1
|
Vera DA, García HA, Carbone NA, Waks-Serra MV, Iriarte DI, Pomarico JA. Retrieval of chromophore concentration changes in a digital human head model using analytical mean partial pathlengths of photons. JOURNAL OF BIOMEDICAL OPTICS 2024; 29:025004. [PMID: 38419755 PMCID: PMC10901244 DOI: 10.1117/1.jbo.29.2.025004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 01/25/2024] [Accepted: 01/26/2024] [Indexed: 03/02/2024]
Abstract
Significance Continuous-wave functional near-infrared spectroscopy has proved to be a valuable tool for assessing hemodynamic activity in the human brain in a non-invasively and inexpensive way. However, most of the current processing/analysis methods assume the head is a homogeneous medium, and hence do not appropriately correct for the signal coming from the scalp. This effect can be reduced by considering light propagation in a layered model of the human head, being the Monte Carlo (MC) simulations the gold standard to this end. However, this implies large computation times and demanding hardware capabilities. Aim In this work, we study the feasibility of replacing the homogeneous model and the MC simulations by means of analytical multilayered models, combining in this way, the speed and simplicity of implementation of the former with the robustness and accuracy of the latter. Approach Oxy- and deoxyhemoglobin (HbO and HbR, respectively) concentration changes were proposed in two different layers of a magnetic resonance imaging (MRI)-based meshed model of the human head, and then these changes were retrieved by means of (i) a typical homogeneous reconstruction and (ii) a theoretical layered reconstruction. Results Results suggest that the use of analytical models of light propagation in layered models outperforms the results obtained using traditional homogeneous reconstruction algorithms, providing much more accurate results for both, the extra- and the cerebral tissues. We also compare the analytical layered reconstruction with MC-based reconstructions, achieving similar degrees of accuracy, especially in the gray matter layer, but much faster (between 4 and 5 orders of magnitude). Conclusions We have successfully developed, implemented, and validated a method for retrieving chromophore concentration changes in the human brain, combining the simplicity and speed of the traditional homogeneous reconstruction algorithms with robustness and accuracy much more similar to those provided by MC simulations.
Collapse
|
2
|
Martelli F, Pifferi A, Farina A, Amendola C, Maffeis G, Tommasi F, Cavalieri S, Spinelli L, Torricelli A. Statistics of maximum photon penetration depth in a two-layer diffusive medium. BIOMEDICAL OPTICS EXPRESS 2024; 15:1163-1180. [PMID: 38404319 PMCID: PMC10890894 DOI: 10.1364/boe.507294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 11/30/2023] [Accepted: 12/20/2023] [Indexed: 02/27/2024]
Abstract
We present numerical results for the probability density function f(z) and for the mean value of photon maximum penetration depth ‹zmax› in a two-layer diffusive medium. Both time domain and continuous wave regime are considered with several combinations of the optical properties (absorption coefficient, reduced scattering coefficient) of the two layers, and with different geometrical configurations (source detector distance, thickness of the upper layer). Practical considerations on the design of time domain and continuous wave systems are derived. The methods and the results are of interest for many research fields such as biomedical optics and advanced microscopy.
Collapse
Affiliation(s)
- Fabrizio Martelli
- Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze, Sesto Fiorentino, Firenze, Italy
| | - Antonio Pifferi
- Dipartimento di Fisica, Politecnico di Milano, Milan, Italy
- Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Milan, Italy
| | - Andrea Farina
- Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Milan, Italy
| | | | - Giulia Maffeis
- Dipartimento di Fisica, Politecnico di Milano, Milan, Italy
| | - Federico Tommasi
- Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze, Sesto Fiorentino, Firenze, Italy
| | - Stefano Cavalieri
- Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze, Sesto Fiorentino, Firenze, Italy
| | - Lorenzo Spinelli
- Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Milan, Italy
| | - Alessandro Torricelli
- Dipartimento di Fisica, Politecnico di Milano, Milan, Italy
- Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Milan, Italy
| |
Collapse
|
3
|
Zhao H, Sathialingam E, Cowdrick KR, Urner T, Lee SY, Bai S, Akbik F, Samuels OB, Kandiah P, Sadan O, Buckley EM. Comparison of diffuse correlation spectroscopy analytical models for measuring cerebral blood flow in adults. JOURNAL OF BIOMEDICAL OPTICS 2023; 28:126005. [PMID: 38107767 PMCID: PMC10723621 DOI: 10.1117/1.jbo.28.12.126005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/19/2023] [Revised: 10/30/2023] [Accepted: 11/21/2023] [Indexed: 12/19/2023]
Abstract
Significance Although multilayer analytical models have been proposed to enhance brain sensitivity of diffuse correlation spectroscopy (DCS) measurements of cerebral blood flow, the traditional homogeneous model remains dominant in clinical applications. Rigorous in vivo comparison of these analytical models is lacking. Aim We compare the performance of different analytical models to estimate a cerebral blood flow index (CBFi) with DCS in adults. Approach Resting-state data were obtained on a cohort of 20 adult patients with subarachnoid hemorrhage. Data at 1 and 2.5 cm source-detector separations were analyzed with the homogenous, two-layer, and three-layer models to estimate scalp blood flow index and CBFi. The performance of each model was quantified via fitting convergence, fit stability, brain-to-scalp flow ratio (BSR), and correlation with transcranial Doppler ultrasound (TCD) measurements of cerebral blood flow velocity in the middle cerebral artery (MCA). Results The homogeneous model has the highest pass rate (100%), lowest coefficient of variation (CV) at rest (median [IQR] at 1 Hz of 0.18 [0.13, 0.22]), and most significant correlation with MCA blood flow velocities (R s = 0.59 , p = 0.010 ) compared with both the two- and three-layer models. The multilayer model pass rate was significantly correlated with extracerebral layer thicknesses. Discarding datasets with non-physiological BSRs increased the correlation between DCS measured CBFi and TCD measured MCA velocities for all models. Conclusions We found that the homogeneous model has the highest pass rate, lowest CV at rest, and most significant correlation with MCA blood flow velocities. Results from the multilayer models should be taken with caution because they suffer from lower pass rates and higher coefficients of variation at rest and can converge to non-physiological values for CBFi. Future work is needed to validate these models in vivo, and novel approaches are merited to improve the performance of the multimodel models.
Collapse
Affiliation(s)
- Hongting Zhao
- Emory University, Georgia Institute of Technology, Wallace H. Coulter Department of Biomedical Engineering, Atlanta, Georgia, United States
| | - Eashani Sathialingam
- Emory University, Georgia Institute of Technology, Wallace H. Coulter Department of Biomedical Engineering, Atlanta, Georgia, United States
| | - Kyle R. Cowdrick
- Emory University, Georgia Institute of Technology, Wallace H. Coulter Department of Biomedical Engineering, Atlanta, Georgia, United States
| | - Tara Urner
- Emory University, Georgia Institute of Technology, Wallace H. Coulter Department of Biomedical Engineering, Atlanta, Georgia, United States
| | - Seung Yup Lee
- Emory University, Georgia Institute of Technology, Wallace H. Coulter Department of Biomedical Engineering, Atlanta, Georgia, United States
- Kennesaw State University, Department of Electrical and Computer Engineering, Marietta, Georgia, United States
| | - Shasha Bai
- Emory University, School of Medicine, Department of Pediatrics, Atlanta, Georgia, United States
| | - Feras Akbik
- Emory University, School of Medicine, Department of Neurology and Neurosurgery, Division of Neurocritical Care, Atlanta, Georgia, United States
| | - Owen B. Samuels
- Emory University, School of Medicine, Department of Neurology and Neurosurgery, Division of Neurocritical Care, Atlanta, Georgia, United States
| | - Prem Kandiah
- Emory University, School of Medicine, Department of Neurology and Neurosurgery, Division of Neurocritical Care, Atlanta, Georgia, United States
| | - Ofer Sadan
- Emory University, School of Medicine, Department of Neurology and Neurosurgery, Division of Neurocritical Care, Atlanta, Georgia, United States
| | - Erin M. Buckley
- Emory University, Georgia Institute of Technology, Wallace H. Coulter Department of Biomedical Engineering, Atlanta, Georgia, United States
- Emory University, School of Medicine, Department of Pediatrics, Atlanta, Georgia, United States
- Children’s Healthcare of Atlanta, Children’s Research Scholar, Atlanta, Georgia, United States
| |
Collapse
|
4
|
Sudakou A, Wabnitz H, Liemert A, Wolf M, Liebert A. Two-layered blood-lipid phantom and method to determine absorption and oxygenation employing changes in moments of DTOFs. BIOMEDICAL OPTICS EXPRESS 2023; 14:3506-3531. [PMID: 37497481 PMCID: PMC10368065 DOI: 10.1364/boe.492168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 05/29/2023] [Accepted: 05/29/2023] [Indexed: 07/28/2023]
Abstract
Near-infrared spectroscopy (NIRS) is an established technique for measuring tissue oxygen saturation (StO2), which is of high clinical value. For tissues that have layered structures, it is challenging but clinically relevant to obtain StO2 of the different layers, e.g. brain and scalp. For this aim, we present a new method of data analysis for time-domain NIRS (TD-NIRS) and a new two-layered blood-lipid phantom. The new analysis method enables accurate determination of even large changes of the absorption coefficient (Δµa) in multiple layers. By adding Δµa to the baseline µa, this method provides absolute µa and hence StO2 in multiple layers. The method utilizes (i) changes in statistical moments of the distributions of times of flight of photons (DTOFs), (ii) an analytical solution of the diffusion equation for an N-layered medium, (iii) and the Levenberg-Marquardt algorithm (LMA) to determine Δµa in multiple layers from the changes in moments. The method is suitable for NIRS tissue oximetry (relying on µa) as well as functional NIRS (fNIRS) applications (relying on Δµa). Experiments were conducted on a new phantom, which enabled us to simulate dynamic StO2 changes in two layers for the first time. Two separate compartments, which mimic superficial and deep layers, hold blood-lipid mixtures that can be deoxygenated (using yeast) and oxygenated (by bubbling oxygen) independently. Simultaneous NIRS measurements can be performed on the two-layered medium (variable superficial layer thickness, L), the deep (homogeneous), and/or the superficial (homogeneous). In two experiments involving ink, we increased the nominal µa in one of two compartments from 0.05 to 0.25 cm-1, L set to 14.5 mm. In three experiments involving blood (L set to 12, 15, or 17 mm), we used a protocol consisting of six deoxygenation cycles. A state-of-the-art multi-wavelength TD-NIRS system measured simultaneously on the two-layered medium, as well as on the deep compartment for a reference. The new method accurately determined µa (and hence StO2) in both compartments. The method is a significant progress in overcoming the contamination from the superficial layer, which is beneficial for NIRS and fNIRS applications, and may improve the determination of StO2 in the brain from measurements on the head. The advanced phantom may assist in the ongoing effort towards more realistic standardized performance tests in NIRS tissue oximetry. Data and MATLAB codes used in this study were made publicly available.
