The quest for an image of brain: a brief historical and technical review of brain imaging techniques.

Each of the brain imaging techniques in common clinical use (skull radiography, midline ultrasonography, isotope scan, pneumoencephalography, angiography and computerized tomography) depicts some structural or functional characteristic of the brain. Each produces a correspondingly restricted concept of the status of the brain. Computerized tomography, which defines the radiodensity of head tissues, has a fundamental advantage over the other techniques in that it defines with quite good resolution a characteristic of brain tissue itself (radiodensity), rather than visualizing some anatomic compartment other than brain parenchyma. It provides an explicit image of the brain quite analogous to gross sections of the brain seen at autopsy. Computerized tomography has already substantially reshaped the practice of neurology wherever it has become available and probably will come to play a role as pivotal in clinical neurology as does bone radiography in orthopedics.