In brief, it is outpatient major neurosurgery, with no intubation, incision, craniotomy or even a hospital stay.
The Gamma Knife is state of the art, non-invasive machine for delivering highly precise radiation on precisely defined targets within the brain in order to get a desired radiobiological effect to treat the person. That effect ranges from killing a metastatic breast tumor in the brain, to causing healing of abnormal blood vessels of an AVM to selectively blocking the face pain fibers in trigeminal neuralgia.
Contact Us
For more information about the CNI Stereotactic Radiosurgery
(Gamma Knife) Service, please contact:
Marcus Keep, MD - Medical Director
CNI Stereotactic Radiosurgery
701 East Hampden Ave, Suite 510
Englewood, CO 80113
(303) 788-9762
(303) 788-4801 Fax
What is the "Gamma" in Gamma Knife?
The Gamma refers to the Gamma ray source of radiation from the radioactive cobalt creating 201 beams that focus on the tumor. Cobalt gamma radiation produces energy beams of exactly 2 closely matched energies-making the dose delivery more predictable than X-rays. X-rays are made by accelerating electrons against metal, producing a scatter spectrum of different strength energy X-ray beams, which need to be filtered to try to get more predictability to the amount of energy being given to a patient. Other types of radiosurgery machines like CyberKnife, Novalis and Tomotherapy machines make X-rays. There are a few "proton beam" radiosurgery centers in the country that accelerate hydrogen atoms toward the speed of light in cyclotrons and related particle physics high energy machines.
Because the Gamma Knife has so many sources of cobalt Gamma beams, each one of the hundreds (201 exactly) can be gentle on the normal body's hair, skin and brain, but where they all focus together, brutally strong on the tumor. The linear accelerator based X-ray machines deliver few beams since they have only one radiation port at a time, so each beam is less gentle on the normal tissue.
What is the "Knife" in Gamma Knife?
The Gamma Knife was developed by pioneer Swedish neurosurgeon Lars Leksell. Since it is a neurosurgery machine, the name "knife" is applied to convey both a surgical aspect, and also the high scalpel-like precision of the radiation delivery. This is to differentiate the Gamma Knife from radiotherapy machines which delivery a wide beam used by radiation oncologists typically to treat the entire brain. There is no actual knife incision with outpatient Gamma Knife radiosurgery.
What can the Gamme Knife treat?
The Gamma Knife treats a wide variety of brain diseases. The main groups are malignant brain tumors, benign brain tumors, vascular malformations and functional neurological disease.
Malignant brain tumors
Metastatic tumors from lung, breast, kidney, skin and other organs can be treated. The Gamma knife can easily treat multiple metastatic tumors, in one session, in one day. Up to 6 individual tumors at a time is considered standard. Patients who have already had whole brain radiation therapy are still candidates for Gamma Knife radiosurgery if their tumors do not go away completely, or start to come back. If new tumors appear months or years after your first Gamma Knife treatment in a new part of the brain, Gamma Knife can be safely used again. Metastatic tumor control rates are about 80%.
Primary brain tumors, such as astrocytoma, oligodendroglioma, pilocytic astrocytoma, and glioblastoma multiformi (GBM) can be treated. These tumors usually affect a wide area of the brain and so usually can not be cured with open neurosurgery or Gamma Knife radiosurgery. In concert with your neuro-oncologist's plan including chemotherapy, biological response modifiers, antiangiogenesis agents, radiotherapy and open neurosurgery, in selected patients Gamma Knife can help extend a meaningful quality and quantity of life.
Benign tumors of structures around the brain
Some of the normal structures surrounding the brain develop slow growing tumors that do not usually invade the brain or metastasize. Because there is so little extra room inside the skull, these benign usually slow growing masses start pushing on the normal brain and causing problems. Gamma Knife is greater than 95% effective in stopping these benign tumors from growing. The three main benign tumors that Gamma Knife is so effective in stopping are acoustic neuromas (also known as vestibular schwannomas), meningiomas and pituitary adenomas. Some of these tumors will already be too big when they are discovered to be treated with the Gamma Knife. If there is any tumor left that your neurosurgeon can not reach with an open neurosurgery to debulk it, or reduce its size, then you can have Gamma Knife afterwards. Also, if you had a successful open neurosurgery in the past, but now your acoustic neuroma, meningioma or pituitary adenoma is starting to grow back, often Gamma Knife is an excellent treatment choice to stop it in its tracks and prevent any further recurrence.
Vascular malformations
Gamma Knife can effectively treat arteriovenous malformations (AVM) and dural fistulas. It is especially useful for deep seated AVMs located in critical structures that are especially dangerous for open neurosurgery such as the thalamus. The radiation makes the AVM close up from within. This internal healing takes time, usually 2 to 3 years. The usual risks of bleeding from an AVM per year are about 3%. This risk remains the same after Gamma Knife (neither higher or lower) until the AVM is gone. For AVMs and dural fistulas in difficult locations for an open neurosurgery, Gamma Knife can be a lifesaver.
Function neurological disorders
Functional neurological disorders include facial pain (trigeminal neuralgia) and hand tremor (from essential type, multiple sclerosis and Parkinson' disease). Trigeminal neuralgia, with its electric intense facial pain, gets a good response in 80% of patients. Half will become completely pain free. It typically only takes a month for the pain to go away. Treatments for hand tremor give gradual improvement over two to four months.
What are the limits of the Gamma Knife
Unfortunately not every type of tumor or AVM can be treated with non-invasive Gamma Knife. The limits of what Gamma Knife can do are based on size and location. The very large tumors greater than 3.5 cm (about the size of a golfball) are too large to benefit from the advantages of Gamma Knife. These tumors need to be treated with traditional open neurosurgery or traditional multi-session radiotherapy. If either open neurosurgery or radiotherapy shrink the tumor enough (but can not get all of it), then you could still be a candidate for Gamma Knife radiosurgery to "mop up" what is left. Location of the tumor next to a critical radiosensitive structure limits the amount of radiation that can be given. Tumors near the optic nerves or brainstem must be carefully selected so as to not cause any harm from the Gamma Knife treatment. The high precision and accuracy of the Gamma Knife allows effective and safe treatments of tumors just millimeters from these critical structures.
The Gamma Knife can only treat lesions in the head, and is the most precise machine for neurosurgical brain lesions. Other machines are needed to treat tumors in the neck, spine and body.
Contact Us
For more information about the CNI Stereotactic Radiosurgery Service, please
contact:
Marcus Keep, MD - Medical Director
CNI Stereotactic Radiosurgery Service
701 East Hampden Ave, Suite 510
Englewood, CO 80113
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