Reassign HU materials

Since version >= 3.75.10

Purpose: to show usage of reassignHU: directive for reassigning HU materials in a given range to a new material.

The syntax of the directive is:

reassignHU:

reassignHU: region material HUmin [HUmax]
where

region is the target region to modify

material is the new material to assign

HUmin is the minimum HU value

HUmax is the maximum HU value (optional; default = HUmin)

All voxels with HU value in the given range, i.e. HUmin <= HU <= HUmax, are assigned the new material.

The new material can be a standard material (such as air, water, PMMA, etc.) or an HU material (such as HU-500 or HU+1300).

Example:

assign to air all voxels with HU in the range [-1000,-300]
reassignHU: phantom air -1000 -300

Here an example where we use the built-in MrHead CT and change voxels in the low HU band to standard air:

# geometry definition
region: phantom; CTscan=MrHead; pivot=[0.5,0.5,0.0]; O=[0,0,0]; score= Dose; lWriteImat=t; lWriteDensity=t;

# replace standard air in a low HU range 
reassignHU: phantom air -1000 -300

# source definition
pbXsec=disc # round cross section with uniform distribution
pbFWHM=5 # diameter of the beam
pbE = 100 # energy of beam[MeV]

nprim=1e5 # no of primary protons to deliver

air reassignment — Density maps before (orig) and after (new) reassignment.

Important

the reassignHU: rules are applied in the order they are found in the input file