Collapse
Affiliation(s)
- Aleh Sudakou
- Nałęcz Institute of Biocybernetics and Biomedical Engineering Polish Academy of Sciences, Warsaw, Poland
| | - Heidrun Wabnitz
- Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany
| | - André Liemert
- Institut für Lasertechnologien in der Medizin und Meßtechnik an der Universität Ulm, Germany
| | - Martin Wolf
- Department of Neonatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Adam Liebert
- Nałęcz Institute of Biocybernetics and Biomedical Engineering Polish Academy of Sciences, Warsaw, Poland
| |
Collapse
|
5
|
Forti RM, Hobson LJ, Benson EJ, Ko TS, Ranieri NR, Laurent G, Weeks MK, Widmann NJ, Morton S, Davis AM, Sueishi T, Lin Y, Wulwick KS, Fagan N, Shin SS, Kao SH, Licht DJ, White BR, Kilbaugh TJ, Yodh AG, Baker WB. Non-invasive diffuse optical monitoring of cerebral physiology in an adult swine-model of impact traumatic brain injury. BIOMEDICAL OPTICS EXPRESS 2023; 14:2432-2448. [PMID: 37342705 PMCID: PMC10278631 DOI: 10.1364/boe.486363] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 03/17/2023] [Accepted: 04/12/2023] [Indexed: 06/23/2023]
Abstract
In this study, we used diffuse optics to address the need for non-invasive, continuous monitoring of cerebral physiology following traumatic brain injury (TBI). We combined frequency-domain and broadband diffuse optical spectroscopy with diffuse correlation spectroscopy to monitor cerebral oxygen metabolism, cerebral blood volume, and cerebral water content in an established adult swine-model of impact TBI. Cerebral physiology was monitored before and after TBI (up to 14 days post injury). Overall, our results suggest that non-invasive optical monitoring can assess cerebral physiologic impairments post-TBI, including an initial reduction in oxygen metabolism, development of cerebral hemorrhage/hematoma, and brain swelling.
Collapse
Affiliation(s)
- Rodrigo M. Forti
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
- Resuscitation Science Center of Emphasis, CHOP Research Institute, Philadelphia, PA 19104, USA
| | - Lucas J. Hobson
- Resuscitation Science Center of Emphasis, CHOP Research Institute, Philadelphia, PA 19104, USA
- Department of Anesthesiology and Critical Care Medicine, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Emilie J. Benson
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Tiffany S. Ko
- Resuscitation Science Center of Emphasis, CHOP Research Institute, Philadelphia, PA 19104, USA
- Department of Anesthesiology and Critical Care Medicine, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Nicolina R. Ranieri
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
- Resuscitation Science Center of Emphasis, CHOP Research Institute, Philadelphia, PA 19104, USA
| | - Gerard Laurent
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
- Resuscitation Science Center of Emphasis, CHOP Research Institute, Philadelphia, PA 19104, USA
| | - M. Katie Weeks
- Resuscitation Science Center of Emphasis, CHOP Research Institute, Philadelphia, PA 19104, USA
- Department of Anesthesiology and Critical Care Medicine, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Nicholas J. Widmann
- Resuscitation Science Center of Emphasis, CHOP Research Institute, Philadelphia, PA 19104, USA
- Department of Anesthesiology and Critical Care Medicine, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Sarah Morton
- Resuscitation Science Center of Emphasis, CHOP Research Institute, Philadelphia, PA 19104, USA
- Department of Anesthesiology and Critical Care Medicine, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Anthony M. Davis
- Resuscitation Science Center of Emphasis, CHOP Research Institute, Philadelphia, PA 19104, USA
- Department of Anesthesiology and Critical Care Medicine, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Takayuki Sueishi
- Resuscitation Science Center of Emphasis, CHOP Research Institute, Philadelphia, PA 19104, USA
- Department of Anesthesiology and Critical Care Medicine, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Yuxi Lin
- Resuscitation Science Center of Emphasis, CHOP Research Institute, Philadelphia, PA 19104, USA
- Department of Anesthesiology and Critical Care Medicine, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Karli S. Wulwick
- Resuscitation Science Center of Emphasis, CHOP Research Institute, Philadelphia, PA 19104, USA
- Department of Anesthesiology and Critical Care Medicine, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Nicholas Fagan
- Resuscitation Science Center of Emphasis, CHOP Research Institute, Philadelphia, PA 19104, USA
- Department of Anesthesiology and Critical Care Medicine, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Samuel S. Shin
- Resuscitation Science Center of Emphasis, CHOP Research Institute, Philadelphia, PA 19104, USA
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Shih-Han Kao
- Resuscitation Science Center of Emphasis, CHOP Research Institute, Philadelphia, PA 19104, USA
- Department of Anesthesiology and Critical Care Medicine, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Daniel J. Licht
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Brian R. White
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- Division of Cardiology, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Todd J. Kilbaugh
- Resuscitation Science Center of Emphasis, CHOP Research Institute, Philadelphia, PA 19104, USA
- Department of Anesthesiology and Critical Care Medicine, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Arjun G. Yodh
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Wesley B. Baker
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
- Resuscitation Science Center of Emphasis, CHOP Research Institute, Philadelphia, PA 19104, USA
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| |
Collapse
|
6
|
Cohen DJF, Li NC, Ioussoufovitch S, Diop M. Fast estimation of adult cerebral blood content and oxygenation with hyperspectral time-resolved near-infrared spectroscopy. Front Neurosci 2023; 17:1020151. [PMID: 36875650 PMCID: PMC9978211 DOI: 10.3389/fnins.2023.1020151] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 01/26/2023] [Indexed: 02/18/2023] Open
Abstract
Near-infrared spectroscopy (NIRS) can measure tissue blood content and oxygenation; however, its use for adult neuromonitoring is challenging due to significant contamination from their thick extracerebral layers (ECL; primarily scalp and skull). This report presents a fast method for accurate estimation of adult cerebral blood content and oxygenation from hyperspectral time resolved NIRS (trNIRS) data. A two-phase fitting method, based on a two-layer head model (ECL and brain), was developed. Phase 1 uses spectral constraints to accurately estimate the baseline blood content and oxygenation in both layers, which are then used by Phase 2 to correct for the ECL contamination of the late-arriving photons. The method was validated with in silico data from Monte-Carlo simulations of hyperspectral trNIRS in a realistic model of the adult head obtained from a high-resolution MRI. Phase 1 recovered cerebral blood oxygenation and total hemoglobin with an accuracy of 2.7 ± 2.5 and 2.8 ± 1.8%, respectively, with unknown ECL thickness, and 1.5 ± 1.4 and 1.7 ± 1.1% when the ECL thickness was known. Phase 2 recovered these parameters with an accuracy of 1.5 ± 1.5 and 3.1 ± 0.9%, respectively. Future work will include further validation in tissue-mimicking phantoms with various top layer thicknesses and in a pig model of the adult head before human applications.
Collapse
Affiliation(s)
| | - Natalie C Li
- School of Biomedical Engineering, Western University, London, ON, Canada
| | | | - Mamadou Diop
- Department of Medical Biophysics, Western University, London, ON, Canada.,School of Biomedical Engineering, Western University, London, ON, Canada.,Imaging Program, Lawson Health Research Institute, London, ON, Canada
| |
Collapse
|
7
|
Helton M, Rajasekhar S, Zerafa S, Vishwanath K, Mycek MA. Numerical approach to quantify depth-dependent blood flow changes in real-time using the diffusion equation with continuous-wave and time-domain diffuse correlation spectroscopy. BIOMEDICAL OPTICS EXPRESS 2023; 14:367-384. [PMID: 36698680 PMCID: PMC9841990 DOI: 10.1364/boe.469419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 11/09/2022] [Accepted: 11/10/2022] [Indexed: 05/11/2023]
Abstract
Diffuse correlation spectroscopy (DCS) is a non-invasive optical technique that can measure brain perfusion by quantifying temporal intensity fluctuations of multiply scattered light. A primary limitation for accurate quantitation of cerebral blood flow (CBF) is the fact that experimental measurements contain information about both extracerebral scalp blood flow (SBF) as well as CBF. Separating CBF from SBF is typically achieved using multiple source-detector channels when using continuous-wave (CW) light sources, or more recently with use of time-domain (TD) techniques. Analysis methods that account for these partial volume effects are often employed to increase CBF contrast. However, a robust, real-time analysis procedure that can separate and quantify SBF and CBF with both traditional CW and TD-DCS measurements is still needed. Here, we validate a data analysis procedure based on the diffusion equation in layered media capable of quantifying both extra- and cerebral blood flow in the CW and TD. We find that the model can quantify SBF and CBF coefficients with less than 5% error compared to Monte Carlo simulations using a 3-layered brain model in both the CW and TD. The model can accurately fit data at a rate of <10 ms for CW data and <250 ms for TD data when using a least-squares optimizer.
