Poster — Thur Eve — 74: A Fan‐Beam Collimator Design for Small Animal Scintigraphy

The objective of the study was to design and conduct a performance study of a fan‐beam collimator for a multi‐modality small‐animal imaging device, which was primarily responsible yielding high‐resolution images with high sensitivity ‐ a necessity for rapid dynamic studies. The device had of a high‐resolution gamma camera that included a 2×2 array of position sensitive photomultiplier tubes and a pixilated NaI(Tl) scintillator array. The collimator's holes were square‐shaped to match the layout of the scintillation detector, with a septal thickness equals t the separation between two consecutive pixel elements. The collimator septal length (l), focal length (f), and septal thickness (t) were calculated. A Monte Carlo model was used to calculate the scattering and noise photons for a homogeneous 3D attenuating medium. The detector pixels were defined as repeated structures of square shaped NaI(Tl) crystal blocks (0.6 cm thick). The outer layer of the detector blocks was surrounded by vacuum to stop external scattering. The collimator was defined as intersecting tungsten plates of thickness 0.02cm each. The angular dependency of the fan‐beam collimator was studied and a signal to noise index was calculated within the central field of view. The detection efficiency of the fan‐beam collimator increased significantly (about 10 2 times more) in comparison to the parallel hole collimator when a point source was placed close to the focal point. The angular effect on the fan‐beam performance showed a minor effect in comparison to that of attenuation effect. The use of the fan‐beam collimator significantly increased the detection efficiency for the gamma camera.