Stereotactic surgery

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Stereotactic surgery Radiosurgery Gamma Knife
Eugen Kvasnak, PhD. Department of Medical
Biophysics and Informatics 3rd Medical Faculty of
Charles University
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• Stereotactic surgery means operations in three
  dimensional planar system (axis x,y,z).
• Any structure or organ, for example brain is
  placed into a three dimensional frame.
• A very fine needle is attached to this frame.
• If we know coordinates of any structure in the
  brain, we can hit it with a tip of the needle
  only by setting coordinates of the structure.

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Organs suitable for this surgery

• For stereotactic surgery is suitable brain,
  because it is placed in the scull.
• The frame for stereotactic surgery can be firmly
  attached to the scull, so there is no movement
  between the scull and the frame.
• The brain does not move inside the scull too.
• So the result is that the brain and the frame for
  stereotactic surgery dont move each other.

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Finding the coordinates

• CT scan and NMRI is used.
• If the organ move out of the frame, coordinates
  can not be set and the stereotactic surgery is
  not possible.
• Radiosurgery is carried out through the
  cooperative efforts of a neurosurgeon, radiation
  oncologist and physicist.
• Initial consultation will help you determine if
  GK radiosurgery is appropriate, effective and
  safe
• Every patient should have information about all
  applicable treatments, the expected outcomes,
  risks, costs and the natural history of the
  untreated disease process. The decision of
  treatment is up to the patient.

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Radiosurgery

• The computer software reduces the treatment plan
  to a list of simple instructions to guide the
  gamma rays to the target.
• The patients stereotactic head frame is fixed
  within the collimator according to these
  instructions.
• Usually several shots are used to cover the
  entire target volume.
• Total treatment time varies from 45 minutes to
  hours.
• Following treatment, the frame is removed and
  patients are observed overnight or are discharged
  home.

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Gamma Knife

• The Gamma Knife contains 201 small Cobalt sources
  of gamma rays arrayed in a hemisphere within a
  thickly shielded structure.
• Collimator aims the radiation emitted by these
  sources to a common focal point.
• This is analogous to focusing the radiant energy
  of the sun with a magnifying glass to a hot
  focus.
• Near the glass there is not much heat, but the
  energy is intense at the focal point.
• Optical lenses can not focus gamma rays, rather
  individual beams are allowed to summate by
  overlapping at the focal point of the collimator,
  achieving the same effect. Collimator allows the
  beam focus size to be adjusted from 4 to 18 mm in
  size.

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Gamma Knife Cure

• The cure of a brain tumor by radiosurgery means
  that the tumor loses its ability to grow and
  remains the same size, never growing again.
• The intensely focused gamma rays destroy the
  ability of the cells to divide.
• Sometimes benign tumors actually shrink over time
  and malignant tumors may completely disappear.
• Arteriovenous malformations usually occlude after
  focused radiosurgery.
• This curative process occurs over months to
  years.

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Radiosurgery

• is a surgical procedure where narrow beams of
  radiation are targeted to a precisely defined
  volume of tissue within the brain.
• This highly focused and destructive dose of
  radiation is given in a single session and avoids
  potentially harmful radiation to surrounding
  brain structures.  

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Radiosurgery history

• Professor Lars Leksell, a Swedish neurosurgeon,
  first developed stereotactic devices (used to
  guide the gamma rays) as well as the very concept
  of radiosurgery in the early 1950s.
• Together with Borje Larsson, a physicist, Leksell
  built the first Gamma Knife unit in Sweden in
  1968.
• Since that time, this non-invasive technique for
  the treatment of brain tumors and vascular
  malformations has enjoyed incredible success.
• More than 60,000 patients have been safely
  treated with focused gamma rays world-wide.

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Comparison to radiation therapy

• Radiosurgery differs from conventional radiation
  therapy in several respects.
• With standard external beam radiation therapy
  techniques, tumors and much or all of the
  surrounding brain are treated to the same dose of
  radiation.
• The radiation dose is given in small increments
  over several weeks to allow normal brain tissue
  to recover from its effect, while tumor tissue is
  less likely to recover. Ultimately, the brain can
  absorb a maximal dose of radiation, beyond which
  no further treatment is advisable.
• There is increasing evidence that over long
  periods of time, high doses of radiation are
  harmful to normally functioning brain. The
  technique of Gamma Knife radiosurgery treats only
  the abnormal tissue, in a single session, without
  significant radiation to adjacent brain.

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Comparison to radiation therapy

• Professor Leksells concept has proved to be a
  true advance in the treatment of intracranial
  disease.
• Stereotactic techniques can also be used to
  accurately aim fractionated doses of gamma rays
  or x-rays to a target administering the
  treatment in small doses over days to weeks.
• This technique is a compromise between
  radiosurgery and conventional radiotherapy and is
  termed stereotactic radiotherapy.

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Abnormalities to treat by Gamma Knife

• Brain tumors
• GlioblastomaAnaplastic astrocytomaGliomas /
  AstrocytomaOligodendrogliomaEpendymomaPilocytic
  astrocytomaMeningiomaPituitary tumorsPineal
  region tumorsAcoustic NeuromaNeuromas of the
  cranial nervesGlomus jugulare tumor Metastatic
  brain tumors
• Vascular abnormalities
• Arteriovenous malformations

• Cavermous malformations
• Skull base tumors
• Invasive squamous and basal cell
  carcinomaChordomaChondrosarcomaEsthesioneurobla
  stoma
• Functional problems
• Trigeminal neuralgia
• Parkinson's disease
• Essential tremor
• Obsessive Compulsive Disorder
•  Ocular tumors
• Uveal melanomaOrbital metastasesOptic nerve
  sheath meningioma

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How it looks
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Example of treatment

• Metastatic Brain Tumors
• Experience has shown that surgical removal of
  single brain metastases followed by radiation
  therapy to the brain benefits patients quality
  of life and survival when compared to treatment
  by brain radiotherapy alone. To achieve this
  benefit, usually there must be control of the
  patients primary tumor. Experience has also
  shown that Gamma Knife radiosurgery is as
  effective as open surgery in the control of
  metastatic brain tumors when combined with
  radiotherapy of the brain. This is being extended
  to the control of multiple brain metastases. In
  selected individuals we do not carry out whole
  brain radiotherapy following Gamma Knife
  radiosurgery. Usually we request close follow-up
  by means of frequent MR images of the brain to
  ensure control. Recurrent or new tumor deposits
  can be retreated by radiosurgery.

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Example of treatment
frontal lobe metastasis
several months after GK radiosurgery
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• Thank you for your attention!