Collapse
Affiliation(s)
- Michael Helton
- Applied Physics Program, University of Michigan, Ann Arbor, USA
| | - Suraj Rajasekhar
- Cell, Molecular and Structural Biology Program, Miami University, Oxford, OH, USA
| | - Samantha Zerafa
- Biomedical Engineering Department, University of Michigan, Ann Arbor, USA
| | - Karthik Vishwanath
- Cell, Molecular and Structural Biology Program, Miami University, Oxford, OH, USA
- Department of Physics, Miami University, Oxford, OH, USA
| | - Mary-Ann Mycek
- Applied Physics Program, University of Michigan, Ann Arbor, USA
- Biomedical Engineering Department, University of Michigan, Ann Arbor, USA
| |
Collapse
|
8
|
Efficient computation of the steady-state and time-domain solutions of the photon diffusion equation in layered turbid media. Sci Rep 2022; 12:18979. [PMID: 36347893 PMCID: PMC9643457 DOI: 10.1038/s41598-022-22649-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 10/18/2022] [Indexed: 11/09/2022] Open
Abstract
Accurate and efficient forward models of photon migration in heterogeneous geometries are important for many applications of light in medicine because many biological tissues exhibit a layered structure of independent optical properties and thickness. However, closed form analytical solutions are not readily available for layered tissue-models, and often are modeled using computationally expensive numerical techniques or theoretical approximations that limit accuracy and real-time analysis. Here, we develop an open-source accurate, efficient, and stable numerical routine to solve the diffusion equation in the steady-state and time-domain for a layered cylinder tissue model with an arbitrary number of layers and specified thickness and optical coefficients. We show that the steady-state ([Formula: see text] ms) and time-domain ([Formula: see text] ms) fluence (for an 8-layer medium) can be calculated with absolute numerical errors approaching machine precision. The numerical implementation increased computation speed by 3 to 4 orders of magnitude compared to previously reported theoretical solutions in layered media. We verify our solutions asymptotically to homogeneous tissue geometries using closed form analytical solutions to assess convergence and numerical accuracy. Approximate solutions to compute the reflected intensity are presented which can decrease the computation time by an additional 2-3 orders of magnitude. We also compare our solutions for 2, 3, and 5 layered media to gold-standard Monte Carlo simulations in layered tissue models of high interest in biomedical optics (e.g. skin/fat/muscle and brain). The presented routine could enable more robust real-time data analysis tools in heterogeneous tissues that are important in many clinical applications such as functional brain imaging and diffuse optical spectroscopy.
Collapse
|
9
|
Lee SY, Brothers RO, Turrentine KB, Quadri A, Sathialingam E, Cowdrick KR, Gillespie S, Bai S, Goldman-Yassen AE, Joiner CH, Brown RC, Buckley EM. Quantifying the Cerebral Hemometabolic Response to Blood Transfusion in Pediatric Sickle Cell Disease With Diffuse Optical Spectroscopies. Front Neurol 2022; 13:869117. [PMID: 35847200 PMCID: PMC9283827 DOI: 10.3389/fneur.2022.869117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Accepted: 05/13/2022] [Indexed: 11/13/2022] Open
Abstract
Red blood cell transfusions are common in patients with sickle cell disease who are at increased risk of stroke. Unfortunately, transfusion thresholds needed to sufficiently dilute sickle red blood cells and adequately restore oxygen delivery to the brain are not well defined. Previous work has shown that transfusion is associated with a reduction in oxygen extraction fraction and cerebral blood flow, both of which are abnormally increased in sickle patients. These reductions are thought to alleviate hemometabolic stress by improving the brain's ability to respond to increased metabolic demand, thereby reducing susceptibility to ischemic injury. Monitoring the cerebral hemometabolic response to transfusion may enable individualized management of transfusion thresholds. Diffuse optical spectroscopies may present a low-cost, non-invasive means to monitor this response. In this study, children with SCD undergoing chronic transfusion therapy were recruited. Diffuse optical spectroscopies (namely, diffuse correlation spectroscopy combined with frequency domain near-infrared spectroscopy) were used to quantify oxygen extraction fraction (OEF), cerebral blood volume (CBV), an index of cerebral blood flow (CBFi), and an index of cerebral oxygen metabolism (CMRO2i) in the frontal cortex immediately before and after transfusion. A subset of patients receiving regular monthly transfusions were measured during a subsequent transfusion. Data was captured from 35 transfusions in 23 patients. Transfusion increased median blood hemoglobin levels (Hb) from 9.1 to 11.7 g/dL (p < 0.001) and decreased median sickle hemoglobin (HbS) from 30.9 to 21.7% (p < 0.001). Transfusion decreased OEF by median 5.9% (p < 0.001), CBFi by median 21.2% (p = 0.020), and CBV by median 18.2% (p < 0.001). CMRO2i did not statistically change from pre-transfusion levels (p > 0.05). Multivariable analysis revealed varying degrees of associations between outcomes (i.e., OEF, CBFi, CBV, and CMRO2i), Hb, and demographics. OEF, CBFi, and CBV were all negatively associated with Hb, while CMRO2i was only associated with age. These results demonstrate that diffuse optical spectroscopies are sensitive to the expected decreases of oxygen extraction, blood flow, and blood volume after transfusion. Diffuse optical spectroscopies may be a promising bedside tool for real-time monitoring and goal-directed therapy to reduce stroke risk for sickle cell disease.
Collapse
Affiliation(s)
- Seung Yup Lee
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
- Department of Electrical and Computer Engineering, Kennesaw State University, Marietta, GA, United States
| | - Rowan O. Brothers
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
| | - Katherine B. Turrentine
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
| | - Ayesha Quadri
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
| | - Eashani Sathialingam
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
| | - Kyle R. Cowdrick
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
| | - Scott Gillespie
- Pediatric Biostatistics Core, Emory University School of Medicine, Atlanta, GA, United States
| | - Shasha Bai
- Pediatric Biostatistics Core, Emory University School of Medicine, Atlanta, GA, United States
| | - Adam E. Goldman-Yassen
- Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, United States
| | - Clinton H. Joiner
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
- Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, United States
- Aflac Cancer & Blood Disorders Center, Children's Healthcare of Atlanta, Atlanta, GA, United States
| | - R. Clark Brown
- Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, United States
- Aflac Cancer & Blood Disorders Center, Children's Healthcare of Atlanta, Atlanta, GA, United States
| | - Erin M. Buckley
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
- Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, United States
- Children's Research Scholar, Children's Healthcare of Atlanta, Atlanta, GA, United States
- *Correspondence: Erin M. Buckley
| |
Collapse
|
10
|
Maria A, Hirvi P, Kotilahti K, Heiskala J, Tuulari JJ, Karlsson L, Karlsson H, Nissilä I. Imaging affective and non-affective touch processing in two-year-old children. Neuroimage 2022; 251:118983. [PMID: 35149231 DOI: 10.1016/j.neuroimage.2022.118983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 12/22/2021] [Accepted: 02/07/2022] [Indexed: 10/19/2022] Open
Abstract
Touch is an important component of early parent-child interaction and plays a critical role in the socio-emotional development of children. However, there are limited studies on touch processing amongst children in the age range from one to three years. The present study used frequency-domain diffuse optical tomography (DOT) to investigate the processing of affective and non-affective touch over left frontotemporal brain areas contralateral to the stimulated forearm in two-year-old children. Affective touch was administered by a single stroke with a soft brush over the child's right dorsal forearm at 3 cm/s, while non-affective touch was provided by multiple brush strokes at 30 cm/s. We found that in the insula, the total haemoglobin (HbT) response to slow brushing was significantly greater than the response to fast brushing (slow > fast). Additionally, a region in the postcentral gyrus, Rolandic operculum and superior temporal gyrus exhibited greater response to fast brushing than slow brushing (fast > slow). These findings confirm that an adult-like pattern of haemodynamic responses to affective and non-affective touch can be recorded in two-year-old subjects using DOT. To improve the accuracy of modelling light transport in the two-year-old subjects, we used a published age-appropriate atlas and deformed it to match the exterior shape of each subject's head. We estimated the combined scalp and skull, and grey matter (GM) optical properties by fitting simulated data to calibrated and coupling error corrected phase and amplitude measurements. By utilizing a two-compartment cerebrospinal fluid (CSF) model, the accuracy of estimation of GM optical properties and the localization of activation in the insula was improved. The techniques presented in this paper can be used to study neural development of children at different ages and illustrate that the technology is well-tolerated by most two-year-old children and not excessively sensitive to subject movement. The study points the way towards exciting possibilities in functional imaging of deeper functional areas near sulci in small children.
Collapse
Affiliation(s)
- Ambika Maria
- University of Turku, Department of Clinical Medicine, Turku Brain and Mind Center, FinnBrain Birth Cohort Study, Finland; University of Turku and Turku University Hospital, Department of Psychiatry, Finland
| | - Pauliina Hirvi
- Aalto University, Department of Neuroscience and Biomedical Engineering, P.O. Box 12200, AALTO FI-00076, Finland; Aalto University, Department of Mathematics and Systems Analysis, Finland
| | - Kalle Kotilahti
- Aalto University, Department of Neuroscience and Biomedical Engineering, P.O. Box 12200, AALTO FI-00076, Finland; University of Turku, Department of Clinical Medicine, Turku Brain and Mind Center, FinnBrain Birth Cohort Study, Finland
| | - Juha Heiskala
- HUS Medical Imaging Center, Clinical Neurophysiology; Clinical Neurosciences, Helsinki, University Hospital and University of Helsinki, Helsinki, Finland
| | - Jetro J Tuulari
- University of Turku, Department of Clinical Medicine, Turku Brain and Mind Center, FinnBrain Birth Cohort Study, Finland; University of Turku and Turku University Hospital, Department of Psychiatry, Finland; Turku Collegium for Science, Medicine and Technology, TCSMT, University of Turku, Finland
| | - Linnea Karlsson
- University of Turku, Department of Clinical Medicine, Turku Brain and Mind Center, FinnBrain Birth Cohort Study, Finland; University of Turku and Turku University Hospital, Department of Psychiatry, Finland; University of Turku and Turku University Hospital, Department of Paediatrics and Adolescent Medicine, Finland; Centre for Population Health Research, Turku University Hospital and University of Turku, Turku, Finland
| | - Hasse Karlsson
- University of Turku, Department of Clinical Medicine, Turku Brain and Mind Center, FinnBrain Birth Cohort Study, Finland; University of Turku and Turku University Hospital, Department of Psychiatry, Finland
| | - Ilkka Nissilä
- Aalto University, Department of Neuroscience and Biomedical Engineering, P.O. Box 12200, AALTO FI-00076, Finland.
| |
Collapse
|
11
|
Roldan M, Chatterjee S, Kyriacou PA. Brain Light-Tissue Interaction Modelling: Towards a non-invasive sensor for Traumatic Brain Injury. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021; 2021:1292-1296. [PMID: 34891522 DOI: 10.1109/embc46164.2021.9630909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Traumatic brain injury (TBI) is one of the leading causes of death worldwide, yet there is no systematic approach to monitor TBI non-invasively. The main motivation of this work is to create new knowledge relating to light brain interaction using a Monte Carlo Model, which could aid in the development of non-invasive optical sensors for the continuous assessment of TBI. To this aim, a multilayer model tissue-model of adult human head was developed and explored at the near-infrared optical wavelength. Investigation reveals that maximum light (40-50%) is absorbed in the skull and the minimum light is absorbed in the subarachnoid space (0-1%). It was found that the absorbance of light decreases with increasing source-detector separation up to 3cm where light travels through the subarachnoid space, after which the absorbance increases with the increasing separation. Such information will be helpful towards the modelling of neurocritical brain tissue followed by the sensor development.
