Radiosurgery - AbsoluteAstronomy.com

Medical procedure

A medical procedure is a course of action intended to achieve a result in the care of persons with health problems.A medical procedure with the intention of determining, measuring or diagnosing a patient condition or parameter is also called a medical test...

that allows non-invasive treatment of benign

Benign

A benign tumor is a tumor that lacks the ability to metastasize. Common examples of benign tumors include moles and uterine fibroids.The term "benign" implies a mild and nonprogressive disease. Indeed, many kinds of benign tumors are harmless to human health...

and malignant

Malignant

Malignancy is the tendency of a medical condition, especially tumors, to become progressively worse and to potentially result in death. Malignancy in cancers is characterized by anaplasia, invasiveness, and metastasis...

tumors. It is also known as stereotactic radiotherapy, (SRT) when used to target lesions in the brain, and stereotactic body radiotherapy (SBRT) when used to target lesions in the body. In addition to cancer, it has also been shown to be beneficial for the treatment of some non-cancerous conditions, including functional disorders such as arteriovenous malformation

Arteriovenous malformation

Arteriovenous malformation or AVM is an abnormal connection between veins and arteries, usually congenital. This pathology is widely known because of its occurrence in the central nervous system, but can appear in any location. An arteriovenous malformation is a vascular anomaly. It is a...

s (AVMs) and trigeminal neuralgia.

Radiosurgery operates by directing highly focused beams of ionizing radiation

Ionizing radiation

Ionizing radiation is radiation composed of particles that individually have sufficient energy to remove an electron from an atom or molecule. This ionization produces free radicals, which are atoms or molecules containing unpaired electrons...

with high precision. It is a relatively recent technique (1951), which is used to ablate, by means of a precise dosage of radiation, intracranial and extracranial tumor

Tumor

A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...

s and other lesions that could be otherwise inaccessible or inadequate for open surgery. There are many nervous diseases for which conventional surgical treatment is difficult or inadvisable due to deleterious consequences for the patient, such as damage to nearby arteries

Artery

Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....

, nerve

Nerve

A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...

s, and other vital structures.

Medical uses

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

Quality of life

The term quality of life is used to evaluate the general well-being of individuals and societies. The term is used in a wide range of contexts, including the fields of international development, healthcare, and politics. Quality of life should not be confused with the concept of standard of...

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.

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 neuroma

Acoustic neuroma

A vestibular schwannoma, often called an acoustic neuroma, is a benign primary intracranial tumor of the myelin-forming cells of the vestibulocochlear nerve . The term "vestibular schwannoma" involves the vestibular portion of the 8th cranial nerve and arises from Schwann cells, which are...

s, germinoma

Germinoma

A germinoma is a type of germ cell tumor which is not differentiated upon examination. It may be benign or malignant.-Classification:The term germinoma most often has referred to a tumor in the brain that has a histology identical to two other tumors: dysgerminoma in the ovary and seminoma in the...

s, meningioma

Meningioma

The word meningioma was first used by Harvey Cushing in 1922 to describe a tumor originating from the meninges, the membranous layers surrounding the CNS ....

s, metastases , trigeminal neuralgia, arteriovenous malformations and skull base tumors among others. 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.

Gamma knife

The Gamma Knife (also known as the Leksell Gamma Knife) is a creation of Elekta AB, a Swedish public company, used to treat brain tumors by administering high-intensity radiation therapy

Radiation therapy

Radiation therapy , radiation oncology, or radiotherapy , sometimes abbreviated to XRT or DXT, is the medical use of ionizing radiation, generally as part of cancer treatment to control malignant cells.Radiation therapy is commonly applied to the cancerous tumor because of its ability to control...

in a manner that concentrates the radiation over a small volume. The device was invented at the Karolinska Institute in Stockholm

Stockholm

Stockholm is the capital and the largest city of Sweden and constitutes the most populated urban area in Scandinavia. Stockholm is the most populous city in Sweden, with a population of 851,155 in the municipality , 1.37 million in the urban area , and around 2.1 million in the metropolitan area...

, Sweden

Sweden

Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

, in 1967 by Lars Leksell

Lars Leksell

Lars Leksell was a Swedish physician and Professor of Neurosurgery at the Karolinska Institute in Stockholm, Sweden. He was the inventor of radiosurgery.-Life and work:...

