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New PET scanners have higher axial and in-plane spatial resolutions but at the expense of reduced per plane sensitivity, which prevents the higher resolution to be fully realized. Normally, Gaussian weighted interplane axial smoothing is used to reduce noise. In this study, the authors developed a new algorithm to first elastically map from adjacent planes to an expected plane location, then by simple averaging with the measured image at the corresponding axial plane location to reduce the image noise level. Compared with those images obtained by conventional axial-directional smoothing method, the images of the new method which are based on matching image features of adjacent planes have improved signal-to-noise ratio. To quantify the observation, both simulated cardiac images and real cardiac PET images were studied. The effective in-plane resolution loss was measured by the "effective global Gaussian resolution" and the noise reduction was evaluated by the cross-correlation coefficient. Various Hanning reconstruction filters with cutoff frequency=0.5, 0.7, 1.0/spl times/Nyquist frequency and Ramp 1.0 filter were tested on simulated images. Results showed that the new method was robust to various noise levels and indicated larger noise reduction or better image feature preservation than by the conventional method.

The authors report the results from a new high resolution gamma ray imaging detector designed for use in a positron emission tomography (PET) system dedicated to small animal imaging. The detectors consist of an 8/spl times/8 array of 2/spl times/2/spl times/10 mm bismuth germanate (BGO) crystals coupled by 2 mm diameter double clad optical fibers to a 64 pixel multi-channel photomultiplier tube (MC-PMT). A charge division readout board is used to convert the 64 output channels into four position sensitive signals which determine the crystal of interaction. Measurements with a pair of these detectors demonstrate an intrinsic spatial resolution of 1.4 mm, a coincidence timing resolution of 15 ns and an energy resolution ranging between 35 and 60%. Based on these encouraging results, the design for a dedicated animal PET tomograph is proposed and simulations of this system project a reconstructed resolution of less than 2 mm within a 5 cm diameter transaxial field of view.