Biomaterial Database

Radiation transmission and scattering for medical linacs producing x rays of 6 and 15 MV: comparison of calculations with measurements. 1985

N J Numark, and K R Kase

We present comparisons of calculated and measured dose equivalent rates outside the shielding and in the entry mazes of 2 medical linac facilities producing x rays at 6 and 15 MV. Calculations were made using the NCRP recommendations for estimating transmission of radiation through a shielding wall and scattering of radiation in a maze. We found that, for walls made of high-density concrete, the x-ray dose rate outside the shield was estimated within 50% if transmission factors measured in the appropriate high-density concrete were used. The dose rate was overestimated by a factor of 2-4 when transmission factors for normal concrete were scaled using a density ratio. Dose equivalent rates calculated for x rays and neutrons in the entry mazes agreed within a factor of 2 with the measurements.

UI	MeSH Term	Description	Entries
D009502	Neutrons	Electrically neutral elementary particles found in all atomic nuclei except light hydrogen; the mass is equal to that of the proton and electron combined and they are unstable when isolated from the nucleus, undergoing beta decay. Slow, thermal, epithermal, and fast neutrons refer to the energy levels with which the neutrons are ejected from heavier nuclei during their decay.	Neutron
D010315	Particle Accelerators	Devices which accelerate electrically charged atomic or subatomic particles, such as electrons, protons or ions, to high velocities so they have high kinetic energy.	Betatrons,Linear Accelerators,Accelerator, Linear,Accelerator, Particle,Accelerators, Linear,Accelerators, Particle,Betatron,Linear Accelerator,Particle Accelerator
D011829	Radiation Dosage	The amount of radiation energy that is deposited in a unit mass of material, such as tissues of plants or animal. In RADIOTHERAPY, radiation dosage is expressed in gray units (Gy). In RADIOLOGIC HEALTH, the dosage is expressed by the product of absorbed dose (Gy) and quality factor (a function of linear energy transfer), and is called radiation dose equivalent in sievert units (Sv).	Sievert Units,Dosage, Radiation,Gray Units,Gy Radiation,Sv Radiation Dose Equivalent,Dosages, Radiation,Radiation Dosages,Units, Gray,Units, Sievert
D011834	Radiation Monitoring	The observation, either continuously or at intervals, of the levels of radiation in a given area, generally for the purpose of assuring that they have not exceeded prescribed amounts or, in case of radiation already present in the area, assuring that the levels have returned to those meeting acceptable safety standards.	Monitoring, Radiation
D011835	Radiation Protection	Methods and practices adopted to protect against RADIATION.	Protection, Radiation
D011882	Radiotherapy, High-Energy	Radiotherapy using high-energy (megavolt or higher) ionizing radiation. Types of radiation include gamma rays, produced by a radioisotope within a teletherapy unit; x-rays, electrons, protons, alpha particles (helium ions) and heavy charged ions, produced by particle acceleration; and neutrons and pi-mesons (pions), produced as secondary particles following bombardment of a target with a primary particle.	Megavolt Radiotherapy,High-Energy Radiotherapy,Radiotherapy, Megavolt,High Energy Radiotherapy,Radiotherapy, High Energy
D012542	Scattering, Radiation	The diversion of RADIATION (thermal, electromagnetic, or nuclear) from its original path as a result of interactions or collisions with atoms, molecules, or larger particles in the atmosphere or other media. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Radiation Scattering,Radiation Scatterings,Scatterings, Radiation