Output factors and dose calculations for blocked x-ray fields

Journal Article · Thu May 01 04:00:00 EDT 1986 · Med. Phys.; (United States)

DOI:https://doi.org/10.1118/1.595885· OSTI ID:5870980

Meli, J A

Output factors for blocked fields have been measured in a polystyrene phantom for four collimator field sizes and two blocking schemes using 6-MV x rays. For all measurements the phantom surface was at the calibration source--surface distance (SSD) because, as is shown, the calculation of dose to any point in a phantom at an arbitrary SSD can be expressed in terms of the output factor for the field size at the calibration distance. It is found that output factors are a function of both the surface field size of the blocked field and the collimator field size. Specifically, the output factor for a blocked field is less than that for the collimator field size used but greater than that for an unblocked field of the same surface field size formed by collimator settings only. A method is proposed for utilizing these data to calculate the output factor for any collimator and blocked field size. The validity of the method is checked by using it to calculate dose to a point in a phantom and comparing this to the measured dose.

• Research Organization: Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut 06510
• OSTI ID: 5870980
• Journal Information: Med. Phys.; (United States), Journal Name: Med. Phys.; (United States) Vol. 13:3; ISSN MPHYA
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
655003* -- Medical Physics-- Dosimetry
CALIBRATION
DOSES
DOSIMETRY
MATERIALS
MEDICINE
MOCKUP
NUCLEAR MEDICINE
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PETROCHEMICALS
PETROLEUM PRODUCTS
PHANTOMS
PLASTICS
POLYMERS
POLYOLEFINS
POLYSTYRENE
POLYVINYLS
RADIATION DOSES
RADIOLOGY
RADIOTHERAPY
STRUCTURAL MODELS
SYNTHETIC MATERIALS
THERAPY
X-RAY DOSIMETRY