Modeling and Validation of a Proton Therapy Couch Top.

Purpose: This paper describes the modeling of the kVue One Proton couch top (CQ Medical, Avondale, PA) for use in treatment planning system (TPS), and the verification of the calculated effect of the model in the TPS against measured radiological properties.

Material And Methods: The kVue One Proton couch top consists of a higher-density shell surrounding a lower-density core. The radiological properties of the kVue One Proton couch top, as assessed by range pullback of direct and oblique incidence proton beams, were measured and used to evaluate different density overrides in a model of the couch top base created in the TPS, RayStation 12ASP1 (RaySearch Laboratories, Stockholm, Sweden). A similar approach was followed for MCsquare implementation.

Results: The average value (of water equivalent thickness) for all water tank measurements in lateral and longitudinal positions in the uniform area of 2 protons kVue One Proton couch top (except the couch ramp) was 6.46 mm. The posterior HU profiles showed a ramp area more extended longitudinally than the 7 cm physical shape of the kVue One Proton Couch Top. This was confirmed with differences in WET measurements and HU profiles observed up to 14 cm inferiorly from the superior part of the couch top, the remaining area being uniform in WET.

Conclusion: A 0.1 g/cm carbon fiber density for both the shell and core showed a maximum difference of 1.5 mm between measurements with a direct beam and the treatment planning model, over the full length of the kVue One Proton Couch Top. Similar results were obtained using oblique incidence proton beams.