Biomaterial Database

Influence of air cavities on central depth dose curves for 33 MV roentgen rays. 1977

C Samuelsson

The relative central absorbed dose preceding and following air layers and channels in a polytetrafluorethylene (teflon) phantom has been measured with LiF-teflon dosimeters. Focus phantom distance is set to 100 cm and the field sizes range from 3 cm X 3 cm to 6 cm X 6 cm. Absorbed dose decrease and build-up factors in front of and behind the air cavity are evaluated. The build-up factor is strongly dependent on field size. Measurements of absorbed dose in water and polystyrene yield approximately the same results as in teflon if the linear dimensions of the irradiation geometry (including depth in phantom) in water and polystyrene are equal to 1.84 and 1.99 respectively times the corresponding parameter in teflon. The underlying transformation procedure is derived. The absorbed dose correction factors in the region behind the slab are discussed in terms of tissue-air-ratio and effective attenuation formulae.

UI	MeSH Term	Description	Entries
D008961	Models, Structural	A representation, generally small in scale, to show the structure, construction, or appearance of something. (From Random House Unabridged Dictionary, 2d ed)	Model, Structural,Structural Model,Structural Models
D011137	Polystyrenes	Polymerized forms of styrene used as a biocompatible material, especially in dentistry. They are thermoplastic and are used as insulators, for injection molding and casting, as sheets, plates, rods, rigid forms and beads.	Polystyrol,Polystyrene,Polystyrols
D011138	Polytetrafluoroethylene	Homopolymer of tetrafluoroethylene. Nonflammable, tough, inert plastic tubing or sheeting; used to line vessels, insulate, protect or lubricate apparatus; also as filter, coating for surgical implants or as prosthetic material. Synonyms: Fluoroflex; Fluoroplast; Ftoroplast; Halon; Polyfene; PTFE; Tetron.	FEP,Fluon,Politef,Polytef,TFE,Teflon,Expanded PTFE,Fluoroplast,GORE-TEX,Goretex,PTFE,Tarflen,GORE TEX,PTFE, Expanded
D011879	Radiotherapy Dosage	The total amount of radiation absorbed by tissues as a result of radiotherapy.	Dosage, Radiotherapy,Dosages, Radiotherapy,Radiotherapy Dosages
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
D000388	Air	The mixture of gases present in the earth's atmosphere consisting of oxygen, nitrogen, carbon dioxide, and small amounts of other gases.
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
D013679	Technology, Radiologic	The application of scientific knowledge or technology to the field of radiology. The applications center mostly around x-ray or radioisotopes for diagnostic and therapeutic purposes but the technological applications of any radiation or radiologic procedure is within the scope of radiologic technology.	Radiologic Technology,Technology, Radiological,Radiological Technology
D013819	Thermoluminescent Dosimetry	The use of a device composed of thermoluminescent material for measuring exposure to IONIZING RADIATION. The thermoluminescent material emits light when heated. The amount of light emitted is proportional to the amount of ionizing radiation to which the material has been exposed.	Dosimetries, Thermoluminescent,Dosimetry, Thermoluminescent,Thermoluminescent Dosimetries