Quattrone
- University of Pennsylvania, Department of Neurosurgery, Perelman School of Medicine, Philadelphia, Pennsylvania, United States
| | - Ramani Balu
- University of Pennsylvania, Department of Neurosurgery, Perelman School of Medicine, Philadelphia, Pennsylvania, United States
- University of Pennsylvania, Department of Neurology, Perelman School of Medicine, Philadelphia, Pennsylvania, United States
| | - W. Andrew Kofke
- University of Pennsylvania, Department of Anesthesiology and Critical Care, Perelman School of Medicine, Philadelphia, Pennsylvania, United States
- University of Pennsylvania, Department of Neurosurgery, Perelman School of Medicine, Philadelphia, Pennsylvania, United States
| | - Arjun G. Yodh
- University of Pennsylvania, Department of Physics and Astronomy, Philadelphia, Pennsylvania, United States
- University of Pennsylvania, Department of Anesthesiology and Critical Care, Perelman School of Medicine, Philadelphia, Pennsylvania, United States
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11
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Gerega A, Milej D, Weigl W, Kacprzak M, Liebert A. Multiwavelength time-resolved near-infrared spectroscopy of the adult head: assessment of intracerebral and extracerebral absorption changes. BIOMEDICAL OPTICS EXPRESS 2018; 9:2974-2993. [PMID: 29984079 PMCID: PMC6033559 DOI: 10.1364/boe.9.002974] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Revised: 04/27/2018] [Accepted: 05/17/2018] [Indexed: 05/23/2023]
Abstract
An optical technique based on diffuse reflectance measurement combined with indocyanine green (ICG) bolus tracking is extensively tested as a method for the clinical assessment of brain perfusion at the bedside. We report on multiwavelength time-resolved diffuse reflectance spectroscopy measurements carried out on the head of a healthy adult during the intravenous administration of a bolus of ICG. Intracerebral and extracerebral changes in absorption were estimated from an analysis of changes in statistical moments (total number of photons, mean time of flight and variance) of the distributions of times of flight (DTOF) of photons recorded simultaneously at 16 wavelengths from the range of 650-850 nm using sensitivity factors estimated by diffusion approximation based on a layered model of the studied medium. We validated the proposed method in a series of phantom experiments and in-vivo measurements. The results obtained show that changes in the concentration of the ICG can be assessed as a function of time of the experiment and depth in the tissue. Thus, the separation of changes in ICG concentration appearing in intra- and extracerebral tissues can be estimated from optical data acquired at a single source-detector pair of fibers/fiber bundles positioned on the surface of the head.
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Affiliation(s)
- Anna Gerega
- Nalecz Institute of Biocybernetics and Biomedical Engineering Polish Academy of Sciences Trojdena 4, 02-109 Warsaw, Poland
| | - Daniel Milej
- Nalecz Institute of Biocybernetics and Biomedical Engineering Polish Academy of Sciences Trojdena 4, 02-109 Warsaw, Poland
- Department of Medical Biophysics, Western University, London, Ontario N6A 5C1, Canada
- Imaging Division, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
| | - Wojciech Weigl
- Anesthesiology and Intensive Care, Department of Surgical Sciences, Uppsala University, Akademiska Hospital, 751 85 Uppsala, Sweden
| | - Michal Kacprzak
- Nalecz Institute of Biocybernetics and Biomedical Engineering Polish Academy of Sciences Trojdena 4, 02-109 Warsaw, Poland
| | - Adam Liebert
- Nalecz Institute of Biocybernetics and Biomedical Engineering Polish Academy of Sciences Trojdena 4, 02-109 Warsaw, Poland
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12
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Confirmation of brain death using optical methods based on tracking of an optical contrast agent: assessment of diagnostic feasibility. Sci Rep 2018; 8:7332. [PMID: 29743483 PMCID: PMC5943525 DOI: 10.1038/s41598-018-25351-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 04/09/2018] [Indexed: 11/20/2022] Open
Abstract
We aimed to determine whether optical methods based on bolus tracking of an optical contrast agent are useful for the confirmation of cerebral circulation cessation in patients being evaluated for brain death. Different stages of cerebral perfusion disturbance were compared in three groups of subjects: controls, patients with posttraumatic cerebral edema, and patients with brain death. We used a time-resolved near-infrared spectroscopy setup and indocyanine green (ICG) as an intravascular flow tracer. Orthogonal partial least squares-discriminant analysis (OPLS-DA) was carried out to build statistical models allowing for group separation. Thirty of 37 subjects (81.1%) were classified correctly (8 of 9 control subjects, 88.9%; 13 of 15 patients with edema, 86.7%; and 9 of 13 patients with brain death, 69.2%; p < 0.0001). Depending on the combination of variables used in the OPLS-DA model, sensitivity, specificity, and accuracy were 66.7–92.9%, 81.8–92.9%, and 77.3–89.3%, respectively. The method was feasible and promising in the demanding intensive care unit environment. However, its accuracy did not reach the level required for brain death confirmation. The potential usefulness of the method may be improved by increasing the depth of light penetration, confirming its accuracy against other methods evaluating cerebral flow cessation, and developing absolute parameters for cerebral perfusion.
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13
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Saito H, Ishikawa T, Tanabe J, Kobayashi S, Moroi J. Bedside assessment of regional cerebral perfusion using near-infrared spectroscopy and indocyanine green in patients with atherosclerotic occlusive disease. Sci Rep 2018; 8:1242. [PMID: 29352217 PMCID: PMC5775286 DOI: 10.1038/s41598-018-19668-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 01/05/2018] [Indexed: 01/13/2023] Open
Abstract
This pilot study aimed to investigate the utility of near-infrared spectroscopy/indocyanine green (NIRS/ICG) for examining patients with occlusive cerebrovascular disease. Twenty-nine patients with chronic-stage atherosclerotic occlusive cerebrovascular disease were included. The patients were monitored using NIRS at the bedside. Using ICG time-intensity curves, the affected-to-unaffected side ratios were calculated for several parameters, including the maximum ICG concentration (ΔICGmax), time to peak (TTP), rise time (RT), and blood flow index (BFI = ΔICGmax/RT), and were compared to the affected-to-unaffected side ratios of the regional cerebral blood flow (rCBF) and regional oxygen extraction fraction (rOEF) obtained using positron emission tomography with 15O-labeled gas. The BFI ratio showed the best correlation with the rCBF ratio among these parameters (r = 0.618; P = 0.0004), and the RT ratio showed the best correlation with the rOEF ratio (r = 0.593; P = 0.0007). The patients were further divided into reduced rCBF or elevated rOEF groups, and the analysis revealed significant related differences. The present results advance the measurement of ICG kinetics using NIRS as a useful tool for the detection of severely impaired perfusion with reduced rCBF or elevated rOEF. This method may be applicable as a monitoring tool for patients with acute ischemic stroke.
