beamtransportinavoxelizedhumanphantommodel-資料下載頁
2025-10-15 18:07本頁面
【導讀】R.A.Lillie,D.E.Peplow,M.L.Williams,B.L.Kirk,M.P.Langer?,T.L.Nichols??andY.Y.Azmy???Background. NIHProposal. Presentation. Local(pointbypoint)andGlobalagreement. Voxelsize. Numberof. Allvoxels. Numberof. P5scattering. Collimatedponent. Scatteredponent
【正文】 NISN total electron flux lies between MCNP and EGSnrc values closer to MCNP except around voxels 37 and 56 OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 18 Mesh Size has Little Effect on ANISN Calculated Total Electron Flux 30 40 50 60Vo xe l N u mber (4 mm th i ck v o xe l s)345Total Electron Flux (cm2 s1)E G S NR CM CN PA NIS N S ! 6 4mmA NIS N S 1 6 2mmA NIS N S 1 6 1mm? Reduce mesh from 4 mm to 2 mm to 1 mm since ? Density in voxels 35 – 40 approximately 4 times higher than surrounding voxels ? Density in voxels 56 60 approximately 10 times higher than surrounding voxels ? Decreasing mesh size ? Improves agreement with MCNP around voxel 56 ? Produces little change around voxel 37 ? Similar changes occur using S32 and S64 quadratures ? Overall effect minimal OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 19 Higher Order Quadratures Improve ANISN Total Electron Flux 30 40 50 60Vo xe l N u mber (4 mm th i ck v o xe l s)345Total Electron Flux (cm2 s1)E G S n r cM CN PA NIS N S ! 6 4mmA NIS N S 3 2 4mmA NIS N S 6 4 4mm? ANISN total electron flux agrees very well with MCNP total electron flux with S32 and S64 quadratures ? Very little difference between S32 and S64 quadratures ? S20 (next higher order quadrature above S16) also improved agreement with MCNP ? Although not shown, agreement with MCNP also improves between voxels 15 and 27 ? Note: All the ANISN results were obtained using double Pl quadratures – similar results were obtained using fully symmetric quadratures OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 20 Closing Remarks ? Photon Only Calculations ? 3D deterministic transport codes (TORT) ? can yield accurate dose distributions in anatomical voxel based models when pared to MC codes ? with less putational cost (than MC codes), and ? possibly much less cost if few collisions are required ? Coupled ElectronPhoton Calculations ? 1D deterministic transport codes (ANISN) using currently available cross sections ? can yield reasonable agreement with MC codes ? with significantly less putational cost ? Further Effort ? Investigate photon discrepancy between ANISN and MC codes (possibly due to poor choice of model) ? Investigate electron flux MC discrepancies (MCNP vs EGSnrc) – MC calculated energy deposited agreed very well ? Similar couple electronphoton calculation with TORT (1D, 2D, and 3D) ? BoltzmannFokkerPlanck equation needed ?
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鄂ICP備17016276號-1