  We investigated the parameter optimization of ridge filter thickness using a
Monte Carlo simulation for carbon ion therapy. For this study, a ridge filter
was designed for the Spread-Out Bragg Peak (SOBP) by considering the relative
biological effect (RBE). The thickness, height, and width of the ridge filter
were designed by using the FLUKA and GEANT4 code, and we analyzed and compared
the results of the physical dose distribution for the FLUKA and GEANT4 coding.
The results show that the minimum width of the groove for the ridge filter
should be at least 0.4cm for the appropriate biological dose. The SOBP sections
are 8cm, 9cm, and 10cm, respectively, when heights are 3.5cm, 4.0cm, and 4.5cm.
The height of the ridge filter is designed to be associated with the SOBP
width. Also, the results for the FLUKA and GEANT4 code show that an average
value of difference is 3% and a maximum error is 5%; however, its trend was
similar. Therefore, the height and width of the groove for the ridge filter are
used for important parameters to decide the length and plateau of SOBP.