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Affiliation(s)
- Hiroshi Saito
- Department of Surgical Neurology, Research Institute for Brain and Blood Vessels-AKITA, Akita, Japan. .,Department of Neurosurgery, Kameda medical center, Chiba, Japan.
| | - Tatsuya Ishikawa
- Department of Surgical Neurology, Research Institute for Brain and Blood Vessels-AKITA, Akita, Japan
| | - Jun Tanabe
- Department of Surgical Neurology, Research Institute for Brain and Blood Vessels-AKITA, Akita, Japan
| | - Shinya Kobayashi
- Department of Surgical Neurology, Research Institute for Brain and Blood Vessels-AKITA, Akita, Japan
| | - Junta Moroi
- Department of Surgical Neurology, Research Institute for Brain and Blood Vessels-AKITA, Akita, Japan
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14
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Verdecchia K, Diop M, Lee A, Morrison LB, Lee TY, St. Lawrence K. Assessment of a multi-layered diffuse correlation spectroscopy method for monitoring cerebral blood flow in adults. BIOMEDICAL OPTICS EXPRESS 2016; 7:3659-3674. [PMID: 27699127 PMCID: PMC5030039 DOI: 10.1364/boe.7.003659] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 07/22/2016] [Accepted: 07/26/2016] [Indexed: 05/21/2023]
Abstract
Diffuse correlation spectroscopy (DCS) is a promising technique for brain monitoring as it can provide a continuous signal that is directly related to cerebral blood flow (CBF); however, signal contamination from extracerebral tissue can cause flow underestimations. The goal of this study was to investigate whether a multi-layered (ML) model that accounts for light propagation through the different tissue layers could successfully separate scalp and brain flow when applied to DCS data acquired at multiple source-detector distances. The method was first validated with phantom experiments. Next, experiments were conducted in a pig model of the adult head with a mean extracerebral tissue thickness of 9.8 ± 0.4 mm. Reductions in CBF were measured by ML DCS and computed tomography perfusion for validation; excellent agreement was observed by a mean difference of 1.2 ± 4.6% (CI95%: -31.1 and 28.6) between the two modalities, which was not significantly different.
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Affiliation(s)
- Kyle Verdecchia
- Imaging Program, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
- Department of Medical Biophysics, University of Western Ontario, London, Ontario N6A 3K7, Canada
| | - Mamadou Diop
- Imaging Program, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
- Department of Medical Biophysics, University of Western Ontario, London, Ontario N6A 3K7, Canada
| | - Albert Lee
- Department of Medical Biophysics, University of Western Ontario, London, Ontario N6A 3K7, Canada
| | - Laura B. Morrison
- Imaging Program, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
- Department of Medical Biophysics, University of Western Ontario, London, Ontario N6A 3K7, Canada
| | - Ting-Yim Lee
- Imaging Program, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
- Department of Medical Biophysics, University of Western Ontario, London, Ontario N6A 3K7, Canada
- Imaging Research Laboratories, Robarts Research Institute, London, Ontario N6G 2V4, Canada
| | - Keith St. Lawrence
- Imaging Program, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
- Department of Medical Biophysics, University of Western Ontario, London, Ontario N6A 3K7, Canada
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15
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Milej D, Abdalmalak A, Janusek D, Diop M, Liebert A, St Lawrence K. Time-resolved subtraction method for measuring optical properties of turbid media. APPLIED OPTICS 2016; 55:1507-13. [PMID: 26974605 DOI: 10.1364/ao.55.001507] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Near-infrared spectroscopy is a noninvasive optical method used primarily to monitor tissue oxygenation due to the absorption properties of hemoglobin. Accurate estimation of hemoglobin concentrations and other light absorbers requires techniques that can separate the effect of absorption from the much greater effect of light scattering. One of the most advanced methods is time-resolved near-infrared spectroscopy (TR-NIRS), which measures the absorption and scattering coefficients of a turbid medium by modeling the recorded distribution time of flight of photons. A challenge with TR-NIRS is that it requires accurate characterization of the dispersion caused by the system. In this study, we present a method for circumventing this problem by applying statistical moment analysis to two time-of-flight distributions measured at separated source-detector distances. Simulations based on analytical models and Monte Carlo code, and tissue-mimicking phantoms, were used to demonstrate its accuracy for source-detector distances typically used in neuroimaging applications. The simplicity of the approach is well suited to real-time applications requiring accurate quantification of the optical properties of a turbid medium.
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16
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Di Sieno L, Wabnitz H, Pifferi A, Mazurenka M, Hoshi Y, Dalla Mora A, Contini D, Boso G, Becker W, Martelli F, Tosi A, Macdonald R. Characterization of a time-resolved non-contact scanning diffuse optical imaging system exploiting fast-gated single-photon avalanche diode detection. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:035118. [PMID: 27036830 DOI: 10.1063/1.4944562] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Accepted: 03/08/2016] [Indexed: 05/20/2023]
Abstract
We present a system for non-contact time-resolved diffuse reflectance imaging, based on small source-detector distance and high dynamic range measurements utilizing a fast-gated single-photon avalanche diode. The system is suitable for imaging of diffusive media without any contact with the sample and with a spatial resolution of about 1 cm at 1 cm depth. In order to objectively assess its performances, we adopted two standardized protocols developed for time-domain brain imagers. The related tests included the recording of the instrument response function of the setup and the responsivity of its detection system. Moreover, by using liquid turbid phantoms with absorbing inclusions, depth-dependent contrast and contrast-to-noise ratio as well as lateral spatial resolution were measured. To illustrate the potentialities of the novel approach, the characteristics of the non-contact system are discussed and compared to those of a fiber-based brain imager.
