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0002 ==========================================================================================
0003 Geant4 - GAMMAKNIFE example
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0005
0006 README file
0007 --------------------------------------------
0008
0009 AUTHORS:
0010 F.Romano* (a)
0011
0012 PAST AUTHORS:
0013 J. Pipek (c), A. Varisano (b), G.Russo (e), G.A.P. Cirrone (b), M.Russo (e), G. Cuttone (b), M.G.Sabini (d)
0014
0015 (a) INFN - Sezione di Catania, Catania, Italy
0016 (b) INFN - Laboratori Nazionali del Sud, Catania, Italy
0017 (c) Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, Czech Republic
0018 (d) UOS Fisica Sanitaria, Ospedale Cannizzaro, Catania, Italy
0019 (e) Fondazione Istituto San Raffaele G.Giglio, Cefalù (Palermo), Italy
0020
0021
0022 *Corresponding author, email to francesco.romano@ct.infn.it
0023
0024 -------------------------------------------------------------------------------------------------
0025
0026
0027 ----> INTRODUCTION.
0028
0029 The GAMMAKNIFE example is a Geant4 application specifically developed to simulate an advanced device for Stereotactic Radiosurgery. In particular, the example reproduces a Leksell Gamma-Knife unit model C, currently active at the Cannizzaro Hospital in Catania. Gamma-Knife Stereotactic Radiosurgery allows in a single session accurate external irradiations with high dose and sharp dose gradient to minimize radiation doses given to adjacent critical brain structures. The unit consists of a cast iron body containing 201 Co60 sources in a hemispherical arrangement. Beams of gamma radiation, coming from different directions focus through a collimation system at the isocentre, where the target volume is positioned.
0030
0031 This example allows to simulate the main components of a Gamma-Knife unit: the source, collimation system and also a spherical phantom used for routinely measurements. All the four available final collimators are reproduced and its dimension can be changed run-time by a macro command. The energy deposited distribution is computed at the end of the simulation in a voxellized geometry, using scoring mesh. GAMMAKNIFE example exploits original solutions for the sources device simulation, providing a very simple configuration of the geometry and primary events: a single source is, indeed, simulated (instead of 201) and the scoring mesh (placed in a spherical water phantom) is rotated at 201 angles correspondent to the real angular displacement of the sources in the device. This is possible thanks to the symmetry of the source positions respect to the isocentre.
0032
0033 The GAMMAKNIFE example has been recently migrated to multi-thread. Thus, according to the number of cores, you can choose the number of threads using the following command:
0034 /run/numberOfThreads <nThread>
0035
0036 The GAMMAKNIFE example contains the following subfolders and files:
0037 - /src: where source .cc files are stored
0038 - /include: where header .hh files are stored
0039 - README file
0040 - MachineAngle.in, where the angular positions of the specific unit model are tabulated
0041 - defaultMacro.mac, where visualization is included and a simple run with few events is done
0042 - simulation.mac, where a whole simulation is performed, changing all the 201 angular positions, storing the deposited energy for each run and saving the total energy deposted at the end of the simulation.
0043
0044
0045 ----> INSTALLATION
0046
0047 GAMMAKNIFE source is currently released inside the official distribution of the Geant4 toolkit in the $G4INSTALL/examples/advanced folder.
0048
0049 To run GAMMAKNIFE you must first install the Geant4 package. Once Geant4 is installed, the example must be first compiled. When compilation has been completed the program can be executed.
0050
0051 A complete guide for the Geant4 installation in different operating systems can be found inside the official installation Geant4 pages.
