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Glossary

A

Abdominal Aorta: Part of the aorta, the largest artery in the body; it supplies oxygenated blood to the abdominal and pelvic organs and legs
Abdominal Aortic Aneurysm: The general definition of AAA is an aorta that is 4cm or greater. It's a disease of elderly men and the most common location is infrarenal. The risk factors of AAA include atherosclerosis, HTN, smoking, male gender, hyperlipidemia and an advanced age. AAA is often associated with other vascular diseases. The commonly used radiologic studies for AAA include Xray, US, CT, MRI, and arteriography.
Abdominal Ct Scan: Computed Tomography scan, sometimes referred to as CAT scan (computerized axial tomography). Used to image the abdomen.
Abdominal Ultrasound: Ultrasound imaging, also known as ultrasound scanning or sonography, is a method of obtaining images from inside the human body through the use of high frequency sound waves. The soundwaves' echoes are recorded and displayed as a real-time, visual image. No ionizing radiation is involved in ultrasound imaging.
Ablation: Also know as radiofrequency ablation. A treatment technique that uses high-frequency alternating electrical current to destroy tissue cells by heating them.
Abscess: A localized infection consisting of pus surrounded by inflamed tissue.
Absorption: 1. In radiology, the uptake of energy from radiation by the tissue or medium through which it passes. 2. In radiation or medical physics, the number of disintegrations per second of a radionuclide.
Angiocardiography: X-ray imaging of the heart and great vessels made visible by injection of a radiopaque solution.
Angiogram: An imaging study depicting blood vessels. In a conventional angiogram, a dye is injected into the bloodstream and x-rays are taken to visualize the blood vessels. In other instances, CT or MRI can be used to create three-dimensional pictures of blood vessels.
Angiographic: Relating to or utilizing angiography.
Artifact: In radiology, something artificial that appears on a medical image but is not a part of the living tissue being examined. The image distortion could be due to an obstruction, such as a surgical metal clip, or to a problem with the imaging equipment.
Attenuation: Loss of energy of a beam of radiant energy due to absorption, scattering, beam divergence, and other causes as the beam propagates through a medium.

B

Becquerel (Bq): The SI unit of measurement of radioactivity, equal to 1 disintegration per second; 1 Bq = 0.027 _ 10-9 Ci.
Brachytherapy: Also called internal radiation therapy. A type of radiation therapy used to treat cancer, involving the placement of a radioactive material, either temporarily or permanently, directly inside the body.

C

Catheter Angiography: An examination of blood vessels by injecting contrast material directly into an artery through a small plastic tube.
Cobalt-60 Radiation Therapy: Cobalt-60-based or photon radiation therapy machines are used exclusively to treat brain tumors and abnormalities.
Color Doppler: Color Doppler uses a computer to convert the Doppler measurements into an array of colors. This color visualization is combined with a standard ultrasound picture of a blood vessel to show the speed and direction of blood flow through the vessel.
Computed Tomography (CT) Angiography: A method of examining blood vessels utilizing x-rays and injection of iodine-containing contrast medium.
Conformal Radiation Therapy: Use of a CT image to tailor the radiotherapy beam to the exact size and shape of a tumor.
Curie (C, C, Ci): A unit of measurement of radioactivity, 3.70 _1010 disintegrations per second; formerly defined as the radioactivity of the amount of radon in equilibrium with 1 gm. of radium; superseded by the S.I. unit, the becquerel (1 disintegration per second). Origin [Marie (1867-1934) and Pierre (1859-1906) Curie, French chemists and physicists and Nobel laureates]
Cyclotron: A type of particle accelerator in which charged particles are propelled by an alternating electric field between two large electrodes in a constant magnetic field created by two large magnets. The particles are injected at the center of the magnet and spiral outward as their energy increases. Protons produced in a cyclotron can be used to treat cancer, and cyclotron-produced protons can create radioisotopes for nuclear medical procedures.
Cystography: Radiography of the bladder, following injection of a radiopaque substance.

