| back-pressure renal atrophy | <radiology> Caliectasis without obstruction, due to repeated episodes of obstruction, gradual loss of renal pyramids (12 Dec 1998) |
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| backache | Non-specific term used to describe back pain; generally refers to pain below the cervical level. (05 Mar 2000) |
| backboard splint | A board splint with slots for fixation by straps; shorter ones are used for neck injuries, longer ones for back injuries. (05 Mar 2000) |
| backbone | <anatomy> The spinal column, found in vertebrate animals, which runs along the dorsal side and contains the central nerve cord (spinal cord). The main structural feature of a polymer (chain-like) molecule from which many side chains branch off. (09 Oct 1997) |
| backed | Having a back; fitted with a back; as, a backed electrotype or stereotype plate. Used in composition; as, broad- backed; hump-backed. Source: Websters Dictionary (01 Mar 1998) |
| backfill | <ecology> Soil, overburden, mine waste or imported material used to replace material removed during mining. (09 Oct 1997) |
| backflow | The reversal of the normal flow of a current. See: regurgitation. (05 Mar 2000) |
| backflushing | <procedure> A process used to clean filters or membranes of particles by reversing the flow of fluid through the system. (09 Oct 1997) |
| background level | The average amount of a substance present in the environment. Originally referring to naturally occurring phenomena. Used in toxic substance monitoring. (05 Dec 1998) |
| background radiation | <radiobiology> Level of environmental radation due to background sources. Background sources can be natural, such as cosmic rays and natural radioactive elements (principally radon, but including other elements such as isotopes of potassium (which people get substantial amounts of in foods like bananas)). They can also be man-made, such as from fossil-fuel combustion, everyday leakage from nuclear activities, and leftover from atmospheric nuclear weapons tests. Background radiation is usually distinguished from acute radiation, such as from medical X-rays, nuclear accidents, radioisotope therapy, or other short-term doses. The man-made contribution to background radiation is quite small compared to the natural contribution, medical uses dominate human exposure to acute radiation. (09 Oct 1997) |
| background retinopathy | <ophthalmology, pathology> Early stage of diabetic retinopathy, it usually does not impair vision. Origin: Gr. Pathos = disease (09 Oct 1997) |
| backing | In dentistry, a metal support which serves to attach a facing to a prosthesis. (05 Mar 2000) |
| backlash | <mechanics> The distance through which one part of connected machinery, as a wheel, piston, or screw, can be moved without moving the connected parts, resulting from looseness in fitting or from wear; also, the jarring or reflex motion caused in badly fitting machinery by irregularities in velocity or a reverse of motion. Origin: Back, adv. + lash. Source: Websters Dictionary (01 Mar 1998) |
| backlog | A large stick of wood, forming the of a fire on the hearth. "There was first a backlog, from fifteen to four and twenty inches in diameter and five feet long, imbedded in the ashes." (S. G. Goodrich) Origin: Back, a. + log. Source: Websters Dictionary (01 Mar 1998) |
| backprojection | In computed tomography or other imaging techniques requiring reconstruction from multiple projections, an algorithm for calculating the contribution of each voxel of the structure to the measured ray data, in order to generate an image; the oldest and simplest method of image reconstruction. Synonym: apical lordotic projection. (05 Mar 2000) |