Category: A

The process of converting an analog signal (the value of some continuously varying quantity) into a discrete digital signal (a series of numbers).  

A process in which nonradioactive source holders are placed in a patient during an operative procedure. These serve to provide radiographic information used for dosimetric evaluation and to receive the radioactive sources after the patient has returned to his room. In brachytherapy, the insertion of the radioactive source after the placement of the applicator has…

A machine that accelerates particles to high energies. Medical accelerators include betatrons, cyclotrons, and linear accelerators (linacs). Accelerators are used for the treatment of tumors and the production of radiopharmaceuticals used for medical imaging. Anything that increases action or function. The revolutionary apparatus propels electrically charged subatomic particles to extraordinary levels of energy. These minute…

Rate of absorption of energy (in milliwatts) per cubic centimeter.  

The energy transferred to material by the interaction of radiation. Dose is specified in joules per kilogram (or ergs per gram). The current S.I. unit of dose is the gray (Gy) which is 1 J /kg. The older unit, the RAD, has a magnitude of 100 erg/g and thus 1 rad = 0.01 Gy. In…

The physical and psychological symptoms that result when a person who is dependent on alcohol suddenly stops drinking. The neurological, psychiatric, and cardiovascular signs and symptoms that result when a person accustomed to consuming large quantities of alcohol suddenly becomes abstinent. Alcohol withdrawal usually follows a predictable pattern. In the first hours of abstinence, patients…

Bleeding from the vagina at times other than during a menstrual period, or bleeding during a period that is heavier than usual. In women of reproductive age, causes of abnormal vaginal bleeding can include the use of birth control pills; hormonal imbalances; infections of the reproductive system, including sexually transmitted diseases; an ectopic pregnancy; and…

Irritation of the bladder that is not caused by infection; also known as noninfectious cystitis. The condition is most common in women of childbearing age and rarely occurs in men. Possible causes include bubble baths, feminine hygiene sprays, sanitary napkins, spermicidal jellies, and sexual intercourse. Syndrome experienced by women, marked by acute dysuria, urinary frequency,…

A type of bean used in many food products that may have significant health benefits. In laboratory tests, a chemical in soybeans has been of benefit in limiting the growth of cancer cells. A number of studies in humans have demonstrated that soy protein lowers total cholesterol and LDL (low-density lipoprotein) cholesterol without lowering HDL…

Disease of the kidneys associated with excessive use of over-the-counter painkillers, or analgesics. Nonprescription analgesics—including aspirin, acetaminophen, ibuprofen, and naproxen—do not cause kidney damage in most people when the recommended dosage is taken. For people who have risk factors such as advanced age, systemic lupus erythematosus, or chronic kidney conditions, and for those who have…