D

Delivery Device: In brachytherapy treatment of cancer, a means of delivering a sealed radioactive substance to the site of a tumor inside the body, such as a catheter, tiny needle or applicator.
Densitometry: A method for imaging density.
Diagnostic Ultrasound: The use of ultrasound to obtain images for medical diagnostic purposes, typically employing frequencies ranging from 2 MHz to about 12 MHz.
Doppler Ultrasound: An application of diagnostic ultrasound used to detect moving blood cells or other moving structures and measure their direction and speed of movement. The Doppler effect is used to evaluate movement by measuring changes in frequency of the echoes reflected from moving structures. In many instances, Doppler ultrasound has replaced x-ray methods such as angiography, as a method to evaluate blood vessels and blood flow. Doppler ultrasound permits real-time viewing of blood flow that cannot be obtained by other methods. Doppler ultrasound has proved a boon in all areas of ultrasound, aiding in the evaluation of the major arteries and veins of the body, the heart, and in obstetrics for fetal monitoring. Types of Doppler ultrasound include Color Doppler, Power Doppler and Spectral Doppler.
Dosimetrists: Dosimetrists carefully calculate the dose of radiation to make sure the tumor gets enough radiation. They develop a number of treatment plans that can best destroy the tumor while sparing the normal tissues. Many of these treatment plans are very complex. Dosimetrists work with the doctor and the medical physicist to choose the treatment plan that is just right for each patient. Many dosimetrists start as radiation therapists, then, with very intensive training, become dosimetrists. Others are graduates of one-to-two-year dosimetry programs. The Medical Dosimetrist Certification Board certifies dosimetrists.

E

Electromagnetic Radiation: Radiation consisting of electric and magnetic waves that travel at the speed of light, such as light, radio waves, gamma rays and x-rays.
Electronic Detector: The part of a digital imaging system that captures and converts x-rays as they pass through a patient into digital signals which are in turn sent to a computer to produce images.
Encephalography: Radiographic representation of the brain.
Endorectal Coil: A wire coil that is inserted through a small plastic tube into the rectum as part of a magnetic resonance imaging (MRI) exam to obtain more detailed images of the prostate gland or other internal body structures.
Endovaginal Ultrasonography: Pelvic ultrasonography using a probe inserted into the vagina.
External Beam Therapy: External beam therapy is used to aim highly focused beams of radiation at the edges of the site where cancer is found in order to destroy any abnormal cells and prevent the growth or regrowth of the tumor.

F

Fluoroscope: A device that projects radiographic (x-ray) images in a movie-like sequence onto a screen monitor.
Fractionation: The process of administering a dose of radiation in smaller units over time, as opposed to a single large dose, to minimize tissue damage.

G

Gamma Camera: A camera that records the distribution of a chemical containing a radionuclide that is attracted to a specific organ or tissue of interest.
Gamma Knife: A cobalt-60 based radiation therapy machine used to treat brain tumors and abnormalities. The Gamma Knife delivers 201 beams of highly focused gamma rays to the treatment site.
Gamma Radiation: (Also called gamma rays.) A very high frequency form of electromagnetic radiation that consists of photons emitted by radioactive elements. Gamma rays can injure and destroy body cells and tissue, especially cell nuclei.
Gantry: A frame housing the x-ray tube, collimators, and detectors in a CT or radiation therapy 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.

H

High-dose Rate (HDR) Brachytherapy: One of two types of temporary brachytherapy, a radiation therapy treatment for cancer that involves the placement of a radioactive material directly inside the body, in or near a tumor, for a specific amount of time and then withdrawn. In HDR brachytherapy, a high dose of radiation is delivered to the tumor in a short burst, lasting only a few minutes. This treatment may be repeated several times in a day or a number of times over one or more weeks.
Hyperfractionation: The process of administering a dose of radiation in smaller units two to three times a day, as opposed to a larger amount once a day.
Hysterosalpingography: Radiography of the uterus and fallopian tubes after the injection of radiopaque material.
Hysterosonography: Sonography of the uterus and fallopian tubes using a transvaginal probe following the injection of sterile saline into the uterus.

