Ablative Dose

The optimized radiation dose that will kill tumor cells while minimizing damage to healthy brain tissue.


Additional cancer treatment that is prescribed after an initial cancer treatment (e.g., radiation treatment after brain tumor surgery); objective is to eliminate any cancer left after the first treatment or prevent the cancer from coming back.


This organ is part of the brain’s limbic system, which supports a variety of functions and emotions; it is located at the end of the hippocampus and is responsible for the response and memory of emotions, especially fear.


The use of medication to put patients into a deep sleep during a surgical procedureso the patient does not feel pain.


The most numerous of the brain’s glial cells; they are large and star-shaped with many branches.


One of the groups of brain tumors called ‘glioma’ tumors; they originate in specific star-shaped glial cells; this is the most common brain tumor, accounting for about half of all primary brain and spinal cord tumors.


A tumor or growth that is typically non-cancerous, grows slowly, and does not spread to other parts of the body. This type of tumor usually causes neurologic problems that are related to its location in the brain. 

Biologically Effective Dose (BED)

The amount of an absorbed compound that reaches targets or sites of action within the body to cause a biologic effect. In this case, the desired biological effect is to kill tumor cells using radiation.


Radiotherapy in which the source of radiation is placed (usually through implantation) in, or close to, the area being treated.

Brain Mapping

A study of the anatomy and functions of the brain and spinal cord through the use of imaging: designed to understand the structures and functions of the brain. It is also used to guide interventions (e.g. surgery or radiation therapy) to minimize potential injury related to treatment.

Brain Stem

The part of the brain composed of the midbrain, pons, and medulla oblongata and connecting the spinal cord with the forebrain and cerebrum; controls the flow of messages between the brain and the rest of the body; controls basic body functions like heart rate, blood pressure, breathing and swallowing.

Central Nervous System (CNS)

The part of the nervous system that includes the brain and spinal cord; sensory impulses are transmitted to the CNS and motor impulses pass out from the CNS; coordinates all neurologic activity.


The back part of the brain that maintains balance and posture; coordinates voluntary and involuntary postural movement and is involved with motor, learning and cognitive functions.

Cerebral Cortex

The outermost layer of the brain; divided into the frontal, parietal, temporal and occipital lobes; the cerebral cortex is responsible for the processes of thought, perception and memory and serves as the seat of advanced motor function, social abilities, language and problem solving. These functions are also called ‘higher cognitive functions.’


Pertaining to or affecting the brain and spinal cord or these two together.

Cerebrospinal Fluid (CSF)

A colorless, watery liquid that occupies the ventricular system around and inside the brain and spinal cord.


The largest part of the brain; it is made up of the two cerebral hemispheres (right and left) and controls and integrates motor, sensory and higher mental function such as thought and reason.


The use of chemicals compounds to treat or control a disease (such as cancer).

Computer-Aided Surgery (CAS)

A surgical concept that uses computer technology for pre-surgical planning, and for guiding or performing brain tumor surgical interventions. Also called image guided surgery, surgical navigation and neuronavigation, CAS guides the surgeon directly to the tumor, minimizing injury to the healthy brain tissue.

Computerized Tomography (CT)

A non-invasive diagnostic test in which a three-dimensional image of the body structure is constructed by computer from a series of cross-sectional images made along the long axis of the body.

Conical Collimators

A metal cone-shaped device that is attached to the linear accelerator to reduce the spread of the beam of radiation as it is emitted from the machine.

Corpus Callosum

A wide, flat bundle of neural fibers beneath the cortex, which connects the right and left hemispheres of the brain and facilitates inter-hemispheric communication.

Course of Treatment

A prescribed medical regimen to be followed for a specific period of time.


A surgical operation in which a bone flap is temporarily removed from the skull to access the brain; a craniotomy is the most commonly performed surgery for brain tumor removal.

Critical Structures

Important parts of the brain with unique and specialized functions, e.g., blood vessels, glands, nerves, brain stem, and central nervous system, whose loss cannot be replaced and results in functional injury.


Treatment that aims to cure the disease or heal the patient not just alleviate symptoms associated with the brain tumor.


A device or substance used for the analysis or detection of diseases or other medical conditions.

Diffusion Tensor Imaging (DTI)

Imaging data that can be used to perform fiber tractography – 3D model of neural tracts – within white matter. Fiber tracking algorithms can be used to track a fiber along its whole length (e.g. tracking the corticospinal tract with a model of the motor information transit from the motor cortex to the spinal cord and the peripheral nerves).


To distort or damage the appearance of (something or someone).

Dose Spillage

The amount of radiation that extends, or spills, into healthy tissue surrounding the tumor.


