Practical methods of electron depth-dose measurement compared to use of the NACP design chamber in water

Journal Article · Sun Nov 01 04:00:00 EST 1987 · Med. Phys.; (United States)

DOI:https://doi.org/10.1118/1.595986· OSTI ID:5958206

Ten Haken, R K; Fraass, B A; Jost, R J

Central axis relative dose versus depth measurements were performed using two different small volume thimble ionization chambers and a p-type silicon diode in a water phantom and with two parallel-plate ionization chambers, thermoluminescent dosimeters, and radiographic film in a popular clear polystyrene phantom. Values obtained were compared to the results of similar measurements in a water phantom performed with a plane-parallel ionization chamber designed and optimized for use in electron beams by the Nordic Association of Clinical Physicists (NACP). The NACP chamber is expected to minimally perturb the electron fluence and be least prone to point of measurement uncertainties. Its use in a water phantom closely approximates the spirit of recent international protocols. Data were obtained for the foil scattered electron beams generated by two different accelerators for field sizes from 6 cm x 6 cm to 25 cm x 25 cm and energies between 6 and 20 MeV. Easily identifiable effective points of measurements were defined for each measurement device and standard corrections were applied to the raw data to obtain depth-dose curves. The degree of agreement between the various techniques and the NACP-water standard was quantitatively analyzed through comparison of the resulting depths of 50% dose and practical range. All methods were found to yield reasonable results when carefully implemented, with average differences of less than 1 mm being easily achievable. Measurements with p-type silicon diode detectors were found to be particularly useful, as they are pointlike and appear from all practical considerations to directly represent relative dose, thus requiring little or no correction to raw readings.

• Research Organization: Department of Radiation Oncology, University of Michigan Medical School, Ann Arbor, Michigan 48109
• OSTI ID: 5958206
• Journal Information: Med. Phys.; (United States), Journal Name: Med. Phys.; (United States) Vol. 14:6; ISSN MPHYA
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
655003* -- Medical Physics-- Dosimetry
BEAMS
CALIBRATION STANDARDS
DEPTH DOSE DISTRIBUTIONS
DOSEMETERS
DOSIMETRY
ELECTRON BEAMS
ELECTRON DOSIMETRY
ENERGY RANGE
HYDROGEN COMPOUNDS
IONIZATION CHAMBERS
LEPTON BEAMS
LUMINESCENT DOSEMETERS
MATERIALS
MEASURING INSTRUMENTS
MEV RANGE
MEV RANGE 01-10
MEV RANGE 10-100
MOCKUP
ORGANIC COMPOUNDS
ORGANIC POLYMERS
OXYGEN COMPOUNDS
PARTICLE BEAMS
PETROCHEMICALS
PETROLEUM PRODUCTS
PHANTOMS
PLASTICS
POLYMERS
POLYOLEFINS
POLYSTYRENE
POLYVINYLS
RADIATION DETECTORS
RADIATION DOSE DISTRIBUTIONS
SPATIAL DOSE DISTRIBUTIONS
STANDARDS
STRUCTURAL MODELS
SYNTHETIC MATERIALS
THERMOLUMINESCENT DOSEMETERS
WATER