SBRT and SRS explained-discussed

[D.ap]

Stereotactic Radiation Therapy-

Two different radiation therapies explained
One for everything but the brain and spine
And one specifically for the brain and spine

There are two types of stereotactic radiation:
Stereotactic radiosurgery (SRS) refers to a singe or several stereotactic radiation treatments of the brain or spine. SRS is delivered by a team involving a radiation oncologist and a neurosurgeon.
Stereotactic body radiation therapy (SBRT) refers to one or several stereotactic radiation treatments with the body, excluding the brain or spine

http://www.rtanswers.org/treatmentinfor ... ation.aspx

Please feel free to discuss one or both

[D.ap]

Other Names for Stereotactic Radiation

There is sometimes confusion about the branding of equipment separate from the terminology of SRS or SBRT. Stereotactic radiation may be delivered by a number of different devices; brand name stereotactic treatment machines you may hear mentioned include: Axesse, CyberKnife, Gamma Knife, Novalis, Primatom, Synergy, X-Knife, TomoTherapy or Trilogy. It is important not to confuse these brand names with the actual type of stereotactic radiation under consideration.

There are three basic kinds of equipment, each of which uses different instruments and sources of radiation:

The Gamma Knife®, which uses 192 or 201 beams of highly focused gamma rays all aiming at the target region. The Gamma Knife is ideal for treating small to medium size intracranial lesions. See the Gamma Knife page (www.RadiologyInfo.org/en/info.cfm?pg=gamma_knife) for more information.

Linear accelerator (LINAC) machines, prevalent throughout the world, deliver high-energy x-rays, also known as photons. The linear accelerator can perform SRS on larger tumors in a single session or during multiple sessions, which is called fractionated stereotactic radiotherapy. Multiple manufacturers make this type of machine, which have brand names such as Novalis Tx™, XKnife™, Axesse™ and CyberKnife®. See the Linear Accelerator page (www.RadiologyInfo.org/en/info.cfm?pg=linac) for more information.

Proton beam or heavy-charged-particle radiosurgery is in limited use in North America, though the number of centers offering proton therapy has increased dramatically in the last several years. See the Proton Therapy page (www.RadiologyInfo.org/en/info.cfm?pg=protonthera) for more information

http://www.radiologyinfo.org/en/info.cf ... ereotactic

[Olga]

Yes, the principal difference is the dose (high for the SRS or regular for SBRT) and the schedule (zip ones or have few treatments). But SRS is now used for different locations not only spine-brain, there are articles like that:
http://www.ncbi.nlm.nih.gov/pubmed/24976937
but there are also notes of caution to not overuse this treatments due to their potential long term toxicity - i.e. radiation treatment related secondary cancers or fibrotic changes in the surrounding healthy tissues.

[D.ap]

Radiosurgery was originally defined by the Swedish neurosurgeon Lars Leksell as “a single high dose fraction of radiation, stereotactically directed to an intracranial region of interest”.[1] In stereotactic radiosurgery (SRS), the word stereotactic refers to a three-dimensional coordinate system that enables accurate correlation of a virtual target seen in the patient's diagnostic images with the actual target position in the patient anatomy.

Technological improvements in medical imaging and computing have led to increased clinical adoption of stereotactic radiosurgery and have broadened its scope in recent years.[2][3] Notwithstanding these improvements, the localization accuracy and precision that are implicit in the word “stereotactic” remain of utmost importance for radiosurgical interventions today. Stereotactic accuracy and precision are significantly increased by using a device known as the N-localizer[4][5][6] that was invented by the American physician and computer scientist Russell Brown and that has achieved widespread clinical use in several stereotactic surgical[7][8][9] and radiosurgical systems.

Recently, the original concept of radiosurgery has been expanded to include treatments comprising up to five fractions, and stereotactic radiosurgery has been redefined as a distinct neurosurgical discipline that utilizes externally generated ionizing radiation to inactivate or eradicate defined targets in the head or spine without the need for a surgical incision.[10] Irrespective of the similarities between the concepts of stereotactic radiosurgery and fractionated radiotherapy, and although both treatment modalities are reported to have identical outcomes for certain indications,[11] the intent of both approaches is fundamentally different. The aim of stereotactic radiosurgery is to destroy target tissue while preserving adjacent normal tissue, where fractionated radiotherapy relies on a different sensitivity of the target and the surrounding normal tissue to the total accumulated radiation dose.[10] Historically, the field of fractionated radiotherapy evolved from the original concept of stereotactic radiosurgery following discovery of the principles of radiobiology: repair, reassortment, repopulation, and reoxygenation.[12] Today, both treatment techniques are complementary as tumors that may be resistant to fractionated radiotherapy may respond well to radiosurgery and tumors that are too large or too close to critical organs for safe radiosurgery may be suitable candidates for fractionated radiotherapy.[11]






http://en.wikipedia.org/wiki/Radiosurgery

[D.ap]

