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GLOSSARY OF TERMS
Arterial Venous MalformationAn abnormal, cluster of tangled blood vessels, arteries
and veins, within the brain or spine that is at risk of bleeding. Depending on the AVM’s location, bleeding can cause
symptoms ranging from headaches and seizures to paralysis and even death.
Benign Tumor A tumor that is not cancerous or malignant. It does not spread to other parts of the body, but can be
equally as dangerous as a cancerous or malignant tumor if it is compressing vital structures, such as blood vessels or nerves
or over producing certain hormones.
Chemotherapy Cancer treatment that is administered through the use of drugs that are injected into the body or taken
orally over a period of time. This is a form of systemic therapy – i.e. as the drugs circulate in the bloodstream, the
entire body is affected.
CNS (Central Nervous System) Referring to the collection of nerves and structures that make up the brain and spinal
cord.
Critical Structure Refers to normal tissues near the tumor. Damage to critical structures can often lead to problems
for patients and side effects. For example, the spinal cord is the primary critical structure of concern when treating spinal
lesions.
CT (Computerized Tomography) A diagnostic imaging technique where an X-ray machine and computer are used to create
detailed 3D images of tissues and structures in the body. A dye, or contrast agent, may be injected into the patient to highlight
structures and abnormalities.
Extracranial Refers to any location of the body “outside of the skull”. Examples of extracranial sites
include the spine, lung, pancreas and other areas of the body.
Fiducials Fiducials are markers that are placed into a tumor for the purpose of better identifying and tracking a
tumor on an X-ray.
Fractionation Fiducials are markers that are placed into a tumor for the purpose of better identifying and tracking
a tumor on an X-ray.
Head Frame (Stereotactic Head Frame)An external metal ring that is attached to the patient’s skull with four
screws. It contains markers (fiducials) that are visualized on a CT and/or MRI scan. Local anesthesia is used during the frame
attachment procedure. The use of a frame is required for some radiosurgery treatments, such as the Gamma Knife®.
Intracranial Refers to “inside the skull” or brain.
Malignant Tumor Abnormal collections of cells that can invade and destroy nearby and distant tissues and organs.
MRI (Magnetic Resonance Imaging)An imaging technique that uses magnetic fields rather than X-rays to create 3D images
of structures in the body. An MRI generally provides more detailed images of soft tissue anatomy (as opposed to bone) compared
to a CT scan. A dye may be injected prior to the scan to improve visualization of many tumors. MRI scans are painless.
PET (Positron Emission Tomography)An imaging technique that provides a picture of cellular activity by measuring
positrons emitted from injected substances "labeled" with a radioactive marker. PET scans help determine if a lesion
has increased activity that may be a sign of rapid cell growth indicating a tumor.
Stereotactic (Stereotaxis or Stereotaxy) Stereo” makes reference to one’s position within 3-dimensional
space. Stereotaxy or stereotaxis is the science and practice of precisely locating a tumor within 3D space.
Treatment Planning Customizing the radiosurgery treatment parameters (such as radiation dose and shape of the field)
to the individual patient using specialized software. The process is typically computer-based and involves integrating information
from CT/MRI scans to delineate and contour the target. The treating physician must define a specific dose and other key treatment
parameters depending on pathology and the location of nearby critical structures. Typically the treating surgeon, radiation
oncologist and medical physicist are all involved in this process.
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