AbstractID: 7669 Title: A computer program for quality assurance of IMRT treatment
plans
Many commercially available treatment planning systems can produce intensity modulated radiotherapy (IMRT) treatment plans,
however, quality assurance (QA) verification of these plans is usually a lengthy procedure involving absolute dose measurements
using ion chambers and relative dose measurements using film or portal images for each beam site. The use of an independent
monitor unit (MU) verification and film/fluence comparison program can greatly simplify this process and was the motivation for the
current work. A comprehensive computer program was developed to perform QA procedures with the CORVUS treatment planning
system. The program runs on both Windows and Mac-OS based PC computers, and comprises an intuitive graphical user interface
which is composed of four modules: (1) beam data visualization/entry, (2) network transfer (ftp) of the multileaf collimator (MLC)
treatment files, (3) MLC animation/visualization and finally (4) dose/fluence calculation and visualization for monitor unit verification
and automatic comparison with measured film data. The program reads the MLC treatment files generated by CORVUS to obtain the
positions and MU of each IMRT sub-field. The dose can be calculated at any point inside a cubic phantom under SAD or SSD
conditions. The dose calculation uses basic measured beam data (Tissue-Phantom Ratio, Scatter-Factor, Collimator-Factor) and is
based on a modified-Clarkson integration over annular sectors assuming radial symmetry of scattered radiation to the point of
calculation. The calculated dose is within +/- 5% of the measured dose and serves as a practical and rapid means of verifying MU
calculations and film/fluence comparison for IMRT.