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Presents information on research which derives explicit relationships between an ideal sinogram in 2 dimensional single photon emission computed tomography (SPECT) and the sinogram after degradation by constant attenuation and by distance-dependent spatial resolution. Results of attempting to reduce statistical variance in the reconstructed image; What was shown by computer-simulation studies; Information on the results of this research; Discussion of these results.

We compare two methods of training artificial neural networks (ANNs) that potentially reduce the risk of the neural network overfitting the training data set. We refer to these methods as training with jitter. In one method of training with jitter, a new random noise vector is added to each training-data vector between successive iterations. In this work, we propose a different method of training with jitter, in which instead of adding different random noise vectors between iterations, a number of random vectors are used to expand the training data set prior to training. This artificially expanded data set is then used to train the artificial neural network in the conventional manner. These two methods are compared to the conventional method of training artificial neural networks. We find that although training with a single expanded training data set does increase the performance of the neural networks, overfitting can still occur after a large number of training iterations. [Copyright &y& Elsevier]