Collapse
|
12
|
Zhao H, Sathialingam E, Buckley EM. Accuracy of diffuse correlation spectroscopy measurements of cerebral blood flow when using a three-layer analytical model. BIOMEDICAL OPTICS EXPRESS 2021; 12:7149-7161. [PMID: 34858706 PMCID: PMC8606134 DOI: 10.1364/boe.438303] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 10/15/2021] [Accepted: 10/15/2021] [Indexed: 05/06/2023]
Abstract
Diffuse correlation spectroscopy (DCS) is a non-invasive optical technology for the assessment of an index of cerebral blood flow (CBFi). Analytical methods that model the head as a three-layered medium (i.e., scalp, skull, brain) are becoming more commonly used to minimize the contribution of extracerebral layers to the measured DCS signal in adult cerebral blood flow studies. However, these models rely on a priori knowledge of layer optical properties and thicknesses. Errors in these values can lead to errors in the estimation of CBFi, although the magnitude of this influence has not been rigorously characterized. Herein, we investigate the accuracy of measuring cerebral blood flow with a three-layer model when errors in layer optical properties or thicknesses are present. Through a series of in silico experiments, we demonstrate that CBFi is highly sensitive to errors in brain optical properties and skull and scalp thicknesses. Relative changes in CBFi are less sensitive to optical properties but are influenced by errors in layer thickness. Thus, when using the three-layer model, accurate estimation of scalp and skull thickness are required for reliable results.
Collapse
Affiliation(s)
- Hongting Zhao
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 1760 Haygood Dr. NE, Atlanta, GA 30322, USA
| | - Eashani Sathialingam
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 1760 Haygood Dr. NE, Atlanta, GA 30322, USA
| | - Erin M. Buckley
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 1760 Haygood Dr. NE, Atlanta, GA 30322, USA
- Department of Pediatrics, Emory University School of Medicine, 2015 Uppergate Dr., Atlanta, GA 30322, USA
- Children’s Research Scholar, Children’s Healthcare of Atlanta, 2015 Uppergate Dr., Atlanta, GA 30322, USA
| |
Collapse
|
13
|
Wojtkiewicz S, Liebert A. Parallel, multi-purpose Monte Carlo code for simulation of light propagation in segmented tissues. Biocybern Biomed Eng 2021. [DOI: 10.1016/j.bbe.2021.03.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
|
14
|
Schommartz I, Dix A, Passow S, Li SC. Functional Effects of Bilateral Dorsolateral Prefrontal Cortex Modulation During Sequential Decision-Making: A Functional Near-Infrared Spectroscopy Study With Offline Transcranial Direct Current Stimulation. Front Hum Neurosci 2021; 14:605190. [PMID: 33613203 PMCID: PMC7886709 DOI: 10.3389/fnhum.2020.605190] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 12/21/2020] [Indexed: 11/13/2022] Open
Abstract
The ability to learn sequential contingencies of actions for predicting future outcomes is indispensable for flexible behavior in many daily decision-making contexts. It remains open whether such ability may be enhanced by transcranial direct current stimulation (tDCS). The present study combined tDCS with functional near-infrared spectroscopy (fNIRS) to investigate potential tDCS-induced effects on sequential decision-making and the neural mechanisms underlying such modulations. Offline tDCS and sham stimulation were applied over the left and right dorsolateral prefrontal cortex (dlPFC) in young male adults (N = 29, mean age = 23.4 years, SD = 3.2) in a double-blind between-subject design using a three-state Markov decision task. The results showed (i) an enhanced dlPFC hemodynamic response during the acquisition of sequential state transitions that is consistent with the findings from a previous functional magnetic resonance imaging (fMRI) study; (ii) a tDCS-induced increase of the hemodynamic response in the dlPFC, but without accompanying performance-enhancing effects at the behavioral level; and (iii) a greater tDCS-induced upregulation of hemodynamic responses in the delayed reward condition that seems to be associated with faster decision speed. Taken together, these findings provide empirical evidence for fNIRS as a suitable method for investigating hemodynamic correlates of sequential decision-making as well as functional brain correlates underlying tDCS-induced modulation. Future research with larger sample sizes for carrying out subgroup analysis is necessary in order to decipher interindividual differences in tDCS-induced effects on sequential decision-making process at the behavioral and brain levels.
Collapse
Affiliation(s)
- Iryna Schommartz
- Chair of Lifespan Developmental Neuroscience, Faculty of Psychology, Technische Universität Dresden, Dresden, Germany
- Department of Developmental Psychology, Institute of Psychology, Goethe University Frankfurt, Frankfurt, Germany
| | - Annika Dix
- Chair of Lifespan Developmental Neuroscience, Faculty of Psychology, Technische Universität Dresden, Dresden, Germany
- Centre for Tactile Internet With Human-in-the-Loop, Technische Universität Dresden, Dresden, Germany
| | - Susanne Passow
- Chair of Lifespan Developmental Neuroscience, Faculty of Psychology, Technische Universität Dresden, Dresden, Germany
| | - Shu-Chen Li
- Chair of Lifespan Developmental Neuroscience, Faculty of Psychology, Technische Universität Dresden, Dresden, Germany
- Centre for Tactile Internet With Human-in-the-Loop, Technische Universität Dresden, Dresden, Germany
| |
Collapse
|
15
|
Yang L, Wabnitz H, Gladytz T, Sudakou A, Macdonald R, Grosenick D. Space-enhanced time-domain diffuse optics for determination of tissue optical properties in two-layered structures. BIOMEDICAL OPTICS EXPRESS 2020; 11:6570-6589. [PMID: 33282509 PMCID: PMC7687957 DOI: 10.1364/boe.402181] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 09/18/2020] [Accepted: 09/28/2020] [Indexed: 05/05/2023]
Abstract
A novel methodology for solving the inverse problem of diffuse optics for two-layered structures is proposed to retrieve the absolute quantities of optical absorption and reduced scattering coefficients of the layers simultaneously. A liquid phantom with various optical absorption properties in the deep layer is prepared and experimentally investigated using the space-enhanced time-domain method. Monte-Carlo simulations are applied to analyze the different measurements in time domain, space domain, and by the new methodology. The deviations of retrieved values from nominal values of both layers' optical properties are simultaneously reduced to a very low extent compared to the single-domain methods. The reliability and uncertainty of the retrieval performance are also considerably improved by the new methodology. It is observed in time-domain analyses that for the deep layer the retrieval of absorption coefficient is almost not affected by the scattering properties and this kind of "deep scattering neutrality" is investigated and overcome as well.
Collapse
Affiliation(s)
- Lin Yang
- Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587 Berlin, Germany
- Institute of Optics and Atomic Physics, Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Heidrun Wabnitz
- Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587 Berlin, Germany
| | - Thomas Gladytz
- Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587 Berlin, Germany
| | - Aleh Sudakou
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Trojdena 4, 02-109 Warsaw, Poland
| | - Rainer Macdonald
- Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587 Berlin, Germany
- Institute of Optics and Atomic Physics, Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Dirk Grosenick
- Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587 Berlin, Germany
| |
Collapse
|
16
|
Sudakou A, Yang L, Wabnitz H, Wojtkiewicz S, Liebert A. Performance of measurands in time-domain optical brain imaging: depth selectivity versus contrast-to-noise ratio. BIOMEDICAL OPTICS EXPRESS 2020; 11:4348-4365. [PMID: 32923048 PMCID: PMC7449735 DOI: 10.1364/boe.397483] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 07/03/2020] [Accepted: 07/03/2020] [Indexed: 05/25/2023]
Abstract
Time-domain optical brain imaging techniques introduce a number of different measurands for analyzing absorption changes located deep in the tissue, complicated by superficial absorption changes and noise. We implement a method that allows analysis, quantitative comparison and performance ranking of measurands under various conditions - including different values of reduced scattering coefficient, thickness of the superficial layer, and source-detector separation. Liquid phantom measurements and Monte Carlo simulations were carried out in two-layered geometry to acquire distributions of times of flight of photons and to calculate the total photon count, mean time of flight, variance, photon counts in time windows and ratios of photon counts in different time windows. Quantitative comparison of performance was based on objective metrics: relative contrast, contrast-to-noise ratio (CNR) and depth selectivity. Moreover, the product of CNR and depth selectivity was used to rank the overall performance and to determine the optimal source-detector separation for each measurand. Variance ranks the highest under all considered conditions.
Collapse
Affiliation(s)
- Aleh Sudakou
- Nalecz Institute of Biocybernetics and Biomedical Engineering Polish Academy of Sciences, Trojdena 4, 02-109 Warsaw, Poland
| | - Lin Yang
- Physikalisch-Technische Bundesanstalt, Abbestraße 2-12, 10587 Berlin, Germany
| | - Heidrun Wabnitz
- Physikalisch-Technische Bundesanstalt, Abbestraße 2-12, 10587 Berlin, Germany
| | - Stanislaw Wojtkiewicz
- 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
| |
Collapse
|
17
|
Tran AP, Yan S, Fang Q. Improving model-based functional near-infrared spectroscopy analysis using mesh-based anatomical and light-transport models. NEUROPHOTONICS 2020; 7:015008. [PMID: 32118085 PMCID: PMC7035879 DOI: 10.1117/1.nph.7.1.015008] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 02/05/2020] [Indexed: 05/04/2023]
Abstract
Significance: Functional near-infrared spectroscopy (fNIRS) has become an important research tool in studying human brains. Accurate quantification of brain activities via fNIRS relies upon solving computational models that simulate the transport of photons through complex anatomy. Aim: We aim to highlight the importance of accurate anatomical modeling in the context of fNIRS and propose a robust method for creating high-quality brain/full-head tetrahedral mesh models for neuroimaging analysis. Approach: We have developed a surface-based brain meshing pipeline that can produce significantly better brain mesh models, compared to conventional meshing techniques. It can convert segmented volumetric brain scans into multilayered surfaces and tetrahedral mesh models, with typical processing times of only a few minutes and broad utilities, such as in Monte Carlo or finite-element-based photon simulations for fNIRS studies. Results: A variety of high-quality brain mesh models have been successfully generated by processing publicly available brain atlases. In addition, we compare three brain anatomical models-the voxel-based brain segmentation, tetrahedral brain mesh, and layered-slab brain model-and demonstrate noticeable discrepancies in brain partial pathlengths when using approximated brain anatomies, ranging between - 1.5 % to 23% with the voxelated brain and 36% to 166% with the layered-slab brain. Conclusion: The generation and utility of high-quality brain meshes can lead to more accurate brain quantification in fNIRS studies. Our open-source meshing toolboxes "Brain2Mesh" and "Iso2Mesh" are freely available at http://mcx.space/brain2mesh.