I

Image Recording Plate: Part of an electronic detector used in a digital imaging system. An x-ray machine produces a small burst of radiation that passes through the body, recording an image either on photographic film or, in a digital system, on the image recording plate of an electronic detector, a device that converts the x-rays into digital signals which are in turn sent to a computer to produce images.
Image-guided Biopsy: The use of imaging modalities, such as ultrasound, mammography or MRI, to assist in targeting a lesion too small to be felt so that cells can be removed from the suspicious area and examined under a microscope to determine whether the abnormality is cancerous.
Interventional Radiologist: A radiologist who specializes in the use of fluoroscopy, CT, and ultrasound to guide passage through the skin by needle puncture, including introduction of wires and catheters for performing procedures such as biopsies, draining fluids, inserting catheters, or dilating or stenting narrowed ducts or vessels.
Intraoperative Radiation Therapy: Radiation treatment of cancer or other diseases done during surgery.
Intraosseous Venography: A procedure in which an x-ray, or venogram, is taken of a bone after a special dye is injected into bone marrow, the soft substance that fills the hollow center of most bones.
Intravenous Pyelography (IVP): Radiography of kidneys, ureters, and bladder following injection of contrast medium into a peripheral vein.
Ionizing Radiation: Radiation of sufficient energy to dissociate atoms or molecules into electrically charged atoms or radicals in the irradiated material.
Irradiation: 1. The subjective enlargement of a bright object seen against a dark background. 2. Exposure to the action of electromagnetic radiation (e.g., heats, lights, x-rays).
Isotope: One of two or more nuclides that are chemically identical, having the same number of protons, yet differ in mass number, since their nuclei contain different numbers of neutrons; individual isotopes are named with the inclusion of their mass number in the superior position (12C) and the atomic number (nuclear protons) in the inferior position (6C). In former usage, the mass numbers follow the chemical symbol (C-12).

L

Linear Accelerator (LINAC): A device imparting high velocity and energy to atomic and subatomic particles; an important device for radiation therapy.
Low Dose Rate (LDR) Brachytherapy: A radiation therapy treatment for cancer that involves the placement of a radioactive material directly inside the body, in or near a tumor, for a specific amount of time and then withdrawn. In LDR brachytherapy, the patient is treated with a low dose of radiation for hours at a time.
Lymphangiography: A diagnostic x-ray procedure that requires surgical incisions and injections directly into the lymphatic system. This procedure has been replaced by lymphoscintigraphy.
Lymphoscintigraphy: A special type of noninvasive nuclear medicine imaging that provides pictures called scintigrams of the lymphatic system.

M

Magnetic Field Gradient: In magnetic resonance imaging, a magnetic field that varies with location, superimposed on the uniform field of the magnet, to alter the resonant frequency of nuclei and allow recovery of their spatial position.
Magnetic Resonance Cholangiopancreatography: Magnetic Resonance Cholangiopancreatography (MRCP) is an examination of the bile ducts and pancreas using magnetic resonance imaging.
Medical Radiation Physicists: Qualified medical physicists work directly with the doctor in the treatment planning and delivery. They oversee the work of the dosimetrist and help ensure that complex treatments are properly tailored for each patient. Qualified medical physicists are responsible for developing and directing quality control programs for equipment and procedures. They are responsible for making sure the equipment works properly. Medical radiation physicists take precise measurements of radiation beam characteristics and do other safety tests on a regular basis. Qualified medical physicists have doctorates or master's degrees. Qualified medical physicists have completed four year of college. They also have had two to four years of graduate school and typically one to two years of clinical physics training. They are certified by the American Board of Radiology or the American Board of Medical Physics.
Milliroentgens: One-thousandth of a roentgen (the international unit of exposure dose for x-rays or gamma rays).
MR Spectroscopy: A form of magnetic resonance imaging that provides chemical information on an organ or structure of the body at the cellular level.
Myelogram: An x-ray taken after injecting contrast material into the space surrounding the spinal cord. Its purpose is to identify spinal lesions caused by disease or injury.
Myelography: A radiographic procedure using contrast material to visualize the spinal column and its contents.

N

Natural Background Exposure: Radiation is a natural part of life. It has existed since the beginning of time and is an integral part of the universe in which we live. Life as we know it on earth has evolved in the presence of radiation. Radiation comes to us from many sources both natural and man-made. These sources include cosmic radiation from outer space, radiation from the soil and buildings, and natural isotopes in our own bodies. Cosmic radiation and terrestrial radiation vary with location.

