AVM (Arteriovenous Malformation)
AVM is an abnormal combination of entangled blood vessels in the brain that are
prone to bleed. This bleeding can cause symptoms ranging from headaches and
seizures to neurological catastrophes and even death.
Benign tumors are not cancerous; however, they may need to be treated. Some
benign tumors may change over time and become malignant.
A bite block is a mouth guard that affixes to the patient’s upper lip. It has
sophisticated markings (fiducials) that are tracked by an optical camera. The
fiducials allow the patient to be precisely positioned on a repeated basis. A
bite block is generally used during a stereotactic radiotherapy (SRT) treatment.
Chemotherapy is a treatment that destroys tumor cells through the use of
chemicals that are injected into the body or taken orally over a period of time.
Conformal radiosurgery shapes the radiation beam to fit the tumor or
malformation perfectly, rather than using the traditional method of multiple
circular beams. Conformal radiosurgery maximizes radiation to the tumor or
malformation and minimizes doses to surrounding healthy tissue.
CNS (Central Nervous System)
The brain and spinal cord together form the CNS.
CT (Computerized Tomography)
A CT scan is a diagnostic imaging technique where an x-ray machine and computer
are used to create a detailed picture of the body’s tissues and structures. A
dye, or contrast agent, may be injected into the patient to highlight
abnormalities in tissue.
Critical structures are areas in the brain that are responsible for such vital
functions as memory, speech, hearing, sight and movement. The spinal cord is the
critical structure in the spine.
CyberKnife Synchrony is a technology developed in order to deliver dynamic
radiosurgery to tumors that move with respiration. The Synchrony system
precisely tracks tumors in or near the lungs as they move, enabling highly
focused beams of radiation to destroy the tumors with minimal damage to adjacent
Fiducials are markings found on either the head frame or bite block.
Additionally, they may be surgically implanted to treat spine or other tumors.
The fiducials act as markers, helping to identify precisely the location of the
Fractionation, or staging, occurs when the total dose of radiation is divided
into smaller doses in order to give healthy tissue time to repair itself.
The Gamma Knife uses older radiation technology that is confined to treating
tumors in the head. The Gamma Knife uses ionizing radiation (gamma rays)
produced by 201 cobalt-60 sources to target the tumor or abnormality.
Gliomas, or tumors that arise from the supportive tissue of the brain, are the
most common primary brain tumors. Astrocytomas, ependymomas, oligodendrogliomas
and tumors with mixtures of two or more of these cell types are the most common
The head frame is a metal halo that is fixed to the patient’s skull. It contains
markings (fiducials), which are visualized on the CT and/or MRI image. Local
anesthesia is used to secure the head frame into position with four micro-pins.
Technologies such as the Gamma Knife use a head frame because they do not have
image guidance capabilities.
Image guidance system
An image guidance system is utilized by the CyberKnife Radiosurgery system that
tracks and verifies tumor location to enable automatic compensation for patient
movement during the procedure. The image guidance system’s sophisticated
technology allows for 100% frameless treatments with the ability to achieve
submillimeter accuracy without the use of a painful head frame.
IMRT (Intensity Modulated Radiation Therapy)
IMRT is a form of three-dimensional conformal radiation therapy (3D-CRT) that
links treatment planning and driver software to the actual treatment delivery
devices. As a result, clinicians can determine and deliver an optimum plan of
individualized radiation for each patient.
An inaccessible tumor cannot be removed surgically because it is located in an
area that is difficult to access surgically without risk to the nervous system
or vital areas of the brain.
Isocentric Treatment Planning
Isocentric treatment, or multi-isocentric treatment, involves packing the lesion
with a single (or multiple, overlapping) spherically shaped dose distributions.
During certain types of radiation treatment, hot spots are areas where radiation
beams overlap, causing overdosing in some areas. Overdosing may increase the
risk of complications as a result of excessive radiation exposure to normal
tissue, including critical structures such as the highly radiosensitive optic
chiasm and acoustic nerves.
During certain types of radiation treatment, cold spots are areas on the target
that receive underdosing. Consequently, tumor cells may not be fully destroyed.
Linac, or linear accelerator, delivers x-ray radiation treatment by moving in an
arc around the patient’s head while delivering narrow beams of collimated
radiation. The ability to reach some tumors may be difficult due to the
restrictions of the arc, making it more challenging to treat some tumors.
A lumbar puncture, or spinal tap, is a procedure used to withdraw a small sample
of cerebrospinal fluid so that it can be examined for abnormal cells.
A malignant tumor is cancerous and behaves in an aggressive manner.
Meningiomas are thin membranes that cover the brain and develop from the
meninges. They appear most often in middle-aged adults and children.
A metastatic tumor is caused by cancer cells that originate elsewhere in the
body and travel to the current site through the bloodstream.
MRI (Magnetic Resonance Imaging)
MRI uses a magnetic field rather than x-rays to produce a better picture of a
tumor that is located near a bone. An MRI does not use radiation.
PET (Positron Emission Tomography)
PET is an imaging technique that provides a picture of brain activity by
measuring levels of injected glucose sugar labeled with a radioactive marker.
Primary Brain Tumor
A primary brain tumor arises from cells in the brain or surrounding tissue.
Multi-jointed robotic arm
Utilized by the CyberKnife Radiosurgery system, the multi-jointed robotic arm
enables access to previously unreachable tumors and reduces damage to
surrounding critical structures.
Non-isocentric treatment is a system of radiation in which beams originate from
arbitrary points in the workspace and are delivered to the lesion. The result is
an even concentration of radiation within the lesion. Non-isocentric radiation
is offered exclusively with CyberKnife Radiosurgery.
Six Degrees of Freedom
The CyberKnife system’s computer-controlled robotic arm has six degrees of
freedom. The robot can position the linac to more than 100 specific locations,
or nodes. Each node has 12 possible approach angles, translating to over 1,200
possible beam positions—the greatest flexibility of approach available in any
stereotactic radiosurgery system.
Stereotactic imaging is the ability for a physician to identify the 3D location
of a tumor with a high degree of accuracy.
Stereotactic radiotherapy (SRT)
Stereotactic radiotherapy delivers lower doses of focused radiation over a
series of treatment sessions, giving a larger overall dose of radiation to the
tumor. Each treatment is called a fraction, therefore, this type of therapy is
sometimes called a “fractionated” therapy. A bite block that fixes to the
patient’s upper teeth or mask may be used in place of a head frame for head
Stereotactic radiosurgery (SRS)
Stereotactic radiosurgery delivers a high dose of radiation, generally in one
treatment. For brain surgery, SRS generally requires the use of a stereotactic
frame that is fixed onto the patient’s skull. The CyberKnife system allows
physicians to perform SRS procedures without the use of a stereotactic frame,
which can be less traumatic and less painful for the patient.
Tight-to-the-Tumor accuracy is available only with the CyberKnife system and
allows for the treatment of complexly shaped tumors. T4 accuracy is made
possible with the CyberKnife system’s unique combination of a proprietary image
guidance system and a multi-jointed robotic arm.
The CyberKnife system provides a wide range of treatment options, including the
ability to use either forward or inverse treatment planning, allowing the
physician to customize each patient’s treatment plan.
Forward treatment planning
The physician determines what dose to deliver from a particular targeting
position. The planning software calculates the total dose within the lesion.
Inverse treatment planning
The physician specifies the total dose to be delivered to the tumor and sets
boundaries to protect critical structures. The software determines targeting
positions and the dose to be delivered from a particular targeting position.