Biomedical Engineering Reference
In-Depth Information
imaging modalities to localize nervous system abnormalities. The first methods
for targeted navigation to plan efficient approaches in the brain were conceived
over one hundred years ago, starting with Horsley and Clark (13). From that
conception, neurosurgeons began to use landmarks identified on plain x-rays of
the skull and spine to guide them to brain and spinal cord regions. In 1918,
Dandy introduced the pneumoencephalogram, the first advance to allow identi-
fication of non-bony structures, by measuring the shift that resulted from intro-
ducing air into the cavities of the brain (10). In 1926, Moniz invented cerebral
angiography, i.e., x-ray visualization of injected radiopaque contrast material
into the carotid arteries supplying blood to the brain (20). The next major imag-
ing advance occurred in the 1960s, when neurosurgeons began to use contrast
encephalograms and myelograms, which also involved the injection of ra-
diopaque contrast material. Unlike angiography, these studies involved direct
injections into brain and spine cavities in order to demonstrate a measurable
displacement and distortion of specific brain and spinal cord structures.
During this entire period, neurologists and surgeons developed extensive
maps of the three-dimensional relationships of focal brain structures and their
functions and connections. By the 1940s the measurement and localization of
the in-vivo and in-vitro electrical and chemical states of the brain and spinal
cord became essential tools for this type of mapping. Through such brain explo-
rations, numerous stereotactic tools evolved to increase the precision, accuracy,
and safety of brain explorations. Starting in the late 1940s, neurosurgeons
Spiegel and Wycis first used these tools to destroy focal areas in the human
brain to alter function (26). Thereafter, the field of stereotactic brain surgery,
using two-dimensional radiographic air contrast images that identified the skull
and the brain ventricular system landmarks to map and locate three-dimensional
points in the physical human brain, quickly advanced. These remarkable techni-
cal achievements rapidly led to effective ablative lesions to relieve the debilitat-
ing symptoms of many chronic brain disorders, particularly Parkinson's disease.
2.3. The Modern Era
Beginning in the 1970s and through the 1990s, the invention of com-
puterized axial tomographic (CAT) scanning, positron emission tomography
(PET), magnetic resonance imaging (MRI), and functional MRI (fMR) (see also
this volume, Part IV, chapter 5, by Breiter, Gasic, and Makris), provided direct
imaging and functional information about the brain and spinal cord. Conse-
quently, an enormous structural and functional database about the nervous sys-
tem, founded upon neurosurgeons' embrace and support of advanced computer
programming and graphics, emerged. How this imaging database was translated
and co-registered into multiple three-dimensional coordinate systems that could
be co-registered to real physical space is one of the remarkable neurosurgical
technical advances of the past 40 years.
