A quality assurance method for analyzing and verifying intensity modulated fields

A quality assurance method is developed for measuring, verifying and analyzing intensity modulated radiation fields. It is applicable for rotational and fixed-beam intensity modulated radiation therapy(IMRT)treatments. A gantry-mount device was constructed to measure the transmission dose of an IMRT field using radiographicfilms. A double-exposure technique with optimal kernel estimate method was developed to minimize the errors from measurements. A χ 2 confidence level test method was developed to detect the discrepancies between measured and prescribed IMRT fluence distributions. Our method was tested for rotational and fixed-beam IMRTtreatment verifications. The method was found insensitive to the hardware-related parameters for rotational and fixed-beam IMRTdeliveries. The χ 2 confidence level test was found to be more sensitive than linear correlation method in detecting relative small errors for cases with a few segments or narrow regions of interest. In conclusion, we demonstrated a quantitative method for verifying and analyzing IMRTtreatmentdeliveries.