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Radiosurgery, also known as stereotactic radiotherapy, is a medical procedure which allows non-invasive treatment of benign and malignant conditions, vascular malformations (AVM's), and some functional disorders by means of directed beams of ionizing radiation. A medical procedure is a course of action intended to achieve a result in the care of patients used by medical or paramedical personnel The term non-invasive in Medicine has two meanings A Medical procedure which does not penetrate mechanically, nor break the Skin Image talkNew_radiation_symbol_ISO_21482svg for details --> Ionizing radiation It is a relatively recent technique (1951), which is used to ablate, by means of a precise dosage of radiation, intracranial and extracranial tumors and other lesions that could be otherwise inaccessible or inadequate for open surgery. Year 1951 ( MCMLI) was a Common year starting on Monday. Events of 1951 January See also Cancer A tumor or tumour is the name for a swelling or lesion formed by an abnormal growth of cells (termed neoplastic There are many nervous diseases for which conventional surgical treatment is difficult or has many deleterious consequences for the patient, due to arteries, nerves, and other vital structures being damaged. This is a list of major and frequently observed Neurological disorders (e Arteries are Blood vessels that carry blood away from the Heart. A nerve is an enclosed cable-like bundle of peripheral Axons (the long slender projections of Neurons.

Contents

Definition and applications

Radiation oncologists make use of highly sophisticated, highly precise and complex instruments, such as stereotactic devices, linear accelerators, gamma knife, computers and laser beams. A radiation oncologist is a doctor who specializes in the treatment of Cancer patients using radiation as the main modality of treatment The Horsley-Clarke apparatus is a device invented in 1908 by British Neurosurgeon and Scientist Sir Victor A A computer is a Machine that manipulates data according to a list of instructions. A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission. The highly precise irradiation of targets within the brain is planned by the radiation oncologist based on images, such as computed tomography (CT), magnetic resonance imaging (MRI), and angiography of the brain and body. Computed tomography (CT is a Medical imaging method employing Tomography. Angiography or arteriography is a Medical imaging technique in which an X-ray image is taken to visualize the inside or lumen, of blood vessels The radiation is applied from an external source, under precise mechanical orientation by a specialized apparatus. Multiple beams are directed (collimated) and centered at the intracranial or extracranial lesion to be treated. In this way, healthy tissues around the target are relatively spared.

Patients can be treated within one to five days and as an outpatient. By comparison, the average hospital stay for a craniotomy (conventional neurosurgery, requiring the opening of the skull) is about 15 days. A craniotomy is a surgical operation in which part of the Skull, called a bone flap, is removed in order to access the brain Radiosurgery costs less than conventional surgery, and with much less morbidity, e. g. mortality, pain and post-surgical complications, such as hemorrhage and infection. Death is the termination of the biological functions that define living Organisms It refers both to a specific Pain, in the sense of physical pain, is a typical sensory experience that may be described as the unpleasant awareness of a noxious stimulus or bodily harm Bleeding, technically known as hemorrhaging / haemorrhaging (see American and British spelling differences) is the loss of Blood from An infection is the detrimental Colonization of a host Organism by a foreign Species. The period of recovery is minimal, and in the day following the treatment the patient may return to his or her normal life style, without any discomfort. The major disadvantage of radiosurgery in relation to open surgery is the duration of time required to achieve the desired effects, while its non-invasive character is perhaps its major advantage.

History

Radiosurgery was first developed at the Karolinska Institute of Stockholm, Sweden in 1949. Karolinska Institutet (often translated from Swedish into English as the Karolinska Institute, and in older texts often as the Royal Caroline ('stɔkhɔlm is Sweden 's Capital and its largest City. It is the site of the national Swedish government, the parliament, and the "Sverige" redirects here For other uses see Sweden (disambiguation and Sverige (disambiguation. It was jointly developed by Dr. Lars Leksell, a neurosurgeon and Bjorn Larsson, a radiobiologist from Uppsala University. Lars Leksell (1907-1986 was a Swedish Physician and Professor of Neurosurgery at the Karolinska Institute in Stockholm, Sweden. Radiobiology (or radiation biology) is the Interdisciplinary field of science that studies the biological effects of ionizing and non-ionizing Uppsala University ( Swedish Uppsala universitet) is a world-class research University in Uppsala, Sweden. Leksell initially used protons from a cyclotron to irradiate brain tumor lesions. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive A cyclotron is a type of Particle accelerator. Cyclotrons accelerate Charged particles using a high- Frequency, alternating Voltage (potential A brain tumor is any intracranial Tumor created by abnormal and uncontrolled cell division, normally either in the Brain itself ( Neurons

In 1968, they developed the Gamma Knife, a new device exclusively for radiosurgery, which consisted of radioactive sources of Cobalt-60 placed in a kind of helmet with central channels for irradiation, using gamma rays. Gamma Knife® (or Leksell Gamma Knife®) is a device used to treat Brain tumors with a high dose of Radiation therapy in one day Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. Cobalt (ˈkoʊbɒlt is a hard lustrous silver-grey Metal, a Chemical element with symbol Co. Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions In the latest version of this device, 192 sources of radioactive cobalt direct gamma radiation to the center of a helmet, where the patient's head is inserted. This is called the Leksell Gamma Knife Perfexion.