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Affiliation(s)
- Laura Di Sieno
- Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo Da Vinci 32, 20133 Milano, Italy
| | - Heidrun Wabnitz
- Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587 Berlin, Germany
| | - Antonio Pifferi
- Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo Da Vinci 32, 20133 Milano, Italy
| | - Mikhail Mazurenka
- Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587 Berlin, Germany
| | - Yoko Hoshi
- Department of Biomedical Optics, Medical Photonics Research Center, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan
| | - Alberto Dalla Mora
- Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo Da Vinci 32, 20133 Milano, Italy
| | - Davide Contini
- Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo Da Vinci 32, 20133 Milano, Italy
| | - Gianluca Boso
- Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, Piazza Leonardo Da Vinci 32, 20133 Milano, Italy
| | - Wolfgang Becker
- Becker and Hickl GmbH, Nahmitzer Damm 30, 12277 Berlin, Germany
| | - Fabrizio Martelli
- Dipartimento di Fisica e Astronomia dell'Università degli Studi di Firenze, Via G. Sansone 1, Sesto Fiorentino, Firenze 50019, Italy
| | - Alberto Tosi
- Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, Piazza Leonardo Da Vinci 32, 20133 Milano, Italy
| | - Rainer Macdonald
- Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587 Berlin, Germany
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17
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Iso N, Moriuchi T, Sagari A, Kitajima E, Iso F, Tanaka K, Kikuchi Y, Tabira T, Higashi T. Monitoring Local Regional Hemodynamic Signal Changes during Motor Execution and Motor Imagery Using Near-Infrared Spectroscopy. Front Physiol 2016; 6:416. [PMID: 26793118 PMCID: PMC4707267 DOI: 10.3389/fphys.2015.00416] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 12/18/2015] [Indexed: 12/04/2022] Open
Abstract
The aim of this study was to clarify the topographical localization of motor-related regional hemodynamic signal changes during motor execution (ME) and motor imagery (MI) by using near-infrared spectroscopy (NIRS), as this technique is more clinically expedient than established methods (e.g., fMRI). Twenty right-handed healthy subjects participated in this study. The experimental protocol was a blocked design consisting of 3 cycles of 20 s of task performance and 30 s of rest. The tapping sequence task was performed with their fingers under 4 conditions: ME and MI with the right or left hand. Hemodynamic brain activity was measured with NIRS to monitor changes in oxygenated hemoglobin (oxy-Hb) concentration. Oxy-Hb in the somatosensory motor cortex (SMC) increased significantly only during contralateral ME and showed a significant interaction between task and hand. There was a main effect of hand in the left SMC. Although there were no significant main effects or interactions in the supplemental motor area (SMA) and premotor area (PMA), oxy-Hb increased substantially under all conditions. These results clarified the topographical localization by motor-related regional hemodynamic signal changes during ME and MI by using NIRS.
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Affiliation(s)
- Naoki Iso
- Unit of Rehabilitation Sciences, Nagasaki University Graduate School of Biomedical SciencesNagasaki, Japan; Medical Corporation Toujinkai Miharadai HospitalNagasaki, Japan
| | - Takefumi Moriuchi
- Unit of Rehabilitation Sciences, Nagasaki University Graduate School of Biomedical SciencesNagasaki, Japan; Medical Corporation Toujinkai Miharadai HospitalNagasaki, Japan
| | - Akira Sagari
- Unit of Rehabilitation Sciences, Nagasaki University Graduate School of Biomedical SciencesNagasaki, Japan; Japanese Red Cross Society Nagasaki Genbaku HospitalNagasaki, Japan
| | - Eiji Kitajima
- Center for Industry, University and Government Cooperation, Nagasaki University Nagasaki, Japan
| | - Fumiko Iso
- Unit of Physical and Occupational Therapy, Nagasaki University Graduate School of Biomedical Sciences Nagasaki, Japan
| | - Koji Tanaka
- Unit of Physical and Occupational Therapy, Nagasaki University Graduate School of Biomedical Sciences Nagasaki, Japan
| | - Yasuki Kikuchi
- Unit of Physical and Occupational Therapy, Nagasaki University Graduate School of Biomedical Sciences Nagasaki, Japan
| | - Takayuki Tabira
- Department of Occupational Therapy, Faculty of Rehabilitation Sciences, Nishikyushu University Saga, Japan
| | - Toshio Higashi
- Unit of Rehabilitation Sciences, Nagasaki University Graduate School of Biomedical Sciences Nagasaki, Japan
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18
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Hametner C, Stanarcevic P, Stampfl S, Rohde S, Veltkamp R, Bösel J. Noninvasive cerebral oximetry during endovascular therapy for acute ischemic stroke: an observational study. J Cereb Blood Flow Metab 2015; 35:1722-8. [PMID: 26243709 PMCID: PMC4635248 DOI: 10.1038/jcbfm.2015.181] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 06/18/2015] [Accepted: 06/22/2015] [Indexed: 01/20/2023]
Abstract
Implementing endovascular stroke care often impedes neurologic assessment in patients who need sedation or general anesthesia. Cerebral near-infrared spectroscopy (NIRS) may help physicians monitor cerebral tissue viability, but data in hyperacute stroke patients receiving endovascular treatment are sparse. In this observational study, the NIRS index regional oxygen saturation (rSO2) was measured noninvasively before, during, and after endovascular therapy via bilateral forehead NIRS optodes. During the study period, 63 patients were monitored with NIRS; 43 qualified for analysis. Before recanalization, 10 distinct rSO2 decreases occurred in 11 patients with respect to time to intubation. During recanalization, two kinds of unilateral rSO2 changes occurred in the affected hemisphere: small peaks throughout the treatment (n=14, 32.6%) and sustained increases immediately after recanalization (n=2, 4.7%). Lower area under the curve 10% below baseline was associated with better reperfusion status (thrombolysis in cerebral infarction ≥ 2b, P=0.009). At the end of the intervention, lower interhemispheric rSO2 difference predicted death within 90 days (P=0.037). After the intervention, higher rSO2 variability predicted poor outcome (modified Rankin scale > 3, P=0.032). Our findings suggest that bi-channel rSO2-NIRS has potential for guiding neuroanesthesia and predicting outcome. To better monitor local revascularization, an improved stroke-specific set-up in future studies is necessary.
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Affiliation(s)
| | - Predrag Stanarcevic
- Neurology Clinic, Clinical Centre of Serbia, University of Belgrade, Belgrade, Serbia
| | - Sibylle Stampfl
- Department of Neuroradiology, University of Heidelberg, Heidelberg, Germany
| | - Stefan Rohde
- Department of Radiology and Neuroradiology, Klinikum Dortmund, Dortmund, Germany
| | - Roland Veltkamp
- Department of Neurology/Stroke, Imperial College, London, UK
| | - Julian Bösel
- Department of Neurology, University of Heidelberg, Heidelberg, Germany
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19
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Milej D, Janusek D, Gerega A, Wojtkiewicz S, Sawosz P, Treszczanowicz J, Weigl W, Liebert A. Optimization of the method for assessment of brain perfusion in humans using contrast-enhanced reflectometry: multidistance time-resolved measurements. JOURNAL OF BIOMEDICAL OPTICS 2015; 20:106013. [PMID: 26509415 DOI: 10.1117/1.jbo.20.10.106013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 10/06/2015] [Indexed: 05/24/2023]
Abstract
The aim of the study was to determine optimal measurement conditions for assessment of brain perfusion with the use of optical contrast agent and time-resolved diffuse reflectometry in the near-infrared wavelength range. The source-detector separation at which the distribution of time of flights (DTOF) of photons provided useful information on the inflow of the contrast agent to the intracerebral brain tissue compartments was determined. Series of Monte Carlo simulations was performed in which the inflow and washout of the dye in extra- and intracerebral tissue compartments was modeled and the DTOFs were obtained at different source-detector separations. Furthermore, tests on diffuse phantoms were carried out using a time-resolved setup allowing the measurement of DTOFs at 16 source-detector separations. Finally, the setup was applied in experiments carried out on the heads of adult volunteers during intravenous injection of indocyanine green. Analysis of statistical moments of the measured DTOFs showed that the source-detector separation of 6 cm is recommended for monitoring of inflow of optical contrast to the intracerebral brain tissue compartments with the use of continuous wave reflectometry, whereas the separation of 4 cm is enough when the higher-order moments of DTOFs are available.
