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Glossary of terms

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narcotic
A substance that is used medically to relive pain and/or produce a state of drowsiness or sleep.

nasal cavity
A system of air channels connecting the nose with the back of the throat.

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.

necrosis
The death of living tissue.

needle aspiration
The removal of living tissue for microscopic examination by suction through a fine needle attached to a syringe. The procedure is used primarily to obtain cells from a lesion containing fluid.

needle biopsy
Removal of tissue or suspensions of cells from living patients through a small needle for diagnostic examination.

needle electrode
A fine wire through which electrical current may flow when attached to a power source; used to carry high frequency electrical currents that create heat or destroy diseased tissue (called radiofrequency ablation) or seal blood vessels. There are two types of needle electrodes: a simple straight needle; and a straight, hollow needle that contains several retractable electrodes that extend when needed. Needle electrodes may also be a part of devices that monitor electrical activity for diagnostic purposes such as in the performance of electromyography and nerve conduction studies.

neoadjuvant treatment
A treatment given prior to the main or primary treatment.

neonatal intensive care unit (NICU)
An intensive care unit containing specialized equipment to treat and care for premature or critically ill newborn babies.

neoplasm
An abnormal tissue that grows by cellular proliferation more rapidly than normal and continues to grow after the stimuli that initiated the new growth cease. Neoplasms show partial or complete lack of structural organization and functional coordination with the normal tissue, and usually form a distinct mass of tissue, which may be either benign (benign tumor) or malignant (cancer).

nephrogenic
Of or related to the kidney.

nephrogenic systemic fibrosis
A rare complication that may occur in some patients with kidney disease who undergo an MRI with contrast material. It causes a thickening of the skin, organs and other tissues.

nephropathy
Damage to or disease of the kidney.

nerve cell
See neuron.

nerve fibers
Also called axons.
Threadlike extensions from a nerve cell.

neuroendovascular treatments
Procedures in which miniature instruments or a catheter containing medications are inserted into a blood vessel in the brain to treat vascular disease or abnormalities.

neurofibrillary tangles
Abnormal structures that form inside neurons considered one of the hallmarks of Alzheimer’s disease (AD).

neurologic
Pertaining to the nervous system and its disorders.

neurologist
A physician who specializes in the diagnosis and treatment of diseases and conditions related to the brain and nervous system.

neuron
Also called a nerve cell.
A specialized cell in the brain and nervous system that receives and sends electrical impulses through networks of connections.

neuro-oncologist
A doctor who specializes in diagnosing and treating brain tumors and other tumors of the nervous system.

neuroradiology
The clinical subspecialty concerned with the diagnostic radiology of diseases of the central nervous system, head, and neck.

neurostimulators
Devices that are implanted into the spine and connected to internal or external generators to stimulate the nerves as a means of disrupting pain signals or causing organs to function more efficiently.

nodule
A small, solid lump. A lump can be benign or malignant.

non-Hodgkin lymphoma
One of two major categories of lymphoma, a cancer of the blood, that begins in either the B cells or T cells of the immune system.

noninvasive
A noninvasive procedure does not require any skin incision or the insertion of any instruments or medical devices. Examples include CT and MR scanning and ultrasound.

non-pharmacological sedation
See sedation, non-pharmacological.

nonradiologic
Not related to radiology.

nonrepudiation
Nonrepudiation ensures that a party cannot argue the validity of a statement or contract, that a transferred message has been sent and received by the parties claiming to have sent and received the message; methods include digital signature, the use of public and private keys, and auditing of all user activity.

NSAID
A non-steroidal anti-inflammatory drug that reduces swelling and pain, such as aspirin and ibuprofen.

nuclear medicine
The clinical discipline concerned with the diagnostic and therapeutic uses of radionuclides (an isotope of artificial or natural origin that exhibits radioactivity), excluding the therapeutic use of sealed radiation sources.

Certain imaging procedures, including PET scanning, employ radionuclides to provide real-time visuals of biochemical processes. One device, a nuclear imaging machine, employs a scintillation camera, which can rotate around the body to pick up radiation emitted by an injected substance (e.g., radioactive iodine, which localizes in the thyroid, or radioactive thallium, which localizes in the heart). A digitized image of a particular organ, or the whole body, is produced.

nucleus
The center part of intervertebral discs, sponge-like cushions between the vertebrae, or bones, of the spine. The nucleus is filled with a soft, rubber-like material.

numbing agent
See local anesthetic ("numbing agent").