This program calculate the dose inside a CT phantom for a set of beam positions and energies.

Note: No [] in the real input file

CT_file = [.img file]
material = [material file, e.g. mat_99.txt]
Beam_Type = [gamma, proton, electron, etc.]
Fixed_Energy_MeV = [fixed energy steps in MeV]
Random_Energy_MeV(Min,Max,N) = [1.0  1.0  0]
Beam_X = [minX maxX stepX]
Beam_Z = [minZ maxZ stepZ]
Error_Target = [dose_pct sim_err]  # the uncertainty of all doses larger than 'dose_pct' must be less than 'sim_err' 
Primary_per_Batch = [# of particles per batch]
Max_Primary = [# of max total particles]
Output_Full = [0/1]  # 1: output full voxels, 0: only save data in the output rante (the next)
Output_Range_mm = [output +/- ## mm from the beam ceter]
Verbose = [0/1/2, verbose level]

• int32, int32, int32: voxel number on X/Y/Z (nx, ny & nz)
• float32, float32, float32: voxel size on X/Y/Z
• int16[nx*ny*nz]: HU number of voxels, in the order of X, Y, and then Z

class img_data in check-img.py demonstrates how to read the .img file.

• int32, int32, int32: voxel number on X/Y/Z (nx, ny & nz)
• float32, float32, float32: voxel size on X/Y/Z
• int32, int32: X/Z voxel index of beam center
• float32: particle energy in MeV
• int32, int32: Xmin, Xmax of the voxel index
• int32, int32: Zmin, Zmax of the voxel index
• float32[(Xmax-Xmin+1)*ny*(Zmax-Zmin+1)]: Dose/Error in voxels, in the order of X, Y, and then Z

class dose_data in check-img.py demonstrates how to read the .dose file.

HU2mat.py defines the coversion of CT number (HU) to the densities and elemental weights of materials, based on the paper of Schneider et al., Phys. Med. Biol. 45 (2000) 459-478.

The densities are linearly interpolated between materials as described in the paper:

Note: To minimize the fluctration of CT scans on air, the HUs in the range from -1000 to the first HU in the material definition file use the density of air (i.e. no interpolation).

However, to have resolutions finer than the 24-bin setting in the paper, some deviations are introduced:

• The paper used the interpolation value at the center of each bin except the bin at 18-80 and those explicitly listed above
• The code interpolate the elemental weights according to Eq. 18.
• The code uses the mean of the interpolated values of all HUs in a bin.

An ouput with 99 bins is given.