VBO stands for Variance Based Optimization. This is the fastest available engine for realizing anatomy based optimization in Brachytherapy and is available in Nucletron's Oncentra Prostate system.

In a few subseconds the engine considers multiple targets and several organs at risk, based on a variety of objective functions. These functions are CTV and several GTV’s, or equivalently CTV 3. VBO can be considered a realtime optimization engine.

For users with experience in the wellknown dose point based optimization that is available in Plato BPS (also available in Oncentra Brachy), VBO offers the smoothest path for moving towards a real anatomy-based inverse optimization.

VBO also enables the consideration of dwell time gradient restrictions (modulation restriction) for each catheter separately and offers dose distributions that are highly conformal to the target volume. This results in the minimum possible dose outside of the target volume.

VBO handles the dose conformity (the concentration of dose to the target) and homogeneity objectives for the target and secures a dose limit, which is called a high dose constraint, for each of the considered organs at risk.

VBO has a multi-year history of continous clinical application, as it was released with version 1.0 of SWIFT (later known as Oncentra Prostate) in 2002 and is available in all versions since then, becoming a standard in brachytherapy treatment planning optimization.