Stereotactic Localization: From 1 Different Sources
the accurate localization, with the help of scans, of structures within the body by using three-dimensional measurements. It enables the accurate positioning within the body of radiotherapy beams or sources for the treatment of tumours and of localizing wires for the biopsy of small tumours. See also stereotaxy; cyberknife; gamma knife.
The procedure using computer-controlled X-ray images whereby precise localisation in space is achieved. It is applied to that branch of surgery known as stereotactic neurosurgery, in which the surgeon is able to localise precisely those areas of the brain on which he or she wishes to operate.... stereotaxis
n. a benign tumour composed of blood vessels or lymph vessels. Cherry angiomas (or Campbell de Morgan spots) are small red spots on the trunk in middle-aged or elderly people. They are completely harmless and consist of a minor vascular malformation. An arteriovenous angioma (or malformation) is a knot of distended blood vessels overlying and compressing the surface of the brain. It may cause epilepsy, or one of the vessels may burst, causing a *subarachnoid haemorrhage or a haemorrhage within the brain (intracerebral haemorrhage). This type of angioma may be suitable for surgical removal or stereotactic radiotherapy (see stereotactic localization). It may be associated with a purple birthmark on the face: this is called the Sturge–Weber syndrome. Arteriovenous malformations may occur in many other parts of the body, where they are often asymptomatic. See also haemangioma; lymphangioma.... angioma
Trademark. a system that uses magnetic localization technology to triangulate the position of a small sensor incorporated into the tip of a cardiac catheter. The signals from several catheters inserted simultaneously are used to create an electrical map of the heart from within, identifying abnormal areas where *ablation may be required.... carto
n. a frameless stereotactic radiotherapy system produced from a small *linear accelerator, which has a robotic arm that allows the beam to be directed from any direction, and which monitors movement of implanted markers to deliver real-time *image-guided radiotherapy.... cyberknife
(pallidectomy) n. a neurosurgical operation to destroy or modify the effects of the globus pallidus (see basal ganglia), formerly used for the relief of *parkinsonism and other conditions in which involuntary movements are prominent before the advent of modern drug therapies. The development of more accurate techniques to localize the globus pallidus has led to a revival in its use: in the modern form of pallidotomy, a lesion is made in the globus pallidus by stereotactic surgery (see stereotaxy). New techniques achieving better results involve the implantation of stimulators (pallidal stimulation).... pallidotomy
an imaging system that allows a PET scan (see positron emission tomography) and a CT scan (see computerized tomography) to be performed very close together, with minimal movement of the patient between scans. This means that the images produced can be co-registered (see co-registration), giving very accurate anatomical localization (from the CT scan) of areas of increased activity (identified on the PET scan). This is very important for determining the site of disease in order to plan treatment.... pet/ct scanning
n. a malignant brain tumour (see cerebral tumour) that occurs during childhood. It is derived from cells that have the apparent potential to mature into neurons and develops in the cerebellum, the part of the brain that is predominantly involved in the control of balance. The flow of cerebrospinal fluid (CSF) may become obstructed, causing *hydrocephalus. Symptoms include headaches, dizziness, and unsteadiness. Treatment involves surgery to remove most of the tumour and restore CSF flow, followed by radiotherapy directed using *stereotactic localization. Medulloblastoma is the second most common form of cancer of childhood (after leukaemia); recent advances have improved the survival rate so that 40% of affected children live for more than five years.... medulloblastoma
(akinetic rigid syndrome) n. a clinical picture characterized by tremor, rigidity, slowness of movement, and postural instability. The commonest symptom is tremor, which often affects one hand, spreading first to the leg on the same side and then to the other limbs. It is most pronounced in resting limbs, interfering with such actions as holding a cup. The patient has an expressionless face, an unmodulated voice, an increasing tendency to stoop, and a shuffling walk. Parkinsonism is a disease process affecting the basal ganglia of the brain and associated with a deficiency of the neurotransmitter *dopamine. Sometimes a distinction is made between Parkinson’s disease, a degenerative disorder, and parkinsonism due to other causes. For example, it may be induced by the long-term use of *antipsychotic drugs and uncommonly it can be attributed to the late effects of *encephalitis or coal-gas poisoning, or to *Wilson’s disease, or to multiple strokes (vascular parkinsonism). Other syndromes of which parkinsonism is a feature are *multiple system atrophy and *progressive supranuclear palsy. Relief of the symptoms may be obtained with *antimuscarinic drugs, dopamine-receptor agonists (see dopamine), *levodopa, and subcutaneous *apomorphine injections and infusions. New surgical treatments include stereotactic *pallidotomy and pallidal stimulation. The latter procedure involves placing an electronic stimulator in the globus pallidus that can be controlled by an external switch or control panel. [J. Parkinson (1755–1824), British physician]... parkinsonism
(PET) a technique in nuclear medicine for *cross-sectional imaging that enables a noninvasive assessment and localization of metabolic activity to be made. Originally used to study activity in the brain, PET is now also used for investigating the chest and abdomen. Emission of a *positron by a radioisotope results in annihilation of the positron on collision with an electron, and the creation of two gamma rays of known energy travelling in exactly opposite directions. The PET scanner has detectors on each side of the patient to detect the simultaneous arrival of the gamma rays. Images are created using reconstruction *algorithms similar to CT scanning. *Fluorodeoxyglucose, labelled with fluorine-18, is used to examine glucose metabolism, and ammonia, labelled with nitrogen-13, gives information on perfusion. Carbon-11 and oxygen-15 can also be used as radioisotopes for PET scanning. Some diseases result in decreased uptake of the radio-labelled material due to decreased function; others show increased glucose metabolism and concentrate the isotope avidly. In this way functional activity of the tissues can be compared with anatomical images obtained by CT or MRI scanning (see PET/CT scanning). Localized areas of increased glucose uptake revealed by PET scans can sometimes signify functional activity of malignant cells, which use more glucose than normal cells, although other processes, such as infection, can produce similar scans. PET scans can help to localize metastatic disease (see metastasis) that is not identified by other scanning techniques. See also tomography. Compare computerized tomography.... positron emission tomography
(stereotactic surgery) n. a surgical procedure in which a deep-seated area in the brain is operated upon after its position has been established very accurately by three-dimensional measurements using CT or MRI. The operation may be performed using an electrical current or by heat, cold, or mechanical techniques. See also leucotomy.... stereotaxy
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