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Fredriksson, IngemarORCID iD iconorcid.org/0000-0002-3454-6576
Publications (10 of 31) Show all publications
Hultman, M., Fredriksson, I., Larsson, M., Alvandpour, A. & Strömberg, T. (2018). A 15.6 frames per second 1 megapixel Multiple Exposure Laser Speckle Contrast Imaging setup. Journal of Biophotonics, 11(2), Article ID e201700069.
Open this publication in new window or tab >>A 15.6 frames per second 1 megapixel Multiple Exposure Laser Speckle Contrast Imaging setup
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2018 (English)In: Journal of Biophotonics, ISSN 1864-063X, E-ISSN 1864-0648, Vol. 11, no 2, article id e201700069Article in journal (Refereed) Published
Abstract [en]

A multiple exposure laser speckle contrast imaging (MELSCI) setup for visualizing blood perfusion was developed using a field programmable gate array (FPGA), connected to a 1000 frames per second (fps) 1-megapixel camera sensor. Multiple exposure time images at 1, 2, 4, 8, 16, 32 and 64 milliseconds were calculated by cumulative summation of 64 consecutive snapshot images. The local contrast was calculated for all exposure times using regions of 4 × 4 pixels. Averaging of multiple contrast images from the 64-millisecond acquisition was done to improve the signal-to-noise ratio. The results show that with an effective implementation of the algorithm on an FPGA, contrast images at all exposure times can be calculated in only 28 milliseconds. The algorithm was applied to data recorded during a 5 minutes finger occlusion. Expected contrast changes were found during occlusion and the following hyperemia in the occluded finger, while unprovoked fingers showed constant contrast during the experiment. The developed setup is capable of massive data processing on an FPGA that enables processing of MELSCI data in 15.6 fps (1000/64 milliseconds). It also leads to improved frame rates, enhanced image quality and enables the calculation of improved microcirculatory perfusion estimates compared to single exposure time systems.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2018
Keywords
blood flow, blood perfusion, FPGA, LASCA, LSCI, microcirculation, multiexposure
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:liu:diva-141201 (URN)10.1002/jbio.201700069 (DOI)000424643600014 ()2-s2.0-85026753968 (Scopus ID)
Funder
Swedish Research Council, 2014-6141
Available from: 2017-09-26 Created: 2017-09-26 Last updated: 2019-09-05Bibliographically approved
Hultman, M., Fredriksson, I., Strömberg, T. & Larsson, M. (2018). Evaluation of a high framerate multi-exposure laser speckle contrast imaging setup. In: Kevin K. Tsia, Keisuke Goda (Ed.), High-Speed Biomedical Imaging and Spectroscopy III: Toward Big Data Instrumentation and Management. Paper presented at SPIE BIOS 27 January - 1 February 2018 San Francisco, California, United States. SPIE - International Society for Optical Engineering
Open this publication in new window or tab >>Evaluation of a high framerate multi-exposure laser speckle contrast imaging setup
2018 (English)In: High-Speed Biomedical Imaging and Spectroscopy III: Toward Big Data Instrumentation and Management / [ed] Kevin K. Tsia, Keisuke Goda, SPIE - International Society for Optical Engineering, 2018Conference paper, Published paper (Refereed)
Abstract [en]

We present a first evaluation of a new multi-exposure laser speckle contrast imaging (MELSCI) system for assessing spatial variations in the microcirculatory perfusion. The MELSCI system is based on a 1000 frames per second 1-megapixel camera connected to a field programmable gate arrays (FPGA) capable of producing MELSCI data in realtime. The imaging system is evaluated against a single point laser Doppler flowmetry (LDF) system during occlusionrelease provocations of the arm in five subjects. Perfusion is calculated from MELSCI data using current state-of-the-art inverse models. The analysis displayed a good agreement between measured and modeled data, with an average error below 6%. This strongly indicates that the applied model is capable of accurately describing the MELSCI data and that the acquired data is of high quality. Comparing readings from the occlusion-release provocation showed that the MELSCI perfusion was significantly correlated (R=0.83) to the single point LDF perfusion, clearly outperforming perfusion estimations based on a single exposure time. We conclude that the MELSCI system provides blood flow images of enhanced quality, taking us one step closer to a system that accurately can monitor dynamic changes in skin perfusion over a large area in real-time

