Study Of Excitation Modes Of Fluorescent Molecular Tomography Based On Dual-modality System

Over the past decade, molecular imaging modalities such as optical molecular imaging are flourishing, which greatly promote the advancement of medical imaging technology. Among these, fluorescent molecular imaging has a broad application prospect in many areas, such as surgical, neurological, cardiovascular disease. Fluorescent molecular imaging can be divided into two-dimensional planar imaging and three-dimensional tomography imaging. The traditional two-dimensional planar imaging can only provide fluorescence distribution on biological surface and can’t provide accurate depth information. FMT is a new three-dimensional imaging technology, which can overcome the shortcoming of not being quantified in two-dimensional planar imaging. It has the advantages of high sensitivity, no ionizing, non-radioactive and gets a widespread concern and the rapid development.The quality of FMT reconstruction results is affected by many factors, among which the projection modes and geometry of light source play an important role on FMT reconstruction results, therefore it is a problem worth studying. This article is based on our optical-CT dual-modality system. We use Micro-CT to get the three-dimensional structural information of phantom, use optical imaging system to acquire fluorescence information of the surface. Then we combine the mathematical model of FMT, by setting different projection modes and geometry of light source, we can study the impacts on FMT reconstruction results.First, we study the impacts of projection modes on reconstruction result. The projection modes discussed in this article include projection number and the location of projection. In full angle, we choose 1、2、3、6、12 as projection number, then we do a numerical simulation on single and double fluorophore. We can calculate the distance error through the gravity of real fluorophore and reconstructed fluorophore, and take it as an evaluation criteria of the quality to reconstruction results. However, in some experimental situations, the object can’t be excited in full angle, such as flat-type mice excitation, this situation belongs to limited angle excitation. We also choose 1、2、3、6、12 as projection number, then we do a numerical simulation on single and double fluorophore.Because the fluorophore location in biological tissues is unknown and the optical parameters are different. These differences can lead to different reconstruction results.It is necessary to study the impact of projection position on reconstruction results. We choose four projection numbers, they are 1、3、6、12. Each projection number has four projection angles, they are 0 degrees, 30 degrees, 60 degrees, 90 degrees respectively. We use standard deviation to measure the impacts of the projection position on reconstruction results. To further verify the simulation results, we conducted phantom experiments. The results show that the more the projection numbers are, the more accurate reconstruction result is; the impact of projection position on the reconstruction results decreases with the increase of projection number.Finally, we study the impacts of geometry of light source on reconstruction results. We choose 3、6、12 as projection number. Each projection number has three kinds of geometry of light source including point excitation, line excitation and surface excitation. We use distance error to judge the quality of the reconstruction result. Then we conducted phantom experiments to further verify the simulation results. The results show that the reconstruction result of point light source is best, followed by line light source, the last is surface light source.