Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Washington Headquarters Senvices, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and AUTHOR(S)Chang Ming Ma, Ph.D. Approved for public release distribution unlimited PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)8 ABSTRACT (Maximum 200 Words)This project is aimed at exploring energy-and intensity-modulated radiotherapy (EIMRT) to deliver dose distributions that closely match the target volume and minimize the dose to critical normal structures. The scope includes (1) to characterize electron beams from Helium-filled accelerators for EIMRT, (2) to develop optimization algorithms for EIMRT using these electron beams, (3) to verify these optimized dose distributions using the Monte Carlo simulation technique, and (4) to compare the optimized dose plans obtained by EIMRT with conventional treatment plans and those obtained by photon intensitymodulated radiotherapy (IMRT).During the first year research, we have performed accurate Monte Carlo simulations of the electron beams in He-filled accelerators. Our results demonstrated that electron beams could be modulated to deliver superior dose distributions for EIMRT. We have implemented practical source models for clinical application and beam commissioning. Different dose algorithms have been compared for "Inverse treatment planning" beamlet calculations. The results confirmed that the Monte Carlo method is needed to generate the dose distributions for EIMRT. Further studies will be performed to verify the dose plans for realistic patients. The outcome will determine whether EIMRT offers a significant advantage over conventional photon/electron treatment and over photon IMRT.14. SUBJECT TERMS IntroductionRadiation therapy has been used for the treatment of all stages of localized breast cancer. Breast conservation with lumpectomy followed by radiation (BCT) has proven to be effective for early stage (TI -T2) patients. This project is aimed at exploring energy-and intensity-modulated electron beams to deliver optimized conformal radiotherapy dose distributions that closely match the target volume and minimize the dose to critical normal structures. The specific aims are (1) to characterize electron beams from Helium-filled accelerators, (2) to develop optimization algorithms for energy-and intensity-modulated radiotherapy (EIMRT) using these electron beams, (3) to verify these optimized dose distributions using the Monte Carlo simulation technique, and (4) to compare the optimized dose plans obtained by EIMRT with conventional treatment plans and those obtained by...