| LD50/30 | a dose that is lethal for 50% of test subjects within 30 days |
|---|---|
| LD100 | lethal dose in all exposed subjects |
| MLD50 | median lethal dose |
| PTLD | posttransplanatation lymphoproliferative disorder; prescribed tumor lethal dose |
| TLD | thermoluminescent dosimeter; thoracic lymphatic duct; tumor lethal dose |
| half-ray | <geometry> A straight line considered as drawn from a center to an indefinite distance in one direction, the complete ray being the whole line drawn to an indefinite distance in both directions. Source: Websters Dictionary (01 Mar 1998) |
|---|---|
| half-reactions | <chemistry> The two parts of an oxidation-reduction reaction, one representing oxidation, the other reduction. (09 Jan 1998) |
| half register | <molecular biology> A misalignment between two identical sets of repeating units of nucleotides within two copies of the same chromosome (one set of repeating units per copy of the chromosome), where repeating unit A from one set is inappropriately aligned with repeating unit B on the other set, so that ABABAB on one set would be aligned with BABABA on the other set instead of the correct ABABAB with ABABAB. (13 Nov 1997) |
| half-tetrad analysis | <genetics> The analysis of tetrad chromosomes (a pair of homologous chromosomes, thus four total chromosomes) after recombination when only half of the tetrad (two of the four chromosomes) can be analysed. (13 Nov 1997) |
| half-time | The time, in a first-order chemical (or enzymic) reaction, for half of the substance (substrate) to be converted or to disappear. Compare: half-life. (05 Mar 2000) |
| half-value layer | <radiobiology> The thickness of a specified material (usually a specific absorber), which attenuates a beam of radiation so that the exposure rate or absorbed dose rate at a specified point is reduced by half. (20 Sep 2002) |
| drug half-life | The amount of time it takes for one-half of an administered drug to be lost through biological processes (metabolism and elimination). (27 Sep 1997) |
| effective half-life | <radiobiology> Time required for a radioactive substance contained in a biological system (such as a person or an animal) to reduce its radioactivity by half, as a combination result of radioactive decay and biological elimination from the system. (09 Oct 1997) |
| elimination half-life | <pharmacology> The time it takes for the body to eliminate or breakdown half of a dose of a pharmacologic agent. (09 Oct 1997) |
| 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) |
| maintenance dose | In chemotherapy, systematic dosage at a level that maintains protection against exacerbation. (05 Mar 2000) |