IMRT involves complex Treatment Planning Process & rigorous plan evaluation. Even when a plan is devised that meets many treatment-planning objectives, limitations in the planner’s ability to further adjust beam characteristics may require the radiation dose prescription to be normalized to an isodose level that best covers the target volume.
Commercial Treatment Planning Systems contain various plan normalization options
e.g
1. No Plan Normalization
2. Plan Normalization at Isocenter
3. Plan Normalization at Target Mean
4. Plan normalization at Target Minimum
5. Plan normalization at Target Maximum
6. % of Volume should Receive _ % of dose
7. Etc.,
Normalization at Isocenter is no long applicable to IMRT
Most of the institute uses no plan normalization. But the pitfall of this normalization method is it may be under dose / over dose to target if the constraints are not properly handled by the planner. So, it is purely depends on the planner constraints & priorities.
I personally would like to use plan "normalization at target mean / Median", which can standardize the plan normalization method in IMRT and it is “independent” of the Planner / user dose constraints & priorities.
I will appreciate if the forum further discuss about plan normalization in IMRT and their institute protocols of IMRT Plan normalization.