TOHR: prototype design and characterization of an original small animal tomograph

The authors have proposed an original method for high resolution in vivo tomography adapted to small animal models studies: TOHR (French acronym for High Resolution Tomograph). They have designed and developed a large solid angle, high resolution and high efficiency focusing collimator which provides a focal point used to scan the animal and finally perform the image. High resolution was improved by using nuclides having a two-photon decay (X- or gamma rays). The authors have built a prototype of a tomograph with a 2/spl pi/ collimator (10 over the 20 sides of an icosahedron). The different parts of the detector (collimator, detector, acquisition) are described. An optimization of the collimator structure and an iso-focusing method of the different modules of the collimator are discussed. Performances of the detector (energy, timing and spatial resolution) are presented using point sources and hot spot phantoms and are compared to numerical simulation results.