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2018
Series
Progress in Biomedical Optics and Imaging - Proceedings of SPIE, ISSN 0277-786X ; 10505
National Category
Medical Engineering
Identifiers
urn:nbn:se:liu:diva-148844 (URN)10.1117/12.2286248 (DOI)000446339000015 ()978-1-5106-1496-3 (ISBN)
Conference
SPIE BIOS 27 January - 1 February 2018 San Francisco, California, United States
Available from: 2018-06-20 Created: 2018-06-20 Last updated: 2018-10-17
Strömberg, T., Saager, R. B., Kennedy, G. T., Fredriksson, I., Salerud, G., Durkin, A. J. & Larsson, M. (2018). Spatial frequency domain imaging using a snap-shot filter mosaic camera with multi-wavelength sensitive pixels. In: Bernard Choi, and Haishan Zeng (Ed.), Proceedings Volume 10467, Photonics in Dermatology and Plastic Surgery 2018; 104670D (2018): . Paper presented at SPIE BIOS, 27 January - 1 February 2018, San Francisco, California, United States. SPIE - International Society for Optical Engineering, 10467, Article ID 104670D.
Open this publication in new window or tab >>Spatial frequency domain imaging using a snap-shot filter mosaic camera with multi-wavelength sensitive pixels
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2018 (English)In: Proceedings Volume 10467, Photonics in Dermatology and Plastic Surgery 2018; 104670D (2018) / [ed] Bernard Choi, and Haishan Zeng, SPIE - International Society for Optical Engineering, 2018, Vol. 10467, article id 104670DConference paper, Published paper (Refereed)
Abstract [en]

Spatial frequency domain imaging (SFDI) utilizes a digital light processing (DLP) projector for illuminating turbid media with sinusoidal patterns. The tissue absorption (μa) and reduced scattering coefficient (μ,s) are calculated by analyzing the modulation transfer function for at least two spatial frequencies. We evaluated different illumination strategies with a red, green and blue light emitting diodes (LED) in the DLP, while imaging with a filter mosaic camera, XiSpec, with 16 different multi-wavelength sensitive pixels in the 470-630 nm wavelength range. Data were compared to SFDI by a multispectral camera setup (MSI) consisting of four cameras with bandpass filters centered at 475, 560, 580 and 650 nm. A pointwise system for comprehensive microcirculation analysis was used (EPOS) for comparison. A 5-min arterial occlusion and release protocol on the forearm of a Caucasian male with fair skin was analyzed by fitting the absorption spectra of the chromophores HbO2, Hb and melanin to the estimatedμa. The tissue fractions of red blood cells (fRBC), melanin (/mel) and the Hb oxygenation (S02 ) were calculated at baseline, end of occlusion, early after release and late after release. EPOS results showed a decrease in S02 during the occlusion and hyperemia during release (S02 = 40%, 5%, 80% and 51%). The fRBC showed an increase during occlusion and release phases. The best MSI resemblance to the EPOS was for green LED illumination (S02 = 53%, 9%, 82%, 65%). Several illumination and analysis strategies using the XiSpec gave un-physiological results (e.g. negative S02 ). XiSpec with green LED illumination gave the expected change in /RBC , while the dynamics in S02 were less than those for EPOS. These results may be explained by the calculation of modulation using an illumination and detector setup with a broad spectral transmission bandwidth, with considerable variation in μa of included chromophores. Approaches for either reducing the effective bandwidth of the XiSpec filters or by including their characteristic in a light transport model for SFDI modulation, are proposed.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-152301 (URN)10.1117/12.2289357 (DOI)000451701900002 ()
Conference
SPIE BIOS, 27 January - 1 February 2018, San Francisco, California, United States
Available from: 2018-11-26 Created: 2018-11-26 Last updated: 2018-12-20Bibliographically approved
Jonasson, H., Fredriksson, I., Larsson, M. & Strömberg, T. (2015). Assessment of the microcirculation using combined model based diffuse reflectance spectroscopy and laser Doppler flowmetry. In: 16th Nordic-Baltic Conference on Biomedical Engineering: 16. NBC & 10. MTD 2014 joint conferences. October 14-16, 2014, Gothenburg, Sweden. Paper presented at 16th Nordic Baltic Conference on Biomedical Engineering, October 14-16, 2014, Gothenburg, Sweden (pp. 52-54). Springer
Open this publication in new window or tab >>Assessment of the microcirculation using combined model based diffuse reflectance spectroscopy and laser Doppler flowmetry
2015 (English)In: 16th Nordic-Baltic Conference on Biomedical Engineering: 16. NBC & 10. MTD 2014 joint conferences. October 14-16, 2014, Gothenburg, Sweden, Springer, 2015, p. 52-54Conference paper, Published paper (Refereed)
Abstract [en]

