HIGH YIELD POINT FOR BASIC RADIOLOGY 2015
http://www.doctorsquiz.com important topics for DNB-CET, AIPGMEE, FMGE, DNB-PDCET, UPSC-CMS online medical examination .
absorbed dose (D): The quotient of dE by dm, where dE is the mean energy imparted by ionizing radiation to matter of mass dm. The unit for absorbed dose is the joule per kilogram (J kg–1), with the special name gray (Gy).
accelerator: In this Report, refers to an electron accelerator, which is a device for imparting kinetic energy to elec- trons, with the kinetic energy being >2 and <50 br="" mev.="">
accelerator head: The part of the accelerator enclosing the x-ray target or source from which the useful beam ema- nates. The accelerator head contains shielding and may rotate about an axis.
activation: The process of inducing radioactivity by irradiation. An example is the process of creating radionuclides by neutron and gamma-ray activation of materials within the treatment room.
activity: The number of spontaneous nuclear transformations that occur in a quantity of a radioactive nuclide per unit time. The unit of activity is one transformation per second (s–1) with the special name becquerel (Bq).
annihilation: The process by which electromagnetic radiation is emitted as a result of the combination and disappear- ance of an electron and a positron. Two gamma rays of 0.511 MeV energy each are emitted in most cases.
as low as reasonably achievable (ALARA): A principle of radiation protection philosophy that requires that exposures to ionizing radiation be kept as low as reasonably achievable, economic and social factors being taken into account. The protection from radiation exposure is ALARA when the expenditure of further resources would be unwarranted by the reduction in exposure that would be achieved.
atomic number (Z) (low-Z, high-Z): The atomic number of a nucleus is the number of protons contained in the nucleus. Low-Z describes nuclei with Z ≤ 26. High-Z describes nuclei with Z > 26.
attenuation: The reduction of dose equivalent or other physical properties of a radiation field upon the passage of radiation through matter. This Report is concerned primarily with broad-beam attenuation that occurs when the area of the radiation field is large at the barrier (in contrast to a small diameter beam).
barn: Special unit for the cross section. 1 barn = 10–28 m2 (10–24 cm2) (see cross section).
barrier (or protective barrier): A protective wall of radiation attenuation material(s) used to reduce the dose equivalent on the side beyond the radiation source (see primary and secondary barriers).
beam-on time: The time that the radiation source is actually producing radiation.
bremsstrahlung: The spectrum of photons produced by the acceleration or deceleration of high-energy electrons, particularly near the coulomb fields of nuclei (see also x-ray target).
broad beam: Conditions of a radiation-shielding situation in which the beam impinging on a barrier surface includes scattered radiation and is laterally extensive.
collimator: A device used to reduce the cross-sectional area of the useful beam of photons or electrons with an absorbing material.
controlled area: A limited-access area in which the occupational exposure of personnel to radiation or to radioactive material is under the supervision of an individual in charge of radiation protection. This implies that access, occu- pancy, and working conditions are controlled for radiation protection purposes.
http://www.doctorsquiz.com important topics for DNB-CET, AIPGMEE, FMGE, DNB-PDCET, UPSC-CMS online medical examination .
absorbed dose (D): The quotient of dE by dm, where dE is the mean energy imparted by ionizing radiation to matter of mass dm. The unit for absorbed dose is the joule per kilogram (J kg–1), with the special name gray (Gy).
accelerator: In this Report, refers to an electron accelerator, which is a device for imparting kinetic energy to elec- trons, with the kinetic energy being >2 and <50 br="" mev.="">
accelerator head: The part of the accelerator enclosing the x-ray target or source from which the useful beam ema- nates. The accelerator head contains shielding and may rotate about an axis.
activation: The process of inducing radioactivity by irradiation. An example is the process of creating radionuclides by neutron and gamma-ray activation of materials within the treatment room.
activity: The number of spontaneous nuclear transformations that occur in a quantity of a radioactive nuclide per unit time. The unit of activity is one transformation per second (s–1) with the special name becquerel (Bq).
annihilation: The process by which electromagnetic radiation is emitted as a result of the combination and disappear- ance of an electron and a positron. Two gamma rays of 0.511 MeV energy each are emitted in most cases.
as low as reasonably achievable (ALARA): A principle of radiation protection philosophy that requires that exposures to ionizing radiation be kept as low as reasonably achievable, economic and social factors being taken into account. The protection from radiation exposure is ALARA when the expenditure of further resources would be unwarranted by the reduction in exposure that would be achieved.
atomic number (Z) (low-Z, high-Z): The atomic number of a nucleus is the number of protons contained in the nucleus. Low-Z describes nuclei with Z ≤ 26. High-Z describes nuclei with Z > 26.
attenuation: The reduction of dose equivalent or other physical properties of a radiation field upon the passage of radiation through matter. This Report is concerned primarily with broad-beam attenuation that occurs when the area of the radiation field is large at the barrier (in contrast to a small diameter beam).
barn: Special unit for the cross section. 1 barn = 10–28 m2 (10–24 cm2) (see cross section).
barrier (or protective barrier): A protective wall of radiation attenuation material(s) used to reduce the dose equivalent on the side beyond the radiation source (see primary and secondary barriers).
beam-on time: The time that the radiation source is actually producing radiation.
bremsstrahlung: The spectrum of photons produced by the acceleration or deceleration of high-energy electrons, particularly near the coulomb fields of nuclei (see also x-ray target).
broad beam: Conditions of a radiation-shielding situation in which the beam impinging on a barrier surface includes scattered radiation and is laterally extensive.
collimator: A device used to reduce the cross-sectional area of the useful beam of photons or electrons with an absorbing material.
controlled area: A limited-access area in which the occupational exposure of personnel to radiation or to radioactive material is under the supervision of an individual in charge of radiation protection. This implies that access, occu- pancy, and working conditions are controlled for radiation protection purposes.
