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Gamma knife

  • Posted on- Jul 07, 2017
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As the name suggests gamma knife doesn't any traditional use of knife, instead gamma knife is a radiosurgery, which uses advance radiation technique that delivers a single, finely focused, high dose of radiation to its target, while causing little or no damage to surrounding tissue.

  • Radiosurgery is the surgery using radiation, destruction of precisely selected areas of tissue using ionizing radiation rather than excision with a blade.
  • Gamma knife is usually used to treat brain cancer, and other certain conditions related to nerves and other parts which are connected to the brain.
  • It is a computerized planning treatment where highly focused radiation is given to the specific areas in the brain to destroy it without damaging the normal tissues.

Conditions for Gamma knife treatment:

There are certain diseases which uses Gamma knife technique as a specialized treatment which are:

  • For tumors:
  • Brain Metastases-These are cancer cells that has spread into brain from other organs of the body. This is the most frequent and mass lesions in the brain.
  • Acoustic Neuroma-Acoustic neuroma is an uncommon, noncancerous (benign) and usually slow-growing tumor that develops on the main nerve leading from your inner ear to your brain. Acoustic neuroma usually grows slowly or not at all.
  • Vestibular Schwannoma-As in case of acoustic neuroma, it is also a benign tumor that occurs in 8th cranial nerve, that transmits sound and equilibrium information from inner ear to brain. But unlike acoustic neuroma, the tumor originate from the schwan cells of the associated nerve instead of the actual neurons.
  • Meningioma-A meningioma is a tumor that forms on membranes that cover the brain and spinal cord just inside the skull. Most of this tumors (around 90%) are slow-growing, i.e. benign.
  • Glioblastoma- It is the most common and fastest growing brain cancer, that occur in cerebrum, the largest part of the brain.
  • Pituitary Adenoma- This are tumours that occurs in the pituitary gland. These are mostly benign, slow-growing tumours.
  • In case of vascular diseases:
  • Arteriovenous Malformation (AVM)- It is a congenital disorder (one present at birth) of blood vessels in the brain, brainstem, or spinal cord that is characterized by a complex, tangled web of abnormal arteries and veins connected by one or more fistulas (abnormal communications).
  • In case of pain and movement disorder:
  • Essential Tremor- It is a nerve disorder characterized by uncontrollable shaking, or "tremors," in different parts and on different sides of the body
  • Trigeminal Neuralgia-It is a nerve disorder that causes sudden, brief episodes of severe stabbing or electric shock-like pain in parts of the face. The pain comes from the trigeminal nerve, the major sensory nerve of the face. This nerve is responsible for sending impulses of touch, pain, pressure and temperature to the brain from the face, jaw, gums and tongue.

Advantages of Gamma knife over traditional radiodsurgery:

  • Gamma Knife's fine-beam technology is specifically designed to treat delicate brain tissue. Whereas normal radiosurgery are used to treat other body organs also.
  • Extra margin or additional volume surrounding the target is rarely added which does not destroy healthy brain tissue. But normal radiosurgery mostly targets the surrounding tissue to ensure total target destruction.
  • With Gamma Knife there are no moving parts during the delivery of radiation. The source of radiation and the target are always in a fixed relationship during treatment, ensuring the highest degree of accuracy. Whereas in normal radiosurgery the source moves, this mostly leads to error in targets.
  • During treatment to the brain, Gamma Knife delivers much lower dose to the brain compared the other body parts, whereas other radiosurgery provides a high dose of radiation than Gamma knife.
  • Gamma knife is a one day treatment, which uses few hours of a body, whereas traditional radiosurgery is commonly a 3-5 days procedure.

Procedure used in Gamma knife:

  • Previous day of the treatment, patients are told about the entire procedure, including the fact that the procedure did not need cutting or removing of any part of the patients hair.
  • During the treatment, a thermoplastic mask is placed over the face or a lightweight frame is attached to the head. This prevents movement during treatment and allows the doctor to accurately locate and treat targets in the brain with microscopic precision.
  • A preoperative MRI image with 1-2 mm thickness is performed to locate the exact position of the target or multiple targets to be treated.
  • Once is target is confirmed, patient are taken on for Gamma knife.
  • When treatment has ended, the thermoplastic mask or head frame is removed. Some patients may experience a mild headache or minor swelling where the head frame was attached.
  • Patient return home on that same day and can get back to their daily routine from the next day.
  • After the treatment, the patients are monitored for their progress, which may include follow-up MRI, CT or angiography images.

Side effects of Gamma knife:

The side effects of Gamma knife is very mild compared to the normal radiosurgery, some of which may include:

  • Minor swelling where the head frame was attached
  • Headache
  • Vomiting
  • Hair loss where are radiation was directed
  • Dizziness
  • Nausea.

The effects are very mild, and mostly vanish after some days of radiation.

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