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Larsson M, Ewerlöf M, Salerud EG, Strömberg T, Fredriksson I. Artificial neural networks trained on simulated multispectral data for real-time imaging of skin microcirculatory blood oxygen saturation. JOURNAL OF BIOMEDICAL OPTICS 2024; 29:S33304. [PMID: 38989257 PMCID: PMC11234456 DOI: 10.1117/1.jbo.29.s3.s33304] [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: 02/02/2024] [Revised: 06/14/2024] [Accepted: 06/14/2024] [Indexed: 07/12/2024]
Abstract
Significance Imaging blood oxygen saturation (SO 2 ) in the skin can be of clinical value when studying ischemic tissue. Emerging multispectral snapshot cameras enable real-time imaging but are limited by slow analysis when using inverse Monte Carlo (MC), the gold standard for analyzing multispectral data. Using artificial neural networks (ANNs) facilitates a significantly faster analysis but requires a large amount of high-quality training data from a wide range of tissue types for a precise estimation ofSO 2 . Aim We aim to develop a framework for training ANNs that estimatesSO 2 in real time from multispectral data with a precision comparable to inverse MC. Approach ANNs are trained using synthetic data from a model that includes MC simulations of light propagation in tissue and hardware characteristics. The model includes physiologically relevant variations in optical properties, unique sensor characteristics, variations in illumination spectrum, and detector noise. This approach enables a rapid way of generating high-quality training data that covers different tissue types and skin pigmentation. Results The ANN implementation analyzes an image in 0.11 s, which is at least 10,000 times faster than inverse MC. The hardware modeling is significantly improved by an in-house calibration of the sensor spectral response. An in-vivo example shows that inverse MC and ANN give almost identicalSO 2 values with a mean absolute deviation of 1.3%-units. Conclusions ANN can replace inverse MC and enable real-time imaging of microcirculatorySO 2 in the skin if detailed and precise modeling of both tissue and hardware is used when generating training data.
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Affiliation(s)
- Marcus Larsson
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
| | - Maria Ewerlöf
- Linköping University, Department of Health, Medicine and Caring Sciences, Linköping, Sweden
| | - E. Göran Salerud
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
| | - Tomas Strömberg
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
| | - Ingemar Fredriksson
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
- Perimed AB, Stockholm, Sweden
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Merdasa A, Berggren J, Tenland K, Stridh M, Hernandez-Palacios J, Gustafsson N, Sheikh R, Malmsjö M. Oxygen saturation mapping during reconstructive surgery of human forehead flaps with hyperspectral imaging and spectral unmixing. Microvasc Res 2023; 150:104573. [PMID: 37390964 DOI: 10.1016/j.mvr.2023.104573] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 06/20/2023] [Accepted: 06/26/2023] [Indexed: 07/02/2023]
Abstract
BACKGROUND Optical spectroscopy is commonly used clinically to monitor oxygen saturation in tissue. The most commonly employed technique is pulse oximetry, which provides a point measurement of the arterial oxygen saturation and is commonly used for monitoring systemic hemodynamics, e.g. during anesthesia. Hyperspectral imaging (HSI) is an emerging technology that enables spatially resolved mapping of oxygen saturation in tissue (sO2), but needs to be further developed before implemented in clinical practice. The aim of this study is to demonstrate the applicability of HSI for mapping the sO2 in reconstructive surgery and demonstrate how spectral analysis can be used to obtain clinically relevant sO2 values. METHODS Spatial scanning HSI was performed on cutaneous forehead flaps, raised as part of a direct brow lift, in eight patients. Pixel-by-pixel spectral analysis, accounting for the absorption from multiple chromophores, was performed and compared to previous analysis techniques to assess sO2. RESULTS Spectral unmixing using a broad spectral range, and accounting for the absorption of melanin, fat, collagen, and water, provided a more clinically relevant estimate of sO2 than conventional techniques, where typically only spectral features associated with absorption of oxygenated (HbO2) and deoxygenated (HbR) hemoglobin are considered. We demonstrate its clinical applicability by generating sO2 maps of partially excised forehead flaps showed a gradual decrease in sO2 along the length of the flap from 95 % at the flap base to 85 % at the flap tip. After being fully excised, sO2 in the entire flap decreased to 50 % within a few minutes. CONCLUSIONS The results demonstrate the capability of sO2 mapping in reconstructive surgery in patients using HSI. Spectral unmixing, accounting for multiple chromophores, provides sO2 values that are in accordance with physiological expectations in patients with normal functioning microvascularization. Our results suggest that HSI methods that yield reliable spectra are to be preferred, so that the analysis can produce results that are of clinical relevance.