An excessive accumulation or abnormal infiltration of serous fluid (any of various body fluids resembling serum, especially lymph) in connective tissue or in a serous cavity.

Effective Dose

The desired radiation dose required to kill tumor cells.


Related to the system of glands that secrete hormones, which are distributed throughout the body via the bloodstream.


A type of tumor that develops from tissue of the central nervous system, typically near the ventricles.

External Beam Radiation

A method for delivering a beam or several beams of high-energy X-Rays to a patient’s tumor. The beams are generated outside the patient and are targeted at the tumor site. This form of treatment is sometimes called teletherapy.

Fiber Tracking

In neuroscience, tractography is a 3D modeling technique used to visually represent neural tracts using data collected by diffusion tensor imaging (DTI). It uses special techniques of magnetic resonance imaging (MRI), and computer-based image analysis. The results are presented in two- and three-dimensional images.


Immobilized or attached using a special headframe for surgical or radiation therapy procedures.


A full dose of radiation can divided into a number of smaller doses called fractions. This allows healthy cells to recover between treatments. All the fractions in a series of treatment sessions make up a course of radiotherapy.


Treatment that does not require the use of a headframe for patient immobilization.

Frameless Stereotactic Radiosurgery

Stereotactic radiosurgery, which is specialized external beam radiation, where a patient wears a non-invasive custom-fitted facemask instead of a frame, which must be attached to the head.


Relating to, or adjacent to the forehead or the frontal bone.


A device that houses the mechanics of a linear accelerator; rotates around the patient to deliver radiation therapy also called radiotherapy and stereotactic radiosurgery; used to treat cancer from different angles. A frame housing the X-Ray tube, collimators, and detectors in a CT machine, with a large opening into which the patient is inserted; a mechanical support for mounting a device to be moved in a circular path.


Specialized organs or cell groups, e.g. pituitary gland that release substances into the body and from the body for many different purposes.


The most abundant cell types in the central nervous system; glia, also called neuroglia, cells have many responsibilities and are often called the ‘glue’ that surrounds and supports the brain’s nerve cells and performs many different functions.


Cells made up of glia.


The most common and most aggressive malignant primary brain tumor in humans derived from glial cells.


A type of tumor that starts in the glial cells of the brain or spine. It is called a glioma because it arises from glial cells.

Global Positioning System (GPS)

Technology that utilizes satellites, computers and receivers that together can determine the latitude and longitude of a receiver on Earth; the same principles are used for neuronavigation or surgical navigation systems.


Either of the two symmetrical halves of the brain’s cerebrum called right brain and left-brain.


It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation; located under the cerebral cortex.

Hyperfractionated Radiation Therapy

Radiation, or radiotherapy treatment in which the total dose of radiation is divided into small doses and treatments are given more than once a day.


Radiation treatment in which the total dose of radiation is divided into large doses and treatments are given once a day or less often. Hypofractionated radiation therapy is given over a shorter period of time (fewer days or weeks) than standard radiation therapy.


Located above the pituitary gland and below the thalamus in the brain; responsible for certain metabolic processes and other activities of the autonomic nervous system; synthesizes and secretes certain neurohormones, often called releasing hormones or hypothalamic hormones, and these in turn stimulate or inhibit the secretion of pituitary hormones; controls body temperature, hunger, important aspects of parenting and attachment behaviors, thirst, fatigue, sleep, and circadian rhythms.

Image Guided Radiation Therapy (IGRT)

Computer technology that uses diagnostic images to create a three-dimensional model of a brain tumor, which is used to help plan the treatment and then guide the radiation beam during treatment delivery.

Image Guided Surgery (IGS)

See definition for Computer-Aided Surgery (CAS).


Rigidly fixed or attached using a non-invasive custom-fit mask or a headframe for surgical and radiation therapy procedures.

Intraoperative Radiation Therapy (IORT)

A specialized cancer treatment where intensive radiation is administered to a tumor during surgery to reach any microscopic cancer that may remain.

Left Brain

Left hemisphere of the brain; controls right side of the body; typically responsible for tasks that involve logic like science and mathematics, language and reasoning although this may be different depending upon whether the person is right- or left-handed.

Limbic System

A group of subcortical structures of the brain that are concerned especially with emotion and motivation.

Linear Accelerator (LINAC)

The device most commonly used for external beam radiation therapy for cancer treatment.

Magnetic Resonance Imaging (MRI)

A technique that uses a strong magnetic field and radio waves to produce detailed images of the organs and tissues inside of a person’s body. Most MRI machines use large tube-shaped magnets.

