See About phantoms and projectors.

These are large files, so you might want to be selective about which ones you download.

Each phantom describes a 3D volume, and includes multiple material "volume fraction maps" (.density_) and one .json file. Each material map has a unique XY size and offset, because only pixels that contain that material are included. This reduces memory required to load the phantom, and improves computational efficiency during simulation.

Some phantoms are also provided as a single slab (one voxel in Z). These are a subset of the 3D phantom of the corresponding name. Because these have a smaller Z extent, they may not include some organs included in the full 3D phantom, and therefore might have fewer material maps. The Z voxel is specified as 50 mm in length, so multi-row simulations are possible, but projections of each row will be almost identical (except for the cosine factor and x-ray source "heel effect" if multiple source samples in Z are specified). With only one Z voxel and minimal material maps, these are convenient for fast, efficient simulations during parameter selection and code development.