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Affiliation(s)
- Aboma Merdasa
- Department of Ophthalmology, Clinical Sciences Lund, Lund University, Sweden.
| | - Johanna Berggren
- Department of Ophthalmology, Clinical Sciences Lund, Lund University, Sweden; Skåne University Hospital, Department of Clinical Sciences Lund, Ophthalmology Lund, Sweden
| | - Kajsa Tenland
- Department of Ophthalmology, Clinical Sciences Lund, Lund University, Sweden; Skåne University Hospital, Department of Clinical Sciences Lund, Ophthalmology Lund, Sweden
| | - Magne Stridh
- Department of Ophthalmology, Clinical Sciences Lund, Lund University, Sweden; Skåne University Hospital, Department of Clinical Sciences Lund, Ophthalmology Lund, Sweden
| | | | - Nils Gustafsson
- Skåne University Hospital, Department of Clinical Sciences Lund, Ophthalmology Lund, Sweden
| | - Rafi Sheikh
- Department of Ophthalmology, Clinical Sciences Lund, Lund University, Sweden; Skåne University Hospital, Department of Clinical Sciences Lund, Ophthalmology Lund, Sweden
| | - Malin Malmsjö
- Department of Ophthalmology, Clinical Sciences Lund, Lund University, Sweden; Skåne University Hospital, Department of Clinical Sciences Lund, Ophthalmology Lund, Sweden
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Jonasson H, Fredriksson I, Bergstrand S, Östgren CJ, Larsson M, Strömberg T. Absorption and reduced scattering coefficients in epidermis and dermis from a Swedish cohort study. JOURNAL OF BIOMEDICAL OPTICS 2023; 28:115001. [PMID: 38078153 PMCID: PMC10704088 DOI: 10.1117/1.jbo.28.11.115001] [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: 07/10/2023] [Revised: 09/25/2023] [Accepted: 10/30/2023] [Indexed: 12/18/2023]
Abstract
Significance Knowledge of optical properties is important to accurately model light propagation in tissue, but in vivo reference data are sparse. Aim The aim of our study was to present in vivo skin optical properties from a large Swedish cohort including 3809 subjects using a three-layered skin model and spatially resolved diffuse reflectance spectroscopy (Periflux PF6000 EPOS). Approach Diffuse reflectance spectra (475 to 850 nm) at 0.4 and 1.2 mm source-detector separations were analyzed using an inverse Monte Carlo method. The model had one epidermis layer with variable thicknesses and melanin-related absorptions and two dermis layers with varying hemoglobin concentrations and equal oxygen saturations. The reduced scattering coefficient was equal across all layers. Results Median absorption coefficients (mm - 1 ) in the upper dermis ranged from 0.094 at 475 nm to 0.0048 at 850 nm and similarly in the lower dermis from 0.059 to 0.0035. The reduced scattering coefficient (mm - 1 ) ranged from 3.22 to 1.20, and the sampling depth (mm) ranged from 0.23 to 0.38 (0.4 mm separation) and from 0.49 to 0.68 (1.2 mm separation). There were differences in optical properties across sex, age groups, and BMI categories. Conclusions Reference material for skin optical properties is presented.