By using a combined inverse model for diffuse reflectance spectroscopy (DRS) and laser Doppler flowmetry (LDF) the tissue fraction of red blood cells (RBCs), their oxygenation and speed-resolved perfusion are estimated in absolute units. DRS spectra (450 to 850 nm) are measured at two source-detector distances; 0.4 and 1.2 mm. LDF spectra are measured at 1.2 mm, integrated in the same fiber-optic probe. Inverse Monte Carlo technique and an adaptive tissue model is used to quantify the microcirculatory parameters. Measurements were done during venous occlusion of the tissue. The model fitting yields a good spectral fit for the two DRS spectra and the LDF spectrum. The physiological responses regarding for example which speed regions respond to provocations follows a priori expectations. The combined model gives quantitative measures of RBC tissue fraction, oxygenation and speed resolved perfusion from the same sampling volume which gives new opportunities to interpret data.

Place, publisher, year, edition, pages
Springer, 2015
Series
IFMBE Proceedings, ISSN 1680-0737 ; 48
Keywords
diffuse reflectance spectroscopy, laser Doppler flowmetry, modeling, Monte Carlo simulations
National Category
Medical Engineering
Identifiers
urn:nbn:se:liu:diva-111403 (URN)10.1007/978-3-319-12967-9_14 (DOI)000347893000014 ()978-3-319-12966-2 (ISBN)978-3-319-12967-9 (ISBN)
Conference
16th Nordic Baltic Conference on Biomedical Engineering, October 14-16, 2014, Gothenburg, Sweden
Available from: 2014-10-16 Created: 2014-10-16 Last updated: 2016-08-31Bibliographically approved
Jonasson, H., Fredriksson, I., Pettersson, A., Larsson, M. & Strömberg, T. (2015). Oxygen saturation, red blood cell tissue fraction and speed resolved perfusion — A new optical method for microcirculatory assessment. Microvascular Research, 102, 70-77
Open this publication in new window or tab >>Oxygen saturation, red blood cell tissue fraction and speed resolved perfusion — A new optical method for microcirculatory assessment
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2015 (English)In: Microvascular Research, ISSN 0026-2862, E-ISSN 1095-9319, Vol. 102, p. 70-77Article in journal (Refereed) Published
Abstract [en]

We have developed a new fiber-optic system that combines diffuse reflectance spectroscopy (DRS) and laser Doppler Flowmetry (LDF) for a multi-modal assessment of the microcirculation. Quantitative data is achieved with an inverse Monte Carlo algorithm based on an individually adaptive skin model. The output parameters are calculated from the model and given in absolute units: hemoglobin oxygen saturation (%), red blood cell (RBC) tissue fraction (%), and the speed resolved RBC perfusion separated into three speed regions; 0–1 mm/s, 1–10 mm/s and above 10 mm/s (% mm/s). The aim was to explore microcirculatory parameters using the new optical method, integrating DRS and LDF in a joint skin model, during local heating of the dorsal foot and venous and arterial occlusion of the forearm in 23 healthy subjects (age 20–28 years). There were differences in the three speed regions in regard to blood flow changes due to local heating, where perfusion for high speeds increased the most. There was also a high correlation between changes in oxygenation and changes in perfusion for higher speeds. Oxygen saturation at baseline was 44% on foot, increasing to 83% at plateau after heating. The larger increase in perfusion for higher speeds than for lower speeds together with the oxygenation increase during thermal provocation, shows a local thermoregulatory blood flow in presumably arteriolar dermal vessels. In conclusion, there are improved possibilities to assess microcirculation using integrated DRS and LDF in a joint skin model by enabling both oxygenation and speed resolved blood flow assessment simultaneously and in the same skin site. Output parameters in absolute units may also yield new insights about the microcirculatory system.

Place, publisher, year, edition, pages
Academic Press, 2015
Keywords
Diffuse reflectance spectroscopy; Hemoglobin oxygen saturation; Laser Doppler flowmetry; Microcirculation; Skin blood flow
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-121774 (URN)10.1016/j.mvr.2015.08.006 (DOI)000362310700010 ()26279347 (PubMedID)
Note

Funding text:  VINNOVA (Swedens innovation agency); Perimed AB through the SamBIO research collaboration program [2008-00149]; Research&Grow program (VINNOVA) [2011-03074]; NovaMedTech - European Union Regional Development Fund [68737, 160382]

Available from: 2015-10-05 Created: 2015-10-05 Last updated: 2017-12-01
Strömberg, T., Karlsson, H., Fredriksson, I., Nyström, F. H. & Larsson, M. (2014). Microcirculation assessment using an individualized model for diffuse reflectance spectroscopy and conventional laser Doppler flowmetry. Journal of Biomedical Optics, 19(5), 057002
Open this publication in new window or tab >>Microcirculation assessment using an individualized model for diffuse reflectance spectroscopy and conventional laser Doppler flowmetry
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2014 (English)In: Journal of Biomedical Optics, ISSN 1083-3668, E-ISSN 1560-2281, Vol. 19, no 5, p. 057002-Article in journal (Refereed) Published
Abstract [en]

