J Korean Soc Ther Radiol.  1986 Dec;4(2):165-172.

A Study on the Effect of Field Shaping on Dose Distribution of Electron Beams

• Kang WS
• Cho MJ

Abstract

In electron therapy, lead cutout or low-melting alloy block is used for shaping the field. Material for shaping electron field affects the output factor as well as the collimation system. The authors measured the output factors of electron beams for shaped fields from Clinac-18 using ionization chamber of Farmer type on polystyrene phantom. They analyzed the incident energy, collimation system and size of shaped field. For shaped field the variation of output factor for the field (A/P) has appearance of a smooth curve for all energy and all applicator collimator combination. The output factors for open field deviate from the curves for shaped fields. An output factor for a given field can be calculated by equivalent field method such as A/P method, if a combination of applicator and collimator is fixed.

Keyword

Electron beam; Shaped field; Output factor and Equivalent field

MeSH Terms

Alloys
Polystyrenes
Alloys
Polystyrenes