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Affiliation(s)
- Daniel Milej
- Polish Academy of Sciences, Nalecz Institute of Biocybernetics and Biomedical Engineering, 4Ks. Trojdena Street 02-109 Warsaw, Poland
| | - Dariusz Janusek
- Polish Academy of Sciences, Nalecz Institute of Biocybernetics and Biomedical Engineering, 4Ks. Trojdena Street 02-109 Warsaw, Poland
| | - Anna Gerega
- Polish Academy of Sciences, Nalecz Institute of Biocybernetics and Biomedical Engineering, 4Ks. Trojdena Street 02-109 Warsaw, Poland
| | - Stanislaw Wojtkiewicz
- Polish Academy of Sciences, Nalecz Institute of Biocybernetics and Biomedical Engineering, 4Ks. Trojdena Street 02-109 Warsaw, Poland
| | - Piotr Sawosz
- Polish Academy of Sciences, Nalecz Institute of Biocybernetics and Biomedical Engineering, 4Ks. Trojdena Street 02-109 Warsaw, Poland
| | - Joanna Treszczanowicz
- Warsaw Praski Hospital, Department of Intensive Care and Anesthesiology, 67 Al. Solidarnosci Street, 03-401 Warsaw, Poland
| | - Wojciech Weigl
- Warsaw Praski Hospital, Department of Intensive Care and Anesthesiology, 67 Al. Solidarnosci Street, 03-401 Warsaw, PolandcUppsala University, Department of Surgical Sciences/Anesthesiology and Intensive Care, 751 85 Uppsala, Sweden
| | - Adam Liebert
- Polish Academy of Sciences, Nalecz Institute of Biocybernetics and Biomedical Engineering, 4Ks. Trojdena Street 02-109 Warsaw, Poland
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20
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Time-Domain Diffuse Optical Imaging of Tissue by Non-contact Scanning. SPRINGER SERIES IN CHEMICAL PHYSICS 2015. [DOI: 10.1007/978-3-319-14929-5_18] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
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21
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Milej D, Kruczkowski M, Kacprzak M, Sawosz P, Maniewski R, Liebert A. Estimation of light detection efficiency for different light guides used in time-resolved near-infrared spectroscopy. Biocybern Biomed Eng 2015. [DOI: 10.1016/j.bbe.2015.05.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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22
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Wabnitz H, Taubert DR, Mazurenka M, Steinkellner O, Jelzow A, Macdonald R, Milej D, Sawosz P, Kacprzak M, Liebert A, Cooper R, Hebden J, Pifferi A, Farina A, Bargigia I, Contini D, Caffini M, Zucchelli L, Spinelli L, Cubeddu R, Torricelli A. Performance assessment of time-domain optical brain imagers, part 1: basic instrumental performance protocol. JOURNAL OF BIOMEDICAL OPTICS 2014; 19:086010. [PMID: 25121479 DOI: 10.1117/1.jbo.19.8.086010] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Accepted: 07/21/2014] [Indexed: 05/20/2023]
Abstract
Performance assessment of instruments devised for clinical applications is of key importance for validation and quality assurance. Two new protocols were developed and applied to facilitate the design and optimization of instruments for time-domain optical brain imaging within the European project nEUROPt. Here, we present the "Basic Instrumental Performance" protocol for direct measurement of relevant characteristics. Two tests are discussed in detail. First, the responsivity of the detection system is a measure of the overall efficiency to detect light emerging from tissue. For the related test, dedicated solid slab phantoms were developed and quantitatively spectrally characterized to provide sources of known radiance with nearly Lambertian angular characteristics. The responsivity of four time-domain optical brain imagers was found to be of the order of 0.1 m² sr. The relevance of the responsivity measure is demonstrated by simulations of diffuse reflectance as a function of source-detector separation and optical properties. Second, the temporal instrument response function (IRF) is a critically important factor in determining the performance of time-domain systems. Measurements of the IRF for various instruments were combined with simulations to illustrate the impact of the width and shape of the IRF on contrast for a deep absorption change mimicking brain activation.
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Affiliation(s)
- Heidrun Wabnitz
- Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin, Germany
| | | | - Mikhail Mazurenka
- Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin, Germany
| | - Oliver Steinkellner
- Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin, Germany
| | - Alexander Jelzow
- Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin, Germany
| | - Rainer Macdonald
- Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin, Germany
| | - Daniel Milej
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, ul. Trojdena 4, 02-109 Warsaw, Poland
| | - Piotr Sawosz
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, ul. Trojdena 4, 02-109 Warsaw, Poland
| | - Michał Kacprzak
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, ul. Trojdena 4, 02-109 Warsaw, Poland
| | - Adam Liebert
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, ul. Trojdena 4, 02-109 Warsaw, Poland
| | - Robert Cooper
- University College London, Department of Medical Physics and Biomedical Engineering, Gower Street, London WC1E 6BT, United Kingdom
| | - Jeremy Hebden
- University College London, Department of Medical Physics and Biomedical Engineering, Gower Street, London WC1E 6BT, United Kingdom
| | - Antonio Pifferi
- Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milano, ItalyeIstituto di Fotonica e Nanotecnologie, CNR, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Andrea Farina
- Istituto di Fotonica e Nanotecnologie, CNR, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Ilaria Bargigia
- Istituto Italiano di Tecnologia, Center for Nano Science and Technology @ PoliMi, via Pascoli 70/3, 20133 Milano, Italy
| | - Davide Contini
- Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Matteo Caffini
- Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Lucia Zucchelli
- Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Lorenzo Spinelli
- Istituto di Fotonica e Nanotecnologie, CNR, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Rinaldo Cubeddu
- Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milano, ItalyeIstituto di Fotonica e Nanotecnologie, CNR, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Alessandro Torricelli
- Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
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Elliott JT, Diop M, Morrison LB, d'Esterre CD, Lee TY, St Lawrence K. Quantifying cerebral blood flow in an adult pig ischemia model by a depth-resolved dynamic contrast-enhanced optical method. Neuroimage 2014; 94:303-311. [PMID: 24650601 DOI: 10.1016/j.neuroimage.2014.03.023] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 02/18/2014] [Accepted: 03/10/2014] [Indexed: 11/19/2022] Open
Abstract
Dynamic contrast-enhanced (DCE) near-infrared (NIR) methods have been proposed for bedside monitoring of cerebral blood flow (CBF). These methods have primarily focused on qualitative approaches since scalp contamination hinders quantification. In this study, we demonstrate that accurate CBF measurements can be obtained by analyzing multi-distance time-resolved DCE data with a combined kinetic deconvolution optical reconstruction (KDOR) method. Multi-distance time-resolved DCE-NIR measurements were made in adult pigs (n=8) during normocapnia, hypocapnia and ischemia. The KDOR method was used to calculate CBF from the DCE-NIR measurements. For validation, CBF was measured independently by CT under each condition. The mean CBF difference between the techniques was -1.7 mL/100 g/min with 95% confidence intervals of -16.3 and 12.9 mL/100 g/min; group regression analysis revealed a strong agreement between the two techniques (slope=1.06±0.08, y-intercept=-4.37±4.33 mL/100 g/min, p<0.001). The results of an error analysis suggest that little a priori information is needed to recover CBF, due to the robustness of the analytical method and the ability of time-resolved NIR to directly characterize the optical properties of the extracerebral tissue (where model mismatch is deleterious). The findings of this study suggest that the DCE-NIR approach presented is a minimally invasive and portable means of determining absolute hemodynamics in neurocritical care patients.
