Comparison of MCNP5 dose calculations inside the RANDO phantom irradiated with a MLC LinAc rhombus-shaped photon beam against treatment planning system PLUNC

Monte Carlo treatment planning techniques provide a very accurate dose calculation compared to `conventional´ deterministic treatment planning systems. In the present work, the irradiation of the RANDO phantom with an Elekta Precise MultiLeaf Collimated rhombus-shaped photon beam is validated throughout the comparison of dose maps calculated with PLanUNC (PLUNC), a set of software tools for radiotherapy treatment planning, and with MCNP5 (Monte Carlo N-Particle transport code). PLUNC was initially coupled with MCNP5 and so exactly the same patient and plan parameters can be utilized in both dose calculation processes. 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. The multileaf collimator of the Elekta Precise unit was designed and validated by means of different beam sizes and shapes. A set of Computer Tomography images of the RANDO phantom was obtained and formatted. The 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. Resulting dose maps are compared.