A voxel-based mouse for internal dose calculations using Monte Carlo simulations (MCNP)

Abstract

Murine models are useful for targeted radiotherapy pre-clinical experiments. These models can help to assess the potential interest of new radiopharmaceuticals. In this study, we developed a voxel-based mouse for dosimetric estimates. A female nude mouse (30 g) was frozen and cut into slices. High-resolution digital photographs were taken directly on the frozen block after each section. Images were segmented manually. Monoenergetic photon or electron sources were simulated using the MCNP4c2 Monte Carlo code for each source organ, in order to give tables of S-factors (in Gy Bq-1 s-1) for all target organs. Results obtained from monoenergetic particles were then used to generate S-factors for several radionuclides of potential interest in targeted radiotherapy. Thirteen source and 25 target regions were considered in this study. For each source region, 16 photon and 16 electron energies were simulated. Absorbed fractions, specific absorbed fractions and S-factors were calculated for 16 radionuclides of interest for targeted radiotherapy. The results obtained generally agree well with data published previously. For electron energies ranging from 0.1 to 2.5 MeV, the self-absorbed fraction varies from 0.98 to 0.376 for the liver, and from 0.89 to 0.04 for the thyroid. Electrons cannot be considered as 'non-penetrating' radiation for energies above 0.5 MeV for mouse organs. This observation can be generalized to radionuclides: for example, the beta self-absorbed fraction for the thyroid was 0.616 for I-131; absorbed fractions for Y-90 for left kidney-to-left kidney and for left kidney-to-spleen were 0.486 and 0.058, respectively. Our voxel-based mouse allowed us to generate a dosimetric database for use in preclinical targeted radiotherapy experiments.

Development of a mouse computational model for MCNPx based on Digimouse (r) images and dosimetric assays

“…Much of the mice used in ionizing radiation experiments are within this weight. However, they were based only on segmentations of a few animals (Hindorf, Ljungberg, Strand, 2004;Kolbert et al, 2003;Stabin et al, 2006;Stout et al, 2002;Bitar et al, 2007;Segars et al, 2004). Indeed, a large group of mouse models, including DM_BRA, were based on images of only two animals: the Digimouse project data (Nude-male) or phantom Moby (C57BL/6-male).…”

“…Situ, Hoffman, Hartmann (2005) and Stabin et al (2006) published voxel phantoms of mice with segmentation process based on MicroCT images. Bitar et al (2007);Bitar, Lisbona, Bardiès (2007) implemented a mouse phantom of a female athymic "nude" strain. In this work, MicroCT or MicroMRI images were not used.…”

Assessment of radiation exposure of murine rodents at the EURT territories

“…for humans, the calculations of dose coefficients relating the intake of radionuclides and the equivalent dose in organs are made using the human voxel models. Recently, a number of animal voxel phantoms, particularly mice voxel phantoms, were developed [23][24][25][26][27].…”

Effect of emaciation and obesity on small-animal internal radiation dosimetry for positron-emitting radionuclides

“…Further improvements led to finer stylized small-animal models including rat [6,7] and mouse models containing more internal organs and even realistic tumour models [8][9][10]. Likewise, various voxel-based smallanimal models have been developed by different groups for radiation dosimetry research using different specimens [11][12][13][14][15][16][17][18][19]. More recently, computational models of laboratory animals based on non-uniform rational B-spline surfaces (NURBS) have become available [20].…”