Computed tomography brain changes in Parkinsonian dementia

Summary In order to evaluate the relationship between brain atrophy and the motor and cognitive function in Parkinson's disease, we have evaluated CT changes in 132 consecutive patients and compared them to measures of physical and mental decline, using intercorrelations and variance analysis. The result demonstrated age as a most important factor relating to brain atrophy. After correction for this determinant, it became clear that the motor and cognitive parameters were interdependent but they affected similar CT parameters. The effect of motor decline was the stronger of the two and it was the only one which correlated with cortical atrophy. The results support the notion of subcortical changes underlying the dementia of Parkinson's disease.     

Emission computerized tomography: Clinical applications

Single photon emission tomography (SPET) is making its impact on the practice of clinical nuclear medicine. Special purpose and general purpose instrumentation has become available with significantly improved performance capabilities. The advantages to be expected from this new approach to noninvasive medical imaging methodology include improvement of contrast resolution of the image and the ability to quantify the information in the three-dimensional section scan. It has been shown that SPET can replace planar imaging of the brain and that it significantly improves lesion detection in the liver. Organ volume measurements can be achieved and tracer uptake parameters calculated. This field is still at its beginning. Instrumentation will change and significant improvements in reconstruction algorithms will extend the clinical usefulness of these techniques. Even if absolute measurements may not be achievable in the body, it is possible to distinguish an abnormal population from a normal one. Sequential data may then be recorded and integrated into serial treatment protocols. Progress in the labeling of clinically useful tracers with suitable radionuclides [123I, 99mTc, 197Rt, 81mKr, 111In, etc.) is needed in order to achieve further significant progress in the areas of clinical applications.     

Single photon emission computed tomography in AIDS dementia complex

Single photon emission computed tomography (SPECT) studies were performed in AIDS dementia complex using IMP in 12 patients (and HM-PAO in four of these same patients). In all patients, SPECT revealed either multiple or focal uptake defects, the latter corresponding with focal signs or symptoms in all but one case. Computerized tomography showed a diffuse cerebral atrophy in eight of 12 patients, magnetic resonance imaging exhibited changes like atrophy and/or leukoencephalopathy in two of five cases. Our data indicate that both disturbance of cerebral amine metabolism and alteration of local perfusion share in the pathogenesis of AIDS dementia complex. SPECT is an important aid in the diagnosis of AIDS dementia complex and contributes to the understanding of the pathophysiological mechanisms of this disorder.     

Emission computed tomography vs perfusion scanning in lung disease

Emission computed tomography has achieved considerable credibility in thallium-201 cardiac imaging and in brain imaging studies. To date the procedure has had only limited application in the study of other organs. In the present study traditional perfusion lung scans were compared with horizontal, sagittal and frontal tomograms in 30 patients. Preliminary results showed agreement between the two methods in most cases. Tomography, however, gave more precise information about the site and extent of areas of deficient lung perfusion. In a small number of cases tomography also revealed defect not seen on conventional scans. In patients with cardiomegaly in whom conventional scanning data were difficult to assess, tomography proved enlightening.     

Emission computed tomography vs perfusion scanning in lung disease

Emission computed tomography has achieved considerable credibility in thallium-201 cardiac imaging and in brain imaging studies. To date the procedure has had only limited application in the study of other organs. In the present study traditional perfusion lung scans were compared with horizontal, sagittal and frontal tomograms in 30 patients. Preliminary results showed agreement between the two methods in most cases. Tomography, however, gave more precise information about the site and extent of areas of deficient lung perfusion. In a small number of cases tomography also revealed defects not seen on conventional scans. In patients with cardiomegaly in whom conventional scanning data were difficult to assess, tomography proved enlightening.     

Emission tomography: a concise theoretical overview

A concise theoretical overview of emission tomography is presented aiming at physical interpretation of the equations so that fundamental concepts, similarities and differences between SPECT and PET, become transparent. The framework is that of an indirect sensing problem and image reconstruction from projections. The projections are expressed in terms of: the activity distribution, the attenuation distribution, the interactions of the radiation with matter, and the measurement geometry. In discussing the attenuation problem, recourse is made to the projections obtained by a gamma-ray (or a hypothetical monoenergetic X-ray) transmission CT scanner. This expression would be the one to which the corresponding expressions for SPECT and PET would reduce to if the attenuation distributions were known. Although the attenuation problem is less severe in PET, its extent is demonstrated with results from computer simulations. Finally, under conditions of 'adequate sampling', equations are given relating administered activity to spatial resolution, time for data collection, noise/signal ratio and system sensitivity.     

