Transcript Stereotactic surgery - Univerzita Karlova

Stereotactic surgery
Radiosurgery
Gamma Knife
Eugen Kvasnak, PhD.
Department of Medical Biophysics and Informatics
3rd Medical Faculty of Charles University
• 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.
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 don’t move each other.
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.
Radiosurgery
• The computer software reduces the treatment plan to a
list of simple instructions to guide the gamma rays to the
target.
• The patient’s 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.
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.
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.
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.
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 1950’s.
• 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.
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.
Comparison to radiation therapy
• Professor Leksell’s 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.
Abnormalities to treat by Gamma Knife
• Brain tumors:
• Glioblastoma
Anaplastic astrocytoma
Gliomas / Astrocytoma
Oligodendroglioma
Ependymoma
Pilocytic astrocytoma
Meningioma
Pituitary tumors
Pineal region tumors
Acoustic Neuroma
Neuromas of the cranial
nerves
Glomus jugulare tumor
Metastatic brain tumors
• Vascular abnormalities:
• Arteriovenous malformations
Cavermous malformations
Skull base tumors
Invasive squamous and basal cell
carcinoma
Chordoma
Chondrosarcoma
Esthesioneuroblastoma
Functional problems:
Trigeminal neuralgia
Parkinson's disease
Essential tremor
Obsessive Compulsive Disorder
Ocular tumors
Uveal melanoma
Orbital metastases
Optic nerve sheath meningioma
How it looks…
Example of treatment
Metastatic Brain Tumors:
• Experience has shown that surgical removal of single brain
metastases followed by radiation therapy to the brain
benefits patient’s quality of life and survival when
compared to treatment by brain radiotherapy alone. To
achieve this benefit, usually there must be control of the
patient’s 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.
Example of treatment
frontal lobe metastasis
several months after GK radiosurgery
Thank you for your attention!