, a neurosurgeon, and Börje Larsson, a radiobiologist from Sweden's Uppsala University

Uppsala University

Uppsala University is a research university in Uppsala, Sweden, and is the oldest university in Scandinavia, founded in 1477. It consistently ranks among the best universities in Northern Europe in international rankings and is generally considered one of the most prestigious institutions of...

.

A Gamma Knife typically contains 201 cobalt-60

Cobalt-60

Cobalt-60, , is a synthetic radioactive isotope of cobalt. Due to its half-life of 5.27 years, is not found in nature. It is produced artificially by neutron activation of . decays by beta decay to the stable isotope nickel-60...

sources of approximately 30 curie

Curie

The curie is a unit of radioactivity, defined asThis is roughly the activity of 1 gram of the radium isotope 226Ra, a substance studied by the pioneers of radiology, Marie and Pierre Curie, for whom the unit was named. In addition to the curie, activity can be measured using an SI derived unit,...

s (1.1 TBq), each placed in a circular array in a heavily shielded assembly. The device aims gamma radiation

Gamma ray

Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...

through a target point in the patient's brain

Brain

The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

. The patient wears a specialized helmet that is surgically fixed to the skull, so that the brain tumor remains stationary at the target point of the gamma rays. An ablative

Ablation

Ablation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes. This occurs in spaceflight during ascent and atmospheric reentry, glaciology, medicine, and passive fire protection.-Spaceflight:...

dose of radiation is thereby sent through the tumor in one treatment session, while surrounding brain tissues are relatively spared.

Radiosurgery uses high doses of radiation

Radiation

In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...

to kill cancer

Cancer

Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

cells and shrink tumor

Tumor

A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...

s, delivered precisely to avoid damaging healthy brain tissue. Gamma Knife radiosurgery is able to accurately focus many beams of high-intensity gamma radiation to converge on one or more tumors. Each individual beam is of relatively low intensity, so the radiation has little effect on intervening brain tissue and is concentrated only at the tumor itself.

Gamma Knife radiosurgery has proven effective for patients with benign

Benign

or malignant

Malignant

brain tumors up to 4 centimeters in size, vascular

Blood vessel

The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...

malformations such as an arteriovenous malformation

Arteriovenous malformation

(AVM), pain

Pain

Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...

or other functional problems. For treatment of trigeminal neuralgia

Trigeminal neuralgia

Trigeminal neuralgia , tic douloureux is a neuropathic disorder characterized by episodes of intense pain in the face, originating from the trigeminal nerve. It has been described as among the most painful conditions known...

, the procedure may be used repeatedly on patients.

The risks of gamma knife radiosurgery treatment are very low, and complications are related to the condition being treated.

Risks

According to the New York Times, radiation overdoses have occurred with the linear accelerator method of radiosurgery, in large part due to inadequate safeguards in equipment retrofitted for stereotactic radiosurgery. The U.S. Food and Drug Administration

Food and Drug Administration

The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...

(FDA) regulates these devices, whereas the Gamma Knife is regulated by the Nuclear Regulatory Commission

Nuclear Regulatory Commission

The Nuclear Regulatory Commission is an independent agency of the United States government that was established by the Energy Reorganization Act of 1974 from the United States Atomic Energy Commission, and was first opened January 19, 1975...

. The NYT article focuses on Varian

Varian Medical Systems

Varian Medical Systems of Palo Alto, California, is a manufacturer of medical devices and software for treating cancer and other medical conditions with radiotherapy, radiosurgery, proton therapy, and brachytherapy. The company supplies informatics software for managing comprehensive cancer...

equipment and associated software, but the problem is not likely limited to that manufacturer.

Definition and applications

Radiation oncologist

A radiation oncologist is a doctor who specializes in the treatment of cancer patients, using radiation therapy as the main modality of treatment. Radiation can be given as a curative modality, either alone or in combination with surgery and/or chemotherapy. It may also be used palliatively, to...

s make use of highly sophisticated, highly precise and complex instruments, such as stereotactic device

Stereotactic surgery

Stereotactic surgery or stereotaxy is a minimally invasive form of 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, biopsy, lesion, injection, stimulation, implantation,...

s, linear accelerators, the gamma knife, computer

Computer

A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

s and laser

Laser

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...

beams. The highly precise irradiation of targets within the brain is planned by the radiation oncologist based on images, such as computed tomography

Computed tomography

X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...

