Measurement of patient entrance surface dose rates for fluoroscopic x-ray units. 1995

C J Martin
Department of Bio-Medical Physics and Bio-Engineering, Aberdeen Royal Hospitals-NHS Trust, Foresterhill, UK.

Measurements of patient entrance surface dose rate provide valuable data for interpreting results from dose-area product studies on fluoroscopic x-ray equipment. Methods for measurement of entrance surface dose rate with backscatter and incident dose rate without backscatter have been investigated. Entrance surface dose rate is measured with an ionization chamber in contact with a tissue-equivalent phantom. Backscattered radiation contributes 27-45% to the measurement and is affected by field size and chamber position. Incident dose rate measured using a copper phantom provides an alternative approach. Consistent relationships between thicknesses of Perspex and copper giving similar incident dose rates under automatic gain control have been established for different tube potentials with and without a grid. This allows measurements of incident dose rate made using copper to be linked to corresponding thicknesses of tissue-equivalent material. Since only a few millimetres of copper are required, contributions from backscatter can be minimized and transport of phantoms is simplified. Incident dose can be related to dose-area product and entrance surface dose derived using backscatter factors. Such measurements play a valuable role in interpreting patient dose data and recommending options to reduce patient dose.

UI MeSH Term Description Entries
D008768 Methylmethacrylates The methyl esters of methacrylic acid that polymerize easily and are used as tissue cements, dental materials, and absorbent for biological substances.
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
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
D003300 Copper A heavy metal trace element with the atomic symbol Cu, atomic number 29, and atomic weight 63.55. Copper-63,Copper 63
D005471 Fluoroscopy Production of an image when x-rays strike a fluorescent screen. Fluoroscopies
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D001703 Biophysics The study of PHYSICAL PHENOMENA and PHYSICAL PROCESSES as applied to living things. Mechanobiology
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
D055592 Biophysical Phenomena The physical characteristics and processes of biological systems. Biophysical Concepts,Biophysical Processes,Biophysical Phenomenon,Biophysical Process,Biophysical Concept,Concept, Biophysical,Concepts, Biophysical,Phenomena, Biophysical,Phenomenon, Biophysical,Process, Biophysical,Processes, Biophysical
D020366 Methylmethacrylate The methyl ester of methacrylic acid. It polymerizes easily to form POLYMETHYL METHACRYLATE. It is used as a bone cement. Methylmethacrylate Methyl Monomer,Cranioplast,Kallocryl,Kallocryl A,Metaplex,Methacrylate Methyl Monomer,Simplex P,Sintex,Zimmer Bone Cement,Bone Cement, Zimmer,Bone Cements, Zimmer,Cement, Zimmer Bone,Cements, Zimmer Bone,Cranioplasts,Kallocryls,Metaplices,Methacrylate Methyl Monomers,Methyl Monomer, Methacrylate,Methyl Monomer, Methylmethacrylate,Methyl Monomers, Methacrylate,Methyl Monomers, Methylmethacrylate,Methylmethacrylate Methyl Monomers,Monomer, Methacrylate Methyl,Monomer, Methylmethacrylate Methyl,Monomers, Methacrylate Methyl,Monomers, Methylmethacrylate Methyl,Sintices,Zimmer Bone Cements

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