In order to achieve a high degree of precision, the patient's head is placed on a rigid frame of reference called a stereotactic frame that is inserted into a metal helmet. The Horsley-Clarke apparatus is a device invented in 1908 by British Neurosurgeon and Scientist Sir Victor A

A linear accelerator (LINAC) may also be used to deliver radiosurgery. LINAC based radiosurgery was pioneered at the University of Florida College of Medicine and introduced by Betti and Colombo in the mid 1980's. Year 1980 ( MCMLXXX) was a Leap year starting on Tuesday (link displays the 1980 Gregorian calendar) High energy, narrowly focused beams of x-rays are employed. X-radiation (composed of X-rays) is a form of Electromagnetic radiation.

This system differs from the Gamma Knife in a variety of ways. The Gamma Knife produces gamma rays from the decay of Co-60 of an average energy of 1. 25 MeV. A LINAC produces x-rays from the impact of accelerated electrons striking a high z target (usually tungsten). A LINAC therefore can generate any number of energy x-rays, though usually 6 MV photons are used. The Gamma Knife has over ~200 sources arrayed in the helmet to deliver a variety of treatment angles. On a LINAC the gantry must move in space to change the delivery angle. Both can move the patient in space to also change the delivery point. Both devices use a stereotactic frame to restrict the patient's movement.

Finally, at some medical centers such as in Boston and in California, particle accelerators built for doing research in high energy physics have been used since the 1960's for the treatment of brain tumors and arteriovenous malformations of the brain in humans. California ( is a US state on the West Coast of the United States, along the Pacific Ocean. Particle physics is a branch of Physics that studies the elementary constituents of Matter and Radiation, and the interactions between them Cerebral arteriovenous malformation Arteriovenous malformation or AVM in the majority of cases is a Congenital disorder consisting of a connection between

How it works

The fundamental principle of radiosurgery is that of selective ionization of tissue, by means of high-energy beams of radiation. Ionization is the physical process of converting an Atom or Molecule into an Ion by adding or removing charged particles such as Electrons Ionization is the production of ions and free radicals which are usually deleterious to the cells. An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge In Chemistry, radicals (often referred to as free radicals) are atoms molecules or ions with Unpaired electrons on an otherwise Open shell The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called These ions and radicals, which may be formed from the water in the cell or from the biological materials can produce irreparable damage to DNA, proteins, and lipids, resulting in the cell's death. Death is the termination of the biological functions that define living Organisms It refers both to a specific Thus, biological inactivation is carried out in a volume of tissue to be treated, with a precise destructive effect. The radiation dose is usually measured in grays, where one gray (Gy) is the absorption of one joule per kilogram of mass. The gray (symbol Gy is the SI unit of absorbed radiation dose. The joule (written in lower case ˈdʒuːl or /ˈdʒaʊl/ (symbol J) is the SI unit of Energy measuring heat, Electricity A unit that attempts to take into account both the different organs that are irradiated and the type of radiation is the sievert, a unit that describes both the amount of energy deposited and the biological effectiveness. The sievert (symbol Sv is the SI derived unit of dose equivalent.

In order to perform optimal radiosurgery, the radiation oncologist chooses the best type of radiation to be used and how it will be delivered. In order to plan the radiation incidence and dosage, the physicists calculate a map portraying the lines of equal absorbed dose of radiation upon the patient's head (this is called an isodose map). Information about the tumor's location is obtained from a series of computerized tomograms, which are then fed to special planning computer software.

Stereotactic radiosurgery generally utilizes gamma rays and x-rays. Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions X-radiation (composed of X-rays) is a form of Electromagnetic radiation. There is also increasing interest in using particle therapy such as protons and carbon ions for radiosurgery, though this is not widely available. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6

The emission head (called "gantry") is mechanically rotated around the patient, in a full or partial circle. Both overhead travelling cranes and gantry cranes are types of crane which lift objects by a hoist which is fitted in a trolley and can move The table where the patient is lying, the 'couch', can also be moved in small linear or angular steps. The combination of the movements of the gantry and of the couch makes possible the computerized planning of the volume of brain tissue which is going to be irradiated. Devices with an energy of 6 MeV are the most suitable for the treatment of the brain, due to the depth of the target. In addition, the diameter of the energy beam leaving the emission head can be adjusted to the size of the lesion by means of interchangeable collimators (an orifice with different diameters, varying from 5 to 40 mm, in steps of 5 mm). A collimator is a device that narrows a beam of particles or waves There are also multileaf collimators, which consist of a number of metal leaflets that can be moved dynamically during treatment in order to shape the radiation beam to conform to the mass to be ablated. Ablation is defined as the removal of material from the surface of an object by Vaporization, Chipping, or other erosive processes Latest generation Linacs are capable of achieving extremely narrow beam geometries, such as 0. 15 to 0. 3 mm. Therefore, they can be used for several kinds of surgeries which hitherto are carried out by open or endoscopic surgery, such as for trigeminal neuralgia, etc. Trigeminal neuralgia (TN, or Tic Doloureux, (also known as prosopalgia is a neuropathic disorder of the Trigeminal nerve that causes episodes of intense

