| threshold percussion | Percussion effected by means of a glass rod as a plessimeter, the rod being inclined to the wall of the chest or abdomen and touching it only by one extremity. (05 Mar 2000) |
|---|---|
| threshold shift | Measurement of the degree of hearing loss or impairment in terms of a decibel shift from an individual's previous audiogram. (05 Mar 2000) |
| threshold stimulus | A stimulus of threshold strength, i.e., one just strong enough to excite. See: adequate stimulus. Synonym: liminal stimulus. (05 Mar 2000) |
| threshold substance | Any material (e.g., glucose) that is excreted in the urine only when its plasma concentration exceeds a certain value, termed its threshold. Synonym: threshold body. (05 Mar 2000) |
| threshold trait | A trait that falls into natural groups that originate not in categorically distinct causes but in whether or not the outcome attains critical values; e.g., gallstones may result from a categorical cause or from unusual levels of causal factors that themselves show no evidence of grouping. Synonym: liminal trait. (05 Mar 2000) |
| transmission threshold | <epidemiology> Occurs for a parasite when the basic reproductive rate Ro is equal to 1. Below this threshold level the disease is unable to maintain itself within the host population. Typically, for directly transmitted parasites there is a transmission threshold for the host population size. (05 Dec 1998) |
| erythema threshold | The amount of radiation that causes redness of the skin. (09 Oct 1997) |
| fibrillation threshold | Least intensity of an electrical stimulus that will initiate fibrillation. (05 Mar 2000) |
| fusion-inferred threshold test | Employment of the phenomenon of cerebral fusion of binaural sounds to substitute for conventional masking in hearing testing. Synonym: FIT test. (05 Mar 2000) |
| light differential threshold | The smallest difference in light intensity that can be appreciated. (05 Mar 2000) |
| absorbed dose | The amount of energy absorbed per unit mass of irradiated material at the target site; in radiation therapy, the former unit for absorbed dose is the rad; the current (S.I.) unit is the gray. (05 Mar 2000) |
| air dose | The radiation dose, expressed in roentgens, delivered at a point in free air. Synonym: air dose. (05 Mar 2000) |
| bone marrow dose | The cumulative dose to the blood-forming organ from therapeutic or nuclear fallout irradiation; the presumed leukemogenic dose. (05 Mar 2000) |
| booster dose | A dose given at some time after an initial dose to enhance the effect, said usually of antigens for the production of antibodies. (05 Mar 2000) |
| breast dose in mammography | <radiology> 180 mrad / view -- mid-breast dose, guideline: less than 1 rad for 2-view exam (12 Dec 1998) |