Evaluation of novel whole-body high-resolution rodent SPECT (Linoview) based on direct acquisition of linogram projections.

Studies of the biodistribution of radiolabeled compounds in rodents frequently are performed during the process of development of new pharmaceutical drugs. This article presents the evaluation of a new whole-body animal SPECT system, called the Linoview SPECT system. METHODS: Linoview SPECT is based on the linear orbit acquisition technique associated with slit-aperture collimators mounted on 4 pixelated CsI(Na) detectors composed of an array of small, individual crystal elements. Sliding iridium rods allow variation of the collimator aperture. Hot-rod and cold-rod phantoms filled with (99m)Tc were imaged. Mice were imaged, and kidney radioactivity was measured after injection of (99m)Tc-dimercaptosuccinic acid and (111)In-diethylenetriaminepentaacetic acid-d-Phe(1)-octreotide ((111)In-pentetreotide; Octreo-Scan(111)). RESULTS: Phantom studies showed that hot rods separated by 0.35 mm can be distinguished and that 0.65-mm-diameter cold rods can be visualized, both at low-counting-rate acquisitions (111 and 59 MBq x h, respectively). In both mouse studies, the SPECT images allowed a clear delineation of the radioactivity concentrated over the cortex area of the kidneys, whereas the pelvis and the pelviureteral junction (1 mm) appeared as cold areas. The quantitative data derived from SPECT were in good agreement with the radioactivity counting obtained with a gamma-counter after isolation of the kidneys. In addition, in the mouse injected with (111)In-pentetreotide, the kidney radioactivity distribution seen with SPECT was in agreement with the ex vivo autoradiograms of the isolated kidneys. CONCLUSION: The phantom studies showed a clear improvement of the spatial resolution over the results reported in the literature with other dedicated small-animal SPECT systems, especially in cold-rod phantom studies. The increased performance can be ascribed to the high stability of the system with regard to the statistical noise present in the acquired data. The mouse studies showed that this system will be most useful for in vivo high-resolution SPECT and quantitative biodistribution studies in rodents, even with medium-energy radioisotopes that are difficult to image, such as (111)In.