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Updated: Jan 30, 2026

Nano-fEM: Protein Localization Using Photo-activated Localization Microscopy and Electron Microscopy
Published on: December 3, 2012
Photo-activated ultrasound localization imaging with laser-activated nanodroplets
Shensheng Zhao1,2,3, Junxi Yi2,3,4, Yueying Qiu1,2,3
1Department of Electrical and Computer Engineering, Grainger College of Engineering, University of Illinois Urbana-Champaign, Urbana, IL, USA.
Photo-activated ultrasound localization (PaUL) imaging uses laser-triggered nanodroplets for super-resolved microvascular visualization. This novel method offers precise control, faster imaging, and extended tracking for enhanced hemodynamic mapping.
Area of Science:
- Biomedical Imaging
- Nanotechnology
- Ultrasound Technology
Background:
- Super-resolution ultrasound localization (UL) imaging visualizes microvasculature beyond the diffraction limit.
- Conventional UL is limited by microbubble circulation time and distribution.
Purpose of the Study:
- To introduce photo-activated UL (PaUL) imaging for super-resolved microvascular visualization.
- To achieve precise spatiotemporal control over contrast generation using laser-triggered nanodroplets.
Main Methods:
- Synthesis of dual-contrast indocyanine green (ICG)-encapsulated perfluoropentane nanodroplets.
- Development of a programmable activation and imaging sequence for PaUL.
- Utilizing laser fluence to tune on-demand contrast generation.
Main Results:
- PaUL imaging achieved 21 µm spatial resolution.
- Vascular reconstruction was 2.4× faster, and tracking lengths were 1.6× longer compared to conventional UL.
- Extended circulation time allowed up to 3× more localization events over 20 minutes.
Conclusions:
- PaUL imaging provides flexible, high-resolution contrast with precise spatiotemporal control.
- Integration with photoacoustic imaging enhances multimodal capabilities.
- PaUL imaging shows promise for microvascular imaging and image-guided therapies like targeted drug delivery.
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