Use of the FLUKA Monte Carlo code for 3D patient-specific dosimetry on PET-CT and SPECT-CT images

Abstract

Patient-specific absorbed dose calculation for nuclear medicine therapy is a topic of increasing interest. 3D dosimetry at the voxel level is one of the major improvements for the development of more accurate calculation techniques, as compared to the standard dosimetry at the organ level. This study aims to use the FLUKA Monte Carlo code to perform patient-specific 3D dosimetry through direct Monte Carlo simulation on PET-CT and SPECT-CT images. To this aim, dedicated routines were developed in the FLUKA environment. Two sets of simulations were performed on model and phantom images. Firstly, the correct handling of PET and SPECT images was tested under the assumption of homogeneous water medium by comparing FLUKA results with those obtained with the voxel kernel convolution method and with other Monte Carlo-based tools developed to the same purpose (the EGS-based 3D-RD software and the MCNP5-based MCID). Afterwards, the correct integration of the PET/SPECT and CT information was tested, performing direct simulations on PET/CT images for both homogeneous (water) and non-homogeneous (water with air, lung and bone inserts) phantoms. Comparison was performed with the other Monte Carlo tools performing direct simulation as well. The absorbed dose maps were compared at the voxel level. In the case of homogeneous water, by simulating 108 primary particles a 2% average difference with respect to the kernel convolution method was achieved; such difference was lower than the statistical uncertainty affecting the FLUKA results. The agreement with the other tools was within 3–4%, partially ascribable to the differences among the simulation algorithms. Including the CT-based density map, the average difference was always within 4% irrespective of the medium (water, air, bone), except for a maximum 6% value when comparing FLUKA and 3D-RD in air. The results confirmed that the routines were properly developed, opening the way for the use of FLUKA for patient-specific, image-based dosimetry in nuclear medicine.

Evaluation of Electron Specific Absorbed Fractions in Organs of Digimouse Voxel Phantom Using Monte Carlo Simulation Code FLUKA

“…FLUKA shows the results similar to those obtained by EGS and MCNP codes for 3D patient specific dosimetry [15]. FLUKA code also shows results similar to those obtained by EGS and MCNP codes for the estimation of external organ dose conversion coefficients [16] and evaluation of SAF values [17] in ICRP reference voxelized phantoms.…”

Calculation of electron and isotopes dose point kernels with fluka Monte Carlo code for dosimetry in nuclear medicine therapy

“…The first is that FLUKA tools allow to develop dedicated routines to import morphofunctional images in the code and perform 3D dose calculation through patient-specific simulations. 42,43 These features are generally desirable but indispensable in case of dosimetry in nonhomogeneous tissues. The development of such Monte Carlo based dosimetry, however, is very demanding, so the real necessity deserves to be deeply investigated, also in consideration of the inaccuracy affecting the activity distribution data.…”

Development and validation of an open source Monte Carlo dosimetry model for wide‐beam CT scanners using Fluka

“…The radiation transport model for the CT scanner is developed using the open source Monte Carlo code Fluka. Although previous studies have utilized Fluka in applications such as radiotherapy and nuclear medicine, Fluka has not been validated for diagnostic dose calculations in CT. As the same voxel geometry and organ segmentation generated for radiotherapy dose simulations can be used for diagnostic dose calculations, the model developed in this work can be extended to calculate total radiation dose for radiotherapy patients using Fluka.…”