Research On Vivo Imaging Of Tissue/Orgran Of Small Animals By Micro-CT

Micro-CT is widely used for animal research due to its high spatial resolution and fast scanning speed,which plays an important role in in-vivo imaging of bone structure,organ and cardiovascular.With the development of technology,the spatial resolution of micro-CT has been improved,which makes it possible to implement the observation on cell scale imaging.However,constrained by X-ray dose,noise,detector response time and so on,the image quality of soft tissue imaging suffers from low density resolution and low time resolution,which limits the applications of micro-CT.In order to exploit the advantages of micro-CT in small animal imaging,it is necessary to study the specific imaging conditions and reconstruction methods of micro-CT.By optimizing scanning parameters,contrast mode,gating technique and the reconstruction algorithm,the density resolution and time resolution can be improved.Therefore,the micro CT can achieve better in-vivo imaging in tissue,stationary organs and blood vessels,and further realize the 4D dynamic cardiac imaging.Based on the above considerations,this paper studies the relationship between the scan parameters and the quality of CT imaging.According to the imaging characteristics of different organs and blood vessels,two kinds of detection phantom are designed,both phantoms are composed of contrast blocks with different density and arrangement modes.These two phantoms are used to study the influence of the X-ray source tube voltage,tube current and projection number on the imaging quality.The experiment results illustrate that,with the tube current and the projection number increasing,the imaging quality can be improved either.Consequently,the radiation dose and imaging time will also pile up.Amplifying the tube voltage can improve the SNR of the image,it also results in unpredictable influence on the contrast of materials.Thus different scanning protocols should be developed based on the different characteristics of the sample organization.In order to improve the imaging quality of in-vivo soft tissue imaging,the gating technique and contrast mode of micro-CT were studied in this paper.A respiratory gating system based on micro camera and body surface marker is designed,and an in-vivo scanning method with variable speed based on multi loop is implemented.By matching the scanning speed with the respiratory rate,the in-vivo scanning method can obtain the CT image without motion artifact in a short scanning time.On the basis of in-vivo scanning,the enhancement effects of different contrast methods,such as abdominal enhancing,intravenous contrast and intravenous perfusion,were analyzed.The experiment illustrate that organ contour can be effectively enhanced by abdominal enhancing,and infusion enhancing has significant effect on the liver,kidney,and vascular tissue.According to the experiment results,the CT image of subcutaneous tumor vessels and intracranial vessels is obtained by intravenous contrast perfusion.In order to obtain dynamic 4D images of heart,the time resolution of micro-CT is also need to be enhanced.In this paper,a micro-CT cardiac 4D imaging method based on ECG gating and reconstruction algorithm is explored.In order to obtain the ECG signal,we proposed an ECG gating system based on AD8232 and 430F5438A,as well as a prior image constrained compressed sensing reconstruction algorithm for cardiac 4D imaging(PICCS-4D).The experimental results illustrate that,compared with the single step scanning and FDK reconstruction method,the PICCS-4D method can achieve higher image quality while reducing the scanning dose and scanning time.