Positron emission tomography and single-photon emission computed tomography brain imaging in the evaluation of dementia

The role of PET and SPECT brain imaging in the initial assessment and differential diagnosis of dementia is beginning to evolve rapidly. Numerous studies confirm the value of functional brain imaging, particularly with FDG-PET imaging, as a potentially cost-effective means of establishing an earlier diagnosis of Alzheimer's disease. Such an approach should allow for a more objective means of establishing which patients will benefit from treatment with cholinesterase inhibitors. In the future, neuroreceptor and plaque burden imaging studies should further enhance the sensitivity and specificity of dementia detection and patient management.     

Computed tomography in patients with dementia probably due to toxic encephalopathy

Computed tomography (CT) was performed in 181 patients with dementia probably caused by organic solvents. No treatable causes of dementia were revealed. All but one of the patients had dementia symptoms for more than one year. Only three patients had focal neurologic signs. No indication for cranial CT was found in this group of patients, owing to the fact that no treatable causes of dementia were revealed.     

Single photon emission computed tomography in motor neuron disease with dementia

Summary Single photon emission computed tomography with [123 I] isopropylamphetamine was carried out on a patient with motor neuron disease with dementia. [123 I] uptake was decreased in the frontal lobes. This would reflect the histopathological findings such as neuronal loss and gliosis in the frontal lobes.     

Emission tomography: its contribution in the detection of subdural haematoma

The technique of emission computed tomography (ECT) was assessed with regards to its value in the detection of subdural haematoma. Results from an anthropomorphic head phantom and a short clinical trial both showed promising signs of better differentiation between normal and abnormal in equivocal results. A simple quantitative index was used to compare ECT with static imaging. The conclusion is that ECT is of value in those patients whose scan results are otherwise equivocal.     

Clinical application of positron emission tomography for diagnosis of dementia

Clinical applications of PET studies for dementia are reviewed in this paper. At the mild and moderate stages of Alzheimer's disease (AD), glucose metabolism is reduced not only in the parietotemporal region but also in the posterior cingulate and precuneus. At the advanced stage of AD, there is also a metabolic reduction in the frontal region. In AD patients, glucose metabolism is relatively preserved in the pons, sensorimotor cortices, primary visual cortices, basal ganglia, thalamus and cerebellum. In patients with dementia with Lewy bodies, glucose metabolism in the primary visual cortices is reduced, and this reduction appears to be associated with the reduction pattern in AD patients. In patients with frontotemporal dementia, reduced metabolism in the frontotemporal region is the main feature of this disease, but reduced metabolism in the basal ganglia, and/or parietal metabolic reduction can be associated with the frontotemporal reduction. When corticobasal degeneration is associated with dementia, the reduction pattern of dementia is similar to the reduction pattern in AD and the hallmarks of diagnosing corticobasal degeneration associated with dementia are a reduced metabolism in the primary sensorimotor region and/or basal ganglia and an asymmetric reduction in the two hemispheres. FDG-PET is a very useful tool for the diagnosis of early AD and for the differential diagnosis of dementia. I also describe clinical applications of PET for the diagnosis of dementia in Japan.     

The use of positron emission tomography in the clinical assessment of dementia

A number of reasons can be cited for performing a test that identifies patients early in their course who have fatal and currently untreatable neurological disorders. At this stage of illness there is clinical ambiguity. The patient, family, and physician are typically faced with a battery of negative test results and an ambiguous clinical impression that can lead to periodic repetition of tests that involve cost, inconvenience, potential morbidity to the patient, and lack of definitive diagnosis. An accurate test would lead to the avoidance of these low-yield, repetitive, and costly evaluations. In addition, such studies can identify homogeneous groups of individuals with degenerative disorders leading to dementia who could be enrolled in experimental therapeutic programs. In these programs therapies could be monitored in an objective and noninvasive fashion using positron emission tomography (PET). The magnitude of the health problems resulting from the dementing illnesses is great in terms of medical practice, economics, and family hardship. The number of individuals with these disorders is predicted to increase dramatically in the future. The ability to provide an accurate diagnosis and more clear prognosis early in the disease course should diminish ambiguity for patients, families, and physicians. Ample evidence is cited in this article to show that PET has the ability to provide such information objectively and noninvasively.