Comparison of MCNP5 Dose Calculations inside the RANDO Phantom Irradiated with a MLC LinAc Photon Beam against Treatment Planning System PLUNC

MC treatment planning techniques provide a very accurate dose calculation compared to ‘conventional’ deterministic treatment planning systems. In the present work, PLanUNC (PLUNC), a set of software tools for radiotherapy treatment planning (RTP), is compared with MCNP5 (Monte Carlo N-Particle transport code) by calculating dose maps inside the RANDO phantom, utilized as the patient model, irradiated with different field sizes with the MultiLeaf Collimated (MLC) Linear Accelerator (LinAc) Elekta Precise. PLUNC was initially coupled with MCNP5 and so exactly the same patient and plan parameters can be utilized in both dose calculation processes. A MLC Linear Accelerator was commissioned for PLUNC and a MCNP5 model used in the calculations. The coupling of MCNP5 with PLUNC has been achieved via a series of Matlab interfaces, which extract patient and beam information created with PLUNC during the treatment plan and write it in MCNP5 input deck format. A set of Computer Tomography images of the RANDO phantom was obtained and formatted. The CT slices are input in PLUNC, which performs the segmentation by defining anatomical structures. The Matlab algorithm developed by the authors, validated in previous works writes the phantom information in MCNP5 input deck format. Both calculations result in mapping of dose distribution inside the phantom. MCNP5 utilizes the FMESH tool, superimposed mesh tally, which allows registering the results over the problem geometry. Resulting dose maps are compared.