IMRT SX1 B

Due to the unflattened nature of the 6MV beam, traditional “2D” treatment techniques cannot be employed on most normal sized targets.  The inverse planning optimizer can be employed to deliver a homogenous dose distribution to the target, which requires a target volume.  In this case the vertebra contours were drawn on just a few CT slices including the desired most superior and inferior slices and the rest of the CTV was created using interpolation.  Then a small uniform expansion was created to make a PTV subtracting a (3mm) margin from the skin surface.  Each plan was then optimized using only the PTV and Normal Tissue Objective (NTO).  Optimization constraints used were as follows:

LPO RPO: PTV 100%  30.3Gy p140; PTV 0% 35Gy p110; NTO auto p25

Alternatively, the irregular surface compensator tool can be used to create a homogeneous dose at depth.  This method would likely involve manual edits to the ideal fluence prior to plan approval thereby maintaining a completely forward planned workflow.

Heterogeneity is improved and acceptable hot spot.  However, there is not full coverage around GTV/CTV

_{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.}