ABSTRACT
Conventional proton therapy is based very much on the concept of the spread-out Bragg peak (SOBP). The single-field optimized (SFUD/SFO) approach then, although involving an optimization and modulation of the fluence of each individual pencil beam of each field, ensures a smooth dose across the target from each field and can therefore be considered as the scanning equivalent of treating with open fields in photon therapy as well as passively scattered proton therapy. In general terms, degeneracy will decrease as the number of goals and constraints defined in the optimization process increase. Uncertainty management is nothing new in radiotherapy. In the 1980s, Goitein and coworkers recommended including error estimates as part of the routine planning process, in the form of “maximum” and “minimum” plans, to encapsulate possible variations of the dose distribution about the nominal values.
