IMRT SX1

Name (ID): UniLateral_HN, (UniLateral_HN)
Plan or PlanSum ID: 7fld1bSX1norm

Unilateral head and neck treated SIB following RTOG 0920.  This seven (7) field IMRT plan was created with custom gantry positions to mimic the irregular volume target shape of the lowest dose target on the transverse planes.  Also, consideration was given to place beam edges so that a sharp gradient could be achieved against the highest value OARs (oral cavity, pharynx, larynx, and esophagus).  From a beam's eye view, unique collimator rotations were selected per field to match the general angle of the target volume.

The challenge was achieving the minimum PTV coverage constraint for targets that were overlapping or abutting OARs which could not be adequately spared due to the target size, location and overlap.  When a protocol enforces a minimum dose to the target, the temptation is to simply perform a uniform expansion on the target and optimize on the expanded target.  However, in this case, an optimization PTV was created and stretched outward only along the edges of the real PTV where the minimum dose was not met.  Careful attention was paid to minimize stretching where the target interfaced/overlapped with an OAR.

This is clearly a more challenging case. The plan is overall adequate. Some remarkable dose gradients and dose falloffs are achieved. The problematic areas are in the overall zones with the oral cavity mostly, but also the larynx, pharynx and mandible. However, these are expected given the overlap with the PTV. If the PTV is corrected, then the overdose areas these OARs are clinically acceptable since the overlaps are very clear. This is a clinically acceptable plan.

_{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.}