(CT), magnetic resonance imaging

Magnetic resonance imaging

Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...

(MRI), and angiography of the brain and body. 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

Craniotomy

A craniotomy is a surgical operation in which a bone flap is temporarily removed from the skull to access the brain. Craniotomies are often a critical operation performed on patients recording, brain imaging, and for neurological manipulations such as electrical stimulation and chemical...

(conventional neurosurgery, requiring the opening of the skull) is about 15 days. Radiosurgery costs less than conventional surgery, and with much less morbidity, e.g. mortality

Death

Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....

, pain

Pain

Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...

and post-surgical complications, such as hemorrhage and infection

Infection

An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...

. 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. However, radiosurgery is not without limitations and disadvantges. It is difficult and dangerous to treat masses larger than 3 cm because it will require very high doses of radiation. Fractionated radiotherapy may be a better option ideally combined with surgical debulking. The duration of time required to achieve the desired effects is much longer than surgery; it can take up to two years for arteriovenous malformations. During that time, the patient remains at risk for a rebleed. For treatment of tumors, it is important to remember that radiosurgery does not physically remove the tumor, rather stops it from growing larger. Therefore, it is not a good option when the tumor presents with significant mass effect on vital structures of the brain or spinal cord and when it causes increased intracranial apressure. Open surgery is needed to relieve pressure, remove the tumor totally or debulk (reduce it in size) it to make it a better target for radiotherapy or radiosurgery. Open surgery and radiosurgery are often used in conjunction for many types of brain tumors. Radiosurgery is a particularly good option for patients who are poor surgical risks due to their medical co-morbidities.

Mechanism of action

The fundamental principle of radiosurgery is that of selective ionization

Ionization

Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...

of tissue, by means of high-energy beams of radiation. Ionization is the production of ion

Ion

An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

s and free radicals which are usually deleterious to the cells

Cell (biology)

The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

. 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. 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

Gray (unit)

The gray is the SI unit of absorbed radiation dose of ionizing radiation , and is defined as the absorption of one joule of ionizing radiation by one kilogram of matter ....

, where one gray (Gy) is the absorption of one joule

Joule

The joule ; symbol J) is a derived unit of energy or work in the International System of Units. It is equal to the energy expended in applying a force of one newton through a distance of one metre , or in passing an electric current of one ampere through a resistance of one ohm for one second...

per kilogram of mass. A unit that attempts to take into account both the different organs that are irradiated and the type of radiation is the sievert

Sievert

The sievert is the International System of Units SI derived unit of dose equivalent radiation. It attempts to quantitatively evaluate the biological effects of ionizing radiation as opposed to just the absorbed dose of radiation energy, which is measured in gray...

, a unit that describes both the amount of energy deposited and the biological effectiveness.

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 ray

Gamma ray

s or x-ray

X-ray

X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...

s. There is also increasing interest in using particle therapy such as proton

Proton

The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....

s and carbon

Carbon

Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

ions for radiosurgery, though this is not widely available.

The emission head (called "gantry

Gantry crane

Gantry cranes, bridge cranes, and overhead cranes, are all types of cranes which lift objects by a hoist which is fitted in a hoist trolley and can move horizontally on a rail or pair of rails fitted under a beam...

") is mechanically rotated around the patient, in a full or partial circle. 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 tissue that 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 collimator

Collimator

A collimator is a device that narrows a beam of particles or waves. To "narrow" can mean either to cause the directions of motion to become more aligned in a specific direction or to cause the spatial cross section of the beam to become smaller.- Optical collimators :In optics, a collimator may...

s (an orifice with different diameters, varying from 5 to 40 mm, in steps of 5 mm). 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

. 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 have been carried out by open or endoscopic surgery, such as for trigeminal neuralgia

Trigeminal neuralgia

, etc. The exact mechanism of its effectiveness for trigemial neuralgia is not known; however, its use for this purpose has become very common. Long term followup data has shown it to be as effective as radiofrequency ablation but inferior to surgery as far as recurrence rate for pain is concerned.

