RadiologyInfo.org

Glossary of terms

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magnetic field gradient
In magnetic resonance imaging, a magnetic field that varies with location, superimposed on the main uniform field of the magnet, to alter the resonant frequency of nuclei and allow detection of their spatial position.

magnetic resonance angiography (MRA)
A method of angiography utilizing the magnetic properties of tissues and body fluids rather than x-rays to record images. For details see the MR Angiography page.

magnetic resonance cholangiopancreatography (MRCP)
A special type of magnetic resonance imaging (MRI) exam that produces detailed images of the hepatobiliary and pancreatic systems, including the liver, gallbladder, bile ducts, pancreas and pancreatic duct. See the MRCP page for additional information.

magnetic resonance imaging (MRI)
A diagnostic radiologic modality, in which the nuclei of the hydrogen atoms in a patient are aligned in a strong, uniform magnetic field, absorb energy from tuned radio pulses, then emit radio signals. These signals are converted into images which appear as cross-sectional slices of the patient’s body.

malignant
Cancerous cells, also called a tumor, able to grow into surrounding tissue, spread to other parts of the body and destroy normal cells. Malignant is also less commonly used to describe other medical conditions that are severe and becoming progressively worse.

mammography
Imaging examination of the breast by means of x-rays, used for screening and diagnosis of breast disease. Ultrasound and magnetic resonance may also be used to image the breast. For details see the Mammography page.

mandible
The lower jaw.

margin
Also called a surgical margin.
A small amount of healthy tissue surrounding a tumor that may be surgically removed with diseased tissue.

maxilla
The upper jaw.

media
One of the two innermost layers of the walls of the carotid arteries.

mediastinum
The central part of the chest cavity, behind the sternum and between the two lungs. This space is mostly occupied by the heart and its major blood vessels, and by the trachea and esophagus.

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 years of college, 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.

melanoma
A malignant tumor, usually in the skin, that develops from a pigmented lesion over a period of months or years.

membrane
A thin layer of tissue that covers a surface, lines a cavity, or divides space in the body.

meninges
Thin layers of tissue, or membrane, that surround and cover the brain and spinal cord.

meningitis
Inflammation in the meninges, the covering of the brain and spinal cord, often caused by a virus or bacteria.

menopause
The point in a woman's life when she stops menstruating, or having periods.

menstrual cycle
A recurring cycle during a woman’s reproductive life in which the lining of the uterus prepares for pregnancy; if pregnancy does not occur the lining is shed.

menstruation
A cyclical shedding of the lining, or endometrium, of a woman’s uterus when no pregnancy occurs. Women typically experience menstruation (also called a period) on a monthly basis throughout their sexually reproductive years, from puberty until menopause, except when pregnant or breastfeeding.

mesentery
Abdominal membrane that connects the intestines to the abdominal cavity.

metabolic rate
The amount of energy or heat expended by the body in a given unit of time as a result of the body's metabolism, or all of its chemical processes.

metabolism
The sum total of all chemical processes in the body that result in growth, energy, waste elimination and other body functions following food digestion and the distribution of nutrients in the blood.

metastases
The spread of a disease process from one part of the body to another, as in the appearance of abnormal tissue growths (malignant or nonmalignant) in parts of the body remote from the site of the primary tumor.

metastasize
To spread to another part of the body, usually through the blood vessels, lymph channels, or spinal fluid.

metastatic tumor
A cancerous tumor formed when cancer cells located elsewhere in the body break away and spread to a new site.