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Affiliation(s)
- Jonathan T Elliott
- Department of Medical Biophysics, Western University, London, Ontario N6A 5C1, Canada; Imaging Division, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada.
| | - Mamadou Diop
- Department of Medical Biophysics, Western University, London, Ontario N6A 5C1, Canada; Imaging Division, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
| | - Laura B Morrison
- Imaging Division, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
| | - Christopher D d'Esterre
- Department of Medical Biophysics, Western University, London, Ontario N6A 5C1, Canada; Imaging Division, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
| | - Ting-Yim Lee
- Department of Medical Biophysics, Western University, London, Ontario N6A 5C1, Canada; Imaging Division, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
| | - Keith St Lawrence
- Department of Medical Biophysics, Western University, London, Ontario N6A 5C1, Canada; Imaging Division, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
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Milej D, Gerega A, Wabnitz H, Liebert A. A Monte Carlo study of fluorescence generation probability in a two-layered tissue model. Phys Med Biol 2014; 59:1407-24. [DOI: 10.1088/0031-9155/59/6/1407] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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25
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Torricelli A, Contini D, Pifferi A, Caffini M, Re R, Zucchelli L, Spinelli L. Time domain functional NIRS imaging for human brain mapping. Neuroimage 2014; 85 Pt 1:28-50. [DOI: 10.1016/j.neuroimage.2013.05.106] [Citation(s) in RCA: 294] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 04/25/2013] [Accepted: 05/21/2013] [Indexed: 02/02/2023] Open
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26
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Milej D, Kruczkowski M, Gerega A, Sawosz P, Maniewski R, Liebert A. An algorithm for assessment of inflow and washout of optical contrast agent to the brain by analysis of time-resolved diffuse reflectance and fluorescence signals. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2013; 2013:1919-22. [PMID: 24110088 DOI: 10.1109/embc.2013.6609901] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In optical measurements of the brain oxygenation and perfusion the problem of contamination of the signals with the components related to the extracerebral tissues remains an obstacle limiting clinical applicability of the technique. In this paper we present an algorithm allowing for derivation of signals related to the changes in absorption in the intracerebral tissues based on analysis of time-resolved diffuse reflectance and fluorescence. The proposed method was validated in series of Monte Carlo simulations in which inflow and washout of an optical contrast agent into the two-layered human head model was considered. It was shown that the decomposed intracerebral component of the signal can be derived with uncertainty of about 5%. This result suggests that the method proposed can be applied in improved estimation of brain perfusion parameters based on the bolus-tracking technique.
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27
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Mazurenka M, Di Sieno L, Boso G, Contini D, Pifferi A, Mora AD, Tosi A, Wabnitz H, Macdonald R. Non-contact in vivo diffuse optical imaging using a time-gated scanning system. BIOMEDICAL OPTICS EXPRESS 2013; 4:2257-68. [PMID: 24156081 PMCID: PMC3799683 DOI: 10.1364/boe.4.002257] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Revised: 09/21/2013] [Accepted: 09/22/2013] [Indexed: 05/19/2023]
Abstract
We report on the design and first in vivo tests of a novel non-contact scanning imaging system for time-domain near-infrared spectroscopy. Our system is based on a null source-detector separation approach and utilizes polarization-selective detection and a fast-gated single-photon avalanche diode to record late photons only. The in-vivo tests included the recording of hemodynamics during arm occlusion and two brain activation tasks. Localized and non-localized changes in oxy- and deoxyhemoglobin concentration were detected for motor and cognitive tasks, respectively. The tests demonstrate the feasibility of non-contact imaging of absorption changes in deeper tissues.
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Affiliation(s)
- M. Mazurenka
- Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587, Berlin, Germany
| | - L. Di Sieno
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano I-20133, Italy
| | - G. Boso
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano I-20133, Italy
| | - D. Contini
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano I-20133, Italy
| | - A. Pifferi
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano I-20133, Italy
| | - A. Dalla Mora
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano I-20133, Italy
| | - A. Tosi
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano I-20133, Italy
| | - H. Wabnitz
- Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587, Berlin, Germany
| | - R. Macdonald
- Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587, Berlin, Germany
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Re R, Contini D, Turola M, Spinelli L, Zucchelli L, Caffini M, Cubeddu R, Torricelli A. Multi-channel medical device for time domain functional near infrared spectroscopy based on wavelength space multiplexing. BIOMEDICAL OPTICS EXPRESS 2013; 4:2231-46. [PMID: 24156079 PMCID: PMC3799681 DOI: 10.1364/boe.4.002231] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 09/12/2013] [Accepted: 09/17/2013] [Indexed: 05/03/2023]
Abstract
We have designed a compact dual wavelength (687 nm, 826 nm) multi-channel (16 sources, 8 detectors) medical device for muscle and brain imaging based on time domain functional near infrared spectroscopy. The system employs the wavelength space multiplexing approach to reduce wavelength cross-talk and increase signal-to-noise ratio. System performances have been tested on homogeneous and heterogeneous tissue phantoms following specifically designed protocols for photon migration instruments. Preliminary in vivo measurements have been performed to validate the instrument capability to monitor hemodynamic parameters changes in the arm muscle during arterial occlusion and in the adult head during a motor task experiment.
