Category: B

The abnormal swinging, flinging, and jerking movements that are sometimes seen in Huntington chorea (a progressive disorder involving degeneration of nerve cells in the cerebrum) or other diseases affecting the basal ganglia (clusters of nerve cells deep within the brain). Ballistic movements are involuntary and uncontrollable. They are caused by irregular muscle contractions and most…

An antibiotic available as a cream, spray, or ointment used to treat infections from minor cuts, scrapes, or burns. Bacitracin is widely available without a prescription, both as a brand name and a generic product. It treats or prevents infections caused by many bacteria, including various types of Staphylococcus and Streptococcus organisms. Discomfort, ranging from…

The majority of x rays produced when electrons strike a target are caused by radiative losses arising from deceleration of these electrons. Thus, bremsstrahlung (German for “braking radiation”) radiation forms the bulk of those x rays emitted from a diagnostic or therapy x-ray unit.  

A plot of the ionization per unit path of an ionizing particle. Certain particles exhibit a peak near the end of the track which means that they have the potential to irradiate deep seated tumors while significantly sparing overlying, normal tissues.  

Electric currents that occur in living tissues. Muscle and nerve tissue, for example, are generators of bioelectricity, although the potentials registered may be less than one millivolt.    

A device used for accelerating electrons which are used for radiotherapy treatments. The electrons may be made to strike a target before leaving the machine, thus producing x rays as a second treatment modality. A circular electron accelerator that produces either high energy electrons or x-ray photons. An apparatus known as a magnetic induction accelerator…

The S.I. unit of radioactivity, equal to one radioactive decay per second. An Si-derived unit of activity of a radionuclide equal to the quantity of the material having one spontaneous nuclear transition, i.e., disintegrations, per second. One curie has 3.7 X 10¹⁰ transitions per second. Thus, one curie is equivalent to 3.7 X 10¹⁰ becquerels.…

Sudden, short episodes of dizziness brought on by a change in the position of the head or body. Benign positional vertigo, also called benign paroxysmal positional vertigo (BPPV), results when small crystals of calcium carbonate collect within a part of the inner ear that is responsible for balance. In half of all cases, the cause…

Blockage or narrowing of the tube that normally drains tears from a child’s eyes. Many babies are born with the condition, usually because the membrane covering the ducts at birth fails to disappear. In older babies and children, blocked tear ducts most often result from an inflammation such as conjunctivitis. In newborns who have blocked…