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Affiliation(s)
- Hanna Jonasson
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
| | - Ingemar Fredriksson
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
- Perimed AB, Järfälla, Stockholm, Sweden
| | - Sara Bergstrand
- Linköping University, Department of Health, Medicine, and Caring Sciences, Linköping, Sweden
| | - Carl Johan Östgren
- Linköping University, Department of Health, Medicine, and Caring Sciences, Linköping, Sweden
- Linköping University, Centre of Medical Image Science and Visualization Linköping, Sweden
| | - Marcus Larsson
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
| | - Tomas Strömberg
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
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Chang M, Lee W, Jeong KY, Kim JW. Optimal Hyperspectral Band Selection for Tissue Oxygenation Mapping with Generative Adversarial Network. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023; 2023:1-4. [PMID: 38082981 DOI: 10.1109/embc40787.2023.10340032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
Tissue oxygenation assessment using hyperspectral imaging is an emerging technique for the diagnosis and pre- and post-treatment monitoring of ischemic patients. However, the high spectral resolution of hyperspectral imaging leads to large data sizes and a long imaging time. In this study, we propose a method that utilizes multi-objective evolutionary algorithms to determine the optimal hyperspectral band combination when developing a deep learning model for predicting tissue oxygenation from hyperspectral images. Our results confirm that the deep learning model effectively predicts tissue oxygenation images for various oxygenation states. Moreover, we demonstrate that a high-performance prediction model can be developed using only a small number of spectral bands, indicating the potential for more efficient non-contact tissue oxygenation mapping with the proposed method.Clinical Relevance- The proposed method allows for the non-contact and efficient acquisition of two-dimensional tissue oxygenation information in various oxygenation states.
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Wang Q, Liu X, Li B, Yang X, Lu W, Li A, Li H, Zhang X, Han J. Sodium pentobarbital suppresses breast cancer cells growth partly via normalizing microcirculatory hemodynamics and oxygenation in tumors. J Pharmacol Exp Ther 2022; 382:11-20. [PMID: 35512800 DOI: 10.1124/jpet.121.001058] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 04/26/2022] [Indexed: 11/22/2022] Open
Abstract
Breast cancer remains the leading cause of cancer-related death among women worldwidely. Sodium pentobarbital was found to play an inhibitory role in glioma growth in rats. In this study, we aim to evaluate the effects of sodium pentobarbital on breast cancer growth both in vitro and in vivo, and its impacts on the microcirculatory changes both on skin and tumor surface in mice bearing subcutaneous xenograft. Cell counting assay was used to assess the anti-proliferative effect of sodium pentobarbital on MDA-MB-231 breast cancer cells. Subcutaneous xenograft model was established to study the role of sodium pentobarbital on in vivo tumor growth. Speed-resolved blood perfusion, hemoglobin oxygen saturation (SO2, %), total hemoglobin tissue concentration (THb, µM), and red blood cell (RBC) tissue fraction (%) were examined simultaneously by using EPOS system, to investigate the effects of sodium pentobarbital on microcirculatory hemodynamics and oxygenation. Sodium pentobarbital suppressed breast tumor growth both in vitro and in vivo Cutaneous blood flux in nutritive capillaries with low-speed flow was significantly increased in tumor-bearing mice, and high dose sodium pentobarbital treatment cause a reduction in this low-speed blood flux, whereas sodium pentobarbital therapy caused an elevated blood flux in larger microvessels with mid- and high-speed in a dose-dependent manner. Different doses of sodium pentobarbital exerted different actions on in SO2, ctTHb and RBC tissue fraction. Collectively, the inhibitory effect of sodium pentobarbital on breast tumor growth was at least partly associated with its ability to normalize microcirculatory hemodynamics and oxygenation in tumors. Significance Statement This study is the first to demonstrate the inhibiting effect of sodium pentobarbital on breast cancer growth both in vitro and in vivo, and such an inhibition was at least partly associated with its ability to normalize microcirculatory hemodynamics and oxygenation in tumors.