Magnetic Resonance Spectroscopy (MRS)

A noninvasive technique that is similar to magnetic resonance imaging but uses a stronger field and is used to monitor body chemistry (as in metabolism) rather than anatomical structures.


A descriptive term for diseases that are very invasive and have the propensity to spread to other parts of the brain, spine, or body.

Margin of Error

The practice of including the area around a tumor in the planned radiation dose to ensure that the tumor is completely covered by the treatment. A margin of error may mean that healthy tissue will receive high doses of radiation, potentially causing side effects.


The inner core or deep part of an organ or body structure; also called medullary substance.

Medulla Oblongata

Located in the lower part of the brain stem; very important part of the brain; responsible for involuntary actions that sustain life like breathing, blood pressure, heart rate, swallowing and transferring messages from the brain to the spinal cord.


Also called cerebellar primitive neuroectodermal tumor (PNET), this malignant primary tumor originates in the region of the brain at the base of the skull called the posterior fossa; can spread to other parts of the brain and spinal cord. 


One or more malignant tumors composed of melanocytes, occurring especially in the skin and often as a result of excessive exposure to sunlight.


Usually benign, these tumors grow slowly and derive from the meninges, the membranous layers surrounding the central nervous system.


Cancer cells that spread to the brain from other sites of the body (e.g. lung or breast tumors).


A type of glia, or non-neural cell; they are the resident macrophages – a type of white blood cell – of the brain and spinal cord, and thus act as the first and main form of active immune defense in the central nervous system.


To move from one place to another; when a cancer is metastatic, it spreads, or migrates, from one part of the body to another.

Minimally Invasive

Used to describe a medical procedure where the surgical incisions are minimized or smaller than traditional incisions to help reduce the impact of the surgery and the trauma to the body.

Multi-Leaf Collimator

A multileaf collimator (MLC) is a device made up of individual "leaves" of metal (usually tungsten) that can move independently in and out of the path of the radiation beam in order to block it. MLCs are used on linear accelerators to provide conformal shaping of radiotherapy treatment beams.


In medicine, a group of clinicians from different specialties and subspecialties that work together to develop the best care plan for the patient.


A body tissue that can contract and produce movement as well as maintain the position of parts of the body.


Localized death of living tissue.


Any of the filamentous bands of nervous tissue that connect parts of the nervous system with the other organs, conduct nerve impulses, and are made up of axons and dendrites together with protective and supportive structures.


See definition of ‘glia.’


A cell that processes information and that is the basic unit of the central nervous system.


See definition for Computer-Aided Surgery (CAS).


Not made up of the brain’s glial cells.


See definition for benign.


Done without cutting the body or entering the body; can also apply to a tumor that does not invade other parts of the brain or body.


A type of glia, or neuroglia, cell; its main functions are to provide support and insulation to axons in the central nervous system.


A rare, slow-growing brain tumor that is believed to originate in the oligodendrocytes or a glial precursor cell.

Optic Nerve

A paired nerve that transmits visual information from the retina to the brain.


The bony socket that contains an eye.


Medical care with the goal of improving quality of life by relieving pain and symptoms caused by a tumor without attempting a cure.

Parietal / Parietal Lobe

Upper posterior, or back of the head or brain; the parietal lobe is one of the four major lobes of the cerebral cortex (see cerebral cortex) and is involved in sensory information and language processing.


In radiation treatment, charged particles may be used and directed at the tumor to shrink it and kill the cancer cells.

Perfusion MRI

A diagnostic tool that uses a contrast agent—a fluid injected into the blood during the brain scan so that the brain’s blood vessels can be studied.


In medicine, a physicist is concerned with clinical service and consultation, research and development and teaching; in radiation oncology, the physicist is responsible for the planning of radiation treatments for cancer patients. They are also responsible for a variety of machine and treatment plan checks to ensure that treatments are safe and delivered as intended.

Physiological / Physiologically

The normal and healthy operation of your body and organs.

Pituitary Adenoma

A tumor that develops from cells in the pituitary gland.


Located above the medulla oblongata; responsible for sending signals or messages between several areas of the brain, especially between the upper and lower parts of the brain; plays a role in sleeping and dreaming.

Position Emission Tomography (PET)

A specialized imaging test that uses a radioactive substance, called a tracer, to identify certain conditions or diseases in the body.

Posterior Cranial Fossa

Part of the intracranial cavity that contains the brainstem and cerebellum.


Generally refers to the care a patient receives before undergoing a surgical procedure; can be used to refer to scans taken before a procedure and also the planning of a procedure.

Primary Brain Tumor

A mass, or group, of abnormal cells that start in the brain.