Collapse
Affiliation(s)
- Anh Phong Tran
- Northeastern University, Department of Chemical Engineering, Boston, Massachusetts, United States
| | - Shijie Yan
- Northeastern University, Department of Electrical and Computer Engineering, Boston, Massachusetts, United States
| | - Qianqian Fang
- Northeastern University, Department of Electrical and Computer Engineering, Boston, Massachusetts, United States
- Northeastern University, Department of Bioengineering, Boston, Massachusetts, United States
- Address all correspondence to Qianqian Fang, E-mail:
| |
Collapse
|
18
|
Wang L, Ayaz H, Izzetoglu M. Investigation of the source-detector separation in near infrared spectroscopy for healthy and clinical applications. JOURNAL OF BIOPHOTONICS 2019; 12:e201900175. [PMID: 31291506 DOI: 10.1002/jbio.201900175] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 07/08/2019] [Accepted: 07/09/2019] [Indexed: 05/20/2023]
Abstract
Understanding near infrared light propagation in tissue is vital for designing next generation optical brain imaging devices. Monte Carlo (MC) simulations provide a controlled mechanism to characterize and evaluate contributions of diverse near infrared spectroscopy (NIRS) sensor configurations and parameters. In this study, we developed a multilayer adult digital head model under both healthy and clinical settings and assessed light-tissue interaction through MC simulations in terms of partial differential pathlength, mean total optical pathlength, diffuse reflectance, detector light intensity and spatial sensitivity profile of optical measurements. The model incorporated four layers: scalp, skull, cerebrospinal-fluid and cerebral cortex with and without a customizable lesion for modeling hematoma of different sizes and depths. The effect of source-detector separation (SDS) on optical measurements' sensitivity to brain tissue was investigated. Results from 1330 separate simulations [(4 lesion volumes × 4 lesion depths for clinical +3 healthy settings) × 7 SDS × 10 simulation = 1330)] each with 100 million photons indicated that selection of SDS is critical to acquire optimal measurements from the brain and recommended SDS to be 25 to 35 mm depending on the wavelengths to obtain optical monitoring of the adult brain function. The findings here can guide the design of future NIRS probes for functional neuroimaging and clinical diagnostic systems.
Collapse
Affiliation(s)
- Lei Wang
- Drexel University, School of Biomedical Engineering, Science and Health Systems, Philadelphia, Pennsylvania
| | - Hasan Ayaz
- Drexel University, School of Biomedical Engineering, Science and Health Systems, Philadelphia, Pennsylvania
- Department of Family and Community Health, University of Pennsylvania, Philadelphia, Pennsylvania
- Children's Hospital of Philadelphia, Center for Injury Research and Prevention, Philadelphia, Pennsylvania
| | - Meltem Izzetoglu
- Villanova University, Electrical and Computer Engineering, Villanova, Pennsylvania
| |
Collapse
|
19
|
Zhang Y, Liu X, Wang Q, Liu D, Yang C, Sun J. Influence of extracerebral layers on estimates of optical properties with continuous wave near infrared spectroscopy: analysis based on multi-layered brain tissue architecture and Monte Carlo simulation. Comput Assist Surg (Abingdon) 2019; 24:144-150. [PMID: 30676092 DOI: 10.1080/24699322.2018.1557902] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
Continuous wave near-infrared spectroscopy (CW-NIRS) can be used to measure cerebral activity because it is noninvasive, simple and portable. However, the performance of the continuous wave near-infrared spectroscopy is distorted by the presence of extracerebral layer. Change of optical parameters in gray matter layer will then be inappropriately converted into the brain activity response. In the current study, a five-layer structure model constitute of scalp, skull, cerebrospinal fluid, gray matter and white matter, have been applied to fabricate human brain tissue. The phantom is made by the mixture of the Intralipid, India ink and agar. The optical parameters of gray matter layer can be flexibly adjusted to simulate the change of the deep brain tissue. The near infrared optical measurement system was designed to detect the changes in the absorption coefficients of the gray matter and quantitative analyze the influence of the extracerebral layers. Monte Carlo technique for the equivalent multi-layered brain tissue models is then performed to compensate partial volume effect introduced by the extracerebral layers. The results of the experiments suggested that the extracerebral layers influence the measurement and the influence of the extracerebral layers can be suppressed by correcting partial volume effect using Monte Carlo simulations.
Collapse
Affiliation(s)
- Yan Zhang
- School of Electrical Engineering and Automaton, Harbin Institute of Technology , Harbin , China
| | - Xin Liu
- School of Transportation Science and Engineering, Harbin Institute of Technology , Harbin , China
| | - Qisong Wang
- School of Electrical Engineering and Automaton, Harbin Institute of Technology , Harbin , China
| | - Dan Liu
- School of Electrical Engineering and Automaton, Harbin Institute of Technology , Harbin , China
| | - Chunling Yang
- School of Electrical Engineering and Automaton, Harbin Institute of Technology , Harbin , China
| | - Jinwei Sun
- School of Electrical Engineering and Automaton, Harbin Institute of Technology , Harbin , China
| |
Collapse
|
20
|
Yang L, Wabnitz H, Gladytz T, Macdonald R, Grosenick D. Spatially-enhanced time-domain NIRS for accurate determination of tissue optical properties. OPTICS EXPRESS 2019; 27:26415-26431. [PMID: 31674524 DOI: 10.1364/oe.27.026415] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
A multivariate method integrating time and space resolved techniques of near-infrared spectroscopy is proposed for simultaneously retrieving the absolute quantities of optical absorption and scattering properties in tissues. The time-domain feature of photon migration is advantageously constrained and regularized by its spatially-resolved amplitude patterns in the inverse procedure. Measurements of tissue-mimicking phantoms with various optical properties are analyzed with Monte-Carlo simulations to validate the method performance. The uniqueness, stability, and uncertainty of the method are discussed.
Collapse
|
21
|
Mahmoodkalayeh S, Ansari MA, Tuchin VV. Head model based on the shape of the subject's head for optical brain imaging. BIOMEDICAL OPTICS EXPRESS 2019; 10:2795-2808. [PMID: 31259052 PMCID: PMC6583357 DOI: 10.1364/boe.10.002795] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 04/24/2019] [Accepted: 05/09/2019] [Indexed: 05/05/2023]
Abstract
Optical imaging methods such as near-infrared spectroscopy and diffuse optical tomography rely on models to solve the inverse problem. Imaging an adult human head also requires a head model. Using a model, which makes describing the structure of the head better, leads to acquiring a more accurate absorption map. Here, by combining the key features of layered slab models and head atlases, we introduce a new two-layered head model that is based on the surface geometry of the subject's head with variable thickness of the superficial layer. Using the Monte Carlo approach, we assess the performance of our model for fitting the optical properties from simulated time-resolved data of the adult head in a null distance source-detector configuration. Using our model, we observed improved results at 70 percent of the locations on the head and an overall 20 percent reduction in relative error compared to layered slab model.
Collapse
Affiliation(s)
- Sadreddin Mahmoodkalayeh
- Department of Physics, Shahid Beheshti University, Velenjak, Tehran, Iran
- Laser and Plasma Research Institute, Shahid Beheshti University, 1983969411, Tehran, Iran
| | - Mohammad Ali Ansari
- Laser and Plasma Research Institute, Shahid Beheshti University, 1983969411, Tehran, Iran
| | - Valery V. Tuchin
- Research-Educational Institute of Optics and Biophotonics, Saratov State University, Saratov, Russia
- Interdisciplinary Laboratory of Biophotonics, Tomsk State University, Tomsk, Russia
- Laboratory of Laser Diagnostics of Technical and Living Systems, Institute of Precision Mechanics and Control of the Russian Academy of Sciences, Saratov, Russia
| |
Collapse
|
22
|
Clinical Brain Monitoring with Time Domain NIRS: A Review and Future Perspectives. APPLIED SCIENCES-BASEL 2019. [DOI: 10.3390/app9081612] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Near-infrared spectroscopy (NIRS) is an optical technique that can measure brain tissue oxygenation and haemodynamics in real-time and at the patient bedside allowing medical doctors to access important physiological information. However, despite this, the use of NIRS in a clinical environment is hindered due to limitations, such as poor reproducibility, lack of depth sensitivity and poor brain-specificity. Time domain NIRS (or TD-NIRS) can resolve these issues and offer detailed information of the optical properties of the tissue, allowing better physiological information to be retrieved. This is achieved at the cost of increased instrument complexity, operation complexity and price. In this review, we focus on brain monitoring clinical applications of TD-NIRS. A total of 52 publications were identified, spanning the fields of neonatal imaging, stroke assessment, traumatic brain injury (TBI) assessment, brain death assessment, psychiatry, peroperative care, neuronal disorders assessment and communication with patient with locked-in syndrome. In all the publications, the advantages of the TD-NIRS measurement to (1) extract absolute values of haemoglobin concentration and tissue oxygen saturation, (2) assess the reduced scattering coefficient, and (3) separate between extra-cerebral and cerebral tissues, are highlighted; and emphasize the utility of TD-NIRS in a clinical context. In the last sections of this review, we explore the recent developments of TD-NIRS, in terms of instrumentation and methodologies that might impact and broaden its use in the hospital.
