TABLE OF CONTENTS The development of dedicated tomographic scanners for experimental animal studies is a field in great expansion. The potential of PET and SPECT imaging in small animals [1] [11] has led to the design of several specialized small animal imaging systems [12] [35]. Some of these will be described in detail below, emphasizing the differences in their design and reasons of the choices made. Both PET and SPECT provide non-invasive methods to perform in-vivo radiopharmaceutical studies, molecular imaging, gene therapy and to evaluate tumor therapy results. Due to the reduced dimensions of small animals, sensitivity and spatial resolution must be very good. Typically the organs under study are small, the animal's metabolic rate is high and the activity used is relatively low.
Although sensitivity and spatial resolution in PET is generally better than in SPECT, PET has the drawback of needing a cyclotron nearby or ideally in the same research centre for producing the necessary short lived radioisotopes. This is particularly true for studies with 11C and 15O whose half lives are respectively 20 and 2 minutes. On the other hand the radioisotopes necessary for SPECT are easier to obtain. Both techniques are therefore interesting and the design of such small animal scanners will be discussed in the following sections.
High resolution...
