Journal: Medical physics

Article Title: Validation of Biomechanical Deformable Image Registration in the Abdomen, Thorax and Pelvis in a Commercial Radiotherapy Treatment Planning System

doi: 10.1002/mp.12307

Figure Lengend Snippet: Comparison of the biomechanical DIR implementations (3 rd party functions listed where applicable).

Article Snippet: Major differences lie in the material properties and boundary conditions. table ft1 table-wrap mode="anchored" t5 caption a7 DIR feature In-house biomechanical DIR Commercial TPS biomechanical DIR Environment MATLAB-based application, imports ROI binary masks or meshes exported from TPS Module within TPS ROI triangular surface meshing Modified marching cubes on binary masks (IDL v6.3, Research Systems Inc., USA) † Model-based segmentation module adapts model mesh to contours by minimizing binarized edge distance Volumetric/multi-organ tetrahedral meshing (HyperMesh, Altair HyperWorks v11.0, Altair Engineering Inc., Troy, USA) (NETGEN, open-source: http://www.hpfem.jku.at/netgen ) Linear elastic material properties Ability to vary properties for any ROI in the reference image; ν =0.40-0.499; E =1.5-500 kPa Ability to vary ν only for controlling ROIs used as boundary conditions; 0.40 for body, 0.48 for all other organs Boundary conditions Fixed interface Guided-surface projection of reference ROI surface mesh to target ROI surface (HyperMorph Altair HyperWorks v11.0, Altair Engineering Inc., Troy, USA) Point-to-point ROI surface mesh correspondence via model-based segmentation Sliding interface Frictionless contact surface where internal ROI elements slide against fixed external elements (RADIOSS, Altair HyperWorks v11.0, Altair Engineering Inc., Troy, USA) Mixed Dirichlet/Neumann conditions where external ROI elements slide against fixed internal elements (FEniCS 16 , 17 , open-source) Finite element analysis solver (RADIOSS, Altair HyperWorks v11.0, Altair Engineering Inc., Troy, USA) (FEniCS 16 , 17 , open-source) Deformation resolution after resampling to cubic grid Equivalent to reference image ‡ 2.5×2.5×2.5 mm 3 (default) Open in a separate window Notes: † TPS meshes from model-based segmentation used for current study, ‡ 4DCT data was down-sampled to 256×256 voxels in-plane due to computer memory limitations.

Techniques: Modification