Tech Glossary

Stereo or binocular vision created by two optical channels. Three-dimensional vision combines the separate images seen by each eye into one composite image, which gives the surgeon the ability to perceive depth and judge distances in the surgical field.

Knowledge of the exact form, position, size and relationship of the various structures of the human body.

Matter composed of antiparticles.

A subatomic particle identical to another subatomic particle in mass but opposite to it in electromagnetic properties.

In chemistry and physics, the smallest particle of a chemical element that retains its chemical properties. Atoms are made up of the subatomic particles electrons, protons and neutrons.

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.

Refers to a tumor that is not considered life-threatening.

Benign tumors are not cancerous; however, they may need to be treated. Some benign tumors may change over time and become malignant.

Material used in PET imaging, less effective than newer LSO crystal technology.

Related to the study of chemical processes in living organisms.

A medical test involving the removal and examination of tissue, cells or fluids.

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.

Cancer of the bladder, the organ that stores urine until it is passed from the body.

A malignant growth or tumor caused by an uncontrolled division of abnormal cells.

A malignant growth or tumor caused by an uncontrolled division of abnormal cells.

The branch of medicine that deals with the study of the heart and its actions and diseases.

Relating to or involving the heart and blood vessels.

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.

The brain and spinal cord together form the CNS.

During certain types of radiation treatment, cold spots are areas on the target that receive underdosing. Consequently, tumor cells may not be fully destroyed.

A heart condition caused by reduced blood flow through the coronary arteries, typically resulting in chest pain or heart damage.

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.


Computed tomography; a diagnostic imaging technique in which a series of two-dimensional x-rays taken from many different vantage points are combined by a computer to form a detailed, three-dimensional image of the body’s internal structures.

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.

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 normal tissue.

A condition caused by insufficient production of insulin and resulting in abnormal metabolism of carbohydrates, fats and proteins.

A negatively charged subatomic particle that orbits the nucleus of the atom.

When an electron collides with its antiparticle, a positron, causing both elements to be completely destroyed and resulting in the emission of gamma rays.

An illuminated usually fiber-optic tubular instrument used to visualize the interior of a hollow organ or other part of the body; often used with a video monitor and camera.

Compounds used in x-ray imaging to improve the visibility of internal bodily structures; also referred to as a contrast agent or radiocontrast agent.


Short for fluorodeoxyglucose; a type of radioactive glucose (sugar) and the most common radioisotope used in PET/CT scanning.

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 tumor.

The physician determines what dose to deliver from a particular targeting position. The planning software calculates the total dose within the lesion.

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.

A form of high-frequency, high-energy light emission produced from subatomic particle interaction, such as electron-positron annihilation.

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 gliomas.

A simple form of sugar and the body’s main source of energy; also referred to as blood sugar.

The branch of medicine that deals with the diseases and routine physical care of the female reproductive system.

The time required for half of the atoms of a radioactive substance to decay.

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.

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.

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 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.

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.

Isocentric treatment, or multi-isocentric treatment, involves packing the lesion with a single (or multiple, overlapping) spherically shaped dose distributions.

Cancer of the kidneys, the organs that remove waste from the blood and help in red blood cell production and blood pressure regulation.

A type of minimally invasive surgery that uses a surgical camera called a laparoscope or endoscope that is inserted into the body through small incisions, providing surgeons with a two-dimensional view of the abdominal cavity.

Abnormal tissue in the body caused by disease or trauma.

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.

Material used in PET imaging; currently allows for the shortest possible scan times and highest quality PET images.

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.

Refers to a tumor that is considered life-threatening.

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.

The process by which organisms convert nutrients into the biochemical tools and structures needed to sustain life.

The spread of cancer cells from the initial or primary site of origin to another part of the body.

A metastatic tumor is caused by cancer cells that originate elsewhere in the body and travel to the current site through the bloodstream.

Also known as MIS, minimal access, keyhole, laparoscopic or endoscopic surgery, minimally invasive surgery was developed to eliminate the most physically and emotionally traumatic elements of conventional open surgery, including pain and lengthy recovery. Advances in minimally invasive surgery allow surgeons access to internal structures through very small incisions.

The inflow valve located between the left upper chamber of the heart (atrium) and the left lower chamber (ventricle). The mitral valve helps keep blood flowing in the right direction by closing when the ventricle contracts in order to prevent blood from escaping back into the atrium.

A surgical heart procedure that corrects the narrowing (stenosis) or leakage (regurgitation) of the mitral valve.


Magnetic resonance imaging; a noninvasive diagnostic technique that uses radio frequency signals to obtain computerized images of internal structures.

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.

Utilized by the CyberKnife Radiosurgery system, the multi-jointed robotic arm enables access to previously unreachable tumors and reduces damage to surrounding critical structures.

The branch of medicine dealing with disorders of the central nervous system (includes brain, brain stem and nerves).

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.

The positively charged center of an atom, comprised of the subatomic particles protons and neutrons.

The medical subspecialty dealing with the study and treatment of cancer.

Any surgical procedure that uses a large incision to allow surgeons direct access the affected organs or tissue.

Any of the basic units of matter and energy (molecule, atom, proton or electron)


Positron emission technology; a diagnostic imaging technique in which a radioisotope injected into the bloodstream is used to create color-coded, computerized images of the body’s metabolic activity.

A single scanner that simultaneously performs PET and CT imaging; one of the most advanced cancer-detecting technologies available today.

PET is an imaging technique that provides a picture of brain activity by measuring levels of injected glucose sugar labeled with a radioactive marker.

A positively charged subatomic particle that is the antiparticle of an electron.

A primary brain tumor arises from cells in the brain or surrounding tissue.

Cancer of the prostate, the male reproductive gland located below the bladder and in front of the rectum responsible for urinary control and the secretion of the fluid component of semen.

Surgical removal of all or part of the prostate to treat and prevent the reoccurrence of prostate cancer.

Emitting particles or energy that is the result of the disintegration of atomic nuclei.

An atom with an unstable nucleus; used in PET/CT scanning to create images of the body’s metabolic activity.

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.

Determining how far cancer has spread, taking into account the size of the tumor, how deep it has penetrated, whether it has invaded adjacent organs, if and how many lymph nodes it has spread to, and whether it has spread to distant organs.

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.

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 treatments.

Stereotactic imaging is the ability for a physician to identify the 3D location of a tumor with a high degree of accuracy.

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.

A duct that transports urine from the kidney to the bladder.

A condition characterized by a blockage in the urinary tract, usually present at birth.

Of or relating to the organs or functions of excretion and reproduction.

The field of medicine that deals with the urinary or urogenital tract.

A disease or condition of the blood vessels.

A condition in which urine backs up into the ureters and/or kidneys as a result of a malfunctioning valve at the junction of the ureter and bladder.

A photograph or digital image obtained by passing electromagnetic radiation through the body’s internal structures and creating images from the different degrees to which the radiation is absorbed.

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.