Fig. 1. Combinations of the sequential optimization procedure. Each combination is described in  table 1. Initially, eight combinations were analyzed (complex 1). Thereafter, the worst combination of the complex (D) was discarded, and a new combination was identified by an optimization model (combination I of complex 2) and tested on an additional group of patients. This procedure was repeated at each subsequent step.  White points represent new combination of a complex. Combinations marked as  X represent the worst combination of each complex and were therefore not included in subsequent complexes.  Black points indicate combinations that were tested at previous steps.