SU-E-P-06: A Novel Hybrid Planning Approach to Allow More Patients Benefited by the Intensity Modulated Proton Therapy




We report a hybrid scattering and scanning beam delivery approach, termed as (HimpsPT), which demonstrated that majority IMPT delivery can be potentially replaced with hybrid IMPT and PSPT delivery with similar or better plan quality.


Three representative clinical cases, including head and neck (HN), skull base chordoma (CNS) and lung cancer, treated in MDACC Proton Therapy Center with IMPT were retrospectively redesigned using HimpsPT. The PSPT plans are designed with the same prescriptions as those of IMPT plans. The whole treatment can be delivered by either alternating or sequential PSPT and IMPT delivery. The dosimetric data and dose distributions of HimpsPT plans are compared with those of IMPT plans. We also performed a worst-case robust analysis for all plans.


The target coverages for all cases are comparable. For the HN case, the mean dose of esophagus larynx, left parotid and right submandibular, oral cavity V20, the max dose of cord is 18.0, 36.1, 23.6, 47.2, 0.1, 31.7 Gy in HimpsPT plan, and 25.5, 33.8, 24.9, 49.1, 0.2, 33.8 Gy in IMPT plan. For the lung case, the lung V5, V20, V30, mean lung dose, heart V40, esophagus V70, cord maximum dose are 50.5%, 37.0%, 31.7%, 21.3 Gy, 7.2%, 4.9%, 35.5 Gy in HimpsPT plan, and 55.4%, 36.7%, 30.1%, 21.3 Gy, 7.7%, 8.4%, 36.8Gy in IMPT plans. For the CNS case, brainstem maximum dose is 50.5 Gy in HimpsPT plan and 55.4 Gy in IMPT plan due to sharp penumbra offered by the aperture of the PSPT plan in HimpsPT technique.


For majority disease sites, the dosimetric advantage of IMPT technique can be achieved by the hybrid PSPT and IMPT technique, which enables the centers equipped with both scattering and scanning beam facilities to treat more patients which can be benefited by the scanning beam.