EBRT Planning Flashcards
What is a cost function?
A cost function is a value that summarises the overall ‘merit’ of a plan. In other words it condenses the evaluation of how optimal a plan is into one, single value for easy of interpretation and is used to drive the optimisation process.
An example of a cost function is the Quadratic Overdose (Monaco) where an optimal dose is specified for a volume, a penalty function is applied if the TPS generates a value that exceeds this (with no penalty applied if within); the TPS then modifies the parameters such as MUs, number of segments, etc. and repeats the calculation and reassesses. The ultimate aim is to find the global minimum penalty whilst attaining the specified dose to the volume.
What is a class solution?
A class solution is basically a starting template that has been established at commissioning by testing many plans of the same site to ascertain the ideal parameters and beam setup for that site.
The idea being that the planner will only need to make small changes for most plans for the site to optimise it for individual patients, thus standardising the plan for patients (allowing fair comparison of patient outcomes) as well as maximising the efficiency of the planning process, thus able to treat the maximum number of patients in the time available.