SRS and SBRT are important alternatives to invasive surgery, especially for patients who are unable to undergo surgery and for tumors and abnormalities that are:
•hard to reach
•located close to vital organs/anatomic regions
•subject to movement within the body

SRS is used to treat:
•many types of brain tumors including:
◦benign and malignant
◦primary and metastatic
◦single and multiple
◦residual tumor cells following surgery
◦intracranial, orbital and base-of-skull tumors
•arteriovenous malformations (AVMs), a tangle of expanded blood vessels that disrupts normal blood flow in the brain and sometimes bleeds.
•other neurological conditions like trigeminal neuralgia (a nerve disorder in the face), tremor, etc.

SBRT is currently used and/or being investigated for use in treating malignant or benign small-to-medium size tumors in the body and common disease sites, including the:
•lung
•liver
•abdomen
•spine
•prostate
•head and neck

SRS fundamentally works in the same way as other forms of radiation treatment. It does not actually remove the tumor; rather, it damages the DNA of tumor cells. As a result, these cells lose their ability to reproduce. Following treatment, benign tumors usually shrink over a period of 18 months to two years. Malignant and metastatic tumors may shrink more rapidly, even within a couple of months. When treated with SRS, arteriovenous malformations (AVMs) may begin to thicken and close off slowly over a period of several years following treatment. Many tumors will remain stable and inactive without any change. Since the aim is to prevent tumor growth, this is considered a success. In some tumors, like acoustic neuromas, a temporary enlargement may be observed following SRS due to an inflammatory response within the tumor tissue that overtime either stabilizes, or a subsequent tumor regression is observed called pseudoprogression.



There are three basic kinds of equipment, each of which uses different instruments and sources of radiation:
•The Gamma Knife®, which uses 192 or 201 beams of highly focused gamma rays all aiming at the target region. The Gamma Knife is ideal for treating small to medium size intracranial lesions. See the Gamma Knife page for more information.
•Linear accelerator (LINAC) machines, prevalent throughout the world, deliver high-energy x-rays, also known as photons. The linear accelerator can perform SRS on larger tumors in a single session or during multiple sessions, which is called fractionated stereotactic radiotherapy. Multiple manufacturers make this type of machine, which have brand names such as Novalis Tx™, XKnife™, Axesse™ and CyberKnife®. See the Linear Accelerator page for more information.•Proton beam or heavy-charged-particle radiosurgery is in limited use in North America, though the number of centers offering proton therapy has increased dramatically in the last several years. See the Proton Therapy page for more information.

SRS and SBRT are important alternatives to invasive surgery, especially for patients who are unable to undergo surgery and for tumors and abnormalities that are:
•hard to reach
•located close to vital organs/anatomic regions
•subject to movement within the body

SRS is used to treat:
•many types of brain tumors including:
◦benign and malignant
◦primary and metastatic
◦single and multiple
◦residual tumor cells following surgery
◦intracranial, orbital and base-of-skull tumors
•arteriovenous malformations (AVMs), a tangle of expanded blood vessels that disrupts normal blood flow in the brain and sometimes bleeds.
•other neurological conditions like trigeminal neuralgia (a nerve disorder in the face), tremor, etc.

