A High Sensitivity Multi-Spectral Three-Dimensional Fluorescence Optical Tomography System for Small Animal Imaging

We have designed a three dimensional (3D) fluorescence optical tomography system for small animal imaging based on an innovative system geometry that uses a truncated conical mirror which permits the entire surface of the animal to be viewed simultaneously by a single CCD camera. Compared with traditional approaches that employ a flat mirror, the conical mirror system has approximately 3 times better measurement sensitivity. By utilizing a fast switching filter wheel (switching time < 100 milliseconds), emission data at multiple wavelengths can be efficiently collected. An array of appropriately shaped neutral density filters, mounted on a linear stage, can be used to increase the system measurement dynamic range by 3 orders of magnitude. An x-y galvo mirror scanning system makes it possible to scan a collimated laser beam to any location on the mouse surface. A pattern of structured light incident on the animal surface is used to extract the surface geometry. A finite element based algorithm is applied to model photon propagation in the turbid media and a preconditioned conjugate gradient (PCG) method is used to solve the large linear system matrix. The reconstruction algorithm and the system performance are evaluated by phantom experiments.