P

Pancreatography: Radiographic demonstration of the pancreatic ducts, after injection of radiopaque material into the distal duct.
Parathyroid Imaging: Evaluation of the parathyroid glands (typically four small raisin sized glands in the neck primarily involved in the regulation of calcium and phosphorus levels in the body) can be accomplished with a nuclear medicine technique using a material called Sestamibi or the parathyroid glands can be imaged with ultrasound, CT or MRI.
Particle Beam Radiation Therapy: Particle or proton beam radiation therapy is a type of radiation therapy that uses protons as the source of radiation rather than x-rays. Protons can pass through healthy tissue without damaging it.
Permanent Brachytherapy: Also called seed implantation. A radiation therapy treatment for cancer in which radioactive material sealed inside a seed or pellet is placed and permanently left inside the body in or near a tumor.
Photon Radiation Therapy: See cobalt-60 radiation therapy.
Portography: Imaging of the portal circulation by x-rays, using contrast material, usually introduced into the spleen or into the portal vein at operation.
Power Doppler: Power Doppler is a newer technique that is more sensitive at detecting blood flow than color Doppler. Power Doppler is able to obtain images that are difficult or impossible to obtain using standard color Doppler and to provide greater detail of blood flow, especially in vessels that are located inside organs. Although power Doppler may be more sensitive than color Doppler for detection and demonstration of blood flow, power Doppler provides no information about the direction of flow. Color and spectral Doppler both reveal the direction of blood flow which can be valuable information.
Prophylactic Cranial Radiation: Exposure of the brain to low-dose radiation in a cancer patient in order to prevent the tumor from spreading to this site.
Proton Beam Radiation Therapy: See particle beam radiation therapy.
Pyelography: Radiologic study of the kidney, ureters, and usually the bladder, performed with the aid of a contrast material either injected intravenously, or directly through a ureteral or nephrostomy catheter or percutaneously.