Collapse
|
23
|
Fantini S, Frederick B, Sassaroli A. Perspective: Prospects of non-invasive sensing of the human brain with diffuse optical imaging. APL PHOTONICS 2018; 3:110901. [PMID: 31187064 PMCID: PMC6559748 DOI: 10.1063/1.5038571] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 07/14/2018] [Indexed: 05/19/2023]
Abstract
Since the initial demonstration of near-infrared spectroscopy (NIRS) for noninvasive measurements of brain perfusion and metabolism in the 1970s, and its application to functional brain studies (fNIRS) in the 1990s, the field of noninvasive optical studies of the brain has been continuously growing. Technological developments, data analysis advances, and novel areas of application keep advancing the field. In this article, we provide a view of the state of the field of cerebral NIRS, starting with a brief historical introduction and a description of the information content of the NIRS signal. We argue that NIRS and fNIRS studies should always report data of both oxy- and deoxyhemoglobin concentrations in brain tissue, as they complement each other to provide more complete functional and physiological information, and may help identify different types of confounds. One significant challenge is the assessment of absolute tissue properties, be them optical or physiological, so that relative measurements account for the vast majority of NIRS and fNIRS applications. However, even relative measurements of hemodynamics or metabolic changes face the major problem of a potential contamination from extracerebral tissue layers. Accounting for extracerebral contributions to fNIRS signals is one of the most critical barriers in the field. We present some of the approaches that were proposed to tackle this challenge in the study of cerebral hemodynamics and functional connectivity. Finally, we critically compare fNIRS and functional magnetic resonance imaging (fMRI) by relating their measurements in terms of signal and noise, and by commenting on their complementarity.
Collapse
Affiliation(s)
- Sergio Fantini
- Department of Biomedical Engineering, Tufts University, Medford, MA, USA
| | - Blaise Frederick
- Brain Imaging Center, McLean Hospital, Belmont, MA, USA
- Department of Psychiatry, Harvard University Medical School, Boston, MA, USA
| | - Angelo Sassaroli
- Department of Biomedical Engineering, Tufts University, Medford, MA, USA
| |
Collapse
|
24
|
Selb J, Wu KC, Sutin J, Lin PY(I, Farzam P, Bechek S, Shenoy A, Patel AB, Boas DA, Franceschini MA, Rosenthal ES. Prolonged monitoring of cerebral blood flow and autoregulation with diffuse correlation spectroscopy in neurocritical care patients. NEUROPHOTONICS 2018; 5:045005. [PMID: 30450363 PMCID: PMC6233866 DOI: 10.1117/1.nph.5.4.045005] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 09/24/2018] [Indexed: 05/13/2023]
Abstract
Monitoring of cerebral blood flow (CBF) and autoregulation are essential components of neurocritical care, but continuous noninvasive methods for CBF monitoring are lacking. Diffuse correlation spectroscopy (DCS) is a noninvasive diffuse optical modality that measures a CBF index ( CBF i ) in the cortex microvasculature by monitoring the rapid fluctuations of near-infrared light diffusing through moving red blood cells. We tested the feasibility of monitoring CBF i with DCS in at-risk patients in the Neurosciences Intensive Care Unit. DCS data were acquired continuously for up to 20 h in six patients with aneurysmal subarachnoid hemorrhage, as permitted by clinical care. Mean arterial blood pressure was recorded synchronously, allowing us to derive autoregulation curves and to compute an autoregulation index. The autoregulation curves suggest disrupted cerebral autoregulation in most patients, with the severity of disruption and the limits of preserved autoregulation varying between subjects. Our findings suggest the potential of the DCS modality for noninvasive, long-term monitoring of cerebral perfusion, and autoregulation.
Collapse
Affiliation(s)
- Juliette Selb
- Massachusetts General Hospital, Optics at Martinos, Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
| | - Kuan-Cheng Wu
- Massachusetts General Hospital, Optics at Martinos, Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
| | - Jason Sutin
- Massachusetts General Hospital, Optics at Martinos, Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
| | - Pei-Yi (Ivy) Lin
- Massachusetts General Hospital, Optics at Martinos, Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
| | - Parisa Farzam
- Massachusetts General Hospital, Optics at Martinos, Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
| | - Sophia Bechek
- Massachusetts General Hospital, Department of Neurology, Boston, Massachusetts, United States
| | - Apeksha Shenoy
- Massachusetts General Hospital, Department of Neurology, Boston, Massachusetts, United States
| | - Aman B. Patel
- Massachusetts General Hospital, Department of Neurology, Boston, Massachusetts, United States
| | - David A. Boas
- Massachusetts General Hospital, Optics at Martinos, Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
| | - Maria Angela Franceschini
- Massachusetts General Hospital, Optics at Martinos, Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
- Address all correspondence to: Maria Angela Franceschini, E-mail:
| | - Eric S. Rosenthal
- Massachusetts General Hospital, Department of Neurology, Boston, Massachusetts, United States
| |
Collapse
|
25
|
Ancora D, Qiu L, Zacharakis G, Spinelli L, Torricelli A, Pifferi A. Noninvasive optical estimation of CSF thickness for brain-atrophy monitoring. BIOMEDICAL OPTICS EXPRESS 2018; 9:4094-4112. [PMID: 30615703 PMCID: PMC6157767 DOI: 10.1364/boe.9.004094] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 07/06/2018] [Accepted: 07/06/2018] [Indexed: 05/29/2023]
Abstract
Dementia disorders are increasingly becoming sources of a broad range of problems, strongly interfering with the normal daily tasks of a growing number of individuals. Such neurodegenerative diseases are often accompanied with progressive brain atrophy that, at late stages, leads to drastically reduced brain dimensions. Currently, this structural change could be followed with X-ray computed tomography (XCT) or magnetic resonance imaging (MRI), but they share numerous disadvantages in terms of usability, invasiveness and costs. In this work, we aim to retrieve information concerning the brain-atrophy stage and its evolution, proposing a novel approach based on non-invasive time-resolved near infra-red (tr-NIR) measurements. For this purpose, we created a set of virtual human-head atlases in which we eroded the brain as it would happen in a clinical brain-atrophy progression. These realistic meshes were used to simulate a longitudinal tr-NIR study, investigating the effects of an increased amount of cerebral spinal fluid (CSF) in the photon diffusion. The analysis of late photons in the time-resolved reflectance curve-obtained via accurate Monte Carlo simulations-exhibited peculiar slope-changes upon CSF layer increase. The visibility of the effect under several measurement conditions suggested good sensitivity to CSF variation, even in the case of real measurement and under different geometrical models. The robustness of the results might promote the technique as a potential indicator of the dementia progression, relying only on fast and non-invasive optical observations.
Collapse
Affiliation(s)
- Daniele Ancora
- Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, Heraklion, Greece
- Department of Materials Science and Technology, University of Crete, Heraklion, Greece
| | - Lina Qiu
- Dipartimento di Fisica, Politecnico di Milano, Milan, Italy
| | - Giannis Zacharakis
- Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, Heraklion, Greece
| | - Lorenzo Spinelli
- Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Milan, Italy
| | - Alessandro Torricelli
- Dipartimento di Fisica, Politecnico di Milano, Milan, Italy
- Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Milan, Italy
| | - Antonio Pifferi
- Dipartimento di Fisica, Politecnico di Milano, Milan, Italy
- Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Milan, Italy
| |
Collapse
|
26
|
Wojtkiewicz S, Durduran T, Dehghani H. Time-resolved near infrared light propagation using frequency domain superposition. BIOMEDICAL OPTICS EXPRESS 2018; 9:41-54. [PMID: 29359086 PMCID: PMC5772588 DOI: 10.1364/boe.9.000041] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 11/15/2017] [Accepted: 11/24/2017] [Indexed: 05/02/2023]
Abstract
Time-resolved temporal point spread function (TPSF) measurement of near infrared spectroscopic (NIRS) data allows the estimation of absorption and reduced scattering properties of biological tissues. Such analysis requires an iterative calculation of the theoretical TPSF curve using mathematical and computational models of the domain being imaged which are computationally complex and expensive. In this work, an efficient methodology for representing the TPSF data using a superposition of cosines calculated in frequency domain is presented. The proposed method is outlined and tested on finite element realistic models of the human neck and head. Using an adult head model containing ~140k nodes, the TPSF calculation at each node for one source is accelerated from 3.11 s to 1.29 s within an error limit of ± 5% related to the time domain calculation method.
Collapse
Affiliation(s)
- Stanislaw Wojtkiewicz
- School of Computer Science, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Turgut Durduran
- ICFO - Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels (Barcelona), Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
| | - Hamid Dehghani
- School of Computer Science, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| |
Collapse
|
27
|
Periyasamy V, Pramanik M. Advances in Monte Carlo Simulation for Light Propagation in Tissue. IEEE Rev Biomed Eng 2017; 10:122-135. [PMID: 28816674 DOI: 10.1109/rbme.2017.2739801] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Monte Carlo (MC) simulation for light propagation in tissue is the gold standard for studying the light propagation in biological tissue and has been used for years. Interaction of photons with a medium is simulated based on its optical properties. New simulation geometries, tissue-light interaction methods, and recording techniques recently have been designed. Applications, such as whole mouse body simulations for fluorescence imaging, eye modeling for blood vessel imaging, skin modeling for terahertz imaging, and human head modeling for sinus imaging, have emerged. Here, we review the technical advances and recent applications of MC simulation.
Collapse
|
28
|
Abstract
Accurate and efficient solutions of the three dimensional radiative transport equation were derived in all domains for the case of layered scattering media. Index mismatched boundary conditions based on Fresnel’s equations were implemented. Arbitrary rotationally symmetric phase functions can be applied to characterize the scattering in the turbid media. Solutions were derived for an obliquely incident beam having arbitrary spatial profiles. The derived solutions were successfully validated with Monte Carlo simulations and partly compared with analytical solutions of the diffusion equation.
Collapse
|
29
|
Milej D, Abdalmalak A, McLachlan P, Diop M, Liebert A, St. Lawrence K. Subtraction-based approach for enhancing the depth sensitivity of time-resolved NIRS. BIOMEDICAL OPTICS EXPRESS 2016; 7:4514-4526. [PMID: 27895992 PMCID: PMC5119592 DOI: 10.1364/boe.7.004514] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 09/13/2016] [Accepted: 09/14/2016] [Indexed: 05/18/2023]
Abstract
The aim of this study was to evaluate enhancing of the depth sensitivity of time-resolved near-infrared spectroscopy with a subtraction-based approach. Due to the complexity of light propagation in a heterogeneous media, and to prove the validity of the proposed method in a heterogeneous turbid media we conducted a broad analysis taking into account a number of parameters related to the method as well as various parameters of this media. The results of these experiments confirm that the depth sensitivity of the subtraction-based approach is better than classical approaches using continuous-wave or time-resolved methods. Furthermore, the results showed that the subtraction-based approach has a unique, selective sensitivity to a layer at a specific depth. In vivo application of the proposed method resulted in a greater magnitude of the hemodynamic changes during functional activation than with the standard approach.
