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Mapping fast tissue dynamics with long camera exposures via intensity modulation.

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Title: Mapping fast tissue dynamics with long camera exposures via intensity modulation.
Authors: Lu, Hengfa1, Fang, Qingwei1, Ashbrook, Jewel A.1,2, Nemchek, Victoria3, Fracassi, Michela3, Jones, Theresa A.3, Dunn, Andrew K.1 adunn@utexas.edu
Source: Proceedings of the National Academy of Sciences of the United States of America. 4/28/2026, Vol. 123 Issue 17, p1-9. 9p.
Subjects: Intensity modulation (Optics), Frequency-domain analysis, Ischemic stroke, Microfluidics, Speckle interferometry, Light scattering, Cerebral circulation
Abstract: Measuring fast dynamic processes with dynamic light scattering over wide fields of view is critical for applications ranging from blood flow imaging to characterizing complex fluids, yet is often limited by the need for expensive, high frame rate cameras. Here, we introduce sinusoidal intensity modulation speckle imaging (SIMSI), a technique that overcomes this hardware limitation by encoding information about fast dynamics into images captured with long camera exposures. Within each exposure, we sinusoidally modulate the illumination intensity, yielding frequency selective speckle variance measurements that sample the power spectral density (PSD) of intensity fluctuations. By sweeping the modulation frequency across exposures, SIMSI maps the PSD while preserving high signal-to-noise long exposures. We fit the measured spectra with a flexible model and report a spectral cutoff frequency fc as a flow index. In controlled flow microfluidic phantoms, SIMSI PSD estimates agree with the reference PSD measurements from a coaligned high-speed detector, and the derived fc varies linearly with the imposed flow velocity (R² > 0.999). In vivo in the mouse cortex, the SIMSI derived fc maps distinguish vascular compartments with distinct spectral signatures. Finally, SIMSI tracks the spatiotemporal evolution of cortical blood flow changes for ten days following ischemic stroke. SIMSI provides a robust and accessible method for wide field, frequency domain characterization of fast dynamics using standard cameras. This advance enables a richer characterization of complex systems and has wide ranging applications in biomedicine, engineering, and physics. [ABSTRACT FROM AUTHOR]
Copyright of Proceedings of the National Academy of Sciences of the United States of America is the property of National Academy of Sciences and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: Engineering Source
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  Data: Mapping fast tissue dynamics with long camera exposures via intensity modulation.
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  Data: <searchLink fieldCode="DE" term="%22Intensity+modulation+%28Optics%29%22">Intensity modulation (Optics)</searchLink><br /><searchLink fieldCode="DE" term="%22Frequency-domain+analysis%22">Frequency-domain analysis</searchLink><br /><searchLink fieldCode="DE" term="%22Ischemic+stroke%22">Ischemic stroke</searchLink><br /><searchLink fieldCode="DE" term="%22Microfluidics%22">Microfluidics</searchLink><br /><searchLink fieldCode="DE" term="%22Speckle+interferometry%22">Speckle interferometry</searchLink><br /><searchLink fieldCode="DE" term="%22Light+scattering%22">Light scattering</searchLink><br /><searchLink fieldCode="DE" term="%22Cerebral+circulation%22">Cerebral circulation</searchLink>
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  Data: Measuring fast dynamic processes with dynamic light scattering over wide fields of view is critical for applications ranging from blood flow imaging to characterizing complex fluids, yet is often limited by the need for expensive, high frame rate cameras. Here, we introduce sinusoidal intensity modulation speckle imaging (SIMSI), a technique that overcomes this hardware limitation by encoding information about fast dynamics into images captured with long camera exposures. Within each exposure, we sinusoidally modulate the illumination intensity, yielding frequency selective speckle variance measurements that sample the power spectral density (PSD) of intensity fluctuations. By sweeping the modulation frequency across exposures, SIMSI maps the PSD while preserving high signal-to-noise long exposures. We fit the measured spectra with a flexible model and report a spectral cutoff frequency fc as a flow index. In controlled flow microfluidic phantoms, SIMSI PSD estimates agree with the reference PSD measurements from a coaligned high-speed detector, and the derived fc varies linearly with the imposed flow velocity (R² > 0.999). In vivo in the mouse cortex, the SIMSI derived fc maps distinguish vascular compartments with distinct spectral signatures. Finally, SIMSI tracks the spatiotemporal evolution of cortical blood flow changes for ten days following ischemic stroke. SIMSI provides a robust and accessible method for wide field, frequency domain characterization of fast dynamics using standard cameras. This advance enables a richer characterization of complex systems and has wide ranging applications in biomedicine, engineering, and physics. [ABSTRACT FROM AUTHOR]
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  Data: <i>Copyright of Proceedings of the National Academy of Sciences of the United States of America is the property of National Academy of Sciences and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
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        Value: 10.1073/pnas.2524940123
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        Text: English
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      – SubjectFull: Intensity modulation (Optics)
        Type: general
      – SubjectFull: Frequency-domain analysis
        Type: general
      – SubjectFull: Ischemic stroke
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      – SubjectFull: Microfluidics
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      – SubjectFull: Speckle interferometry
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      – SubjectFull: Light scattering
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      – SubjectFull: Cerebral circulation
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      – TitleFull: Mapping fast tissue dynamics with long camera exposures via intensity modulation.
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            NameFull: Lu, Hengfa
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              Text: 4/28/2026
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              Y: 2026
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