| These techniques are, by and large, used
primarily in the research setting. The complex equipment and the high costs of performing
these scans prohibit their use in general practice. The advent of functional imaging
enabled patterns of metabolic activity and blood flow in the brain to be revealed without
the need for invasive techniques. These changes in metabolic activity are reflected in the
patterns of cerebral blood flow. Positron
Emission Tomography (PET) is a complex technology and requires specialized staff. Although
supporting the clinical diagnosis of AD, this procedure is largely limited to research
institutes. This procedure utilizes positron-emitting isotopes, and can monitor many
functional parameters, e.g. metabolic activity (i.e. glucose metabolism), cerebral blood
flow, cerebral volume, neurotransmitter activities and receptor binding. As a consequence,
changes in the brain associated with normal aging and AD can be quantified.
Single Photon Emission Computed Tomography
(SPECT) requires relatively simple equipment and visualizes regional cerebral blood flow
which reflects cerebral activity at a specific moment in time.
A three-dimensional analysis of blood flow
can be built up. SPECT is a potentially valuable tool in the differential diagnosis of AD.
Indeed, there is increasing evidence that SPECT can support the diagnosis of AD,
especially in cases where the diagnosis in unclear.
Electroencephalography (EEG) is a
non-invasive technique for investigating the brain. Different regions of the brain produce
characteristic EEG activity. AD and other dementias generate non-specific changes in EEG
traces, such as slowing of background activity. The following areas can be examined; EEG
peak frequency, theta and delta activity, beta activity, and P300 latency. |
A Guide to the
Diagnosis and Assessment of Alzheimer's Disease
