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Stereotactic Radiosurgery and Radiotherapy in India

Stereotactic Radiosurgery

Stereotactic radiosurgery (SRS) is a form of radiation therapy that focuses high-power energy on a small area of the body. Despite its name, radiosurgery is a treatment, not a surgical procedure. Incisions (cuts) are not made on your body. Stereo means 3-dimensional (3-D) and tactic means to probe. Stereotactic radiation therapy allows radiation beams to be given to a very specific area, usually the brain.

There are 2 ways to deliver stereotactic radiation therapy treatment.

  • Stereotactic radiosurgery (SRS) delivers a single high dose of radiation to the tumour (called a single fraction). This treatment doesn’t involve surgery. An incision (cut) is not made and tissue is not surgically removed.
  • Stereotactic radiotherapy (SRT) gives smaller doses of radiation over a number of treatment sessions (called multiple fractions), until the desired total dose is given.

Diseases and Conditions Treated by Stereotactic Radiosurgery
·  rigeminal Neuralgia

  • Brain Metastases
  • Parkinson’s Disease
  • Some causes of Epilepsy
  • Acoustic Neuroma and other Head and Neck Cancers
  • Movement Disorders
  • Spinal Cord Tumors
  • Neurological Problems
  • Pituitary Tumors
  • Movement Disorders
  • Cancer of the Eye (Uveal Melanoma)
  • Blood Vessel Problems like Arteriovenous Malformations

Types of Stereotactic Radiation

Stereotactic Body Radiation Therapy (SBRT) also known as stereotactic ablative radiotherapy, administers very high doses of radiation, using several beams of various intensities aimed at different angles to precisely target the tumor. SBRT is used for treating:

  • Pediatric Cancers
  • Bladder Cancer
  • Lung Cancer
  • Head and Neck Cancers
  • Pancreatic Cancer
  • Liver Cancer
  • Kidney Cancer

Stereotactic Radiosurgery (SRS) is a non-invasive treatment that uses dozens of tiny radiation beams to accurately target brain tumors with a single high dose of radiation. Despite its name, SRS is not a surgical procedure and does not require an incision or anesthesia. However, the radiation beams are as small and precise as a scalpel. SRS is primarily used for treating spinal and brain cancers.

Equipments used for Stereotactic Radiosurgery

Stereotactic radiation delivery (Equipment) systems include:

Gamma Knife

The Gamma Knife is not a knife. It is a machine that precisely focuses about 200 beams of gamma radiation (usually cobalt) at a tumour. The radiation is delivered at the point where the beams cross or intersect. It is usually given as a single high-dose treatment. The technique is sometimes called Gamma Knife surgery (GKS).

Linear accelerator (LINAC)

The LINAC machine delivers radiation in several x-ray beams that follow arcs. The treatment may be given over several sessions. Each session may take 30 minutes or longer.

CyberKnife

CyberKnife is an advanced type of linear accelerator. A robotic system points the linear accelerator in a variety of positions. Several x-ray cameras (or imaging devices) and computers are used to track the person’s position. If a person moves slightly, the robotic system can adjust. by repositioning the linear accelerator before the beam of radiation is delivered. This type of treatment may need to be given over a period of days.

The use of CyberKnife is not limited to brain tumours. It can be used for tumours in other parts of the body, such as the spine or lung. Small, local tumours seem to benefit most from this treatment. A stereotactic frame is not needed, but other immobilization devices or special markers may be used.

Procedure of Stereotactic Radiosurgery

Stereotactic Radiosurgery by using Linear Accelerator (LINAC) :  This procedure is considered same as Gamma Knife procedure and has been categorized into 4 phases-

  • Imaging
  • Computerized Dose Planning
  • Head Frame Placement
  • Radiation Delivery

Radiation beams are delivered from many angles using gantry (a part of the LINAC machine) that rotates around the patient. Large tumors can be effectively treated with less repositioning and more uniformity as it delivers larger x-ray beam.

Stereotactic Radiosurgery Using the Gamma Knife: Four phases are involved in this procedure –

  • Placement of the Head Frame : Pins are used for attaching the skull with a box-shaped light- weight aluminum head frame. These pins prevent the movement of the skull till the treatment session finishes. This frame is primarily used for focusing gamma rays on the specific site where the treatment is required.
  • Imaging of the Tumor Location: Magnetic Resonance Imaging (MRI) or a computed tomography (CT) scan is performed for locating the precise location of the tumor in respect to the head frame.
  • Computerized Dose Planning : The tumor is then radiated by performing a computer-aided treatment plan.
  • Radiation Delivery : Radiation beams are then targeted on a specific area of the brain. These beams enter from the different holes in the helmet that is attached with the head frame so as to enable these beams to target the exact site in the brain. The treatment then starts and the patient talks to the physician by using a microphone present inside the helmet. A physician can see the patient during the procedure through a camera which is also there in the helmet. A click and a chime is then heard when the helmet locks into the radiation source. The entire procedure takes about 2-4 hours and the head frame is removed after the completion of the procedure.