SU-FF-T-350: A Comparative Dosimetric Study of Three-Dimensional Conformal, Dynamic Conformal Arc, and Intensity Modulated Radiation Therapy for Brain Tumor Treatment

Abstract

Purpose: To investigate dosimetric differences among three‐dimensional conformal (3D‐CRT), dynamic conformal arc therapy (DCAT) and intensity modulated radiotherapy(IMRT) for braintumortreatment for a broad range of braintumor volumes and shapes in an effort to determine whether a preferred method can be identified based upon pre‐treatment characteristics. Method and Materials: Fifteen patients treated with Novalis were selected. We performed 3D‐CRT, DCAT and IMRT plans for all the cases. The beam numbers in 3D‐CRT or IMRT plans were the same as the arc numbers in the DCAT plans, and the gantry angle of each beam in 3D‐CRT or IMRT plans was the middle angle of each arc in the DCAT plans. The PTV margin was re‐chosen as 1mm, and the specific prescription dose was re‐set to 90% for all the plans. The target coverage at prescription dose (TV90%), conformity index (CI) and heterogeneity index (HI) were used to compare the different plans. V50% and V80% of the organs at risk (OAR) were also calculated. Results: For small braintumors (PTV⩽2cc), three dosimetric parameters had approximate values for both 3D‐CRT and DCAT plans ( TV 90% ¯ ∼93%, CI ¯ ∼1.7, HI ¯ ∼1.4) . The CI for IMRT plans was high ( CI ¯ =3) . For medium braintumors (2cc<PTV⩽100cc), the three plans were competitive with each other. IMRT plans had higher CI and better TV90% and HI. For large braintumors (PTV⩾100cc), IMRT plan had nearly perfect TV90% and HI and the approximate CI values as those in both 3D‐CRT and DCAT plans. Conclusions: DCAT is suitable for most cases in the treatment of braintumors. For a small target, 3D‐CRT is still useful, and IMRT is not recommended. For larger braintumors,IMRT is superior to 3D‐CRT, and very competitive in sparing critical structures near the target, especially for the treatment of a big braintumor.