AbstractID: 7431 Title: Clinical Implementation of Electron Output Calculation Method
A modified sector integration method that predicts electron output at any point on the beam axis as a function of geometry of the irradiated field and a given
source to surface distance has been developed. The main concept of this method is that the shape is divided into small sectors, and the contribution
calculated from the radius for an arbitrary electron field at any depth and SSD. A computer program based on this method to calculate electron output factors
at various SSDs (Source surface distances) has been made. This program can interface to the digital camera as well as automatic block cutter to create input
data file of the shape of an electron insert. To obtain the basic data table for calculation, the measurement was performed for several diameters (more than
3cm) of circular inserts and SSD in range of 100 cm to 125 cm with 5-cm interval by using ionization chambers (0.015 cm3 PinPoint ion chamber, PTWFreiburg, Germany). We compared the calculated results with measured ones of output factors and percent depth doses for various rectangular inserts and
some typical irregular shaped inserts used in the clinic with different SSDs. The rectangular inserts are designed to a series of elongated shapes with ratios of
the long-to-short axis between 1:1 and 7:1 in order to figure out what the geometric limitations of this algorithm are. The agreement between calculation and
measurement of the electron output and PDD is generally within 2% (or 2mm) for energies from 6 to 20 MeV.