Mitochondria are considered to be sensitive radiation targets since they control processes vital to the cell’s functioning. These organelles are starting to get attention and some studies are ...investigating the radiation dose inside them. In previous studies, mitochondria are represented as simple ellipsoids inside the cell not taking into consideration the complexity of their shape. In this study, realistic phantoms are built based on deconvolved widefield fluorescent microscopic images of the mitochondrial networks of fibroblast cells. The phantoms are imported into Geant4 as tessellated volumes taking into account the geometrical complexity of these organelles. Irradiation with 250 keV photons is performed and the lineal energy is calculated. The lineal energy distributions inside the produced phantoms are compared with those calculated inside simple volumes, a sphere and an ellipsoid, where the effect of the shape and volume is clearly seen on lineal energies.
•3D realistic phantom of human fibroblast mitochondria is produced.•The realistic phantom is successfully imported into Geant4 as a tetrahedral mesh.•The phantom describes the complexity of the ...mitochondria structure.•Tracking of 250keV photons is performed.•Microdosimetric quantities are calculated inside the phantom.
Mitochondria are considered to be sensitive radiation targets since they control processes vital to the cell’s functioning. These organelles are starting to get attention and some studies are investigating the radiation dose inside them. In previous studies, mitochondria are represented as simple ellipsoids inside the cell not taking into consideration the complexity of their shape. In this study, realistic phantoms are built based on deconvolved widefield fluorescent microscopic images of the mitochondrial networks of fibroblast cells. The phantoms are imported into Geant4 as tessellated volumes taking into account the geometrical complexity of these organelles. Irradiation with 250keV photons is performed and the lineal energy is calculated. The lineal energy distributions inside the produced phantoms are compared with those calculated inside simple volumes, a sphere and an ellipsoid, where the effect of the shape and volume is clearly seen on lineal energies.
The goal of this study is to tune the design of the absorber detector of a Compton camera for prompt γ-ray imaging during ion beam therapy. The response of the Compton camera to a photon point source ...with a realistic energy spectrum (corresponding to the prompt γ-ray spectrum emitted during the carbon irradiation of a water phantom) is studied by means of Geant4 simulations. Our Compton camera consists of a stack of 2 mm thick silicon strip detectors as a scatter detector and of a scintillator plate as an absorber detector. Four scintillators are considered: LYSO, NaI, LaBr 3 and BGO. LYSO and BGO appear as the most suitable materials, due to their high photo-electric cross-sections, which leads to a high percentage of fully absorbed photons. Depth-of-interaction measurements are shown to have limited influence on the spatial resolution of the camera. In our case, the thickness which gives the best compromise between a high percentage of photons that are fully absorbed and a low parallax error is about 4 cm for the LYSO detector and 4.5 cm for the BGO detector. The influence of the width of the absorber detector on the spatial resolution is not very pronounced as long as it is lower than 30 cm.
The GATE Monte Carlo simulation platform based on the Geant4 toolkit is in constant improvement for dosimetric calculations. In this paper, we present the integration of Geant4-DNA processes into the ...GATE 7.0 platform in the objective to perform multi-scale simulations (from macroscopic to nanometer scale). We simulated three types of clinical and preclinical beams: a 6MeV electron clinical beam, a X-ray irradiator beam and a clinical proton beam for which we validated depth dose distributions against measurements in water. Frequencies of energy depositions and DNA damage were evaluated using a specific algorithm in charge of allocating energy depositions to atoms constituting DNA molecules represented by their PDB (Protein Data Bank) description.
The construction and first proton beam tests of a demonstrator dedicated to the beam ballistic control in hadrontherapy cancer treatments are described. This cost-effective demonstrator, called large ...area pixelized detector, is a PET-like detector used for in-beam ballistic control. It was built to test the feasibility of monitoring in real time, during irradiation, the ion range in the patient through the measurement of the beam-induced β + activity distribution. Achieving this goal necessitates to overcome several challenges. One of them is the rejection of the beam-induced background. Another one is the definition of fast event selection and reconstruction techniques so that real time monitoring is possible. Strategies employed to tackle these problems are presented and tested with the 65 MeV Medicyc proton beam of the cancer treatment center in Nice, France. In particular, an original fast reconstruction technique is presented. First performances obtained during irradiation of polymethyl methacrylate targets are described.
Collisions of Au on Au at incident energies of 150, 250 and 400
A·MeV were studied with the FOPI-facility at GSI Darmstadt. Nuclear charge (
Z ⩽ 15) and velocity of the products were detected with ...full azimuthal acceptance at laboratory angles 1° ⩽
θlab ⩽ 30°. Isotope separated light charged particles were measured with movable multiple telescopes in an angular range of 6–90°. Central collisions representing about 1% of the reaction cross section were selected by requiring high total transverse energy, but vanishing side flow. The velocity space distributions and yields of the emitted fragments are reported. the data are analysed in terms of a thermal model including radial flow. A comparison with predictions of the quantum molecular model is presented.
We investigate, by means of Geant4 simulations, a real-time method to control the position of the Bragg peak during ion therapy, based on a Compton camera in combination with a beam tagging device ...(hodoscope) in order to detect the prompt gamma emitted during nuclear fragmentation. The proposed set-up consists of a stack of 2
mm thick silicon strip detectors and a LYSO absorber detector. The
γ
emission points are reconstructed analytically by intersecting the ion trajectories given by the beam hodoscope and the Compton cones given by the camera. The camera response to a polychromatic point source in air is analyzed with regard to both spatial resolution and detection efficiency. Various geometrical configurations of the camera have been tested. In the proposed configuration, for a typical polychromatic photon point source, the spatial resolution of the camera is about 8.3
mm FWHM and the detection efficiency 2.5×10
−4 (reconstructable photons/emitted photons in
4
π
). Finally, the clinical applicability of our system is considered and possible starting points for further developments of a prototype are discussed.
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