SBRT is currently used and/or being investigated for use in treating malignant or benign small-to-medium size tumors in the body and common disease sites, including the:
•lung
•liver
•abdomen
•spine
•prostate
•head and neck

- SRS fundamentally works in the same way as other forms of radiation treatment. It does not actually remove the tumor; rather, it damages the DNA of tumor cells. As a result, these cells lose their ability to reproduce. Following treatment, benign tumors usually shrink over a period of 18 months to two years. Malignant and metastatic tumors may shrink more rapidly, even within a couple of months. When treated with SRS, arteriovenous malformations (AVMs) may begin to thicken and close off slowly over a period of several years following treatment. Many tumors will remain stable and inactive without any change. Since the aim is to prevent tumor growth, this is considered a success. In some tumors, like acoustic neuromas, a temporary enlargement may be observed following SRS due to an inflammatory response within the tumor tissue that overtime either stabilizes, or a subsequent tumor regression is observed called pseudoprogression.





http://www.radiologyinfo.org/en/info.cf ... ereotactic

[D.ap]

Yes, the principal difference is the dose (high for the SRS or regular for SBRT) and the schedule (zip ones or have few treatments). But SRS is now used for different locations not only spine-brain, there are articles like that:
http://www.ncbi.nlm.nih.gov/pubmed/24976937
but there are also notes of caution to not overuse this treatments due to their potential long term toxicity - i.e. radiation treatment related secondary cancers or fibrotic changes in the surrounding healthy tissues.

Thank you Olga
We should all take heed to warning and plan accordingly
Radiation is given in units called gray units

Need some more research to give this in laymans terms

Radiation therapy is a very scary phrase to say .

National cancer center has this to say-

What is radiation therapy?


Radiation therapy uses high-energy radiation to shrink tumors and kill cancer cells (1). X-rays, gamma rays, and charged particles are types of radiation used for cancer treatment.

The radiation may be delivered by a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body near cancer cells (internal radiation therapy, also called brachytherapy).

Systemic radiation therapy uses radioactive substances, such as radioactive iodine, that travel in the blood to kill cancer cells.

About half of all cancer patients receive some type of radiation therapy sometime during the course of their treatment.


2.How does radiation therapy kill cancer cells?


Radiation therapy kills cancer cells by damaging their DNA (the molecules inside cells that carry genetic information and pass it from one generation to the next) (1). Radiation therapy can either damage DNA directly or create charged particles (free radicals) within the cells that can in turn damage the DNA.

Cancer cells whose DNA is damaged beyond repair stop dividing or die. When the damaged cells die, they are broken down and eliminated by the body’s natural processes.


3.Does radiation therapy kill only cancer cells?


No, radiation therapy can also damage normal cells, leading to side effects (see Question 10).

Doctors take potential damage to normal cells into account when planning a course of radiation therapy (see Question 5). The amount of radiation that normal tissue can safely receive is known for all parts of the body. Doctors use this information to help them decide where to aim radiation during treatment.


4.Why do patients receive radiation therapy?


Radiation therapy is sometimes given with curative intent (that is, with the hope that the treatment will cure a cancer, either by eliminating a tumor, preventing cancer recurrence, or both) (1). In such cases, radiation therapy may be used alone or in combination with surgery, chemotherapy, or both.

Radiation therapy may also be given with palliative intent. Palliative treatments are not intended to cure. Instead, they relieve symptoms and reduce the suffering caused by cancer.

Some examples of palliative radiation therapy are:

Radiation given to the brain to shrink tumors formed from cancer cells that have spread to the brain from another part of the body (metastases).
Radiation given to shrink a tumor that is pressing on the spine or growing within a bone, which can cause pain.
Radiation given to shrink a tumor near the esophagus, which can interfere with a patient’s ability to eat and drink.

5.How is radiation therapy planned for an individual patient?


A radiation oncologist develops a patient’s treatment plan through a process called treatment planning, which begins with simulation.

During simulation, detailed imaging scans show the location of a patient’s tumor and the normal areas around it. These scans are usually computed tomography (CT) scans, but they can also include magnetic resonance imaging (MRI), positron emission tomography (PET), and ultrasound scans.

Computed Tomography Scanner
Computed Tomography Scanner. CT scans are often used in treatment planning for radiation therapy. During CT scanning, pictures of the inside of the body are created by a computer linked to an x-ray machine.CT scans are often used in treatment planning for radiation therapy. During CT scanning, pictures of the inside of the body are created by a computer linked to an x-ray machine.

During simulation and daily treatments, it is necessary to ensure that the patient will be in exactly the same position every day relative to the machine delivering the treatment or doing the imaging. Body molds, head masks, or other devices may be constructed for an individual patient to make it easier for a patient to stay still. Temporary skin marks and even tattoos are used to help with precise patient positioning.

Patients getting radiation to the head may need a mask. The mask helps keep the head from moving so that the patient is in the exact same position for each treatment.

After simulation, the radiation oncologist then determines the exact area that will be treated, the total radiation dose that will be delivered to the tumor, how much dose will be allowed for the normal tissues around the tumor, and the safest angles (paths) for radiation delivery.

Radiation Therapy Head Mask
Radiation Therapy Head Mask. Patients getting radiation to the head may need a mask. The mask helps keep the head from moving so that the patient is in the exact same position for each treatment.The staff working with the radiation oncologist (including physicists and dosimetrists) use sophisticated computers to design the details of the exact radiation plan that will be used. After approving the plan, the radiation oncologist authorizes the start of treatment. On the first day of treatment, and usually at least weekly after that, many checks are made to ensure that the treatments are being delivered exactly the way they were planned.

Radiation doses for cancer treatment are measured in a unit called a gray (Gy), which is a measure of the amount of radiation energy absorbed by 1 kilogram of human tissue. Different doses of radiation are needed to kill different types of cancer cells.

Radiation can damage some types of normal tissue more easily than others. For example, the reproductive organs (testicles and ovaries) are more sensitive to radiation than bones. The radiation oncologist takes all of this information into account during treatment planning.

If an area of the body has previously been treated with radiation therapy, a patient may not be able to have radiation therapy to that area a second time, depending on how much radiation was given during the initial treatment. If one area of the body has already received the maximum safe lifetime dose of radiation, another area might still be treated with radiation therapy if the distance between the two areas is large enough.

The area selected for treatment usually includes the whole tumor plus a small amount of normal tissue surrounding the tumor. The normal tissue is treated for two main reasons:

To take into account body movement from breathing and normal movement of the organs within the body, which can change the location of a tumor between treatments.
To reduce the likelihood of tumor recurrence from cancer cells that have spread to the normal tissue next to the tumor (called microscopic local spread).

6.How is radiation therapy given to patients?


Radiation can come from a machine outside the body (external-beam radiation therapy) or from radioactive material placed in the body near cancer cells (internal radiation therapy, more commonly called brachytherapy). Systemic radiation therapy uses a radioactive substance, given by mouth or into a vein, that travels in the blood to tissues throughout the body.

The type of radiation therapy prescribed by a radiation oncologist depends on many factors, including:

The type of cancer.
The size of the cancer.
The cancer’s location in the body.
How close the cancer is to normal tissues that are sensitive to radiation.
How far into the body the radiation needs to travel.
The patient’s general health and medical history.
Whether the patient will have other types of cancer treatment.
Other factors, such as the patient’s age and other medical conditions.

http://www.cancer.gov/cancertopics/fact ... /radiation

[D.ap]

There are three basic kinds of equipment, each of which uses different instruments and sources of radiation:
•The Gamma Knife®, which uses 192 or 201 beams of highly focused gamma rays all aiming at the target region. The Gamma Knife is ideal for treating small to medium size intracranial lesions. See the Gamma Knife page for more information.
•Linear accelerator (LINAC) machines, prevalent throughout the world, deliver high-energy x-rays, also known as photons. The linear accelerator can perform SRS on larger tumors in a single session or during multiple sessions, which is called fractionated stereotactic radiotherapy. Multiple manufacturers make this type of machine, which have brand names such as Novalis Tx™, XKnife™, Axesse™ and CyberKnife®. See the Linear Accelerator page for more information.•Proton beam or heavy-charged-particle radiosurgery is in limited use in North America, though the number of centers offering proton therapy has increased dramatically in the last several years. See the Proton Therapy page for more information.

Gamma knife from the link below-

Gamma Knife[edit]

"Gamma Knife" redirects here. For the album by Kayo Dot, see Gamma Knife (album).





NRC graphic of the Leksell 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 cobalt radiation therapy in a manner that concentrates the radiation over a small volume. The device was invented at the Karolinska Institute in Stockholm, Sweden, in 1967 by Lars Leksell, Ladislau Steiner, a Romanian born neurosurgeon, and Börje Larsson, a radiobiologist from Sweden's Uppsala University.

A Gamma Knife typically contains 201 cobalt-60 sources of approximately 30 curies (1.1 TBq), each placed in a circular array in a heavily shielded assembly. The device aims gamma radiation through a target point in the patient's brain. 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 dose of radiation is thereby sent through the tumor in one treatment session, while surrounding brain tissues are relatively spared.

Gamma Knife therapy, like all radiosurgery, uses doses of radiation to kill cancer cells and shrink tumors, delivered precisely to avoid damaging healthy brain tissue. Gamma Knife radiosurgery is able to accurately focus many beams of 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 or malignant brain tumors up to 4 centimeters in size, vascular malformations such as an arteriovenous malformation (AVM), pain or other functional problems.[26][27][28][29] For treatment of trigeminal neuralgia, the procedure may be used repeatedly on patients.

While acute complications following gamma knife radiosurgery are rare,[30] and complications are related to the condition being treated,[31][32] the mid- and long-term risks and adverse effects of ionizing radiation on human tissue have not been fully examined, for ethical reasons.

Linear accelerator also from the link below-

Linear accelerator based therapies[edit]

Main article: megavoltage X-rays

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 MeV 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, or CyberKnife from Accuray, can also be used with non-invasive immobilization devices coupled with real-time imaging to detect any patient motion during a treatment.

Linear accelerators emit high energy X-rays, usually referred to as "X-ray therapy" or "photon therapy." The term "gamma ray" is usually reserved for photons that are emitted from a radioisotope such as cobalt-60 (see below). Such radiation is not substantially different from that emitted by high voltage accelerators. In linear accelerator therapy, the emission head (called "gantry") 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 collimators (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. 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, etc. The exact mechanism of its effectiveness for trigeminal 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.

A type of linear accelerator therapy which uses a small accelerator mounted on a moving arm to deliver X-rays to a very small area which can be seen on fluoroscopy, is called Cyberknife therapy. Several generations of the frameless robotic Cyberknife system have been developed since its initial inception in 1990. It was invented by John R. Adler, a Stanford University 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. 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 Apollo Specialty hospitals and HCG Bangalore Institute of Oncology.

Cyberknife may be compared to Gamma Knife therapy (see above), but it does not use radioisotopes and thus by definition, does not use gamma rays. It also does not use a frame to hold the patient, as a computer monitors the patient's position during treatment, using fluoroscopy. The robotic concept of Cyberknife radiosurgery allows for tracking the tumor, rather than fixing the patient with a stereotaxic frame. Since no frame is needed, some of the radiosurgical concepts can be extented to treat extracranial tumors. In this case, the Cyberknife robotic arm tracks the tumor motion (i.e. respiratory motion).[33] A combination of stereo x-ray imaging and infrared tracking sensors determines the tumor position in real-time.

Proton Beam from the link

Proton beam therapy[edit]

Main article: Proton therapy

Protons may also be used in radiosurgery in a procedure called Proton Beam Therapy (PBT) or simply proton therapy. Protons are produced by a medical synchrotron or cyclotron, 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 effect, proton therapy has advantages over 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 or brainstem. In recent years, however, "intensity modulated" techniques have allowed for similar conformities to be attained using linear accelerator radiosurgery

http://en.wikipedia.org/wiki/Radiosurgery#Gamma_Knife

[D.ap]

http://en.wikipedia.org/wiki/Radiosurgery#Gamma_Knife

Radiosurgery discussed from link

Clinical applications[edit]

Radiosurgery is performed by a multidisciplinary team of radiation oncologists, and medical physicists to operate and maintain highly sophisticated, highly precise and complex instruments, like medical Linacs and the Gamma Knife. The highly precise irradiation of targets within the brain and spine is planned using information from medical images that are obtained via computed tomography, magnetic resonance, and angiography.

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. Patients can be treated within one to five days and on an outpatient basis. By comparison, the average hospital stay for a craniotomy (conventional neurosurgery, requiring the opening of the skull) is about 15 days. Radiosurgery outcome may not be evident until 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. Expansion of stereotactic radiotherapy to extracranial lesions is increasing, and includes metastases, liver cancer, lung cancer, pancreatic cancer, etc.

Mechanism of action[edit]




Planning CT scan with IV contrast in a patient with left cerebellopontine angle vestibular schwannoma
The fundamental principle of radiosurgery is that of selective ionization of tissue, by means of high-energy beams of radiation. Ionization is the production of ions and free radicals which are usually deleterious to the cells. 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, where one gray (Gy) is the absorption of one joule 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, a unit that describes both the amount of energy deposited and the biological effectiveness.