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Affiliation(s)
- Rebecca Re
- Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milan, Italy
| | - Davide Contini
- Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milan, Italy
| | - Massimo Turola
- Division of Optometry and Visual Sciences, City University London, Northampton Square, EC1V 0HB London, UK
| | | | - Lucia Zucchelli
- Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milan, Italy
| | - Matteo Caffini
- Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, Via Golgi 39, 20133 Milan, Italy
| | - Rinaldo Cubeddu
- Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milan, Italy
| | - Alessandro Torricelli
- Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milan, Italy
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Weigl W, Milej D, Gerega A, Toczylowska B, Kacprzak M, Sawosz P, Botwicz M, Maniewski R, Mayzner-Zawadzka E, Liebert A. Assessment of cerebral perfusion in post-traumatic brain injury patients with the use of ICG-bolus tracking method. Neuroimage 2013; 85 Pt 1:555-65. [PMID: 23831529 DOI: 10.1016/j.neuroimage.2013.06.065] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Revised: 06/15/2013] [Accepted: 06/20/2013] [Indexed: 11/17/2022] Open
Abstract
The aim of this study was to verify the usefulness of the time-resolved optical method utilizing diffusely reflected photons and fluorescence signals combined with intravenous injection of indocyanine green (ICG) in the assessment of brain perfusion in post-traumatic brain injury patients. The distributions of times of flight (DTOFs) of diffusely reflected photons were acquired together with the distributions of times of arrival (DTAs) of fluorescence photons. The data analysis methodology was based on the observation of delays between the signals of statistical moments (number of photons, mean time of flight and variance) of DTOFs and DTAs related to the inflow of ICG to the extra- and intracerebral tissue compartments. Eleven patients with brain hematoma, 15 patients with brain edema and a group of 9 healthy subjects were included in this study. Statistically significant differences between parameters obtained in healthy subjects and patients with brain hematoma and brain edema were observed. The best optical parameter to differentiate patients and control group was variance of the DTOFs or DTAs. Results of the study suggest that time-resolved optical monitoring of inflow of the ICG seems to be a promising tool for detecting cerebral perfusion insufficiencies in critically ill patients.
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Affiliation(s)
- W Weigl
- Medical University of Warsaw, I Department of Anesthesiology and Intensive Care, Warsaw, Poland; Warsaw Praski Hospital, Department of Intensive Care and Anesthesiology, Warsaw, Poland.
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A wearable multi-channel fNIRS system for brain imaging in freely moving subjects. Neuroimage 2013; 85 Pt 1:64-71. [PMID: 23810973 DOI: 10.1016/j.neuroimage.2013.06.062] [Citation(s) in RCA: 233] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 06/19/2013] [Accepted: 06/20/2013] [Indexed: 11/21/2022] Open
Abstract
Functional near infrared spectroscopy (fNIRS) is a versatile neuroimaging tool with an increasing acceptance in the neuroimaging community. While often lauded for its portability, most of the fNIRS setups employed in neuroscientific research still impose usage in a laboratory environment. We present a wearable, multi-channel fNIRS imaging system for functional brain imaging in unrestrained settings. The system operates without optical fiber bundles, using eight dual wavelength light emitting diodes and eight electro-optical sensors, which can be placed freely on the subject's head for direct illumination and detection. Its performance is tested on N=8 subjects in a motor execution paradigm performed under three different exercising conditions: (i) during outdoor bicycle riding, (ii) while pedaling on a stationary training bicycle, and (iii) sitting still on the training bicycle. Following left hand gripping, we observe a significant decrease in the deoxyhemoglobin concentration over the contralateral motor cortex in all three conditions. A significant task-related ΔHbO2 increase was seen for the non-pedaling condition. Although the gross movements involved in pedaling and steering a bike induced more motion artifacts than carrying out the same task while sitting still, we found no significant differences in the shape or amplitude of the HbR time courses for outdoor or indoor cycling and sitting still. We demonstrate the general feasibility of using wearable multi-channel NIRS during strenuous exercise in natural, unrestrained settings and discuss the origins and effects of data artifacts. We provide quantitative guidelines for taking condition-dependent signal quality into account to allow the comparison of data across various levels of physical exercise. To the best of our knowledge, this is the first demonstration of functional NIRS brain imaging during an outdoor activity in a real life situation in humans.
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Obrig H. NIRS in clinical neurology - a 'promising' tool? Neuroimage 2013; 85 Pt 1:535-46. [PMID: 23558099 DOI: 10.1016/j.neuroimage.2013.03.045] [Citation(s) in RCA: 151] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 03/14/2013] [Accepted: 03/21/2013] [Indexed: 12/13/2022] Open
Abstract
Near-infrared spectroscopy (NIRS) has become a relevant research tool in neuroscience. In special populations such as infants and for special tasks such as walking, NIRS has asserted itself as a low resolution functional imaging technique which profits from its ease of application, portability and the option to co-register other neurophysiological and behavioral data in a 'near natural' environment. For clinical use in neurology this translates into the option to provide a bed-side oximeter for the brain, broadly available at comparatively low costs. However, while some potential for routine brain monitoring during cardiac and vascular surgery and in neonatology has been established, NIRS is largely unknown to clinical neurologists. The article discusses some of the reasons for this lack of use in clinical neurology. Research using NIRS in three major neurologic diseases (cerebrovascular disease, epilepsy and headache) is reviewed. Additionally the potential to exploit the established position of NIRS as a functional imaging tool with regard to clinical questions such as preoperative functional assessment and neurorehabilitation is discussed.
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Affiliation(s)
- Hellmuth Obrig
- Clinic for Cognitive Neurology, University Clinic Leipzig, Leipzig, Germany; Max-Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; Dept. Neurology, Charité, University Medicine Berlin, Berlin, Germany.
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Elliott JT, Milej D, Gerega A, Weigl W, Diop M, Morrison LB, Lee TY, Liebert A, St. Lawrence K. Variance of time-of-flight distribution is sensitive to cerebral blood flow as demonstrated by ICG bolus-tracking measurements in adult pigs. BIOMEDICAL OPTICS EXPRESS 2013; 4:206-18. [PMID: 23413183 PMCID: PMC3567707 DOI: 10.1364/boe.4.000206] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 10/22/2012] [Accepted: 11/20/2012] [Indexed: 05/03/2023]
Abstract
Variance of time-of-flight distributions have been shown to be more sensitive to cerebral blood flow (CBF) during dynamic-contrast enhanced monitoring of neurotrauma patients than attenuation. What is unknown is the degree to which variance is affected by changes in extracerebral blood flow. Furthermore, the importance of acquiring the arterial input function (AIF) on quantitative analysis of the data is not yet clear. This animal study confirms that variance is both sensitive and specific to changes occurring in the brain when measurements are acquired on the surface of the scalp. Furthermore, when the variance data along with the measured AIF is analyzed using a nonparametric deconvolution method, the recovered change in CBF is in good agreement with CT perfusion values.
