Use of a target complexity index in radiosurgical plan evaluation

There is a great need for reliable tools for radiosurgery plan evaluation. With the increasing sophistication of radiosurgical treatment planning systems, the radiosurgeon finds a more challenging treatment environment and feels the need to utilize more sophisticated methods of plan evaluation. Ultimately, these methods carry the promise of assisting treatment decisions, or even replacing some of them with consistent, reliable, and verifiable measures of probable treatment success. Among the most common are indices of homogeneity, dose uniformity across the target area, and conformity, the shaping of the radiation dose to the target area. These can often be expressed as simple ratios of treatment target and normal tissue volumes receiving certain radiation doses, although more complicated forms exist. The importance of these tools lies in their rendering of complex concepts into simple values, allowing either more sophisticated additions to multiple clinical treatment parameters, or more simplification of a limited treatment parameter set to a limited metric.