| ICRU | International Commission on Radiation Units and Measurements |
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| IRP | immunoreactive plasma; immunoreactive proinsulin; incus replacement prosthesis; insulin-releasing po... |
| IRTIS | Integrated Radiation Therapy Information System |
| LASER | light amplification by stimulated emission of radiation |
| LRT | local radiation therapy; long terminal repeat; lower respiratory tract |
| secondary radiation | Secondary radiation emitted from the interaction of X-rays with matter; generally lower in energy, with a directional distribution which depends on the energy of the incident radiation. Synonym: secondary radiation. (05 Mar 2000) |
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| homogeneous radiation | Radiation consisting of a narrow band of frequencies, the same energy, or a single type of particle. (05 Mar 2000) |
| pyramidal radiation | Corticospinal fibres passing from the cortex into the pyramid. Synonym: radiatio pyramidalis. (05 Mar 2000) |
| neutron radiation | An emission of neutrons from the nucleus of an atom by decay or fission. (05 Mar 2000) |
| synchrotron radiation | <physics> Electromagnetic energy radiated from a charged particle moving in a curved orbit (typically in a magnetic field), due to the acceleration required to change the direction of the particle's velocity. See: bremsstrahlung. Synonym: cyclotron radiation. (13 Jan 1998) |
| dose-response relationship, radiation | The relationship between the dose of administered radiation and the response of the organism or tissue to the radiation. (12 Dec 1998) |
| infrared radiation | Electromagnetic radiation with wavelengths between 750 nanometres and 1,000,000 nanometres (or 1 millimetre). This is more commonly known as heat energy. (09 Oct 1997) |
| internal radiation therapy | Radiation therapy in which radioactive material is placed in or near a tumour. (12 Dec 1998) |
| interstitial radiation | Radiation therapy in which a radioactive material is placed directly into a tumour. (12 Dec 1998) |
| interstitial radiation therapy | <oncology> The implantation of radioactive seeds directly into a tumour. (10 Jan 1998) |
| intraoperative radiation therapy | Treating a tumour site withradiation immediately following surgery to destroy the tumour. (09 Oct 1997) |
| ionising radiation | <radiobiology> Radiation sufficiently energetic to dislodge electrons from an atom. Ionising radiation includes x and gamma radiation, electrons (beta radiation), alpha particles (helium nuclei) and heavier charge atomic nuclei. Neutrons ionise indirectly by colliding with atomic nuclei. Alpha and gamma radiation are far more effective at producing ionisation (and therefore more likely to cause tissue or cell damage) than beta radiation or neutrons. (16 Dec 1997) |
| ionizing radiation | Corpuscular (e.g., neutrons, electrons) or electromagnetic (e.g., gamma) radiation of sufficient energy to ionise the irradiated material. (05 Mar 2000) |
| occipitothalamic radiation | The massive, fanlike fibre system passing from the lateral geniculate body of the thalamus to the visual cortex (striate or calcarine cortex, area 17 of Brodmann); the fibres follow the retrolenticular and sublenticular limbs of the internal capsule into the corona radiata but they curve back along the lateral wall of the temporal and occipital horns of the lateral ventricle to the striate cortex on the medial surface and pole of the occipital lobe. Synonym: radiatio optica, geniculocalcarine radiation, geniculocalcarine tract, Gratiolet's fibres, Gratiolet's radiation, occipitothalamic radiation, Wernicke's radiation. (05 Mar 2000) |
| optic radiation | The massive, fanlike fibre system passing from the lateral geniculate body of the thalamus to the visual cortex (striate or calcarine cortex, area 17 of Brodmann); the fibres follow the retrolenticular and sublenticular limbs of the internal capsule into the corona radiata but they curve back along the lateral wall of the temporal and occipital horns of the lateral ventricle to the striate cortex on the medial surface and pole of the occipital lobe. Synonym: radiatio optica, geniculocalcarine radiation, geniculocalcarine tract, Gratiolet's fibres, Gratiolet's radiation, occipitothalamic radiation, Wernicke's radiation. (05 Mar 2000) |