5.1.2 PENTRAN Model
As shown in Figure 5-5, we simulated equivalent three phantoms to those simulated with
Monte Carlo. The heterogeneous models consisted of three key components; an X-ray source
(15 x1 x15 cm3) with flat weighted 8 MV source, divided into 16 energy groups, a soft tissue
phantom (45x45x45 cm3), eqUIValent layers of bone and lung tissue identical to that used in the
Monte Carlo simulations. Models were divided into 3 z-levels; each z-level was divided equally
into 9 coarse meshes containing (15 x15 x15) fine mesh cells for each coarse mesh; a total of
91,125 fine mesh cells were used in the SN problems. Although lower quadrature set (S32) aef
sufficient to produce accurate SN results for similar calculations (Chapter 1), to assure minimum
ray-effects on the SN calculations, these simulations were based on the use of an S62 angUarT
Legendre-Chebychev quadrature with P3 Scattering anisotropy using the CEPXS library.
SSSSSSS SSSBSSS SBLLBSS
Figure 5-5. Three SN phantoms equivalent to the one used in the Monte Carlo simulation.
Phantom SSSSSSS is a homogeneous soft-tissue phantom; phantoms SSBBSSS and
SBLLBSS are heterogeneous phantoms consisting of combinations of soft and bone
tissue, and soft, bone, and lung tissue-equivalent materials, respectively