Metformin
See Glucophage.

microstent
A small wire mesh tube-like device used to hold open an artery following balloon angioplasty.

midline catheter
A special type of catheter used in a vascular access procedure that is inserted inside a major vein for a period of weeks so that blood can be repeatedly drawn or medication and nutrients can be injected into the patient’s bloodstream on regular basis. Unlike a standard intravenous catheter (IV) which is for short term use, a vascular access catheter is more durable and does not easily become blocked or infected. The midline catheter is 4-6 inches in length.

migraine headache
A type of headache that may include intense, throbbing pain often on one side of the head, nausea, vomiting and sensitivity to light, sound and exertion, as well as a visual disturbance called an aura.

mild cognitive impairment (MCI)
A condition in which memory or other cognitive functions are below normal but do not interfere with daily functioning. MCI is considered a transitional state between normal forgetfulness and dementia.

mild traumatic brain injury
See concussion.

milk ducts
Small tubes within the breast that carry breast milk from the lobule to the nipple.

milliroentgens
One-thousandth of a roentgen (the international unit of exposure dose for x-rays or gamma rays).

mini stroke
See Transient Ischemic Attack (TIA).

minimal and moderate sedation
See sedation, minimal and moderate.

minimally invasive
A minimally invasive procedure requires a small skin puncture or very limited incision to perform the intervention, which typically involves the insertion of miniaturized instruments. Common examples of minimally invasive procedures would be stereotactic breast biopsy, heart catheterization or temporary placement of an implanted port for chemotherapy.

modality
A form of application or employment of a therapeutic agent or regimen.

monoclonal antibodies
A laboratory-produced molecule that is engineered to recognize and bind to the surface of cancer cells. Monoclonal antibodies mimic the antibodies naturally produced by the body's immune system that attack invading foreign substances, such as bacteria and viruses.

monoclonal antibody therapy
Also called targeted therapy
A treatment involving laboratory-produced molecules called monoclonal antibodies that are engineered to recognize and bind to the surface of cancer cells. When combined with a chemotherapy drug or radioactive material, monoclonal antibodies are able to deliver the cancer-killing agent directly to the cancer cell.

mortality
The rate of death from a particular disease or condition in a defined population.

MR enterography
A special type of magnetic resonance imaging (MRI) performed with a contrast material to produce detailed images of the small intestine.

MR spectroscopy (MRS)
A variation of conventional magnetic resonance imaging (MRI). This diagnostic imaging technique measures the concentration of metabolites, which are produced by chemical reactions in the brain and other areas of the body, and displays the results as a graph. The peaks in the graph represent various metabolites. The concentration of these metabolites can be altered by many diseases, including tumor, infections and trauma.

mucous
A slimy substance secreted by glands in mucous membranes. Mucous helps protect and lubricate surfaces within the body.

multi-detector computed tomography (MDCT)
A form of computed tomography technology with a two-dimensional (2-D) detector that produces multiple, thinner slices in a single rotation and a shorter period of time allowing for more detail and additional view capabilities.

multiple myeloma
An uncommon disease that occurs more frequently in men than in women and is associated with anemia, hemorrhage, recurrent infections, and weakness.

multiple sclerosis
A degenerative disease affecting the central nervous system in which the sheaths around nerve fibers in the brain and spinal cord are damaged.

musculoskeletal
Relating to muscles and to the skeleton, as, for example, the musculoskeletal system.

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. See the Myelography page for more information.

myeloma
A tumor of the bone marrow. Multiple myeloma is an uncommon cancer of the white blood cells in the bone marrow that is associated with anemia, hemorrhage, recurrent infections, and weakness.

myocardial infarction
Also known as a heart attack, it occurs when the supply of blood to the heart is blocked. If blood flow is not quickly restored, the section of the heart wall involved may begin to die.

myocardial perfusion scan
The most common cardiac nuclear medicine procedure, which results in imaging of blood-flow patterns to the heart muscles.

myomas
Masses of fiber and muscle tissue in the wall of the uterus, also known as leiomyomas or fibroid tumors. Although these tumors are not cancerous, they may cause heavy menstrual bleeding, pain in the pelvic region and pressure on the bladder or bowel.

myomectomy
The surgical removal of fibroids from a woman’s uterus.

myometrium
The muscular walls of the uterus.

myopathy
A muscle disease characterized by muscle weakness that usually results in the deterioration of muscle.