PURPOSE: To investigate the dosimetric benefits of @entity4653 ( @entity4653 ) compared with passive scattered (PS) proton therapy for treatment of pediatric head_neck @entity1 as a function of the @entity4653 spot size and explore the advantages of using apertures in @entity4653 . METHODS: Ten pediatric @entity1 with @entity135 treated by PS proton therapy at our institution were retrospectively selected. The histologies included @entity980 , @entity424 , @entity816 , @entity976 and @entity3438 . The prescribed dose ranged from 36 to 54 Gy(RBE). Five @entity4653 plans were created for each @entity1 using variable spot size (average sigma at isocenter) and choice of beam specific apertures: (1) 10mm spots, (2) 10mm spots with apertures, (3) 6mm spots, (4) 6mm spots with apertures, and (5) 3mm spots. The plans were optimized for intensity modulated proton therapy (IMPT) with no single beam uniformity constraints. Dose volume indices as well as equivalent uniform dose (EUD) were compared between PS and @entity4653 plans. RESULTS: Although target coverage was clinically adequate for all cases, the plans with largest (10mm) spots provide inferior quality compared with PS in terms of dose to organs-at-risk (OAR). However, adding apertures to these plans ensured lower OAR dose than PS. The average EUD difference between @entity4653 and PS plans over all @entity1 and organs at risk were (1) 2.5%, (2) -5.1%, (3) -5%, (4) -7.8%, and (5) -9.5%. As the spot size decreased, more conformal plans were achieved that offered similar target coverage but lower dose to the neighboring healthy organs, while alleviating the need for using apertures. CONCLUSION: The application of @entity4653 does not always translate to better plan qualities compared to PS depending on the available beam spot size. We recommend that institutions with spot size larger than    6mm at isocenter consider using apertures to guarantee clinically comparable or superior dosimetric efficacy to PS treatments.

SU-F-BRD-12: When Does Pencil Beam Scanning Become Superior to Passive Scattered Proton Therapy for Pediatric XXXX ?

@entity1 :: ('9606', 'Species') :: ['patients', 'patient'] @entity135 :: ('MESH:D006258', 'Disease') :: ['head_neck cancers'] @entity424 :: ('MESH:D004806', 'Disease') :: ['ependymoma'] @entity976 :: ('MESH:D003397', 'Disease') :: ['craniopharyngioma'] @entity816 :: ('MESH:D001254', 'Disease') :: ['astrocytoma'] @entity980 :: ('MESH:D012208', 'Disease') :: ['rhabdomyosarcoma'] @entity3438 :: ('MESH:D018237', 'Disease') :: ['germinoma'] @entity4653 :: ('MESH:D004401', 'Disease') :: ['pencil beam scanning', 'PBS']
@entity135 :: (MESH:D006258,Disease) :: ['Head and Neck Cancers']
