IMRT SX1

Name (ID): Saudi_PC2016, FEB-2016 (AhmadPC LT BREAST)
Plan or PlanSum ID: SX1_2IsoID

This international plan competition, held by a group in Saudi Arabia, used a large intact breast and involved lymph node case.  The target (including the superior nodes) proved too large (head to foot) to fit inside a single isocenter beam arrangement on this linear accelerator.  Two isocenters were placed with a single 10cm head to foot shift to accommodate the large target.  Ten (10) non equally spaced beams were placed on each isocenter with beams arranged closely on the further medial and lateral sides and further apart in the center of the breast.  All twenty (20) beams were optimized together in a single plan and the plans were then broken into two separate single isocenter plans for treatment delivery as required by the inital delivery system software release.  Dose constraints for the scoring metric on this case were built from a superset of those constraints found in RTOG-1304.  The biggest challenges in this case were:

1. Forcing dose out of the heart, lung and contralateral breast with higher OAR objectives in the inverse planning optimizer
2. Controlling the location of the max dose to be inside the lumpectomy cavity as defined in the scoring metrics. 

Retrospectivly, this plan scored higher than 95% of the plans originally submitted into the competition.  The critical components contributing the plan performance were:

1. The flattening filter free beam employed by this machine inherently produces less out of field dose than a “flattened” beam
2. the dual layer stacked and staggered MLC with reduced interleaf leakage

_{Any reference to a "plan study" are simply what the organizers call each case and may not be a "study" in the FDA sense as they may not have been published in a peer reviewed journal.
Varian does not provide medical advice and these are illustrative examples only.
Leading plans by expert planner. Your results may vary.}