Collapse
Affiliation(s)
- Daniel Milej
- Department of Medical Biophysics, Western University, London, ON, Canada
- Imaging Division, Lawson Health Research Institute, London, ON, Canada
| | - Androu Abdalmalak
- Department of Medical Biophysics, Western University, London, ON, Canada
- Imaging Division, Lawson Health Research Institute, London, ON, Canada
| | - Peter McLachlan
- 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
| | - Adam Liebert
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Warsaw, Poland
| | - Keith. St. Lawrence
- Department of Medical Biophysics, Western University, London, ON, Canada
- Imaging Division, Lawson Health Research Institute, London, ON, Canada
| |
Collapse
|
30
|
Tachtsidis I, Scholkmann F. False positives and false negatives in functional near-infrared spectroscopy: issues, challenges, and the way forward. NEUROPHOTONICS 2016; 3:031405. [PMID: 27054143 PMCID: PMC4791590 DOI: 10.1117/1.nph.3.3.031405] [Citation(s) in RCA: 277] [Impact Index Per Article: 34.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 02/05/2016] [Indexed: 05/20/2023]
Abstract
We highlight a significant problem that needs to be considered and addressed when performing functional near-infrared spectroscopy (fNIRS) studies, namely the possibility of inadvertently measuring fNIRS hemodynamic responses that are not due to neurovascular coupling. These can be misinterpreted as brain activity, i.e., "false positives" (errors caused by wrongly assigning a detected hemodynamic response to functional brain activity), or mask brain activity, i.e., "false negatives" (errors caused by wrongly assigning a not observed hemodynamic response in the presence of functional brain activity). Here, we summarize the possible physiological origins of these issues and suggest ways to avoid and remove them.
Collapse
Affiliation(s)
- Ilias Tachtsidis
- University College London, Department of Medical Physics and Biomedical Engineering, Gower Street, Malet Place Engineering Building, WC1E 6BT, London, United Kingdom
| | - Felix Scholkmann
- University Hospital Zurich, University of Zurich, Department of Neonatology, Biomedical Optics Research Laboratory, Frauenklinikstr. 10, 8091 Zurich, Switzerland
- Address all correspondence to: Felix Scholkmann, E-mail:
| |
Collapse
|
31
|
Tachtsidis I, Scholkmann F. False positives and false negatives in functional near-infrared spectroscopy: issues, challenges, and the way forward. NEUROPHOTONICS 2016. [PMID: 27054143 DOI: 10.1117/1.nph.3.3.030401] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
We highlight a significant problem that needs to be considered and addressed when performing functional near-infrared spectroscopy (fNIRS) studies, namely the possibility of inadvertently measuring fNIRS hemodynamic responses that are not due to neurovascular coupling. These can be misinterpreted as brain activity, i.e., "false positives" (errors caused by wrongly assigning a detected hemodynamic response to functional brain activity), or mask brain activity, i.e., "false negatives" (errors caused by wrongly assigning a not observed hemodynamic response in the presence of functional brain activity). Here, we summarize the possible physiological origins of these issues and suggest ways to avoid and remove them.
Collapse
Affiliation(s)
- Ilias Tachtsidis
- University College London , Department of Medical Physics and Biomedical Engineering, Gower Street, Malet Place Engineering Building, WC1E 6BT, London, United Kingdom
| | - Felix Scholkmann
- University Hospital Zurich, University of Zurich , Department of Neonatology, Biomedical Optics Research Laboratory, Frauenklinikstr. 10, 8091 Zurich, Switzerland
| |
Collapse
|
32
|
Rackebrandt K, Gehring H. Calibration and evaluation of a continuous wave multi-distance NIRS system in simulated desaturation investigations. Biomed Phys Eng Express 2016. [DOI: 10.1088/2057-1976/2/3/035017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
33
|
Placati S, Guermandi M, Samore A, Scarselli EF, Guerrieri R. Parallel Solver for Diffuse Optical Tomography on Realistic Head Models With Scattering and Clear Regions. IEEE Trans Biomed Eng 2015; 63:1874-1886. [PMID: 26625406 DOI: 10.1109/tbme.2015.2504178] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Diffuse optical tomography is an imaging technique, based on evaluation of how light propagates within the human head to obtain the functional information about the brain. Precision in reconstructing such an optical properties map is highly affected by the accuracy of the light propagation model implemented, which needs to take into account the presence of clear and scattering tissues. We present a numerical solver based on the radiosity-diffusion model, integrating the anatomical information provided by a structural MRI. The solver is designed to run on parallel heterogeneous platforms based on multiple GPUs and CPUs. We demonstrate how the solver provides a 7 times speed-up over an isotropic-scattered parallel Monte Carlo engine based on a radiative transport equation for a domain composed of 2 million voxels, along with a significant improvement in accuracy. The speed-up greatly increases for larger domains, allowing us to compute the light distribution of a full human head ( ≈ 3 million voxels) in 116 s for the platform used.
Collapse
|
34
|
Martelli F, Del Bianco S, Spinelli L, Cavalieri S, Di Ninni P, Binzoni T, Jelzow A, Macdonald R, Wabnitz H. Optimal estimation reconstruction of the optical properties of a two-layered tissue phantom from time-resolved single-distance measurements. JOURNAL OF BIOMEDICAL OPTICS 2015; 20:115001. [PMID: 26524677 DOI: 10.1117/1.jbo.20.11.115001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 09/25/2015] [Indexed: 05/02/2023]
Abstract
In this work, we have tested the optimal estimation (OE) algorithm for the reconstruction of the optical properties of a two-layered liquid tissue phantom from time-resolved single-distance measurements. The OE allows a priori information, in particular on the range of variation of fit parameters, to be included. The purpose of the present investigations was to compare the performance of OE with the Levenberg–Marquardt method for a geometry and real experimental conditions typically used to reconstruct the optical properties of biological tissues such as muscle and brain. The absorption coefficient of the layers was varied in a range of values typical for biological tissues. The reconstructions performed demonstrate the substantial improvements achievable with the OE provided a priori information is available. We note the extreme reliability, robustness, and accuracy of the retrieved absorption coefficient of the second layer obtained with the OE that was found for up to six fit parameters, with an error in the retrieved values of less than 10%. A priori information on fit parameters and fixed forward model parameters clearly improves robustness and accuracy of the inversion procedure.
Collapse
Affiliation(s)
- Fabrizio Martelli
- Università degli Studi di Firenze, Dipartimento di Fisica e Astronomia, Via G. Sansone 1, Sesto Fiorentino 50019, Firenze, Italy
| | - Samuele Del Bianco
- Istituto di Fisica Applicata Nello Carrara del Consiglio Nazionale delle Ricerche, Via Madonna del Piano 10, Sesto Fiorentino 50019, Italy
| | - Lorenzo Spinelli
- Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Piazza Leonardo da Vinci 32, Milano 20133, Italy
| | - Stefano Cavalieri
- Università degli Studi di Firenze, Dipartimento di Fisica e Astronomia, Via G. Sansone 1, Sesto Fiorentino 50019, Firenze, Italy
| | - Paola Di Ninni
- Università degli Studi di Firenze, Dipartimento di Fisica e Astronomia, Via G. Sansone 1, Sesto Fiorentino 50019, Firenze, Italy
| | - Tiziano Binzoni
- University of Geneva, Département de Neurosciences Fondamentales, 1, rue Michel-Servet 1211 Genève 4, SwitzerlandeUniversity Hospital, Département de l'Imagerie et des Sciences de l'Information Médicale, 1, 4 rue Gabrielle-Perret-Gentil, 1211 Geneva 14, S
| | - Alexander Jelzow
- Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin, Germany
| | - Rainer Macdonald
- Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin, Germany
| | - Heidrun Wabnitz
- Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin, Germany
| |
Collapse
|
35
|
Wijeakumar S, Spencer JP, Bohache K, Boas DA, Magnotta VA. Validating a new methodology for optical probe design and image registration in fNIRS studies. Neuroimage 2015; 106:86-100. [PMID: 25705757 DOI: 10.1016/j.neuroimage.2014.11.022] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Functional near-infrared spectroscopy (fNIRS) is an imaging technique that relies on the principle of shining near-infrared light through tissue to detect changes in hemodynamic activation. An important methodological issue encountered is the creation of optimized probe geometry for fNIRS recordings. Here, across three experiments, we describe and validate a processing pipeline designed to create an optimized, yet scalable probe geometry based on selected regions of interest (ROIs) from the functional magnetic resonance imaging (fMRI) literature. In experiment 1, we created a probe geometry optimized to record changes in activation from target ROIs important for visual working memory. Positions of the sources and detectors of the probe geometry on an adult head were digitized using a motion sensor and projected onto a generic adult atlas and a segmented head obtained from the subject's MRI scan. In experiment 2, the same probe geometry was scaled down to fit a child's head and later digitized and projected onto the generic adult atlas and a segmented volume obtained from the child's MRI scan. Using visualization tools and by quantifying the amount of intersection between target ROIs and channels, we show that out of 21 ROIs, 17 and 19 ROIs intersected with fNIRS channels from the adult and child probe geometries, respectively. Further, both the adult atlas and adult subject-specific MRI approaches yielded similar results and can be used interchangeably. However, results suggest that segmented heads obtained from MRI scans be used for registering children's data. Finally, in experiment 3, we further validated our processing pipeline by creating a different probe geometry designed to record from target ROIs involved in language and motor processing.
Collapse
|
36
|
Farina A, Torricelli A, Bargigia I, Spinelli L, Cubeddu R, Foschum F, Jäger M, Simon E, Fugger O, Kienle A, Martelli F, Di Ninni P, Zaccanti G, Milej D, Sawosz P, Kacprzak M, Liebert A, Pifferi A. In-vivo multilaboratory investigation of the optical properties of the human head. BIOMEDICAL OPTICS EXPRESS 2015. [PMID: 26203385 PMCID: PMC4505713 DOI: 10.1364/boe.6.002609] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The in-vivo optical properties of the human head are investigated in the 600-1100 nm range on different subjects using continuous wave and time domain diffuse optical spectroscopy. The work was performed in collaboration with different research groups and the different techniques were applied to the same subject. Data analysis was carried out using homogeneous and layered models and final results were also confirmed by Monte Carlo simulations. The depth sensitivity of each technique was investigated and related to the probed region of the cerebral tissue. This work, based on different validated instruments, is a contribution to fill the existing gap between the present knowledge and the actual in-vivo values of the head optical properties.