R

Rad: The unit for the dose absorbed from ionizing radiation, equivalent to 100 ergs per gram of tissue; 100 rad = 1 Gy. Symbol for radian. Abbreviation for racemic.
Radiation: The act or condition of diverging in all directions from a center; the sending forth of light, short radio waves, ultraviolet or x-rays, or any other rays for treatment or diagnosis or for other purpose; radiant energy from waves or subatomic particles.
Radiation Dermatosis: Skin changes at the site of ionizing radiation, particularly redness of the skin due to capillary dilatation in the acute stage, temporary or permanent loss of hair, and chronic changes in the epidermis and dermis resembling a premalignant warty lesion.
Radiation Oncologist: Radiation oncologists are the doctors who oversee the care of each cancer patient undergoing radiation treatment. They develop and prescribe each cancer patient's treatment plan. They make sure that every treatment is accurately given. They monitor the patient's progress and adjust treatment to make sure patients get quality care throughout treatment. Radiation oncologists also help identify and treat any side effects of radiation therapy. They work closely with other physicians, and all members of the radiation oncology team. Radiation oncologists have completed four years of college, four years of medical school, one year of general medical training, then four years of residency (specialty) training in radiation oncology. They have extensive training in the safe use of radiation to treat disease. If they pass a special examination, they are certified by the American Board of Radiology. Patients should ask if their doctor is board certified.
Radiation Oncology: The medical specialty of radiation therapy; the study of radiation treatment of abnormal tissue growths (malignant or nonmalignant).
Radiation Pneumonitis: Inflammation of lung tissue caused by exposure to radiation therapy.
Radiation Therapist: Radiation therapists work with radiation oncologists. They administer the daily radiation treatment under the doctor's prescription and supervision. They maintain daily records and regularly check the treatment machines to make sure they are working properly. Radiation therapists go through a two-to-four year educational program following high school or college. They take a special examination and must be certified by the American Registry of Radiologic Technologists. In addition, many states require that radiation therapists be licensed.
Radiation Therapy: Treatment for non-malignant conditions and/or cancer through the use of x-rays or radionuclides.
Radiation Units: There are a number of units to measure radiation dose and exposure: (1) rad or radiation absorbed doseÑthe amount of radiant energy absorbed in a certain amount of tissue; (2) rem or roentgen-equivalent-man--the amount of radiant energy absorbed in a certain amount of tissue. A unit of measurement that takes into account different biological responses to different kinds of radiation. The radiation quantity measured by the rem is called equivalent dose; millirem--one thousandth of a rem, the unit for measuring equivalent dose; roentgen (R, r)--the international unit of exposure dose for x-rays or gamma rays. Roentgens are named after Professor Wilhelm Konrad Roentgen, the man who discovered x-rays in 1895; sievert (Sv)--the unit for measuring ionizing radiation effective dose, which accounts for relative sensitivities of different tissues and organs exposed to radiation. The radiation quantity measured by the sievert is called effective dose; millisievert (mSv)--one thousandth of a sievert, the unit for measuring effective dose.
Radioactive Iodine I-131: Also called radioiodine I-131. A radioactive isotope created from iodine to emit radiation for medical use.
Radioactive Iodine I-131 Therapy: The use of radioactive iodine I-131 to treat an overactive thyroid, a condition called hyperthyroidism. When a small amount of I-131 is swallowed, it is absorbed into the bloodstream in the gastrointestinal (GI) tract and concentrated from the blood by the thyroid gland, where it begins destroying the glandÕs cells.
Radioactive Material: Also called radioactive substance. As used in the brachytherapy treatment of cancer, a radioactive material is sealed inside a seed or pellet and placed inside the body, in or near a tumor. The radiation material used in brachytherapy comes from radioactive iodine 125, strontium 89, phosphorous, palladium, cesium, iridium, phosphate, or cobalt.
Radiographic: Referring to the examination of any part of the body for diagnostic purposes by means of x-rays or other diagnostic modalities.
Radiography: Examination of any part of the body for diagnostic purposes by means of x-rays with the record of the findings usually impressed upon a photographic film.
Radioisotope Bone Scan: A nuclear imaging examination that produces pictures of bones to help detect abnormalities caused by disease or injury. During a bone scan, a small amount of radioactive material is injected into the body and collects in the bones.
Radiologist: A physician trained in the diagnostic and/or therapeutic use of x-rays and radionuclides, radiation physics, and biology; a diagnostic radiologist may also be trained in diagnostic ultrasound and magnetic resonance imaging and applicable physics.
Radionuclide: An isotope of artificial or natural origin that exhibits radioactivity. Radionuclides serve as agents in nuclear medicine and genetic engineering, play a role in computer imaging for diagnosis and experiment, and account for a percentage of background radiation to which humans are exposed. In cancer therapy, radionuclides are used to destroy tumors.
Radiopaque: Impenetrable by x-rays or any other form of radiation.
Radiotherapy: The medical specialty concerned with the use of electromagnetic or particulate radiation in the treatment of disease.
Roentgen (R, R): The international unit of exposure dose for x-rays or gamma rays; that quantity of radiation that will produce in 1 cm of air at STP, or 0.001293 g of air, 2.08 _109 ions of both signs, each totaling 1 electrostatic unit (e.s.u.) of charge; in the MKS system this is 2.58 _10-4 coulombs per kg of air.

