skip to main content


Title: An ICCD camera-based time-domain ultrasound-switchable fluorescence imaging system
Abstract

Fluorescence imaging in centimeter-deep tissues with high resolution is highly desirable for many biomedical applications. Recently, we have developed a new imaging modality, ultrasound-switchable fluorescence (USF) imaging, for achieving this goal. In our previous work, we successfully achieved USF imaging with several types of USF contrast agents and imaging systems. In this study, we introduced a new USF imaging system: an intensified charge-coupled device (ICCD) camera-based, time-domain USF imaging system. We demonstrated the principle of time-domain USF imaging by using two USF contrast agents. With a series of USF imaging experiments, we demonstrated the tradeoffs among different experimental parameters (i.e., data acquisition time, including CCD camera recording time and intensifier gate delay; focused ultrasound (FU) power; and imaging depth) and the image qualities (i.e., signal-to-noise ratio, spatial resolution, and temporal resolution). In this study, we also discussed several imaging strategies for achieving a high-quality USF image via this time-domain system.

 
more » « less
NSF-PAR ID:
10153637
Author(s) / Creator(s):
; ;
Publisher / Repository:
Nature Publishing Group
Date Published:
Journal Name:
Scientific Reports
Volume:
9
Issue:
1
ISSN:
2045-2322
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Ultrasound-switchable fluorescence (USF) is a novel imaging technique that provides high spatial resolution fluorescence images in centimeter-deep biological tissue. Recently, we successfully demonstrated the feasibility ofin vivoUSF imaging using a frequency-domain photomultiplier tube-based system. In this work, for the first time we carried outin vivoUSF imaging via a camera-based USF imaging system. The system acquires a USF signal on a two-dimensional (2D) plane, which facilitates the image acquisition because the USF scanning area can be planned based on the 2D image and provides high USF photon collection efficiency. We demonstratedin vivoUSF imaging in the mouse’s glioblastoma tumor with multiple targets via local injection. In addition, we designed the USF contrast agents with different particle sizes (70 nm and 330 nm) so that they could bio-distribute to various organs (spleen, liver, and kidney) via intravenous (IV) injections. The results showed that the contrast agents retained stable USF properties in tumors and some organs (spleen and liver). We successfully achievedin vivoUSF imaging of the mouse’s spleen and liver via IV injections. The USF imaging results were compared with the images acquired from a commercial X-ray micro computed tomography (micro-CT) system.

     
    more » « less
  2. Abstract

    The conventional fluorescence imaging has limited spatial resolution in centimeter-deep tissue because of the tissue’s high scattering property. Ultrasound-switchable fluorescence (USF) imaging, a new imaging technique, was recently proposed to realize high-resolution fluorescence imaging in centimeter-deep tissue. However,in vivoUSF imaging has not been achieved so far because of the lack of stable near-infrared contrast agents in a biological environment and the lack of data about their biodistributions. In this study, for the first time, we achievedin vivoUSF imaging successfully in mice with high resolution. USF imaging in porcine heart tissue and mouse breast tumor via local injections were studied and demonstrated.In vivoandex vivoUSF imaging of the mouse spleen via intravenous injections was also successfully achieved. The results showed that the USF contrast agent adopted in this study was very stable in a biological environment, and it was mainly accumulated into the spleen of the mice. By comparing the results of CT imaging and the results of USF imaging, the accuracy of USF imaging was proved.

     
    more » « less
  3. Abstract

    Fluorescence imaging is a remarkable tool for molecular targeting and multicolor imaging, but it suffers from low resolution in centimeter‐deep tissues. The recently developed ultrasound‐switchable fluorescence (USF) imaging has overcome this challenge and achieved in vivo imaging in a mouse with help from the indocyanine green (ICG) dye encapsulated poly(N‐isopropylacrylamide) (ICG‐PNIPAM) contrast agent. However, the ICG‐PNIPAM has shortcomings, such as concerns about cytotoxicity and blueshifted excitation and emission spectra. This study introduces a newly developed ICG‐encapsulated liposome to broaden the contrast agent selection for USF imaging and resolve the issues mentioned above. The emission peak of the ICG‐liposome is 836 nm with excellent biostability and USF imaging capability. Furthermore, the cell viability test verifies the low cytotoxicity feature. Eventually, both ex vivo and in vivo USF imaging are successfully achieved and 3D USF images are acquired. The ex vivo result confirms that the ICG‐liposome maintains the thermoresponsive characteristic at the right lobe of the liver and is able to conduct the USF imaging. The further in vivo USF imaging demonstrates that although the whole liver emitted fluorescence, only the right lobe of the liver contains the working ICG‐liposome.

     
    more » « less
  4. We present high-resolution, high-speed fluorescence lifetime imaging microscopy (FLIM) of live cells based on a compressed sensing scheme. By leveraging the compressibility of biological scenes in a specific domain, we simultaneously record the time-lapse fluorescence decay upon pulsed laser excitation within a large field of view. The resultant system, referred to as compressed FLIM, can acquire a widefield fluorescence lifetime image within a single camera exposure, eliminating the motion artifact and minimizing the photobleaching and phototoxicity. The imaging speed, limited only by the readout speed of the camera, is up to 100 Hz. We demonstrated the utility of compressed FLIM in imaging various transient dynamics at the microscopic scale.

     
    more » « less
  5. Abstract

    A promising new field of genetically encoded ultrasound contrast agents in the form of gas vesicles has recently emerged, which could extend the specificity of medical ultrasound imaging. However, given the delicate genetic nature of how these genes are integrated and expressed, current methods of producing gas vesicle‐expressing mammalian cell lines requires significant cell processing time to establish a clonal/polyclonal line that robustly expresses the gas vesicles sufficiently enough for ultrasound contrast. Here, we describe an inducible and drug‐selectable acoustic reporter gene system that can enable gas vesicle expression in mammalian cell lines, which we demonstrate using HEK293T cells. Our drug‐selectable construct design increases the stability and proportion of cells that successfully integrate all plasmids into their genome, thus reducing the amount of cell processing time required. Additionally, we demonstrate that our drug‐selectable strategy forgoes the need for single‐cell cloning and fluorescence‐activated cell sorting, and that a drug‐selected mixed population is sufficient to generate robust ultrasound contrast. Successful gas vesicle expression was optically and ultrasonically verified, with cells expressing gas vesicles exhibiting an 80% greater signal‐to‐noise ratio compared to negative controls and a 500% greater signal‐to‐noise ratio compared to wild‐type HEK293T cells. This technology presents a new reporter gene paradigm by which ultrasound can be harnessed to visualize specific cell types for applications including cellular reporting and cell therapies.

     
    more » « less