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 vivo USF 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 achieved in vivo USF 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 vivo and ex vivo USF 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.
Highlights
The conventional fluorescence imaging has limited spatial resolution in centimeter-deep tissue because of the tissue’s high scattering property
Besides fluorescence microscopy, imaging based on fluorescence contrast in deep tissues attracts a lot of interests too because it has many unique advantages compared with other modalities, such as x-ray, ultrasound, magnetic resonance imaging (MRI), and positron-emission tomography (PET)
To quantify how the high-intensity focused ultrasound (HIFU) driving voltage affect the spatial resolution of the frequency-domain (FD)-Ultrasound-switchable fluorescence (USF) system, we performed the USF imaging in a silicone tube-based tissue phantom
Summary
The conventional fluorescence imaging has limited spatial resolution in centimeter-deep tissue because of the tissue’s high scattering property. Nonspecific photons, which may come from tissue autofluorescence, laser leakage, or stray light in the environment, are always noises and reduce the specificity and sensitivity of signal to its contrast agents in deep tissues To address these challenges, several technologies have been or are being investigated, such as ultrasound-modulated fluorescence[10,11] or luminescence[12], ultrasound-induced temperature-controlled fluorescence[13,14,15] or luminescence[16], and time-reversed ultrasonically encoded optical focusing[17,18,19,20,21].
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