Research On Dual-modality Imaging System For Small Animals

Different modals of small animal imaging system are playing a more and more important part in biomedical research, as the requirement of observation of the molecular information in vivo in disease research, new drug discovery. Fluorescence molecular tomography (FMT) is a three-dimensional imaging system with quantitative measurement of fluorescence in small animals in vivo. However, FMT could provide no anatomical information of small animals, which would lead to misunderstand the imaging result. Multi-modality imaging has been introduced to address this issue.Dual-modality imaging system of FMT combined with micro-CT is constructed in this thesis. Micro-CT based on micro-focus X-ray tube and amorphous-silicon-based flat panel detector is applied to provide high resolution image of small animals. FMT consists of laser diode and cooled charge coupled device. The rotation scanning is used in micro-CT, while line scanning is used in FMT. The FMT is mounted orthogonally with micro-CT, and the imaging chamber is fixed on the rotation stage at the middle of the system. A non-image based approach is proposed to couple the FMT with micro-CT. The method utilize the imaging chamber imaged with micro-CT and the inside space of the chamber imaged with FMT to confirm the relation between the Cartesian of micro-CT and FMT.The system performance is analysed and evaluated with phantom study. The resolution of the system is measured with tungsten wire. The uniformity of micro-CT is corrected and measured. The sensitivity and of FMT, the contrast-to-noise ratio (CNR) and linearity of micro-CT are evaluated. The researches reveal the resolution of micro-CT and FMT are 13mm-1 and 3 mm, respectively. The imaging of water phantom shows the error of 20 HU between center and edge. The sensitivity of FMT with DiR-BOA and the depth of 7 mm is more than 100 nM while the quantification error is less than 5%. The CNR of fat phantom reaches 2.2 with radiation dose of 185 mGy. The safe of X-ray imaging is estimated, and the result shows a low-level dose rate of both small animals and operators.The application of FMT-CT dual-modality imaging system is also demonstrated. Nude mice bearing tumor targeted with DiR-BOA is imaged with the system in vivo. A femur of a rabbit is also imaged ex vivo. The results show the feasibility of FMT-CT in living small animal research for offering molecular and structural information at the same time.