Microvascular assessment would benefit from co-registration of blood flow and hemoglobin oxygenation dynamics during stimulus response tests. We used a fiber-optic probe for simultaneous recording of white light diffuse reflectance (DRS; 475-850 nm) and laser Doppler flowmetry (LDF; 780 nm) spectra at two source-detector distances (0.4 and 1.2 mm). An inverse Monte Carlo algorithm, based on a multiparameter three-layer adaptive skin model, was used for analyzing DRS data. LDF spectra were conventionally processed for perfusion. The system was evaluated on volar forearm recordings of 33 healthy subjects during a 5-min systolic occlusion protocol. The calibration scheme and the optimal adaptive skin model fitted DRS spectra at both distances within 10%. During occlusion, perfusion decreased within 5 s while oxygenation decreased slowly (mean time constant 61 s; dissociation of oxygen from hemoglobin). After occlusion release, perfusion and oxygenation increased within 3 s (inflow of oxygenized blood). The increased perfusion was due to increased blood tissue fraction and speed. The supranormal hemoglobin oxygenation indicates a blood flow in excess of metabolic demands. In conclusion, by integrating DRS and LDF in a fiber-optic probe, a powerful tool for assessment of blood flow and oxygenation in the same microvascular bed has been presented.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2014
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-107715 (URN)10.1117/1.JBO.19.5.057002 (DOI)000338334600033 ()24788373 (PubMedID)
Available from: 2014-06-19 Created: 2014-06-19 Last updated: 2017-12-05Bibliographically approved
Fredriksson, I., Larsson, M. & Strömberg, T. (2014). Model-Based Quantification of Skin Microcirculatory Perfusion (1ed.). In: Bernard Querleux (Ed.), Computational Biophysics of the Skin: (pp. 395-420). Singapore: Pan Stanford Publishing
Open this publication in new window or tab >>Model-Based Quantification of Skin Microcirculatory Perfusion
2014 (English)In: Computational Biophysics of the Skin / [ed] Bernard Querleux, Singapore: Pan Stanford Publishing, 2014, 1, p. 395-420Chapter in book (Other academic)
Place, publisher, year, edition, pages
Singapore: Pan Stanford Publishing, 2014 Edition: 1
National Category
Medical Equipment Engineering
Identifiers
urn:nbn:se:liu:diva-107986 (URN)978-981-4463-84-3 (ISBN)978-981-4463-85-0 (ISBN)
Available from: 2014-06-24 Created: 2014-06-24 Last updated: 2016-08-31Bibliographically approved
Karlsson, H., Fredriksson, I., Larsson, M. & Strömberg, T. (2014). Speed resolved assessment of the microcirculation using combined model based diffuse reflectance spectroscopy and laser Doppler flowmetry. In: : . Paper presented at International Conferance on Laser Applications in Life Sciences, Ulm, Germany, June 29-July 2, 2014.
Open this publication in new window or tab >>Speed resolved assessment of the microcirculation using combined model based diffuse reflectance spectroscopy and laser Doppler flowmetry
2014 (English)Conference paper, Oral presentation with published abstract (Other academic)
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-109342 (URN)
Conference
International Conferance on Laser Applications in Life Sciences, Ulm, Germany, June 29-July 2, 2014
Available from: 2014-08-14 Created: 2014-08-14 Last updated: 2016-08-31
Strömberg, T., Karlsson, H., Fredriksson, I. & Larsson, M. (2013). Experimental results using a three-layer skin model for diffuse reflectance spectroscopy. In: Bruce J. Tromberg, Arjun G. Yodh, Eva M. Sevick-Muraca (Ed.), Optical Tomography and Spectroscopy of Tissue X: . Paper presented at Optical Tomography and Spectroscopy of Tissue X, 2 February 2013, San Francisco, California, USA (pp. 857834-1-857834-8). SPIE - International Society for Optical Engineering
Open this publication in new window or tab >>Experimental results using a three-layer skin model for diffuse reflectance spectroscopy
2013 (English)In: Optical Tomography and Spectroscopy of Tissue X / [ed] Bruce J. Tromberg, Arjun G. Yodh, Eva M. Sevick-Muraca, SPIE - International Society for Optical Engineering, 2013, p. 857834-1-857834-8Conference paper, Published paper (Other academic)
Abstract [en]

