Dosimetry
Dosimetry module can be activated to compute absorbed dose. For the moment only photons are simulated, electrons are ignored.
Dosimetry module is ‘GGEMSDosimetryCalculator’:
dosimetry = GGEMSDosimetryCalculator()
A navigator phantom must be attached to GGEMSDosimetryCalculator using:
dosimetry.attach_to_navigator('phantom')
Size of voxel (dosel) for dosimetry image could be set, if not the dosel size is the same than voxel phantom size:
dosimetry.set_dosel_size(0.5, 0.5, 0.5, 'mm')
Absorbed dose is computed in gray (Gy). By default dose in computed using materials in phantom. Otherwize the user can set water material everywhere in phantom.
dosimetry.water_reference(True)
A custom density threshold can be set. If density of phantom is below this threshold the dose value in 0 Gy.
dosimetry.minimum_density(0.1, 'g/cm3')
Since GGEMS v1.2, TLE method (Track Length Estimated) proposed in [Smekens2014] can be activated to improve statistics.
dosimetry.set_tle(is_tle)
Many informations can be registered such as: uncertainty values of the dose, the deposited energy in dosel, the squared of deposited energy in dosel and the number of interactions (hits) in dosel:
dosimetry.set_output('dosimetry')
dosimetry.uncertainty(True)
dosimetry.edep(True)
dosimetry.hit(True)
dosimetry.edep_squared(True)
There is a special output named ‘photon tracking’. This output registers the number of photons crossing a dosel. To use this option, the size of dosel has to be the same than the phantom voxel size, otherwize GGEMS will throw an error:
dosimetry.photon_tracking(True)
Baldacci, A. Mittone, A. Bravin, P. Coan, F. Delaire, C. Ferrero, S. Gasilov, J. M. Létang, D. Sarrut, F. Smekens, et al., “A track length estimator method for dose calculations in low-energy x-ray irradiations: implementation, properties and performance”, Zeitschrift Fur Medizinische Physik, 2014.