Stereotactic surgery
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[[Image:Brain biopsy under stereotaxy.jpg|thumb|right|Brain biopsy using a needle mounted on a stereotactic frame]]
'''Stereotactic surgery''' or '''stereotaxy''' is a [[minimally-invasive]] form of [[surgery|surgical]] intervention which makes use of a three-dimensional [[coordinates]] system to locate small targets inside the body and to perform on them some action such as [[ablation]] (removal), [[biopsy]], [[lesion]], injection, [[Deep brain stimulation|stimulation]], implantation, [[radiosurgery]] (SRS) etc. "Stereotactic" in Greek (another accepted spelling is "stereotaxic") means movement in space.
In theory, any organ system inside the body can be subjected to stereotactic surgery. Difficulties in setting up a reliable frame of reference (such as [[bone|bony]] landmarks which bear a constant spatial relation to soft tissues), however, mean that its applications have been limited to [[neurosurgery|brain surgery]]. Besides the [[brain]], biopsy and surgery of the [[breast]] are done routinely to locate, sample (biopsy) and remove tissue. Plain X-ray images (mammography) and CT can be used to guide the procedure.
==History==
The stereotactic method was first developed by two British scientists in 1908, working at [[University College London]] Hospital, Sir [[Victor Horsley]], a physician and neurosurgeon, and Robert H. Clarke, an engineer. The [[Horsley-Clarke apparatus]] they developed was used for [[animal experimentation]] and implemented a [[Cartesian]] (three-orthogonal axis) system. Improved designs of their original device came into use in the 1930s for animal experimentation and are still in wide use today in all animal [[neuroscience]] laboratories.
Using the Horsley-Clarke apparatus for human brains was difficult because of the high variability of spatial relations between the [[skull]] and the [[brain]]. However, by using contrasted brain [[radiography]] (particularly [[pneumoencephalogram]]s and [[ventriculography]]) reference points ''inside'' the brain could be used, instead of bone landmarks. The first stereotactical devices for humans used the [[pineal gland]] as a landmark and the [[foramen of Monro]]. Later, other structures, such as the [[anterior commissure|anterior]] and [[posterior commissure]]s, became the most commonly used internal cerebral landmarks.
Using this approach between 1947 and 1949, two American neurosurgeons, [[Ernest A. Spiegel]] and [[Henry T. Wycis]], and a Swedish neurosurgeon, [[Lars Leksell]], developed the first stereotactic device used for brain surgery in humans. Spiegel and Wycis used the Cartesian coordinate system (also called the translational system) for their device. Leksell's device was of the [[polar coordinate]] type (also called spherical), and was far easier to use and [[calibrate]] in the operating room. The stereotactic localization system was also used by Leksell in his next invention, a device for [[radiosurgery]] of the brain. This system is also used by the [[Gamma Knife]] device, and by other neurosurgeons, using [[linear accelerator]]s, [[Proton Beam Therapy]] and [[Neutron Capture Therapy]]. [[Lars Leksell]] went on to commercialize his inventions by founding [[Elekta]].
In 1976, a system was developed to use computer assisted imaging to help make the location of the target more precise. It was developed jointly by the [[University of Toronto]] and [[Toronto General Hospital]]. The system used a pre-scanned image of the brain loaded into a [[Tektronix]] graphics terminal in the operating room. Low level voltages were applied to the brain and the co-ordinates and patient response entered by keyboard, the image on the screen showed the brain overlaid by graphics images (such as a hand) indicating the type of response.<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=801856&dopt=Abstract Sensory organization of the human thalamus. [Appl Neurophysiol. 1976-1977] - PubMed Result<!-- Bot generated title -->]</ref>
<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=335811&query_hl=2&itool=pubmed_docsum Computerized graphic display of results of subcort...[Acta Neurochir (Wien). 1977] - PubMed Result<!-- Bot generated title -->]</ref>
The method continued to evolve, and at present uses a complex mixture of [[image-guided surgery]] using intraroom [[computed tomography]], [[magnetic resonance imaging]] and stereotactic localization.