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Affiliation(s)
- Jonathan T. Elliott
- Department of Medical Biophysics, Western University, 1151 Richmond Street, London, Ontario, N6A 3K7, Canada
- Imaging Division, Lawson Health Research Institute, St. Joseph’s Hospital, 268 Grosvenor Street, London, Ontario, N6A 4V2, Canada
| | - Daniel Milej
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Trojdena 4, 02-109, Warsaw, Poland
| | - Anna Gerega
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Trojdena 4, 02-109, Warsaw, Poland
| | - Wojciech Weigl
- Medical University of Warsaw, Department of Anesthesiology and Intensive Care, W. Lindleya 4, 02-005 Warsaw, Poland
| | - Mamadou Diop
- Imaging Division, Lawson Health Research Institute, St. Joseph’s Hospital, 268 Grosvenor Street, London, Ontario, N6A 4V2, Canada
| | - Laura B. Morrison
- Imaging Division, Lawson Health Research Institute, St. Joseph’s Hospital, 268 Grosvenor Street, London, Ontario, N6A 4V2, Canada
| | - Ting-Yim Lee
- Department of Medical Biophysics, Western University, 1151 Richmond Street, London, Ontario, N6A 3K7, Canada
- Imaging Division, Lawson Health Research Institute, St. Joseph’s Hospital, 268 Grosvenor Street, London, Ontario, N6A 4V2, Canada
| | - Adam Liebert
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Trojdena 4, 02-109, Warsaw, Poland
| | - Keith St. Lawrence
- Department of Medical Biophysics, Western University, 1151 Richmond Street, London, Ontario, N6A 3K7, Canada
- Imaging Division, Lawson Health Research Institute, St. Joseph’s Hospital, 268 Grosvenor Street, London, Ontario, N6A 4V2, Canada
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Oldag A, Goertler M, Bertz AK, Schreiber S, Stoppel C, Heinze HJ, Kopitzki K. Assessment of cortical hemodynamics by multichannel near-infrared spectroscopy in steno-occlusive disease of the middle cerebral artery. Stroke 2013; 43:2980-5. [PMID: 23091122 DOI: 10.1161/strokeaha.112.656710] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE In a pilot study we evaluated near-infrared spectroscopy as to its potential benefit in monitoring patients with steno-occlusive disease of a major cerebral artery for alterations in cortical hemodynamics. METHODS Cortical maps of time-to-peak (TTP) in 10 patients unilaterally affected by severe stenosis or occlusion of the middle cerebral artery were acquired by multichannel near-infrared spectroscopy after bolus application of indocyanine green. Hemodynamic manifestations were assessed by comparison between affected and unaffected hemisphere and evaluated for common constituents by principal component analysis. In one patient, TTP values were compared with those obtained by dynamic susceptibility contrast imaging. RESULTS TTP was increased on the affected hemisphere in 9 patients. Mean difference in TTP between hemispheres was 0.44 second (P<0.05) as compared with a mean lateral difference of 0.12 second found in a control group of 10 individuals. In group analysis a significant rise in TTP was found in the distribution of the affected middle cerebral artery, whereas principal component analysis suggests augmentation of hemodynamic effects toward the border zones as a dominant pattern. A linear correlation of 0.61 between TTP values determined by dynamic susceptibility contrast MRI and near-infrared spectroscopy was found to be statistically significant (P<0.001). CONCLUSIONS Multichannel near-infrared spectroscopy might facilitate detection of disease-related hemodynamic changes as yet only accessible by tomographic imaging modalities. Being indicative for hypoperfusion and collateral flow increased values of TTP, as found to a varying extent in the present patient group, might be of clinical relevance.
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Affiliation(s)
- Andreas Oldag
- Department of Neurology, Otto-von-Guericke University, Madgeburg, Germany
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Elliott JT, Wright EA, Tichauer KM, Diop M, Morrison LB, Pogue BW, Lee TY, St. Lawrence K. Arterial input function of an optical tracer for dynamic contrast enhanced imaging can be determined from pulse oximetry oxygen saturation measurements. Phys Med Biol 2012. [DOI: 10.1088/0031-9155/57/24/8285] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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35
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Ku T, Choi C. Noninvasive optical measurement of cerebral blood flow in mice using molecular dynamics analysis of indocyanine green. PLoS One 2012; 7:e48383. [PMID: 23119000 PMCID: PMC3485229 DOI: 10.1371/journal.pone.0048383] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Accepted: 09/24/2012] [Indexed: 11/18/2022] Open
Abstract
In preclinical studies of ischemic brain disorders, it is crucial to measure cerebral blood flow (CBF); however, this requires radiological techniques with heavy instrumentation or invasive procedures. Here, we propose a noninvasive and easy-to-use optical imaging technique for measuring CBF in experimental small animals. Mice were injected with indocyanine green (ICG) via tail-vein catheterization. Time-series near-infrared fluorescence signals excited by 760 nm light-emitting diodes were imaged overhead by a charge-coupled device coupled with an 830 nm bandpass-filter. We calculated four CBF parameters including arrival time, rising time and mean transit time of a bolus and blood flow index based on time and intensity information of ICG fluorescence dynamics. CBF maps were generated using the parameters to estimate the status of CBF, and they dominantly represented intracerebral blood flows in mice even in the presence of an intact skull and scalp. We demonstrated that this noninvasive optical imaging technique successfully detected reduced local CBF during middle cerebral artery occlusion. We further showed that the proposed method is sufficiently sensitive to detect the differences between CBF status in mice anesthetized with either isoflurane or ketamine–xylazine, and monitor the dynamic changes in CBF after reperfusion during transient middle cerebral artery occlusion. The near-infrared optical imaging of ICG fluorescence combined with a time-series analysis of the molecular dynamics can be a useful noninvasive tool for preclinical studies of brain ischemia.
