Determination of electron beam mean incident energy from d50 (ionization) values. 1987

R K Ten Haken, and B A Fraass
Department of Radiation Oncology, University of Michigan Medical School, Ann Arbor 48109.

Depth-ionization measurements have been obtained with an air-filled Nordic Association of Clinical Physicists (NACP) design parallel-plate ionization chamber in a water phantom for ten foil-scattered electron beams from two different machines with nominal energies between 6 and 20 MeV and field sizes from 6 X 6 to 25 X 25 cm2. Depths of 50% ionization and practical range have been determined from least-squares fits to both the raw data and values corrected to parallel-beam geometry using measured virtual source distances. Depths of 50% dose have also been obtained from fits to divergence-corrected depth-dose measurements performed under identical conditions using, a p-type silicon diode detector. Utilizing accepted conversion factors between mean incident energy (E0) and depth of 50% dose for parallel incident beams, and taking advantage of the fact that p-type silicon diode detector readings are nearly directly indicative of relative dose, conversion factors between E0 and depth of 50% ionization for divergence-corrected and raw, uncorrected finite source-surface distance depth-ionization data are empirically determined. Those values, obtained using the results of both ETRAN and EGS4 dose calculations as base lines, are compared to values currently recommended for use in clinical dosimetry.

UI MeSH Term Description Entries
D007477 Ions An atom or group of atoms that have a positive or negative electric charge due to a gain (negative charge) or loss (positive charge) of one or more electrons. Atoms with a positive charge are known as CATIONS; those with a negative charge are ANIONS.
D011878 Radiotherapy The use of IONIZING RADIATION to treat malignant NEOPLASMS and some benign conditions. Radiotherapy, Targeted,Targeted Radiotherapy,Radiation Therapy,Radiation Therapy, Targeted,Radiation Treatment,Targeted Radiation Therapy,Radiation Therapies,Radiation Therapies, Targeted,Radiation Treatments,Radiotherapies,Radiotherapies, Targeted,Targeted Radiation Therapies,Targeted Radiotherapies,Therapies, Radiation,Therapies, Targeted Radiation,Therapy, Radiation,Therapy, Targeted Radiation,Treatment, Radiation
D011879 Radiotherapy Dosage The total amount of radiation absorbed by tissues as a result of radiotherapy. Dosage, Radiotherapy,Dosages, Radiotherapy,Radiotherapy Dosages
D004583 Electrons Stable elementary particles having the smallest known negative charge, present in all elements; also called negatrons. Positively charged electrons are called positrons. The numbers, energies and arrangement of electrons around atomic nuclei determine the chemical identities of elements. Beams of electrons are called CATHODE RAYS. Fast Electrons,Negatrons,Positrons,Electron,Electron, Fast,Electrons, Fast,Fast Electron,Negatron,Positron
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man

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