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Physical aspects of a rotational total skin electron irradiation
Author(s) -
Podgorsak E. B.,
Pla C.,
Pla M.,
Lefebvre P. Y.,
Heese R.
Publication year - 1983
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 - 10.1118/1.595296
Subject(s) - beam (structure) , irradiation , linear particle accelerator , ionization chamber , percentage depth dose curve , materials science , cathode ray , atomic physics , electron , scattering , calibration , optics , ionization , dose profile , dosimetry , range (aeronautics) , physics , nuclear medicine , nuclear physics , ion , medicine , composite material , quantum mechanics
A technique for rotational total skin electron irradiation is presented in which the patient stands on a slowly rotating platform (SSD=285 cm) in a large uniform linear accelerator electron field ( E 0 =3.5 MeV). The beam is scattered by the transmission ionization chamber and by a special lead/aluminum scattering filter, and then degraded by a sheet of Lucite. A Farmer chamber is used as a patient dose monitor and a method for absolute dose calibration is presented. The field is uniform to within ±5% for dimensions of 180×40 cm 2 . The surface dose for rotational therapy is equal to 45% of the maximum dose in a stationary beam. The rotating beam exhibits a dose maximum on the surface, falls to 80% at 0.5 cm and has an x‐ray contamination of ∼4%. The surface dose rate is about 25 cGy/min for the rotating beam. The rotational beam percentage depth dose distributions, calculated using stationary beam information, agree well with measured data. The stationary beam exhibits a dose maximum at 4 mm in tissue, a surface dose of 93%, 80% dose at a depth of 1 cm, a practical range of 1.75 cm, and an x‐ray contamination of 2.5%. The rotational total skin electron irradiation significantly reduces the patient treatment and setup time and solves the problem of beam matching, when compared to standard multiple‐beam techniques.