Photon Base Data File

This page describes the format and the variables as part of the particle base data files protons_Generic.mat and carbon_Generic.mat. The base data is stored using MATLAB’s structure format. The first sub level of the structure ‘machine’ contains two fields named ‘meta’ and ‘data’ which are explained separately next.

machine.version

Specifies the version of the machine file. If not present, version 1 is assumed. Currently version 1 and 2 are supported. Version 2 is the current standard used in matRad. It’s main difference to version 1 is that kernel normalization does not imply a convolution grid of 0.5 mm.

machine.meta

Stores relevant isolated meta information describing the actual base data file that does not fit into the machine.data structure.

machine.meta.name

Actual machine name as string to identify the base data set during runtime.

machine.meta.radiationMode

The radiationMode stores the radiation modality the base data is describing. Logically, protons_Generic.mat models protons in water and the corresponding field machine.meta.radiationMode is set to ‘protons’.

machine.meta.SAD

This subfield holds the geometrical source to axis distance in millimeter. In case of the generic base data set, we use a value of 1000 [mm].

machine.meta.SCD

This subfield holds the geometrical source to collimator distance in millimeter. In case of the generic base data set, we use a value of 500 [mm]. This value is mainly used to convert between penumbra and source width.

machine.data

This subfield contains the detailed dosimetric machine information. It is currently only storing decomposed pencil-beam kernels according to Bortfeld et al. (1993) Medical Physics.

machine.data.energy

Maximum photon energy in MeV. Corresponds to the acceleration potential in MV.

machine.data.betas

Beta factors for the individual kernels. Row array with length of number of kernels.

machine.data.m

Attenuation factor (obtained from kernel fitting).

machine.data.primaryFluence

Radial fluence distribution of a photon beam.

machine.data.kernelPos

Lateral Kernel evaluation positions in [mm]. Alle kernels in machine.data.kernel are tabulated at these positions.

machine.data.penumbraFWHMatIso

Penumbra full width half maximum (FWHM) at isocenter in [mm]. This value is used to convert between penumbra and source width and in kernel convolution with the field function.

machine.data.kernel

Structure Array with all kernels by SSD. Each kernel struct contains the field SSD to tell the corresponding SSD for which the kernel components were fitted. Further fields enumerate the kernels, i.e.: kernel1, kernel2, kernel3, etc. Each kernel is tabulated at the positions given in machine.data.kernelPos and has been fitted to the measured data. Number of kernels must match the length of machine.data.betas.