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Brain imaging is one of the most marked medical and scientific developments in history. Its implications are widespread and its uses, innumerable. The ability to see the structure and function of the brain has changed the face of medicine forever.
Neuroimaging has come a long way since its discovery by Walter Dandy in 1918. The first brain images were taken by a procedure known as ventriculography. Doctors drilled holes into the patient's skull and injected air into the lateral ventricles of the brain in order to obtain more accurate x-ray images. This procedure, although precise, was tremendously risky and invasive. Throughout the 20th and 21st centuries, various, less invasive and more precise methods of brain imaging have been developed.
Electroencephalography, a process of measuring electrical movement in brain activity, was also developed early on. In this method, physicians connect electrodes to the patient's scalp in order to read electrical activity in the brain. Although electroencephalography (EEG) was, and still is, an effective way to measure brain activity, computers revolutionized the way the world experienced brain imaging. In the 1970s, the introduction of computerized axial tomography (CAT or CT scanning) allowed physicians to employ computer aided x-ray technology to obtain more precise, three dimensional images of the brain. Doctors were able to see detailed cross-sections of the brain for the first time.
Positron emission tomography (PET) and single photon emission computed tomography (SPECT) both depend on the injection of radioactive tracers into the bloodstream. These tracers work their way into the brain and the scanner observes where the tracers congregate within the brain. Doctors can use these images to determine if there are any defects in various sections of the brain.
Magnetic resonance imaging (MRI) uses magnetic fields and radio waves instead of radioactive materials to create brain images. The protons in the brain react to these stimuli, producing signals which can be used to create a map of the brain. Not only can MRI afford an excellent display of the brain's structure, but it can also reveal the way the brain functions. Functional MRI (fMRI), along with PET and SPECT scans, have numerous implications for the diagnosis and treatment of innumerable diseases and disorders.
From its onset, brain imaging has made diagnosis of numerous neurological disorders, including depression, schizophrenia and bipolar disorder, more palpable. Brain imaging can also pinpoint symptoms of stroke and dementia before their occurrence. Not only does brain imaging support the diagnosis of neurological disorders, but because it makes observation of the brain's reaction to foreign stimuli possible, it is helpful in the development of drugs to correct these disorders.