Collapse
Affiliation(s)
- Andrea Farina
- Consiglio Nazionale delle Ricerche - Istituto di Fotonica e Nanotecnologie, Piazza L. da Vinci 32, I-20133 Milano,
Italy
| | - Alessandro Torricelli
- POLIMI, Politecnico di Milano, Dipartimento di Fisica, Piazza L. Da Vinci 32, I-20133 Milano,
Italy
| | - Ilaria Bargigia
- Center for Nano-Science and Technology @POLIMI, Istituto Italiano di Tecnologia, via G. Pascoli 70/3, 20133 Milano,
Italy
| | - Lorenzo Spinelli
- Consiglio Nazionale delle Ricerche - Istituto di Fotonica e Nanotecnologie, Piazza L. da Vinci 32, I-20133 Milano,
Italy
| | - Rinaldo Cubeddu
- POLIMI, Politecnico di Milano, Dipartimento di Fisica, Piazza L. Da Vinci 32, I-20133 Milano,
Italy
| | - Florian Foschum
- ILM, Institut für Lasertechnologien in der Medizin und Meßtechnik an der Universität Ulm, Helmholtzstraße 12, D-89081 Ulm,
Germany
| | - Marion Jäger
- ILM, Institut für Lasertechnologien in der Medizin und Meßtechnik an der Universität Ulm, Helmholtzstraße 12, D-89081 Ulm,
Germany
| | - Emanuel Simon
- ILM, Institut für Lasertechnologien in der Medizin und Meßtechnik an der Universität Ulm, Helmholtzstraße 12, D-89081 Ulm,
Germany
| | - Oliver Fugger
- ILM, Institut für Lasertechnologien in der Medizin und Meßtechnik an der Universität Ulm, Helmholtzstraße 12, D-89081 Ulm,
Germany
| | - Alwin Kienle
- ILM, Institut für Lasertechnologien in der Medizin und Meßtechnik an der Universität Ulm, Helmholtzstraße 12, D-89081 Ulm,
Germany
| | - Fabrizio Martelli
- UNIFI, Università degli Studi di Firenze - Dipartimento di Fisica e Astronomia, Via G. Sansone, N. 1, 50019 Sesto Fiorentino, Firenze,
Italy
| | - Paola Di Ninni
- UNIFI, Università degli Studi di Firenze - Dipartimento di Fisica e Astronomia, Via G. Sansone, N. 1, 50019 Sesto Fiorentino, Firenze,
Italy
| | - Giovanni Zaccanti
- UNIFI, Università degli Studi di Firenze - Dipartimento di Fisica e Astronomia, Via G. Sansone, N. 1, 50019 Sesto Fiorentino, Firenze,
Italy
| | - Daniel Milej
- IBIB, Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw,
Poland
| | - Piotr Sawosz
- IBIB, Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw,
Poland
| | - Michał Kacprzak
- IBIB, Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw,
Poland
| | - Adam Liebert
- IBIB, Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw,
Poland
| | - Antonio Pifferi
- Consiglio Nazionale delle Ricerche - Istituto di Fotonica e Nanotecnologie, Piazza L. da Vinci 32, I-20133 Milano,
Italy
- POLIMI, Politecnico di Milano, Dipartimento di Fisica, Piazza L. Da Vinci 32, I-20133 Milano,
Italy
| |
Collapse
|
37
|
Near Infrared Light Scattering Changes Following Acute Brain Injury. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 876:139-144. [PMID: 26782205 PMCID: PMC5973267 DOI: 10.1007/978-1-4939-3023-4_17] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Acute brain injury (ABI) is associated with changes in near infrared light absorption reflecting haemodynamic and metabolic status via changes in cerebral oxygenation (haemoglobin oxygenation and cytochrome-c-oxidase oxidation). Light scattering has not been comprehensively investigated following ABI and may be an important confounding factor in the assessment of chromophore concentration changes, and/or a novel non-invasive optical marker of brain tissue morphology, cytostructure, hence metabolic status. The aim of this study is to characterize light scattering following adult ABI. Time resolved spectroscopy was performed as a component of multimodal neuromonitoring in critically ill brain injured patients. The scattering coefficient (μ's), absorption coefficient and cerebral haemoglobin oxygen saturation (SO2) were derived by fitting the time resolved data. Cerebral infarction was subsequently defined on routine clinical imaging. In total, 21 patients with ABI were studied. Ten patients suffered a unilateral frontal infarction, and mean μ' s was lower over infarcted compared to non-infarcted cortex (injured 6.9/cm, non-injured 8.2/cm p=0.002). SO2 did not differ significantly between the two sides (injured 69.3%, non-injured 69.0% p=0.7). Cerebral infarction is associated with changes in μ' s which might be a novel marker of cerebral injury and will interfere with quantification of haemoglobin/cytochrome c oxidase concentration. Although further work combining optical and physiological analysis is required to elucidate the significance of these results, μ' s may be uniquely placed as a non-invasive biomarker of cerebral energy failure as well as gross tissue changes.
Collapse
|
38
|
Arifler D, Zhu T, Madaan S, Tachtsidis I. Optimal wavelength combinations for near-infrared spectroscopic monitoring of changes in brain tissue hemoglobin and cytochrome c oxidase concentrations. BIOMEDICAL OPTICS EXPRESS 2015; 6:933-47. [PMID: 25798316 PMCID: PMC4361446 DOI: 10.1364/boe.6.000933] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Revised: 02/09/2015] [Accepted: 02/11/2015] [Indexed: 05/19/2023]
Abstract
We analyze broadband near-infrared spectroscopic measurements obtained from newborn piglets subjected to hypoxia-ischemia and we aim to identify optimal wavelength combinations for monitoring cerebral tissue chromophores. We implement an optimization routine based on the genetic algorithm to perform a heuristic search for discrete wavelength combinations that can provide accurate concentration information when benchmarked against the gold standard of 121 wavelengths. The results indicate that it is possible to significantly reduce the number of measurement wavelengths used in conjunction with spectroscopic algorithms and still achieve a high performance in estimating changes in concentrations of oxyhemoglobin, deoxyhemoglobin, and oxidized cytochrome c oxidase. While the use of a 3-wavelength combination leads to mean recovery errors of up to 10%, these errors drop to less than 4% with 4 or 5 wavelengths and to even less than 2% with 8 wavelengths.
Collapse
Affiliation(s)
- Dizem Arifler
- Physics Group, Middle East Technical University, Northern Cyprus Campus, Kalkanli, via Mersin 10
Turkey
| | - Tingting Zhu
- Department of Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT,
UK
| | - Sara Madaan
- Department of Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT,
UK
| | - Ilias Tachtsidis
- Department of Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT,
UK
| |
Collapse
|
39
|
Gunadi S, Leung TS, Elwell CE, Tachtsidis I. Spatial sensitivity and penetration depth of three cerebral oxygenation monitors. BIOMEDICAL OPTICS EXPRESS 2014; 5:2896-912. [PMID: 25401006 PMCID: PMC4230856 DOI: 10.1364/boe.5.002896] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 07/16/2014] [Accepted: 07/16/2014] [Indexed: 05/03/2023]
Abstract
The spatial sensitivities of NIRO-100, ISS Oximeter and TRS-20 cerebral oxygenation monitors are mapped using the local perturbation method to inform on their penetration depths and susceptibilities to superficial contaminations. The results show that TRS-20 has the deepest mean penetration depth and is less sensitive than the other monitors to a localized absorption change in the superficial layer. However, an integration time of more than five seconds is required by the TRS-20 to achieve an acceptable level of signal-to-noise ratio, which is the poorest amongst the monitors. With the exception of NIRO-100 continuous wave method, the monitors are not significantly responsive to layer-wide absorption change that occurs in the superficial layer.
Collapse
|
40
|
Selb J, Boas DA, Chan ST, Evans KC, Buckley EM, Carp SA. Sensitivity of near-infrared spectroscopy and diffuse correlation spectroscopy to brain hemodynamics: simulations and experimental findings during hypercapnia. NEUROPHOTONICS 2014; 1:015005. [PMID: 25453036 PMCID: PMC4247161 DOI: 10.1117/1.nph.1.1.015005] [Citation(s) in RCA: 104] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 06/12/2014] [Accepted: 06/25/2014] [Indexed: 05/18/2023]
Abstract
Near-infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS) are two diffuse optical technologies for brain imaging that are sensitive to changes in hemoglobin concentrations and blood flow, respectively. Measurements for both modalities are acquired on the scalp, and therefore hemodynamic processes in the extracerebral vasculature confound the interpretation of cortical hemodynamic signals. The sensitivity of NIRS to the brain versus the extracerebral tissue and the contrast-to-noise ratio (CNR) of NIRS to cerebral hemodynamic responses have been well characterized, but the same has not been evaluated for DCS. This is important to assess in order to understand their relative capabilities in measuring cerebral physiological changes. We present Monte Carlo simulations on a head model that demonstrate that the relative brain-to-scalp sensitivity is about three times higher for DCS (0.3 at 3 cm) than for NIRS (0.1 at 3 cm). However, because DCS has higher levels of noise due to photon-counting detection, the CNR is similar for both modalities in response to a physiologically realistic simulation of brain activation. Even so, we also observed higher CNR of the hemodynamic response during graded hypercapnia in adult subjects with DCS than with NIRS.
Collapse
Affiliation(s)
- Juliette Selb
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Department of Radiology, Optics Division, 149 13th Street, Charlestown, Massachusetts 02129, United States
- Address all correspondence to: Juliette Selb, E-mail:
| | - David A. Boas
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Department of Radiology, Optics Division, 149 13th Street, Charlestown, Massachusetts 02129, United States
| | - Suk-Tak Chan
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Department of Radiology, Optics Division, 149 13th Street, Charlestown, Massachusetts 02129, United States
| | - Karleyton C. Evans
- Massachusetts General Hospital, Harvard Medical School, Department of Psychiatry, 149 13th Street, Charlestown, Massachusetts 02129, United States
| | - Erin M. Buckley
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Department of Radiology, Optics Division, 149 13th Street, Charlestown, Massachusetts 02129, United States
| | - Stefan A. Carp
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Department of Radiology, Optics Division, 149 13th Street, Charlestown, Massachusetts 02129, United States
| |
Collapse
|