Techniques to improve the spatial sampling of microPET - A high resolutionanimal PET tomograph

A method is described to improve the spatial sampling:of microPET, a high r esolution PET scanner designed for imaging small laboratory animals. The hi gh intrinsic resolution of the microPET detector (1.58 mm FWHM), in combina tion with the stationary ring:geometry of the tomograph, generate an imagin g system which is inherently spatially undersampled, As a result the imagin g resolution measured with a three-dimensional (3-D) filtered backprojectio n (FBP) algorithm for a point source at the center of the field of view (CF OV) is only 1.8 mm FWHM and has large fluctuations at positions near the CF OV. A small wobble motion was introduced via a circular motion of the scann er bed in the transverse plane, with a wobble radius of 300 mu m The data w as acquired with a step and-shoot method by dividing the wobble circle into a number of equidistantly sampled intervals. The separate sinograms were i nterpolated to a finely resampled sinogram, which was reconstructed with th e 3-D filtered backprojection algorithm The resulting images demonstrated f ull recovery of the intrinsic detector resolution and elimination of the lo cal nonuniformities of the point spread function (PSF) at the CFOV, with th ree wobble samples. The resulting average resolution improvement for the ce ntral 5 cm of the FOV was approximately 13% in the radial and 19% in the ta ngential direction, with an associated 50% penalty in the reconstructed ima ge noise.