Improving the buildup and depth-dose characteristics of high energy photon beams by using electron filters

Journal Article · Sun Jul 01 00:00:00 EDT 1979 · Med. Phys.; (United States)

OSTI ID:6210740

Ling, C C; Biggs, P J

The attributes of high energy photon beams, i.e., low surface dose, large d/sub max/ and improved %DD, are compromised with increase in field size. This is due to the relative increase with field size of the electron component in the beam, as shown by recent experiments done here using a sweeping magnet. The present study shows that the advantages can be partially regained with the use of foils to remove electrons. Various thicknesses of Al, Cu, Sn, and Pb were placed in a 25-MV linac x-ray beam at several sites in the treatment head. Buildup curves were measured with a ''pancake'' chamber for various SSD and field sizes. The magnitude of improvement achieved is dependent upon field size, SSD, the atomic number of the foil material, and foil thickness. Pb foil (0.55 g cm/sup -2/) provided the best overall improvement. Surface dose reduction of 10%--20% can be achieved along with significant increase in d/sub max/ and %DD. These findings suggest a new design feature for the next generation of high energy linacs.

• Research Organization: Division of Radiation Biophysics, Department of Radiation Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114
• OSTI ID: 6210740
• Journal Information: Med. Phys.; (United States), Vol. 6:4
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
PHOTON BEAMS
BUILDUP
DEPTH DOSE DISTRIBUTIONS
RADIOTHERAPY
FILTERS
X-RAY DOSIMETRY
ALUMINIUM
COPPER
ELECTRONS
ISODOSE CURVES
LEAD
LINEAR ACCELERATORS
SHIELDING MATERIALS
TIN
X RADIATION
ACCELERATORS
BEAMS
DOSIMETRY
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
IONIZING RADIATIONS
LEPTONS
MEDICINE
METALS
NUCLEAR MEDICINE
RADIATION DOSE DISTRIBUTIONS
RADIATIONS
RADIOLOGY
SPATIAL DOSE DISTRIBUTIONS
THERAPY
TRANSITION ELEMENTS
655003* - Medical Physics- Dosimetry