Risks[edit]

According to a December 2010 article in 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.[25] The U.S. Food and Drug Administration (FDA) regulates these devices, whereas the Gamma Knife is regulated by the Nuclear Regulatory Commission. The NYT article focuses on Varian equipment and associated software, but the problem is not likely limited to that manufacturer.

[D.ap]

Stereotactic radiosurgery using the Leksell Gamma Knife Perfexion unit in the management of patients with 10 or more brain metastases

Clinical article
Ramesh Grandhi, M.D.1, Douglas Kondziolka, M.D.1,2,3,4, David Panczykowski, M.D.1, Edward A. Monaco III, M.D., Ph.D.1, Hideyuki Kano, M.D., Ph.D.1,3, Ajay Niranjan, M.Ch., M.B.A.1,3, John C. Flickinger, M.D.2,3 and L. Dade Lunsford, M.D.1,2,3,4
1Departments of Neurological Surgery and 2Radiation Oncology; 3Center for Image-Guided Neurosurgery; and 4University of Pittsburgh Cancer Institute, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
J Neurosurg. 2012 Aug;117(2):234-5; discussion 235-6.

Abstract
OBJECT: To better establish the role of stereotactic radiosurgery (SRS) in treating patients with 10 or more intracranial metastases, the authors assessed clinical outcomes and identified prognostic factors associated with survival and tumor control in patients who underwent radiosurgery using the Leksell Gamma Knife Perfexion (LGK PFX) unit.

METHODS: The authors retrospectively reviewed data in all patients who had undergone LGK PFX surgery to treat 10 or more brain metastases in a single session at the University of Pittsburgh. Posttreatment imaging studies were used to assess tumor response, and patient records were reviewed for clinical follow-up data. All data were collected by a neurosurgeon who had not participated in patient care.

http://www.ncbi.nlm.nih.gov/m/pubmed/22 ... 20/related

[D.ap]

Other Names for Stereotactic Radiation

There is sometimes confusion about the branding of equipment separate from the terminology of SRS or SBRT. Stereotactic radiation may be delivered by a number of different devices; brand name stereotactic treatment machines you may hear mentioned include: Axesse, CyberKnife, Gamma Knife, Novalis, Primatom, Synergy, X-Knife, TomoTherapy or Trilogy. It is important not to confuse these brand names with the actual type of stereotactic radiation under consideration.

Strahlenther Onkol. 2014 Nov 22. [Epub ahead of print]

Intracranial stereotactic radiosurgery with an adapted linear accelerator vs. robotic radiosurgery : Comparison of dosimetric treatment plan quality.
Abstract

BACKGROUND AND PURPOSE:

Stereotactic radiosurgery with an adapted linear accelerator (linac-SRS) is an established therapy option for brain metastases, benign brain tumors, and arteriovenous malformations. We intended to investigate whether the dosimetric quality of treatment plans achieved with a CyberKnife (CK) is at least equivalent to that for linac-SRS with circular or micromultileaf collimators (microMLC).

PATIENTS AND METHODS:

A random sample of 16 patients with 23 target volumes, previously treated with linac-SRS, was replanned with CK. Planning constraints were identical dose prescription and clinical applicability. In all cases uniform optimization scripts and inverse planning objectives were used. Plans were compared with respect to coverage, minimal dose within target volume, conformity index, and volume of brain tissue irradiated with ≥ 10 Gy.

RESULTS:

Generating the CK plan was unproblematic with simple optimization scripts in all cases. With the CK plans, coverage, minimal target volume dosage, and conformity index were significantly better, while no significant improvement could be shown regarding the 10 Gy volume. Multiobjective comparison for the irradiated target volumes was superior in the CK plan in 20 out of 23 cases and equivalent in 3 out of 23 cases. Multiobjective comparison for the treated patients was superior in the CK plan in all 16 cases.

CONCLUSION:

The results clearly demonstrate the superiority of the irradiation plan for CK compared to classical linac-SRS with circular collimators and microMLC. In particular, the average minimal target volume dose per patient, increased by 1.9 Gy, and at the same time a 14 % better conformation index seems to be an improvement with clinical relevance.





http://www.ncbi.nlm.nih.gov/pubmed/25416146

[D.ap]

Found an England link to their description of SRS

http://www.cancerresearchuk.org/about-c ... in-tumours

[D.ap]

Maybe a reason to low and or different exposure radiation to a patients brain for different reasoning ?

http://www.mayoclinic.org/tests-procedu ... c-20014760