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Affiliation(s)
- Taeyun Ku
- Graduate School of Medical Science and Engineering, KAIST, Daejeon, Republic of Korea
| | - Chulhee Choi
- Graduate School of Medical Science and Engineering, KAIST, Daejeon, Republic of Korea
- Department of Bio and Brain Engineering, KAIST, Daejeon, Republic of Korea
- KI for the BioCentury, KAIST, Daejeon, Republic of Korea
- * E-mail:
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Milej D, Gerega A, Żołek N, Weigl W, Kacprzak M, Sawosz P, Mączewska J, Fronczewska K, Mayzner-Zawadzka E, Królicki L, Maniewski R, Liebert A. Time-resolved detection of fluorescent light during inflow of ICG to the brain—a methodological study. Phys Med Biol 2012; 57:6725-42. [DOI: 10.1088/0031-9155/57/20/6725] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Liebert A, Wabnitz H, Elster C. Determination of absorption changes from moments of distributions of times of flight of photons: optimization of measurement conditions for a two-layered tissue model. JOURNAL OF BIOMEDICAL OPTICS 2012; 17:057005. [PMID: 22612144 DOI: 10.1117/1.jbo.17.5.057005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Time-resolved near-infrared spectroscopy allows for depth-selective determination of absorption changes in the adult human head that facilitates separation between cerebral and extra-cerebral responses to brain activation. The aim of the present work is to analyze which combinations of moments of measured distributions of times of flight (DTOF) of photons and source-detector separations are optimal for the reconstruction of absorption changes in a two-layered tissue model corresponding to extra- and intra-cerebral compartments. To this end we calculated the standard deviations of the derived absorption changes in both layers by considering photon noise and a linear relation between the absorption changes and the DTOF moments. The results show that the standard deviation of the absorption change in the deeper (superficial) layer increases (decreases) with the thickness of the superficial layer. It is confirmed that for the deeper layer the use of higher moments, in particular the variance of the DTOF, leads to an improvement. For example, when measurements at four different source-detector separations between 8 and 35 mm are available and a realistic thickness of the upper layer of 12 mm is assumed, the inclusion of the change in mean time of flight, in addition to the change in attenuation, leads to a reduction of the standard deviation of the absorption change in the deeper tissue layer by a factor of 2.5. A reduction by another 4% can be achieved by additionally including the change in variance.
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Affiliation(s)
- Adam Liebert
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Trojdena 4, 02-109 Warsaw, Poland.
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Jelzow A, Wabnitz H, Obrig H, Macdonald R, Steinbrink J. Separation of indocyanine green boluses in the human brain and scalp based on time-resolved in-vivo fluorescence measurements. JOURNAL OF BIOMEDICAL OPTICS 2012; 17:057003. [PMID: 22612142 DOI: 10.1117/1.jbo.17.5.057003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Non-invasive detection of fluorescence from the optical tracer indocyanine green is feasible in the adult human brain when employing a time-domain technique with picosecond resolution. A fluorescence-based assessment may offer higher signal-to-noise ratio when compared to bolus tracking relying on changes in time-resolved diffuse reflectance. The essential challenge is to discriminate the fluorescence originating from the brain from contamination by extracerebral fluorescence and hence to reconstruct the bolus kinetics; however, a method to reliably perform the necessary separation is missing. We present a novel approach for the decomposition of the fluorescence contributions from the two tissue compartments. The corresponding sensitivity functions pertaining to the brain and to the extracerebral compartment are directly derived from the in-vivo measurement. This is achieved by assuming that during the initial and the late phase of bolus transit the fluorescence signal originates largely from one of the compartments. Solving the system of linear equations allows one to approximate time courses of a bolus for each compartment. We applied this method to repetitive measurements on two healthy subjects with an overall 34 boluses. A reconstruction of the bolus kinetics was possible in 62% of all cases.
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Affiliation(s)
- Alexander Jelzow
- Physikalisch-Technische Bundesanstalt (PTB), Abbestrasse 2-12, 10587 Berlin, Germany
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Steinkellner O, Wabnitz H, Jelzow A, Macdonald R, Gruber C, Steinbrink J, Obrig H. Cerebral Perfusion in Acute Stroke Monitored by Time-domain Near-infrared Reflectometry. Biocybern Biomed Eng 2012. [DOI: 10.1016/s0208-5216(12)70028-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Obrig H, Steinbrink J. Non-invasive optical imaging of stroke. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2011; 369:4470-94. [PMID: 22006902 DOI: 10.1098/rsta.2011.0252] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The acute onset of a neurological deficit is the key clinical feature of stroke. In most cases, however, pathophysiological changes in the cerebral vasculature precede the event, often by many years. Persisting neurological deficits may also require long-term rehabilitation. Hence, stroke may be considered a chronic disease, and diagnostic and therapeutic efforts must include identification of specific risk factors, and the monitoring of and interventions in the acute and subacute stages, and should aim at a pathophysiologically based approach to optimize the rehabilitative effort. Non-invasive optical techniques have been experimentally used in all three stages of the disease and may complement the established diagnostic and monitoring tools. Here, we provide an overview of studies using the methodology in the context of stroke, and we sketch perspectives of how they may be integrated into the assessment of the highly dynamic pathophysiological processes during the acute and subacute stages of the disease and also during rehabilitation and (secondary) prevention of stroke.
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Affiliation(s)
- Hellmuth Obrig
- Department of Cognitive Neurology, University Hospital Leipzig, Liebigstraße 16, 04103 Leipzig, Germany.
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Liebert A, Sawosz P, Milej D, Kacprzak M, Weigl W, Botwicz M, Maczewska J, Fronczewska K, Mayzner-Zawadzka E, Królicki L, Maniewski R. Assessment of inflow and washout of indocyanine green in the adult human brain by monitoring of diffuse reflectance at large source-detector separation. JOURNAL OF BIOMEDICAL OPTICS 2011; 16:046011. [PMID: 21529080 DOI: 10.1117/1.3574018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Recently, it was shown in measurements carried out on humans that time-resolved near-infrared reflectometry and fluorescence spectroscopy may allow for discrimination of information originating directly from the brain avoiding influence of contaminating signals related to the perfusion of extracerebral tissues. We report on continuation of these studies, showing that the near-infrared light can be detected noninvasively on the surface of the tissue at large interoptode distance. A multichannel time-resolved optical monitoring system was constructed for measurements of diffuse reflectance in optically turbid medium at very large source-detector separation up to 9 cm. The instrument was applied during intravenous injection of indocyanine green and the distributions of times of flight of photons were successfully acquired showing inflow and washout of the dye in the tissue. Time courses of the statistical moments of distributions of times of flight of photons are presented and compared to the results obtained simultaneously at shorter source-detector separations (3, 4, and 5 cm). We show in a series of experiments carried out on physical phantom and healthy volunteers that the time-resolved data acquisition in combination with very large source-detector separation may allow one to improve depth selectivity of perfusion assessment in the brain.
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Affiliation(s)
- Adam Liebert
- Polish Academy of Sciences, Nalecz Institute of Biocybernetics and Biomedical Engineering, Trojdena 4, 02-109 Warsaw, Poland.
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