Page 38 - The Memory Program How to Prevent Memory Loss and Enhance Memory Power

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Claustrophobia can develop in the MRI machine, which makes a loud banging noise. “Open” MRI
is a method recently developed for people who have claustrophobia, but because it is open (the head
is only partially enclosed) the magnetic field used is weaker and the sensitivity of the technique is
much lower than that of a regular MRI.

Both SPECT and PET involve the intravenous injection of a radioactive tracer that is taken up by
the brain. A combination of high-resolution cameras and sophisticated computers produces a 3-D
image of radioactive tracer counts, representing blood flow or glucose metabolism (consumption),
throughout the brain. SPECT or PET can reveal subtle deficits in blood flow or glucose consumption
that have not led to changes in brain structure— the subject may still have a normal MRI. The first
patient described in the introduction, David Finestone, had a subtle blood flow deficit on SPECT in
the presence of a normal MRI, and this information proved very useful in his clinical management.

Brain Imaging to Diagnose Early Alzheimer's Disease

Recent studies show that a reduction in size of the hippocampus (which can be detected by using
MRI) and a reduction in temporal and parietal lobe blood flow (SPECT) and glucose metabolism
(PET) are often early diagnostic features of Alzheimer's disease. However, using MRI to assess the
hippocampus requires sophisticated, labor-intensive research techniques (visual inspection isn't good
enough). Also, these abnormalities detected by MRI and SPECT/PET can occur as part of normal
aging and in other neurologic disorders. Although none of these techniques are diagnostic by
themselves, they can help when the clinical picture is unclear.

Functional MRI is a new technique that involves looking at changes in hemoglobin oxygen
saturation (indicates brain tissue oxygen use), usually while the subject is performing a test of
attention or memory. Functional MRI is in its infancy but may well become the wave of the future. A
major problem is that its results are worthless if people cannot keep their heads completely still while
they lie in the scanner.

The decision about which brain imaging technique to use remains in the hands of your physician.
Nonetheless, if you have memory loss, knowing the basics outlined here will make you a more
informed consumer about the role of these brain imaging procedures in diagnosing the cause of your
memory loss.