Protons, may also be used in radiosurgery Proton Beam Therapy (PBT). Proton therapy is a type of Particle therapy which utilizes a beam of Protons to irradiate diseased tissue most often in the treatment of cancer Protons are produced by a medical synchrotron, extracting them from proton donor materials and accelerating them in successive travels through a circular, evacuated conduit, using powerful magnets, until they reach sufficient energy (usually about 200 MeV) to enable them to approximately traverse a human body, then stop. A synchrotron is a particular type of cyclic Particle accelerator in which the magnetic field (to turn the particles so they circulate and the electric field (to accelerate They are then released toward the irradiation target which is region in the patient's body. In some machines, which deliver only a certain energy of protons, a custom mask made of plastic will be interposed between the initial beam and the patient, in order to adjust the beam energy for a proper amount of penetration. Because of the Bragg Peak effect, proton therapy has advantages over other the other forms of radiation, since most of the proton's energy is deposited within a limited distance, so tissue beyond this range (and so some extent also tissue inside this range) is spared from the effects of radiation. The Bragg curve plots the energy loss of Ionizing radiation during its travel through matter Proton therapy is a type of Particle therapy which utilizes a beam of Protons to irradiate diseased tissue most often in the treatment of cancer This property of protons, which has been called the "depth charge effect" allows for conformal dose distributions to be created around even very irregularly shaped targets, and for higher doses to targets surrounded or backstopped by radiation-sensitive structures such as the optic chiasm or brainstem. The optic chiasm ( Greek χίασμα "crossing" from the Greek χλαζειν 'to mark with an X' after the Greek letter ' Χ ' chi) is the In recent years, however, "intensity modulated" techniques have allowed for similar conformities to be attained using linear accelerator radiosurgery.

The selection of the proper kind of radiation and device depends on many factors including lesion type, size and location in relation to critical structures. Data suggests that similar clinical outcomes are possible with all of these methods. More important than the device used are issues regarding indications for treatment, total dose delivered, fractionation schedule and conformity of the treatment plan.

Radiosurgery of brain tumors

Radiosurgery has been especially helpful for the localized, highly precise treatment of brain tumors. Due to the steep fall off of the irradiation fields (isodoses) from the center of the target to be ablated, normal structures such as the brain, and other vascular and neural structures around it, are relatively spared. This is achieved through the high mechanical precision of the radiation source, and the assured reproducibility of the target. The precision in the positioning of the patient, in the calculation of dosages, and in the safety of the patient, are all extremely high.

Radiosurgery is indicated primarily for the therapy of tumors, vascular lesions and functional disorders. Significant clinical judgment must be used with this technique and considerations must include lesion type, pathology if available, size, location and age and general health of the patient. General contraindications to radiosurgery include excessively large size of the target lesion or lesions too numerous for practical treatment.

The non-interference with the quality of life of the patient in the post-operatory period competes with the inconvenience of the latency of months until the result of the radiosurgery is accomplished. Quality of life is the degree of well-being felt by an individual or group of people

Outcome may not be evident for months after the treatment. Since radiosurgery does not remove the tumor, but results in a biological inactivation of the tumor, lack of growth of the lesion is normally considered to be treatment success. General indications for Radiosurgery include many kinds of brain tumors, such as acoustic neuromas, germinomas, meningiomas, metastases , trigeminal neuralgia, arteriovenous malformations and skull base tumors among others. An acoustic neuroma, also called a vestibular Schwannoma, is a Benign primary Intracranial tumor of the Myelin -forming cells A germinoma is a type of Germ cell tumor which is not differentiated upon examination Meningiomas are the most common Benign Tumors of the Brain (95% of benign tumors Metastasis ( Greek: displacement μετά=next + στάσις=placement, plural metastases) sometimes abbreviated mets, Expansion of stereotactic radiotherapy to extracranial lesions is increasing, and includes metastases, liver cancer, lung cancer, pancreatic cancer, etc. It has been demonstrated by the thousands of successfully treated cases, that radiosurgery can be a very safe and efficient method for the management of many difficult brain lesions, while it avoids the loss in quality of life associated to other more invasive methods.

See also

Notes

References

External links

Manufacturers

Dictionary

radiosurgery

-noun

  1. (medicine) The use of a directed beam of X-rays or other ionizing radiation to destroy diseased tissue
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