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Affiliation(s)
- Qin Wang
- Institute of Microcirculation, China
| | | | | | | | - Wenbao Lu
- Institute of Microcirculation, China
| | - Ailing Li
- Institute of Microcirculation, China
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Henricson J, Sjöberg F, Iredahl F, Strömberg T, Wilhelms D. In vivo dose-response analysis to acetylcholine: pharmacodynamic assessment by polarized reflectance spectroscopy. Sci Rep 2022; 12:6594. [PMID: 35449189 PMCID: PMC9023454 DOI: 10.1038/s41598-022-10617-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 04/11/2022] [Indexed: 11/22/2022] Open
Abstract
Transdermal iontophoresis offers an in vivo alternative to the strain-gauge model for measurement of vascular function but is limited due to lack of technical solutions for outcome assessment. The aims of this study were to, after measurement by polarized reflectance spectroscopy (PRS), use pharmacodynamic dose–response analysis on responses to different concentrations of acetylcholine (ACh); and to examine the effect of three consecutively administered iontophoretic current pulses. The vascular responses in 15 healthy volunteers to iontophorised ACh (5 concentrations, range 0.0001% to 1%, three consecutive pulses of 0.02 mA for 10 min each) were recorded using PRS. Data were fitted to a four-parameter logistic dose response model and compared. Vascular responses were quantifiable by PRS. Similar pharmacodynamic dose response curves could be generated irrespectively of the ACh concentration. Linearly increasing maximum vasodilatory responses were registered with increasing concentration of ACh. A limited linear dose effect of the concentration of ACh was seen between pulses. Polarized reflectance spectroscopy is well suited for measuring vascular responses to iontophoretically administrated ACh. The results of this study support further development of iontophoresis as a method to study vascular function and pharmacological responses in vivo.
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Affiliation(s)
- Joakim Henricson
- Department of Emergency Medicine, Local Health Care Services in Central Östergötland, 58182, Linköping, Sweden. .,Department of Biomedical and Clinical Sciences, Faculty of Health Sciences, Linköping University, Linköping, Sweden.
| | - Folke Sjöberg
- Department of Hand, Plastic Surgery, Burns and Intensive Care, Linköping University Hospital, 58182, Linköping, Sweden.,Department of Health, Medicine and Caring Sciences, Division of Community Medicine, Linköping University, Linköping, Sweden
| | - Fredrik Iredahl
- Department of Primary Health Care, Region Östergötland, 58182, Linköping, Sweden.,Department of Medical and Health Sciences, Faculty of Health Sciences, Linköping University, Linköping, Sweden
| | - Tomas Strömberg
- Department of Biomedical Engineering, Linköping University, Linköping, Sweden
| | - Daniel Wilhelms
- Department of Emergency Medicine, Local Health Care Services in Central Östergötland, 58182, Linköping, Sweden.,Department of Biomedical and Clinical Sciences, Faculty of Health Sciences, Linköping University, Linköping, Sweden
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Ewerlöf M, Strömberg T, Larsson M, Salerud EG. Multispectral snapshot imaging of skin microcirculatory hemoglobin oxygen saturation using artificial neural networks trained on in vivo data. JOURNAL OF BIOMEDICAL OPTICS 2022; 27:036004. [PMID: 35340134 PMCID: PMC8957373 DOI: 10.1117/1.jbo.27.3.036004] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Accepted: 03/03/2022] [Indexed: 06/14/2023]
Abstract
SIGNIFICANCE Developing algorithms for estimating blood oxygenation from snapshot multispectral imaging (MSI) data is challenging due to the complexity of sensor characteristics and photon transport modeling in tissue. We circumvent this using a method where artificial neural networks (ANNs) are trained on in vivo MSI data with target values from a point-measuring reference method. AIM To develop and evaluate a methodology where a snapshot filter mosaic camera is utilized for imaging skin hemoglobin oxygen saturation (SO2), using ANNs. APPROACH MSI data were acquired during occlusion provocations. ANNs were trained to estimate SO2 with MSI data as input, targeting data from a validated probe-based reference system. Performance of ANNs with different properties and training data sets was compared. RESULTS The method enables spatially resolved estimation of skin tissue SO2. Results are comparable to those acquired using a Monte-Carlo-based approach when relevant training data are used. CONCLUSIONS Training an ANN on in vivo MSI data covering a wide range of target values acquired during an occlusion protocol enable real-time estimation of SO2 maps. Data from the probe-based reference system can be used as target despite differences in sampling depth and measurement position.
