The role of conventional MR and CT in the work-up of dementia patients

[Correction of Partial Volume Effect Using CT Images in Brain 18F-FDG PET]

PURPOSE

We performed partial volume effect correction of PET images using ¹⁸F-FDG-PET and CT images taken consecutively, compared it with correction using MRI images, and investigated the usefulness of correction using CT images.

METHODS

A total of 9 clinically normal subjects were included in the study, and the CT and MRI images of each subject were segmented and normalized. PET images were coregistered to each morphological image and then normalized. The normalized morphological images of each subject were used to mask the brain atlas and to correct for the partial volume effect. For each brain region, comparison of counts, two-group test between CT- and MRI-corrected groups, and correlation analysis were performed.

RESULTS

As a result of correction, some error was observed between the two groups. Correlation analysis showed strong positive correlations in many areas, but weak correlations were found in some areas. In the region where significant differences were found, the two groups showed strong positive correlation, and in the region where weak correlation was found, the error tended to be small.

CONCLUSION

It is suggested that the correction by CT can be performed with the same accuracy, although some errors are generated compared with MRI.

Magnetic resonance imaging in dementia

OBJECTIVE

To describe and illustrate the key findings on structural magnetic resonance imaging (MRI) in the most common dementias of neurodegenerative origin: Alzheimer's disease, vascular dementia, dementia with Lewy bodies, variants of frontotemporal dementia, progressive supranuclear palsy, variants of multiple system atrophy, Parkinson dementia, and corticobasal degeneration.

CONCLUSION

Today the role of MRI is no longer limited to ruling out underlying causes of cognitive deterioration. MRI can show patterns of atrophy with a predictive value for certain dementias which, although not specific or unique to each disease, can help to confirm diagnostic suspicion or to identify certain processes. For this reason, it is important for radiologists to know the characteristic findings of the most common dementias.

Vascular dementia: Diagnostic criteria and supplementary exams. Recommendations of the Scientific Department of Cognitive Neurology and Aging of the Brazilian Academy of Neurology. Part I

Vascular dementia (VaD) is the most prevalent form of secondary dementia and the second most common of all dementias. The present paper aims to define guidelines on the basic principles for treating patients with suspected VaD (and vascular cognitive impairment - no dementia) using an evidence-based, systematized approach. The knowledge used to define these guidelines was retrieved from searches of several databases (Medline, Scielo, Lilacs) containing scientific articles, systematic reviews, meta-analyses, largely published within the last 15 years or earlier when pertinent. Information retrieved and selected for relevance was used to analyze diagnostic criteria and to propose a diagnostic system encompassing diagnostic criteria, anamnesis, as well as supplementary and clinical exams (neuroimaging and laboratory). Wherever possible, instruments were selected that had versions previously adapted and validated for use in Brazil that take into account both schooling and age. This task led to proposed protocols for supplementary exams based on degree of priority, for application in clinical practice and research settings.