In this work is presented a method for analytically cdculating the distribution of photons detected in SPECT projections. The technique is appLicabIe to sources in homogeneous and non-homogeneous media. The photon distribution (primary, first and second order Compton scatter, and first order Rayleigh scatter) is computed using precdculated camera-dependent lookup tables in conjunction with an attenuation map of the scattering object aad a map of the activity distribution.The resdts of the technique are in excellent agreement with those of Monte Carlo simulation and experimental phantom studies. It has b e n validated with respect to sources in both homogeneous and noa-homogeneous media.Compared with a similar andyticd technique, it offers a factor of 40-60 decrease in the cdculation time for higher order Compton scatter distributions. For small sources, it improves on computation tirne required by Monte Carlo simulators by a factor of 20-150.Finally, this method has been applied to the problem of correcting for cross-taik in 1231-99mT~ dual-isotope SPECT studies. It has demonstrated the ability to accurately reproduce the shape of the cross-talk distribution and to reproduce the absolute activity of the sources to within 7%, dowing accurate removai of cross-talk contamination. Abstract. . 11

Positron emission tomography (PET) with fluorodeoxyglucose (FDG), magnetic resonance imaging (MRI), and CT were carried out in a patient with Alzheimer's disease 16 months before he died. At autopsy, the gross appearance of the brain correlated with MRI and CT, which showed some regional atrophy. These were much less revealing than PET, which correlated with microscopic findings of neuronal loss and proliferation of glia. In areas of moderately impaired local cerebral metabolic rate of glucose, as revealed by reduced FDG uptake, there was some gliosis, primarily around the numerous senile plaques. In areas of severe metabolic impairment, there was a profound loss of neurons, extensive gliosis, and a diminished appearance of plaques. PET-FDG is a better measure of the severity of Alzheimer's disease than MRI or CT, because it reflects the degree of neuronal pathology.

No abstract

We studied 10 patients with early Huntington's disease and 7 normal age-matched controls with positron emission tomography (PET) using fluorodeoxyglucose. Subjects had little or no caudate nucleus atrophy and had not received any medications. The results demonstrated that hypometabolism of glucose preceded tissue loss. Furthermore, patients with minimal neurologic or psychiatric symptoms and no obvious CT changes may be differentiated from normal persons with high accuracy by PET. PET is helpful in the early diagnosis of Huntington's disease irrespective of the mode of presentation. PET may also be useful for preclinical detection and may supplement information from DNA studies.

In a previous paper [1] it was proved, among other results, that a closed disjunction of intuitionistic elementary number theory N can be proved if and only if at least one of its disjunctands is provable and that a closed formula of the type (Ex)B(x) is provable in N if and only if B(n) is provable for some numeral n. The method of proof was to show that, as far as closed formulas are concerned, N is equivalent to a calculus N1 for which the result is immediate. The main step in the proof consisted in showing that the set of provable formulas of N1 is closed under modus ponens. This was done by obtaining a subset of the set which is closed under modus ponens and contains all members of the original set, with which it is therefore identical.