Protons, may also be used in radiosurgery Proton Beam Therapy (PBT). Protons are produced by a medical synchrotron

Synchrotron

A synchrotron is a particular type of cyclic particle accelerator in which the magnetic field and the electric field are carefully synchronised with the travelling particle beam. The proton synchrotron was originally conceived by Sir Marcus Oliphant...

or cyclotron

Cyclotron

In technology, a cyclotron is a type of particle accelerator. In physics, the cyclotron frequency or gyrofrequency is the frequency of a charged particle moving perpendicularly to the direction of a uniform magnetic field, i.e. a magnetic field of constant magnitude and direction...

, extracting them from proton donor materials and accelerating them in successive travels through a circular, evacuated conduit or cavity, using powerful magnets, until they reach sufficient energy (usually about 200 MeV) to enable them to approximately traverse a human body, then stop. 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

Bragg Peak

The Bragg peak is a pronounced peak on the Bragg curve which plots the energy loss of ionizing radiation during its travel through matter. For protons, α-rays, and other ion rays, the peak occurs immediately before the particles come to rest...

effect, proton therapy

Proton therapy

Proton therapy is a type of particle therapy which uses a beam of protons to irradiate diseased tissue, most often in the treatment of cancer. The chief advantage of proton therapy is the ability to more precisely localize the radiation dosage when compared with other types of external beam...

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 to some extent also tissue inside this range) is spared from the effects of radiation. 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

Optic chiasm

The optic chiasm or optic chiasma is the part of the brain where the optic nerves partially cross...

or brainstem. 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.

History

Radiosurgery was first developed at the Karolinska Institute of Stockholm

Stockholm

, Sweden

Sweden

in 1949. It was jointly developed by Dr. Lars Leksell

Lars Leksell

Lars Leksell was a Swedish physician and Professor of Neurosurgery at the Karolinska Institute in Stockholm, Sweden. He was the inventor of radiosurgery.-Life and work:...

, a neurosurgeon and Bjorn Larsson, a radiobiologist

Radiobiology

Radiobiology , as a field of clinical and basic medical sciences, originated from Leopold Freund's 1896 demonstration of the therapeutic treatment of a hairy mole using a new type of electromagnetic radiation called x-rays, which was discovered 1 year previously by the German physicist, Wilhelm...

from Uppsala University

Uppsala University

. Leksell initially used proton

Proton

s from a cyclotron

Cyclotron

to irradiate brain tumor

Brain tumor

A brain tumor is an intracranial solid neoplasm, a tumor within the brain or the central spinal canal.Brain tumors include all tumors inside the cranium or in the central spinal canal...

lesions.

In 1968, they developed the Gamma Knife, a new device exclusively for radiosurgery, which consisted of radioactive sources of Cobalt

Cobalt

Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....

-60 placed in a kind of helmet with central channels for irradiation, using gamma ray

Gamma ray

s. 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.

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 1980s. Modern LINACs optimized for radiosurgery applications include the Trilogy machine from Varian Medical Systems, and the Novalis Tx radiosurgery platform, produced by Varian and BrainLAB.

These systems differ 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 moves in space to change the delivery angle. Both can move the patient in space to also change the delivery point. Both systems use a stereotactic frame to restrict the patient's movement, although on the Novalis Shaped Beam Radiosurgery system and the Novalis Tx radiosurgery platform, BrainLAB pioneered a frameless, non-invasive technique with X-ray imaging that has proven to be both comfortable for the patient and accurate. The Trilogy, from Varian, can also be used with non-invasive immobilization devices coupled with real-time imaging to detect any patient motion during a treatment.

At some medical centers such as in Boston

Boston

Boston is the capital of and largest city in Massachusetts, and is one of the oldest cities in the United States. The largest city in New England, Boston is regarded as the unofficial "Capital of New England" for its economic and cultural impact on the entire New England region. The city proper had...

and in California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, particle accelerators built for doing research in high energy physics have been used since the 1960s for the treatment of brain tumors and arteriovenous malformation

Arteriovenous malformation

s of the brain in humans.