S

Scan(s): 1. To survey by traversing with an active or passive sensing device; 2. The image, record, or data obtained by scanning, usually identified by the technology or device employed; e.g., CT scan, radionuclide scan, ultrasound scan, etc.; 3. Abbreviated form of scintiscan (scintigraphy), usually identified by the organ or structure examined; e.g., brain scan, bone scan, etc.
Scintigraphy: A diagnostic procedure consisting of the administration of a radionuclide with an affinity for the organ or tissue of interest, followed by recording the distribution of the radioactivity with a stationary or scanning external scintillation camera.
Screening Mammography: Imaging examination of the breast by means of x-rays, of individuals usually without symptoms to detect those with a high probability of having breast disease.
Short-bore MRI System: type of magnetic resonance imaging (MRI) unit. The traditional MRI unit is a large cylinder-shaped tube surrounded by a circular magnet. The patient lies on a moveable examination table that slides in the center of the magnet. The short-bore system is designed so that the body part that is being scanned remains in the magnet. The short-bore nature of the magnet allows the body part not being scanned to potentially be "outside" of the magnet. Patients often report the short-bore MRI system is less claustrophobic than a traditional MRI unit.
Sonographer: An allied health professional who has been specifically trained to perform ultrasound examinations. Many sonographers are certified by a registry of sonographers, provided they meet strict training requirements and pass examinations in basic ultrasound science and clinical applications.
Sonography: The location, measurement, or delineation of deep structures by measuring the reflection or transmission of high frequency or ultrasonic waves. Computer calculation of the distance to the sound reflecting or absorbing surface plus the known orientation of the sound beam gives a two- or three-dimensional image. Syn: ultrasonography.
Spectral Doppler: Instead of displaying Doppler measurements visually as in the color and power Doppler methods, spectral Doppler displays the blood flow measurements graphically, in terms of the distance traveled per unit of time.
Splenoportography: Introduction of radiopaque material into the spleen to obtain an x-ray visualization of the portal vessel of the portal circulation.
Spot Films: X-rays of a localized region, usually under study by fluoroscopy.
Stereotactic Biopsy: An x-ray procedure that uses multiple coordinates to precisely determine the location of a tumor or nodule so that a tissue sample may be obtained.
Stereotactic Radiosurgery: A highly precise form of radiation therapy that directs narrow beams of radiation from different angles at a brain tumor or abnormality. Using a device that keeps the head completely still, this treatment minimizes the amount of radiation to healthy brain tissue.
Stereotactic Radiotherapy: A form of stereotactic radiosurgery using fractionated radiation dose (smaller dose over a period of days or weeks) or hyperfractioned dose (smaller dose two to three times a day), as opposed to a single large dose, to minimize tissue damage.
Synchrotron: A cyclic particle accelerator in which the magnetic field (to turn the particles so they circulate) and the electric field (to accelerate the particles) are synchronized with the traveling particle beam. While the cyclotron uses a constant magnetic field and a constant frequency electric field, both are varied in the synchrotron. This allows for construction of large rings that can accelerate particles to much higher energies than a cyclotron which has a limited magnet size. The synchrotron uses multiple separate bending magnets and narrow bore tubes to connect them. It can be used to produce high energy protons and other particles such as carbon ions that are used to treat cancer. In addition the energy of the particles can be varied as needed which is very difficult in a cyclotron.

T

Technetium-99m: A radiotracer commonly used in nuclear medicine for many different types of examination. It decays within 24 hours, leaving no residual radiation.
Temporary Brachytherapy: A radiation therapy treatment for cancer in which radioactive material sealed inside a seed or pellet is placed inside the body in or near a tumor for a specified amount of time and then withdrawn. This treatment can be administered at a low dose rate (LDR) or high dose rate (HDR).
Therapeutic Radiology: A medical specialty and the study of radiation treatment of abnormal tissue (nonmalignant or cancerous) through the use of x-rays or radionuclides.
Thyroid Scan: A nuclear medicine examination that helps evaluate the structure of the thyroid. The thyroid is a gland in the neck that controls metabolism, a chemical process that regulates the rate at which the body functions.

U

Ultrasonography: The location, measurement, or delineation of deep structures by measuring the reflection or transmission of high frequency or ultrasonic waves. Computer calculation of the distance to the sound-reflecting or absorbing surface plus the known orientation of the sound beam gives a two- or three-dimensional image.
Ultrasound, Diagnostic: Ultrasound imaging, also known as ultrasound scanning or sonography, is a method of obtaining images from inside the human body through the use of high frequency sound waves. The soundwaves' echoes are recorded and displayed as a real-time, visual image. No ionizing radiation is involved in ultrasound imaging.
Urography: Radiography of any part (kidneys, ureters, or bladder) of the urinary tract.

V

Vasography: Radiography of the the secretory duct of the testicle (vas deferens), to determine patency (the state of being freely open), by injecting contrast medium into its opening either through the urethra or by incision into the vas deferens.
Venogram: X-ray imaging of the veins following contrast material injection into the veins.
Venography: A type of x-ray in which contrast material is injected into a vein to show the details of its structure and any abnormality that may be present.

X

X-ray: 1. The ionizing electromagnetic radiation emitted from a highly evacuated tube, resulting from the excitation of the inner orbital electrons by the bombardment of the target anode with a stream of electrons from a heated cathode. 2. Ionizing electromagnetic radiation produced by the excitation of the inner orbital electrons of an atom by other processes, such as nuclear delay and its sequelae. 3. A radiograph.
X-ray Therapy: A medical specialty and the study of radiation treatment of abnormal tissue (nonmalignant or cancerous) through the use of x-rays or radionuclides.