Currently Available Neuroimaging Approaches in Alzheimer Disease (AD) Early Diagnosis [chapter]

Laura Ortiz-Teran, Juan MR, Maria de las Nieves Cabrera Martin, Tomas Ortiz
2011 The Clinical Spectrum of Alzheimer's Disease -The Charge Toward Comprehensive Diagnostic and Therapeutic Strategies  
Computerized Tomography (CT) Nowadays CT is not considered a standard technique for diagnosing AD, least of all in early stages. Its main usefulness is in differential diagnosis since it is less expensive, faster and more widely available than MRI. CT allows ruling out some clinical situations which lead to www.intechopen.com The Clinical Spectrum of Alzheimer's Disease -The Charge Toward Comprehensive Diagnostic and Therapeutic Strategies 148 behavioural alterations but are not AD, e.g.,
more » ... ensive hydrocephalus, intra and extraaxial bleeding, etc. Neuroimaging technique Finding CT Tissue atrophy. MRI Tissue atrophy. It is more specific about grey matter. fMRI Changes in blood oxygenation level (BOLD signal) representing synaptic activity. DTI Connectivity and organization in white matter tracts. Spectroscopy Chemical content of the brain, such as NAA/Cr ratio or others. SPECT Changes in cerebral perfusion. PET Changes in glucose metabolism. PET-amyloid Measures accumulation of -amyloid, an AD-specific protein. MEG Measures magnetic fields and, indirectly, yields rather precise information about brain electrical activity CT = computerized tomography; MRI = magnetic resonance imaging; fMRI = functional magnetic resonance imaging; DTI = diffusion tensor imaging; SPECT = single-photon emission computed tomography; PET = positron emission tomography; MEG = magnetoencephalography; BOLD = blood oxygen level-dependent; NAA = N-acetyl aspartate; Cr = Creatinine; AD = Alzheimer's disease Positron emission tomography (PET) Recently a new technique using PET with Pittsburg compound B (PIB; PIB-PET) has emerged. PIB is a tracer which allows marking β-amyloid plaques. This technique has been highly efficacious to detect β-amyloid in vivo and, therefore, could be rather useful to detect AD in its early phases. Magnetoencephalography (MEG) MEG is a technique which measures brain magnetic fields both during basal state and during cognitive activation. Its time resolution is measured in milliseconds. It is precisely this very high temporal resolution which allows evaluating small changes in brain processing during cognitive stimulation. These changes may help to differentiate between AD, MCI and normality as well as providing some clues about differences in information processing in these same conditions Different studies carried out with MEG show a decrease in magnetic fields in people with AD in temporal mesial areas during memory tasks. People suffering from AD exhibit increased slow frequencies in temporoparietal areas in basal evaluation.
doi:10.5772/17012 fatcat:7pxfsz3bgfdbnbaxakb33j3zci