2D and 3D imaging of small animals and the human radial artery with a high resolution detector for PET

The performance of a pair of multicrystal, high-resolution, bismuth germanate (BGO) block detectors for positron emission tomography (PET) has been investigated. Utilizing the detectors at a separation of 100 mm, the spatial resolutions and count rate response of the block have been measured. These measurements indicate maximum spatial resolutions of 3.6 and 4.5 mm (FWHM) in the two axes of the block and a maximum coincidence rate of 3400 cps. The system has been used to observe the regional kinetics of positron-emitting radionuclides in the rat brain and the human radial artery. Designs for a small diameter, no-septa tomograph incorporating these detectors have been considered. Simulations demonstrate the possibilities of following tracer uptake within the rat brain and radial artery. Three-dimensional tomographic data-sets of a 20-mm uniform cylinder, obtained from rotating the two blocks, indicate good uniformity in the field of view (FOV) of 25 mm.     

Fully three-dimensional reconstruction for a PET camera with retractable septa

A fully 3-D reconstruction algorithm has been developed to reconstruct data from a 16 ring PET camera (a Siemens/CTI 953B) with automatically retractable septa. The tomograph is able to acquire coincidences between any pair of detector rings and septa retraction increases the total system count rate by a factor of 7.8 (including scatter) and 4.7 (scatter subtracted) for a uniform, 20 cm diameter cylinder. The reconstruction algorithm is based on 3-D filtered backprojection, expressed in a form suitable for the multi-angle sinogram data. Sinograms which are not measured due to the truncated cylindrical geometry of the tomograph, but which are required for a spatially invariant response function, are obtained by forward projection. After filtering, the complete set of sinograms is backprojected into a 3-D volume of 128x128x31 voxels using a voxel-driven procedure. The algorithm has been validated with simulation, and tested with both phantom and clinical data from the 953B.     

Using geodemographics to launch a telephone referral service

Mercy Health Services, a diversified, $1.5 billion, 23-hospital system based in Indiana, Iowa, Michigan and New York, purchased a microcomputer-based marketing support system in November 1988. Two marketers affiliated with the hospital describe the system's use in determining the feasibility of developing a direct mail campaign for a referral service.