==How it works==
Stereotactic surgery works on the basis of three main components:
* A stereotactic [[atlas]] of the targeted anatomical structures
* A stereotactic device or apparatus
* A stereotactic localization and placement procedure
The stereotactic atlas is a series of cross sections of anatomical structure (for example, a human brain), depicted in reference to a two-coordinate frame. Thus, each brain structure can be easily assigned a range of three coordinate numbers, which will be used for positioning the stereotactic device. In most atlases, the three dimensions are: latero-lateral (x), dorso-ventral (y) and rostro-caudal (z).
The stereotactic apparatus uses a set of three coordinates (x, y and z) in an orthogonal frame of reference ([[cartesian coordinates]]), or, alternatively, a [[polar coordinates]] system, also with three coordinates: angle, depth and antero-posterior location. The mechanical device has head-holding clamps and bars which puts the head in a fixed position in reference to the coordinate system (the so-called zero or origin). In small laboratory animals, these are usually [[bone]] landmarks which are known to bear a constant spatial relation to soft tissue. For example, brain atlases often use the [[ear|external auditory meatus]], the inferior [[eye|orbital]] ridges, the median point of the [[maxilla]] between the [[Incisor|incisive teeth]]. or the [[bregma]] (confluence of sutures of frontal and parietal bones), as such landmarks. In humans, the reference points, as described above, are intracerebral structures which are clearly discernible in a radiograph of tomogram.
Guide bars in the x, y and z directions (or alternatively, in the polar coordinate holder), fitted with high precision [[vernier scale]]s allow the neurosurgeon to position the point of a probe (an [[electrode]], a [[cannula]], etc.) inside the brain, at the calculated coordinates for the desired structure, through a small trephined hole in the skull.
Currently, a number of manufacturers produce stereotactic devices fitted for [[neurosurgery]] in humans, as well as for animal experimentation.
==See also==
* [[Cyberknife]]
* [[Interventional radiology]]
* [[Novalis radiosurgery]]
* [[Psychosurgery]]
==Notes==
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==References ==
* [[Robert Levy]], ''[http://www.neurosurgery.org/cybermuseum/stereotactichall/stereoarticle.html A Short History of Stereotactic Surgery]'', Cyber Museum of Neurosurgery. This is based on
** [[Patrick J. Kelly, MD|Patrick J. Kelly]], "Introduction and Historical Aspects", ''Tumor Stereotaxis'', Philadelphia: [[W.B. Saunders Company]] (1991)
** [[Philip L. Gildenberg]], "Stereotactic Surgery: Present and Past", ''Stereotactic Neurosurgery'', (Editor: [[M. Peter Heilbrun]]) Baltimore: [[Williams and Wilkins]] (1988)
* [[Renato M.E. Sabbatini|Sabbatini, RME]]: [http://www.cerebromente.org.br/n02/historia/stereotactic.htm Stereotactic Neurosurgery]. In: The History of Psychosurgery. [http://www.cerebromente.org.br Brain & Mind Magazine], 2, 1997.
* Lawrence Chin, MD and William Regine, MD, (Editors), [http://www.springer.com/medicine/surgery/book/978-0-387-71069-3 Principles and Practice of Stereotactic Radiosurgery](2008)
==External links==
*[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=801856&dopt=Abstract|Sensory Organization of the human thalamus.]
*[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=335811&query_hl=2&itool=pubmed_docsum|Computerized graphic display of results of subcortical stimulation during stereotactic surgery]
*[http://www.adeor.com/data/stereotaxy_e.html Stereotactic Apparatus.]
[[Category:Neurology]]
[[Category:Neurosurgery]]
[[Category:Computer assisted surgery]]
[[de:Stereotaktische Hirnoperation]]
[[fr:Stéréotaxie]]
[[it:Radiochirurgia stereotassica]]