Radiation Oncologist

A specialist physician who uses radiation in the treatment of cancer.

Radiation Therapist

A specialist on the radiation oncology team who works with patients being treated for cancer.


A medical procedure used to treat tumors with the precise delivery of a high-dose of radiation in a single treatment session. Focused radiation beams are delivered to a targeted area of the brain or body; this procedure is non-invasive meaning there is no surgical incision.


A naturally occurring radioactive chemical element.

Registration (in Radiation Therapy)

The concept and set of methods needed to orient or correlate a live patient’s position with a virtual 3D data set gathered by computer medical imaging. This procedure is crucial in image guided surgery in order to track the clinical situation of the patient during surgery via the preoperative registration data.

Renal Cell Carcinoma(s)

The most common type of kidney cancer, renal cell carcinoma begins in the lining of the renal tubules in the kidney. The renal tubules filter the blood and produce urine. Also called hypernephroma, renal cell adenocarcinoma, and renal cell cancer.

Right Brain

Right half of the brain; controls left side of the body; typically responsible for tasks that involve creativity like imagination, intuition and insight, art, music and three-dimensional forms although this may be different depending upon whether the person is right- or left-handed.


A tumor or tumors that begin in bone or in the soft tissues of the body, including cartilage, fat, muscle, blood vessels, fibrous tissue, or other connective or supportive tissue. Different types of sarcoma are based on where the cancer forms. For example, osteosarcoma forms in bone, liposarcoma forms in fat, and rhabdomyosarcoma forms in muscle.


Relating to the senses themselves—sight, smell, hearing, touch, taste; also relating to sensation or the perception of stimulus or to the voyage made by incoming nerve impulses from the sense organs to the nerve centers or to the senses.


In stereotactic radiosurgery (SRS), the word "stereotactic" refers to a three-dimensional coordinate system. This system enables accurate correlation of a virtual target seen in the patient's diagnostic images with the actual target position in the patient.

Stereotactic Radiosurgery (SRS)

A radiation therapy procedure that uses specialized equipment to position the patient and precisely deliver a large radiation dose to a tumor and not to healthy tissue. This is not a traditional surgery where an incision is made and tissue removed. It is used to treat brain tumors and other brain disorders by delivering ablative (obliterative) radiation doses. It is also being studied in the treatment of other types of cancer, such as lung cancer. Also called radiation surgery, radiosurgery, stereotactic external beam radiation, stereotactic radiation therapy and stereotactic radiosurgery.

Stereotactic Surgery

Surgery guided by a coordinate system (or imaging), designed to be minimally invasive.

Sub-Millimetric Accuracy

Accuracy, in this case for radiosurgery, measured in units that are smaller than a millimeter; very highly accurate.

Surface Matching

A computerized process that allows doctors to match and orient actual patient anatomy to a three-dimensional computer model made from diagnostic exams (also referred to as “registration”); used in image guided surgery and stereotactic radiosurgery for precision treatment of tumors. An alternative (traditional) technique for registration is the use of fiducial - or land marking - markers attached to the patient’s head. An additional scan (CT or MR) including the markers allows for their detection on the images and a point-to-point matching of their position using the pointer.

Surgical Navigation

See definition for Computer-Aided Surgery (CAS).


To appoint as a substitute, in this case, using facial, or surface, markers instead of internal anatomy to define a focal point for radiation.

Systemic Radio-isotope Therapy

Cancer treatment that uses radioactive substances, such as radioactive iodine, to treat certain types of cancer via the blood stream; also called nuclear medicine.


The uppermost part of the midbrain also called the ceiling; located at the back section of the brain stem; processes auditory input as well as some visual reflexes.


A general area within the brainstem; located between the ventricular system and distinctive basal or ventral structures at each level.


Near the temple or the sides of the skull behind the orbits; the temporal lobe is one of the four major lobes of the cerebral cortex (see cerebral cortex) and is involved in processing sensory input.


Located below the corpus callosum; responsible for directing sensory signals to the appropriate lobes of the cerebral cortex that arrive in the brain from other parts of the body.


Concerned with the treatment of disease.


The path of an object; in image guided surgery, the prescribed pathway to the tumor as defined by the neuronavigation system.

Treatment Couch

Specialized table that the patient lies on while radiation treatment is being delivered.

Vestibular Schwannoma

A benign, slow-growing tumor that develops from the balance and hearing nerves supplying the inner ear. Also called an acoustic neuroma and is located in the cerebellum-pontine angle (CPA).


Noun: Powerful invisible rays that can pass through various objects and that make it possible to see inside things (such as the human body) Verb: To examine and make images of (things, such as the bones and organs inside the body) by X-Rays.