Life time imaging with pulsed x-ray based x-ray luminescence computed tomography

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SUMMARY Lifetime imaging, such as fluorescence lifetime imaging, is able to provide extensive physiological information in cells or tissues. Fluorescence lifetime imaging is mainly applied to superficial targets or objects that can be reached by an optical guidance. For deep targets, fluorescence lifetime imaging suffers low spatial resolution and poor image quality due to strong optical scattering. In this proposal, we will develop a unique, novel biophotonics imaging modality, time domain x-ray luminescence computed tomography (tdXLCT), which combines the spatial resolution of x-ray imaging with the high detection sensitivity of optical imaging. The tdXLCT will be a new approach to explore lifetime imaging in deep targets. In the tdXLCT, an ultrafine pulsed x-ray beam will excite nanophosphors in deep targets and the emitted photons will be measured with a sensitive photomultiplier tube module. In this administrative supplement proposal, the supported graduate student will build a lifetime measurement system for samples, evaluate the lifetime in different environments, as well as synthesize and characterize x-ray excitable nanophosphors with better emission efficiency. Furthermore, he will build, for the first time, a tdXLCT system and evaluate its performance with phantom imaging experiments. The proposed tdXLCT will explore the applicability of x-ray as a molecular imaging tool and as a means to obtain information on the physiochemical characteristics of microenvironments in deep tissues (e.g. oxygenation level). The proposed tdXLCT will be of interest to many biological researchers in the fields of nanomedicine and cancer therapy because it has the potential to overcome limitations associated with radiolabeling (limited half-life) and fluorescence tagging (poor spatial resolution at depths). Relationship to the parent grant: This proposal is closely related to the parent grant. Both of them explore the application of x-ray luminescence imaging. However, the parent grant aims to explore the high spatial resolution XLCT imaging in the continue wave (CW) domain. This proposal aims to explore the applications of pulsed x-ray luminescence in time domain. This proposal will also utilize the synthesized nanoparticles from the parent grant.