Several generations of the frameless robotic Cyberknife

Cyberknife

The CyberKnife is a frameless robotic radiosurgery system used for treating benign tumors, malignant tumors and other medical conditions. The system was invented by John R. Adler, a Stanford University Professor of Neurosurgery and Radiation Oncology, and Peter and Russell Schonberg of Schonberg...

system have been developed since its initial inception in 1990. It was invented by John R. Adler

John R. Adler

John R. Adler M.D. is a neurosurgeon, the Dorothy and Thye King Chan Endowed Professor of Neurosurgery at Stanford University School of Medicine and Vice Chair for Innovation and Technology in the Department of Neurosurgery at Stanford University School of Medicine.Clinically, Dr. Adler...

, a Stanford University

Stanford University

The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...

Professor of Neurosurgery and Radiation Oncology and Russell and Peter Schonberg at SCHONBERG RESEARCH, and is sold by the Accuray company, located in Sunnyvale, California

Sunnyvale, California

Sunnyvale is a city in Santa Clara County, California, United States. It is one of the major cities that make up the Silicon Valley located in the San Francisco Bay Area...

. Many such CyberKnife systems are available world-wide, and more recently it has been introduced in countries like India at leading cancer care hospitals like HCG Bangalore Institute of Oncology.

Varian Medical Systems

Varian Medical Systems

of Palo Alto, California, made its first linear accelerator optimized for stereotactic radiosurgery in 1992, the Clinac 600SR. The Trilogy is another platform offered by Varian that incorporates tools for delivering highly-accurate image-guided radiotherapy and radiosurgery treatments, including cone-beam (3-D) and kV (2-D) imaging as well as respiratory gating to compensate for tumor motion during treatment. The Trilogy machine can also be outfitted with RapidArc for faster treatment delivery.

In 2007, the Novalis Tx radiosurgery platform was introduced by Varian and BrainLAB. The Novalis Tx radiosurgery platform incorporates sophisticated beam shaping technology, precision targeting computers and robotics that sculpt the treatment beam so that it envelops the tumor while avoiding the surrounding tissues and organs as much as possible. The Novalis Tx radiosurgery platform also offers a broad range of image-guidance tools to further enhance treatment precision. Clinicians are able to generate 3-D scans of the tumor and surrounding tissues prior to every treatment, to ensure that tumors are targeted accurately. The Novalis Shaped Beam Radiosurgery and Novalis Tx radiosurgery platforms are available worldwide, including the US, Europe, Japan, India, Australia, the Asia Pacific region, and the Middle East.

The latest radiosurgery technology available as of 2009 included the CyberKnife and Gamma Knife systems, the Novalis Tx radiosurgery platform, and the Trilogy linear accelerator.

Stereotactic radiosurgery can successfully treat many different types of tumors, both benign and malignant. The malignant brain tumors treated most often are the "brain metastases" or tumors that have spread to the brain. A study in 2008 by the University of Texas M. D. Anderson Cancer Center indicated that stereotactic radiosurgery (SRS) and whole brain radiation therapy (WBRT) for the treatment of metastatic brain tumours have more than twice the risk of developing learning and memory problems than those treated with SRS alone. “While both approaches are in practice and both are equally acceptable, data from this study suggest that oncologists should offer SRS alone as the upfront, initial therapy for patients with up to three brain metastases,”

External links

International RadioSurgery Association
Understanding Stereotactic Radiosurgery. University of Florida.
Academic Clinical Oncology & Radiobiology Research Network An NCRI initiative to revitalise radiotherapy research in the UK
Computer Assisted Neurosurgery, University of Alabama at Birmingham
Proton-Beam Radiosurgery, Massachusetts General Hospital, Harvard University.
Gamma Knife Surgery for Tumors and Arteriovenous Malformations - University of Virginia Radiosurgical Center
RTAnswers - Answers to Your Radiation Therapy Questions
Gamma Knife Radiosurgery - Neurologic & Orthopedic Hospital of Chicago
Sutter Gamma Knife Center - About Gamma Knife Radiosurgery, Physicians, Neurological Diseases Treated, Gamma Knife Video, FAQs
Linear Particle Accelerator (Linac) Animation by Ionactive
Leksell Gamma Knife Society
Novalis Circle - Novalis Circle worldwide network of clinicians dedicated to the advancement of radiosurgery

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.