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Affiliation(s)
- Maria Ewerlöf
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
| | - Tomas Strömberg
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
| | - Marcus Larsson
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
| | - E. Göran Salerud
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
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Frantz D, Jönsson J, Berrocal E. Multi-scattering software part II: experimental validation for the light intensity distribution. OPTICS EXPRESS 2022; 30:1261-1279. [PMID: 35209290 DOI: 10.1364/oe.445394] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Accepted: 12/12/2021] [Indexed: 05/18/2023]
Abstract
This article, Part II of an article series on GPU-accelerated Monte Carlo simulation of photon transport through turbid media, focuses on the validation of the online software Multi-Scattering. While Part I detailed the implementation of the computational model, simulated and experimental results are now compared for the distribution of the scattered light intensity. The scattering phantoms prepared here are aqueous dispersions of polystyrene microspheres of diameter D = 0.5, 2 and 5 μm and at various concentrations, resulting in optical depth ranging from OD = 1 to 17.5. The Lorenz-Mie scattering phase functions used in the simulations have been verified experimentally at low particle concentrations by analyzing the angular light intensity distribution at the Fourier plane of a collecting lens. The validation approach herein accounts for the specific light collection and image formation by the camera. The front and side surfaces of the medium are imaged and the corresponding light intensity distributions are compared qualitatively and quantitatively. It is concluded that the model enables reliable simulations over the tested parameters, offering predictive simulations of transmitted intensities with a mean relative error ≤~19% over the full range. The online software is available at: https://multi-scattering.com/.
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Hultman M, Aronsson S, Fredriksson I, Zachrisson H, Pärsson H, Larsson M, Strömberg T. Comprehensive imaging of microcirculatory changes in the foot during endovascular intervention - A technical feasibility study. Microvasc Res 2022; 141:104317. [PMID: 35016873 DOI: 10.1016/j.mvr.2022.104317] [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: 09/21/2021] [Revised: 12/17/2021] [Accepted: 01/03/2022] [Indexed: 10/19/2022]
Abstract
Chronic limb-threatening ischemia (CLTI) has a major impact on patient's lives and is associated with a heavy health care burden with high morbidity and mortality. Treatment by endovascular intervention is mostly based on macrocirculatory information from angiography and does not consider the microcirculation. Despite successful endovascular intervention according to angiographic criteria, a proportion of patients fail to heal ischemic lesions. This might be due to impaired microvascular perfusion and variations in the supply to different angiosomes. Non-invasive optical techniques for microcirculatory perfusion and oxygen saturation imaging have the potential to provide the interventionist with additional information in real-time, supporting clinical decisions during the intervention. This study presents a novel multimodal imaging system, based on multi-exposure laser speckle contrast imaging and multi-spectral imaging, for continuous use during endovascular intervention. The results during intervention display spatiotemporal changes in the microcirculation compatible with expected physiological reactions during balloon dilation, with initially induced ischemia followed by a restored perfusion, and local administration of a vasodilator inducing hyperemia. We also present perioperative and postoperative follow-up measurements with a pulsatile microcirculation perfusion. Finally, cases of spatial heterogeneity in the observed oxygen saturation and perfusion are discussed. In conclusion, this technical feasibility study shows the potential of the methodology to characterize changes in microcirculation before, during, and after endovascular intervention.
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Affiliation(s)
- Martin Hultman
- Department of Biomedical Engineering, Linköping University, Linköping, Sweden.
| | - Sofie Aronsson
- Department of Health, Medicine, and Caring Sciences, Division of Diagnostics and Specialist Medicine, Linköping University Hospital, Linköping, Sweden
| | - Ingemar Fredriksson
- Department of Biomedical Engineering, Linköping University, Linköping, Sweden; Perimed AB, Datavägen 9A, Järfälla, Stockholm, Sweden
| | - Helene Zachrisson
- Department of Health, Medicine, and Caring Sciences, Division of Diagnostics and Specialist Medicine, Linköping University Hospital, Linköping, Sweden
| | - Håkan Pärsson
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Marcus Larsson
- Department of Biomedical Engineering, Linköping University, Linköping, Sweden
| | - Tomas Strömberg
- Department of Biomedical Engineering, Linköping University, Linköping, Sweden
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