Premium
Computer dosimetry for flattened and wedged fast‐neutron beams
Author(s) -
Hogstrom Kenneth R.,
Smith Alfred R.,
Almond Peter R.,
Otte Victor A.,
Smathers James B.
Publication year - 1976
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.594225
Subject(s) - dosimetry , beam (structure) , neutron , physics , flattening , computational physics , line (geometry) , cyclotron , optics , nuclear medicine , mathematics , nuclear physics , geometry , plasma , astronomy , medicine
Beam flattening by the use of polyethylene filters has been developed for the 50‐MeV d →Be fast‐neutron therapy beam at the Texas A&M Variable‐Energy Cyclotron (TAMVEC) as a result of the need for a more uniform dose distribution at depth within the patient. A computer algorithm has been developed that allows the use of a modified decrement line method to calculate dose distributions; standard decrement line methods do not apply because of off‐axis peaking. The dose distributions for measured flattened beams are transformed into distributions that are physically equivalent to an unflattened distribution. In the transformed space, standard decrement line theory yields a distribution for any field size which, by applying the inverse transformation, generates the flattened dose distribution, including the off‐axis peaking. A semiempirical model has been constructed that allows the calculation of dose distributions for wedged beams from open‐beam data.