Poster — Wed Eve—42: IMRT Dosimetry for Prostate, Breast and Head‐and‐Neck: Comparing Biologically Based Step‐and‐Shoot IMRT with Dynamic Helical Tomotherapy

We have dosimetrically compared two treatment planning systems used in our clinic to create intensity‐modulated radiation therapy(IMRT) plans. A new commercial inverse treatment planning system (Monaco, CMS, Inc, St. Louis, Missouri) allowing Monte‐Carlo calculations, aperture based optimization, and biological cost functions was compared to the TomoTherapy Hi‐ART (Tomo‐Therapy, Madison, WI) planning system. Six clinical test cases (head and neck, prostate, and breast) were planned and compared using DVHs and dosimetric parameters (maximum dose, mean dose, conformity and homogeneity indexes). Both treatment planning systems provided adequate deliverable plans. Overall, tomotherapy plans provided a better conformality and dose homogeneity in most of the clinical cases also with improved sparing of major organs at risk. The dosimetric analysis shows that although the treatment planning systems have differences, they are each capable of producing substantially equivalent treatment plans in term of target coverage and normal tissue sparing.