We have previously presented an inverse Monte Carlo algorithm based on a three-layer semi-infinite skin model for analyzing diffuse reflectance spectroscopy (DRS) data. The algorithm includes pre-simulated Monte Carlo data for a range of physiologically relevant epidermal thicknesses and tissue scattering levels. The simulated photon pathlength distributions in each layer are stored and the absorption effect from tissue chromophores added in the post-processing. Recorded DRS spectra at source-detector distances of 0.4 and 1.2 mm were calibrated for the relative intensity between the two distances and matched to simulated spectra in a non-linear optimization algorithm. This study evaluates the DRS spectral fitting accuracy and presents data on the main output parameters; the tissue fraction of red blood cells and local oxygenation (SO2). As a reference, the microcirculatory perfusion (Perf) was measured simultaneously in the same probe using laser Doppler Flowmetry. Data were recorded on the volar forearm of three healthy subjects in a protocol involving a 5 min systolic occlusion. The DRS spectra were modeled with an rms-error < 2%. In two subjects, SO2 decreased during occlusion to <10%, and increased to above baseline after hyperemia, while Perf increased >7 times compared to baseline. In the third subject the SO2 decreased less during occlusion and increased to baseline values at hyperemia with only a 2-fold increase in Perf. The observed difference could be due to different microvascular beds being probed. It is concluded that integrating DRS and LDF enables new possibilities to deduce microcirculation status.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2013
Series
Proceedings of SPIE, ISSN 0277-786X, E-ISSN 1996-756X ; 8578
Keywords
Microcirculation, diffuse reflectance spectra, Monte Carlo simulations, skin modeling, laser Doppler flowmetry
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-97046 (URN)10.1117/12.2014323 (DOI)9780819493477 (ISBN)
Conference
Optical Tomography and Spectroscopy of Tissue X, 2 February 2013, San Francisco, California, USA
Funder
VINNOVA, 2011-03074
Available from: 2013-09-04 Created: 2013-09-04 Last updated: 2017-02-21Bibliographically approved
Fredriksson, I., Burdakov, O., Larsson, M. & Strömberg, T. (2013). Inverse Monte Carlo in a multilayered tissue model: merging diffuse reflectance spectroscopy and laser Doppler flowmetry. Journal of Biomedical Optics, 18(12), 127004-1-127004-14
Open this publication in new window or tab >>Inverse Monte Carlo in a multilayered tissue model: merging diffuse reflectance spectroscopy and laser Doppler flowmetry
2013 (English)In: Journal of Biomedical Optics, ISSN 1083-3668, E-ISSN 1560-2281, Vol. 18, no 12, p. 127004-1-127004-14Article in journal (Refereed) Published
Abstract [en]

The tissue fraction of red blood cells (RBCs) and their oxygenation and speed-resolved perfusion areestimated in absolute units by combining diffuse reflectance spectroscopy (DRS) and laser Doppler flowmetry(LDF). The DRS spectra (450 to 850 nm) are assessed at two source–detector separations (0.4 and 1.2 mm), allowingfor a relative calibration routine, whereas LDF spectra are assessed at 1.2mmin the same fiber-optic probe. Data areanalyzed using nonlinear optimization in an inverse Monte Carlo technique by applying an adaptive multilayeredtissue model based on geometrical, scattering, and absorbing properties, as well as RBC flow-speed information.Simulations of 250 tissue-like models including up to 2000 individual blood vessels were used to evaluatethe method. The absolute root mean square (RMS) deviation between estimated and true oxygenation was 4.1percentage units, whereas the relative RMS deviations for the RBC tissue fraction and perfusion were 19% and23%, respectively. Examples of in vivo measurements on forearm and foot during common provocations arepresented. The method offers several advantages such as simultaneous quantification of RBC tissue fractionand oxygenation and perfusion from the same, predictable, sampling volume. The perfusion estimate is speedresolved, absolute (% RBC × mm∕s), and more accurate due to the combination with DRS.

Place, publisher, year, edition, pages
Bellingham, WA, United States: SPIE - International Society for Optical Engineering, 2013
Keywords
diffuse reflectance spectroscopy; laser Doppler flowmetry; modeling; Monte Carlo simulations; inverse engineering; nonlinear optimization; blood oxygen saturation; speed-resolved perfusion
National Category
Medical Equipment Engineering
Identifiers
urn:nbn:se:liu:diva-102707 (URN)10.1117/1.JBO.18.12.127004 (DOI)000331706500045 ()
Funder
VINNOVA, 2011-03074
Available from: 2013-12-19 Created: 2013-12-19 Last updated: 2017-12-06Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3454-6576

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