An on-axis Fresnel zone plate imaging system with a germanium gamma ray camera and computer reconstruction

This study examines the feasibility of obtaining germanium gamma camera images by using a Fresnel zone plate aperture to produce shadowgrams and by digital reconstruction of images from the shadowgrams produced. Parametric equations relating zone plate, detector, and field of view parameters are derived. Based on these equations, a general method of designing a zone plate system for any detector is established, and this method is applied to a system with a square high-purity germanium detector. The feasibility of computer reconstruction of shadowgrams is demonstrated, and the kinds of source distributions which are imaged well by the system are established by digital simulation of shadowgrams. Because the system considered contains a small germanium detector, the largest imageable source is one with a frontal area of 12 sq cm. Potential clinical applications for the system include detection of tumors in the skeletal system, the location of myocardial infarcts, and the imaging of small intracranial lesions.