- For Patients

Glossary of terms

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data integrity
When transferring information, it is necessary to verify that the information arrived exactly as it was sent and was not modified.

To reduce the size of a tumor without completely eliminating it, by surgical or other means. This often makes the tumor more responsive to chemotherapy or radiotherapy.

deep sedation
See sedation, deep.

deep vein thrombosis
A condition in which a blood clot forms in a main vein that returns blood flow from the extremities back to the heart and lungs. This type of clot may grow big enough to completely block the vein or can pose a serious risk if part of it breaks off and travels to the lungs.

Also called implanted cardiac defibrillator (ICD). A pacemaker-like device that continuously monitors the heart rhythm and delivers lifesaving shocks if a dangerous heart rhythm is detected.

definitive treatment
Primary treatment designed to provide a disease cure.

The process of modifying identifiers within medical data so that the information does not include protected health information (PHI).

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.

A method for imaging density.

Thickness or mass.

deoxyribonucleic acid (DNA)
Acid found in cell nuclei that is the basis of heredity.

diabetes (diabetes mellitus)
AA metabolic disease in which carbohydrate utilization is reduced while lipid and protein usage is enhanced; it is caused by a complete or relative deficiency of insulin and is characterized in more severe cases by chronic hyperglycemia, glycosuria, water and electrolyte loss, ketoacidosis, and coma. Long-term complications include: development of disorders of the nervous system, eyes and kidneys; generalized degenerative changes in large and small blood vessels; and an increased susceptibility to infection.

diagnostic ultrasound
Procedure that uses - a transducer (probe) to generate high frequency sound waves (2-12MHz) to produce images of the body’s internal structures for medical diagnostic purposes.

A method of removing waste materials from the body when the kidneys are not working properly.

dialysis arteriovenous fistula
A surgically created connection between an artery and vein in the arm of patients who need to undergo hemodialysis, a process in which blood is removed from the body, cleansed and then returned to the body. The fistula causes the vein to become enlarged, and allows blood to be easily withdrawn and replaced during dialysis.


  1. A plate-like muscular structure that separates the chest from the abdominal cavity.
  2. The dividing membrane between the chest and abdominal cavity.

diaphragmatic hiatus
An abnormal opening in the diaphragm.

An abnormally frequent discharge of semisolid or fluid fecal matter from the bowel.

Dietitians work with patients to help maintain nutrition. They monitor patients' weight and nutritional problems. Dietitians educate patients and may provide them with recipes and nutritional supplements to improve their nutritional status before, during and after treatment. Dietitians attend four years of college then usually take part in a one-year internship. The American Dietetic Association registers dietitians who have passed a professional examination.

diffuse axonal injury
See shear injury.

diffusion tensor imaging (DTI)
A variation of conventional magnetic resonance imaging (MRI) that creates vivid color pictures of the paths of innumerable nerve fibers in the white matter of the brain by analyzing the movement of water molecules along the fibers. Pictures of these fiber pathways can be helpful in assessing damage to brain by many disease processes, including trauma and brain tumors.

digestive system
A complex process that enables the body to break down and absorb food and eliminate waste; it includes the digestive tract, a long twisting tube that extends from the mouth to the anus (the digestive tract) and various organs.

digestive tract
A series of hollow organs joined in a long, twisting tube from the mouth to the anus that is part of the digestive system, a complex process that enables the body to break down and absorb food and eliminate waste.

digital certificate
A special secure data file that accompanies an electronic message to verify the identity of the user sending the message, and enabling the user to encrypt the message so that it can only be read by its intended recipient.

digital rectal exam
An examination of the lower rectum and the prostate gland in males to check for abnormalities. The term "digital" refers to the clinician's use of a lubricated finger to conduct the exam.

dilation and curettage (D&C)
A procedure in which the cervix is dilated and the inner lining of the uterus is scraped to remove the uterine contents.

A device or substance used to enlarge a hollow structure or opening.

A tear in the wall of a blood vessel that allows blood under pressure to flow between the layers of the wall, making the tear worse.

An inflammation or infection of the diverticulum.

A pouch or a pocket-like opening in the bowel wall, usually in the colon. You might think of it as a "bubble" through a weak point in the bowel wall.

See deoxyribonucleic acid (DNA).

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:

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.

Double-contrast barium enema (DCBE)
Also called lower GI tract radiography
A test in which a barium solution and air are introduced into the colon and a series of x-rays are taken of the entire colon and rectum. A single-contrast barium enema without air also is available.

A medication that is injected into the membranes lining the pleural cavity, causing an inflammatory reaction that shrinks the space between the lungs and chest wall to minimize the buildup of fluid in the cavity.

drug-eluting stent
A semi-rigid, tube-like device used to keep an artery open after angioplasty. The stent is made of metal and coated with medication that is slowly released (eluted) to help prevent the growth of scar tissue in the artery lining.

ductal carcinoma in situ (DCIS)
A breast cancer that has not spread beyond the lining (epithelium) of the milk ducts into the surrounding breast tissue. While DCIS must be treated to prevent it from developing into an invasive breast cancer, it is not harmful at this stage.

The first part of the small intestine immediately below the stomach.

dura mater
The outermost layer of three meninges, or membranes, that surround the spinal cord and the brain. In Latin, it means "tough mother." The name is apt, because the membrane is thick and strong, and normally firmly attached to the inner side of the skull.

Impaired swallowing.