Imaging the Brain in
The development of imaging techniques within the last 15 years has dramatically altered the field of neurosciences. A variety of techniques capable of imaging the brain became available in the late 1980s. Brain anatomy now can be mapped in exquisite detail.Changes in brain metabolic activity due to emotional, motor, and cognitive aberrations can be documented by new imaging techniques It is now possible to identify the anatomic, metabolic, and neurochemical bases of numerous mental illnesses, The techniques that permit observation of the brain can be divided into two broad groups:
A picture is worth a thousand words.
|1.||Techniques measuring structure (anatomic imaging)|
|2.||Techniques that measure function (functional imaging)|
Anatomic imaging techniques include Computerized Tomography (CT) and Magnetic Resonance Imaging (MRI). In both, brain anatomy and alterations in brain structure are depicted by anatomic techniques.
Functional imaging techniques include Single-Photon Emission Computed Tomography (SPEW) and Positron Emission Tomography (PET), which measure metabolic and neurotransmitter functions. In Alitheimer's disease, anatomic imaging alone is often inadequate.
As a general rule, structural changes in the brain are late findings in Alzheimer's disease; in some mental illnesses, no structural changes are discernible at all. Functional imaging in Alzheimer's disease is clearly beneficial for this reason.
The earliest of these techniques is Computerized Tomography (CT). Abnormalities in CT scans are not specific to any type of mental illness and, therefore, do not serve as a specific test for any such illness. Nonspecific abnormalities in