Employing line-laser illumination for 3D fluorescence imaging and tomography in a tri-modal SPECT-CT-OT imaging system

The adoption of axially oriented line illumination patterns for fluorescence excitation in small animals for fluorescence surface imaging (FSI) and fluorescence optical tomography (FOT) is being investigated. To conduct this study, a tri-modal SPECT-CT-OT small animal imaging system is being modified for employment of both, point and line laser excitation sources which can be arbitrarily positioned around the imaged object. The line source is set to illuminate the imaged object along its entire axial direction. Comparative evaluation of point and line illumination patterns for FSI and FOT is provided involving phantom as well as mouse data. Provided the tri-modal setup, computer tomography (CT) data are used to guide both optical imaging approaches by providing accurate boundary information. Furthermore, FOT results are also being compared to single photon emission computed tomography (SPECT). Results show that line laser illumination pattern yields a larger axial field-of-view (FOV) in FSI mode, and practically acceptable FOT reconstruction results throughout the whole animal. Also, superimposed SPECT and FOT data provide interesting information on the similarities as well as the differences in the distribution and uptake of both probe types (optical, nuclear); fused CT data enhance further the anatomical localization of optical and nuclear tracer distribution in vivo.