IMRT

This SBRT prostate plan was generated using the Ethos Treatment Management system with the intent of daily online adaptive treatments. Planning directives were used to guide the intelligent optimization engine (IOE) for the most optimal balance of target coverage and OAR sparing. For this case, the clinical directives ranked with high importance were used to maximize the balance between Prostate + PTV coverage and Urethra + neurovascular bundle sparing.  High importance was also placed on the maximum dose in the rectum and skin.

Ethos can automatically derive PTV, PRV, and optimization structures based on templates with saved Boolean operations. These structures can help guide the dose distribution for initial and adaptive treatment plans. For this case, PRV’s of 2mm margins were utilized for both the neurovascular bundles and urethra. These PRV’s helped guide the dose gradient between the Urethra / Prostate and the neurovascular bundles / PTV. A PRV structure with an expansion of 3mm was also utilized to push dose further away from the skin surface. A “PTV_Opti” structure was utilized to focus dose heterogeneities away from the PTV and toward the center of prostate target. This structure was derived from cropping the PTV from the prostate.

The plan utilized twelve (12) equidistant fields with 10-degree collimator rotations as pre-determined by the plan creation options from the Ethos TPS. The IMRT plan had improved neurovascular bundle and urethra sparing while reducing dose Heterogeneities over the VMAT plan. The tradeoff being that the IMRT plan had higher skin and femoral head dose compared to VMAT. 

_{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.
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