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Measurements of dose from secondary radiation outside a treatment field

Journal Article · · Int. J. Radiat. Oncol., Biol. Phys.; (United States)
; ; ;
Radiation dose to organs outside the radiotherapy treatment field can be significant and therefore is of clinical interest. Measurements of dose have been made at distances up to 70 cm from the central axes of 5 x 5, 15 x 15 and 25 x 25 cm radiation fields of 300 kVp, 4 MV and 8 MV x rays, and /sup 60/Co gamma rays, at the surface and at depths in water of 5 and 10 cm. Contributions to the total secondary radiation dose from water scatter, machine (collimator) scatter and leakage radiation have been separated. We have found that the component of dose from water scatter can be described by a simple exponential function of distance from the central axis of the radiation field for all energies and field sizes. Machine scatter contributes 20 to 40% of the total secondary dose depending on machine, field size and distance from the field. Leakage radiation contributes very little dose, but becomes the dominant component at distances beyond 60 cm from the central axis. Estimates of the risk of second tumors in long term survivors indicate a small incremental increase above the natural incidence rate based on information from the 1980 BEIR Committee report.
Research Organization:
Harvard Medical School, Boston, MA
OSTI ID:
5744347
Journal Information:
Int. J. Radiat. Oncol., Biol. Phys.; (United States), Journal Name: Int. J. Radiat. Oncol., Biol. Phys.; (United States) Vol. 9:8; ISSN IOBPD
Country of Publication:
United States
Language:
English

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Related Subjects

550603 -- Medicine-- External Radiation in Therapy-- (1980-)
560151* -- Radiation Effects on Animals-- Man
61 RADIATION PROTECTION AND DOSIMETRY
62 RADIOLOGY AND NUCLEAR MEDICINE
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
655003 -- Medical Physics-- Dosimetry
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARCINOGENESIS
COBALT 60
COBALT ISOTOPES
DOSES
DOSIMETRY
ELECTROMAGNETIC RADIATION
GAMMA RADIATION
GEOMETRY
HARD X RADIATION
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IONIZATION CHAMBERS
IONIZING RADIATIONS
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
MATHEMATICS
MEASURING INSTRUMENTS
MEDICINE
MINUTES LIVING RADIOISOTOPES
MOCKUP
NUCLEAR MEDICINE
NUCLEI
ODD-ODD NUCLEI
PATHOGENESIS
PATIENTS
PHANTOMS
RADIATION DETECTORS
RADIATION DOSES
RADIATIONS
RADIOISOTOPES
RADIOLOGY
RADIOTHERAPY
RISK ASSESSMENT
SCATTERING
SIDE EFFECTS
STRUCTURAL MODELS
THERAPY
X RADIATION
YEARS LIVING RADIOISOTOPES