0052
0053 If some troubles are faced with the Geant4 installation please send an e-mail to us.
0054
0055
0056 ----> HOW TO RUN THE EXAMPLE
0057
0058 The defaultMacro.mac is executed if no macro file is specified.
0059
0060 For a realistic simulation of the Gamma-Knife device, including the irradiation of all the sources, the macro simulation.mac has to be used, defining the number of particles shooted per each angle (that is, for each "source"). The following commands have to be used to this aim:
0061 /gammaknife/loadAngles MachineAngle.in --> rotation agles file is called
0062 /gammaknife/beamOn <number-of-events> --> <number-of-events> are shooted for each angle
0063
0064
0065 ----> PRIMARY EVENTS GENERATION
0066
0067 The primary particle beam parameter are:
0068 - energy of gamma: 1.17 and 1.33 MeV with the same probability
0069 - X Y Z positions sampled in a cylinder 20 mm lenght and 1 mm of radius
0070 - angular biasing within an angle of 3 degree: it has been checked not to influence final results (respect to a 4p isotropic sampling) drastically decreasing computatuin time
0071 GPS (General Particle Source) class is used to generate the primary events.The GPS.in macro is called and executed when yoo use bot simulation.mac and defaultMacro.mac macro.
0072
0073
0074 ----> GEOMETRICAL SET-UP.
0075
0076 The Gamma-Knife unit consists of a cast-iron body containing the 60Co sources and the collimation system. Sources are displaced along five parallel rings at the same distance from the isocentre. Depending on the specific ring, sources are located with a different spacing, respectively with an angle of 7.6°, 8°, 9°, 9° and 10°. These angles represent the rotation angles of the scoring mesh (contained in the MachineAngle.in file). Gamma radiation (1.17 and 1.33 MeV), emitted by Co60 sources arranged in a hemispherical shape, focuses on the isocentre, located 401 mm far from the source. The radiation beam is collimated by means of fixed and mobile collimation systems in order to obtain four possible beam diameters at the isocentre: 4, 8, 14 and 18 mm.
0077
0078 The elements simulated are:
0079
0080 - cobalt cylinder source (20 mm length, 1 mm radius)
0081 - a stainless steel covering of the source
0082 - a first tungsten cylindrical collimator (65 mm length)
0083 - a second truncate cone lead collimator (92.5 mm lenght)
0084 - final truncated cone tungsten collimator (60 mm lenght), with four available final apertures simulating the mobile helmet
0085 - tungsten, iron and stainless steel surrounding the collimation system for shielding
0086 - a spherical water phantom (8 mm radius) simulating the phantom typically used for dosimetrical measurements and routinely quality check
0087
0088 To change the diameter of the final truncated collimator (mobile helmet) the following command has to be used for chaching the diameter:
0089 /calorimeter/helmetSize <diameter in mm>
0090 Notice that, as in the real device, only four final diameters are allowed: 4, 8, 14 and 18 mm. These are not the physical apertures of the diameter but represent the final diameter of the beam at the isocentre. In the GammaKnifeDetectorConstruction::UpdateHelmet() method more details can be found in this concern.
0091
0092 Important note: the GAMMAKNIFE application is meant as an example of simulation of a device for Stereotactic Radiosurgery. Thus, all the main geometrical features of the Gamma-Knife device are accurately simulated but the geometrical displecement of the some elements is not exactly correspondent to the real one, because covered by a patent. In case you need detailed geometrical information, please contact the Elekta Company.
0093
0094
0095 ----> PHYSICS
0096
0097 Local PhysicsList is activated by default (GammaKnifePhysicsList.cc), which includes the G4EmStandardPhysics_option3.
0098
0099 Anyhow, it is recommended the use of the Reference Physics List QGSP_BIC_EMY, which is the suggested on for medical applications.
0100
0101 ----> VISUALISATION
0102
0103 The user can visualise the experimental set-up with OpenGL, DAWN and vrml.
0104
0105
0106 ----> SIMULATION OUTPUT
0107
0108 At the end of the simulation the energy deposited in each voxel of the scoring mesh inside the spherical phantom is registered in the eDep_scorer.out file. Default voxelization is 45 x 45 x 45 cubic voxels 1 mm of side. User can change dimension and shape of box the mesh and the voxel.
0109 Alternatively, the dose deposited can be also stored using the appropriate scoring commands
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0112
0113
0114 For comments, advices and questions please contact:
0115 francesco.romano@ct.infn.it
0116
0117 last modified: F.Romano, 03/11/2020
0118
0119
