Spectra Scorers
FRED is capable to score spectra of a given quantity with a predefined binning for each voxel of a voxelized geometry. The results are saved to multicomponent MetaImage files (MHD), where each voxel is a vector of the spectrum values. Additionally, the binning definition and the spectrum unit are saved as spectrumBins and spectrumUnit private tags, respectively, whereas the bins are defined as the bin edges, with the accordance to the numpy.histogram definition. To enable the spectrum scorer for a given region, the spectra parameter must be set as one of the scorer in the region definition (e.g. score = [Dose, spectra]). The type of the specrum and binning definition can be controlled in a spectraScorer multi-line definition with the following parameters:
- spectrumTypeobligatory
Type of the spectrum to score (e.g. LETMethodC, see the description below)
- binningTypeobligatory
Type of the binning. lin` or log` for linear or logarithmic binning.
- binningMin0 for lin, 1E-6 for log`
Minimum value of the binning. In case of the logarithmic binning and binningMin=0, the value will be internally set to 1E-6.
- binningMax100
Maximum value of the binning.
- binningStepNo100
Number of bins. The bin size is calculated to evenly distrubute bins between binningMin and binningMax in linear or logarithmic scale.
- The following spectra types are implemented with the symbols used in the formulas:
\(s\) - energy deposition step
\(S\) - total number of energy deposition steps of a particle in a voxel
\(\epsilon_s\) - deposited energy by the particle during the step \(s\)
\(l_s\) - length of the step \(s\)
\(SP^{el}\) - electronic stopping power table
The methods of the LET computation have been implemented and named as methods A, B and C based on the Cortes-Giraldo and Carabe (PMB, 2015, doi:10.1088/0031-9155/60/7/2645) paper.
Kinetic energy
spectrumType = EkinIn
The spectrum of kinetic energy of protons entering a voxel, i.e. \(E_{kine}^{in}\). Only the kinetic energy of protons that enter a voxel (primary and secondary) are scored but no secondaries produced in the voxel.
spectrumType = EkinInProd
The spectrum of proton kinetic energy entering a voxel and the initial energy of protons produced in the voxel, i.e. \(E_{kine}^{in+prod}\). The kinetic energy of protons that enter a voxel (primary and secondary) are scored, as well as the initial energy of secondary protons produced in the voxel.
Deposited energy
spectrumType = Edep
The spectrum of the total deposited energy of protons in a voxel. The deposited energy of a single proton in a voxel is calculated as:
The deposited energy is summed in a voxel for each proton entering the voxel and produced in the voxel, separately.
spectrumType = EkinEdep
The spectrum of kinetic energy differential in deposited energy, i.e. \(E_{kine}(E_{dep})\). This scorer requires a float type of multi-component image.
Track length
spectrumType = TrackLength
The spectrum of the total track length of protons in a voxel. The track length of a single particle in a voxel is calculated as:
The total step lengths are summed in a voxel for each proton entering the voxel and produced in the voxel, separately.
Linear energy transfer
spectrumType = LETSPEkinIn - Electronic stopping power of incoming particles
The spectrum of LET calculated as the stopping power value of the particle entering a voxel, taken from the SPT. The LET of a single particle is given by:
spectrumType = LETMethodA - Method A: averaging over each step
The LET of a single proton is calculated for each step and then averaged by the total energy deposited. The LET of a single particle is given by:
spectrumType = LETMethodB - Method B: averaging over total track
The LET of a single particle is calculated as the ratio of its total energy deposition to total track length within a voxel, i.e.:
spectrumType = LETMethodC - Method C: averaging stopping power with deposited energy
The spectrum of LET for each step is calculated as the electronic stopping power, \(SP^{el}_{s}\), taken from the precomputed electronic stopping power tables, for the arithmetic mean kinetic energy of the values at pre- and post-step points, i.e. \(\overline{E}^{s}_{kine} = (E^{A}_{kine} + E^{B}_{kine}) \cdot 0.5\). The LET is then averaged by the total energy deposited, and the LET of a single particle is given by: