Dosimetric verification of dynamic wedged fields

Abstract

Purpose

Verification of dynamic wedge algorithm generation in the Clinac 2100 CD accelerator, and in the Cad Plan- Treatment Planing System.

Material

In order to calculate the dose distribution for dynamic wedge modified fields, the Cad Plan planning system uses an algorithm which is a combination of measurement results for open fields and the GSTT files. No additional measurement data are required from the user.

Method

: To this end, measurements verifying the calculations of monitor units realized by the planning system for dynamically modified fields were conducted. The following profiles were compared: the measured profile and the profile generated by the Varian system. The measurements were carried out for the energy of 6 MeV, for EDW 15°, 20°, 30° and 45°, using a water phantom and ionization chambers with active volumes of 0.6 ccm and 0.1 ccm.

Results

The results are presented in the form of diagrams and tables. Differences in the calculations of monitor units do not exceed 3%. The differences between the analyzed profile areas averaged out at 2.4%.

Discussion

: The compliances confirmed by measurements corroborate the correctness of the system operation. The measurements became a guideline for the creation of a routine system of dynamic wedge control.