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114 CMOS IMAGERS AS DOSIMETRIC DEVICES IN INTERVENTIONAL RADIOLOGY PROCEDURES.
S46 (immunofluorescence through γ-H2AX assay) at different times post irradiation showing the different rate at which plateau and peak DNA insults are repaired. Analysis of foci size (FWHM) and residual number of foci at 24 h post irradiation have also been performed to relate the severity of DNA damage induced to the cellular outcome and compare it to other type of radiations (X-rays, protons and antiprotons). Out of field measurements also suggest significant DNA damage being induced in cells not directly exposed but which share medium with exposed cells (bystander effect). This damage appears to be independent from the dose delivered but with a small LET contribution. Finally, chromosome aberration studies reveal substantial chromosome rearrangement induced in both the plateau and the SOBP region. Interestingly, the aberration rate appears to be dose dependent in the plateau region but not in the SOBP. Moreover, the quality of the aberrations detected also shows an interesting pattern with transmissible aberrations dominating in the plateau response while lethal rearrangement and chromosome fragments are the majority in the SOBP. 113 MONTE-CARLO SIMULATION TO OPTIMIZE SPECT-HARDWARE DEDICATED TO IN-BEAM CONTROL OF PARTICLE THERAPY H. Rohling1, F. Fiedler2, U. Dersch1, S. Schöne2, A. Müller1, C. Golnik1, T. Kormoll1, W. Enghardt1 1 OncoRay TU Dresden, Germany 2 Helmholtz-Zentrum Dresden-Rossendorf, Germany Therapeutic irradiation with ions and protons is superior to a treatment with gammas with respect to tumour conformity of dose and damage of normal tissue. On the other hand, mispositioning of the patient or density changes in the treated volume may easily compromise the success of treatment. For this reason, non-invasive, in-situ dose verification is necessary. The only clinically proven method up to now is Positron Emission Tomography [Eng04]. This method does not allow direct dose quantification due to limited angle artefacts and washout in the patient. Another promising approach is in-beam SPECT: the detection of prompt gamma-rays following nuclear interaction between the ions and the atoms of the penetrated tissue. Detection systems based on Compton-scattering and pair-conversion are now under investigation. So far, Compton-cameras have been used for diagnostic imaging in nuclear medicine and astronomy. In telescopes also pair-creation cameras are established [Zog04]. In contrast to this, in-beam dose verification systems have to manage the specific energy range and low count rates due to the patient dose. A prototype of a Compton-camera is under construction at OncoRay [Kor10, Fie11, Kor11]. It consists of a scatter layer made from CZT and an absorption layer (LSO). From the energy deposited in the detector planes a cone surface of all possible directions of the incident photon can be reconstructed [Sch11]. The expected energy distribution of the prompt gammas is calculated by means of simulations based on treatment plan data [Fie11]. To optimize the setup simulations are required. Therefore, the Monte-Carlo framework GEANT4 is used for:
ICTR-PHE 2012 (1) Analysis of the efficiency in dependence of the geometry; (2) Study of background caused by backscattered photons and other secondary particles; (3) Development of filters for event selection; (4) Study parameters influencing the spatial resolution of the reconstructed image (multiple Compton-scattering inside a detector layer, escape of energy, intrinsic radioactivity of the detector material, Dopplerbroadening); (5) Creation of test data sets as input for the reconstruction. For photon energies above 7 MeV the pair production is the dominant electromagnetic process in CZT. To use these events the Compton-camera might be combined with a pair-conversion camera by adding thin silicon layers in between to track the path of the electron and the positron produced during pair conversion. Exploiting this information the direction of the incident photon can be deduced. Unfortunately, the angular resolution is heavily degraded especially for photons with rather low incident energies by small-angle scattering of the secondary particles and by the recoil of the nuclei when a pair production takes place [Gol11]. Both effects were studied whereas the latter is not included in the GEANT4 code version 9.3. This simulation serves as basis for the development of an iterative reconstruction algorithm dedicated to in-beam SPECT with a pair production camera. Apart from the analysis of efficiency, angular resolution and noise, the combination of a pair production and a Comptoncamera is a challenging task. Results on simulations for optimizing the setup and the refinement of the reconstruction algorithm for a clinical dose verification system will be presented. [Eng04] W. Enghardt et al., Nucl. Instr. and Meth. A 525 (2004) 284. [Fie11] F. Fiedler et al., Nucl. Sci. Symp. IEEE (2011), accepted. [Gol11] C. Golnik et al., Nucl. Sci. Symp. IEEE (2011), accepted. [Kor10] T. Kormoll et al., Nucl. Instr. Meth. A 626/627 (2011) 114. [Kor11] T. Kormoll et al., Nucl. Sci. Symp. IEEE (2011), accepted. [Ric10] M.-H. Richard et al., IEEE Transactions on Nuclear Science (2010) [Sch11] S. Schöne et al., Proc. Fully 3D Meeting (2011). [Zog04] A. Zoglauer et al., Nucl. Sci. Symp. Conf. Rec. IEEE (2004). 114 CMOS IMAGERS AS DOSIMETRIC DEVICES IN INTERVENTIONAL RADIOLOGY PROCEDURES. L. Servoli1, M. Biasini1, P. Placidi1, D. Passeri2, L. Fano1, B. Checcucci3, 1 Universita e INFN Perugia, Italy 2 University of Perugia, Italy 3 INFN Sez. Di Perugia c/o Dipt. Di Fisica (INFN), Italy Interventional Radiology (IR) is a subspecialty of radiology comprehensive of all minimally invasive diagnostic and therapeutic procedures performed using radiological devices to obtain image guidance. The interventional procedures are potentially harmful for interventional radiologists and medical staff due to the X-ray diffusion by the patient's body. The characteristic energy range of the diffused photons spans few tens of keV.
S47 In this work we propose an active pixel device to be used as X-ray dosimeter for individual operators. APS have shown a good capability as ionizing radiation detectors for the X-ray energy range of interest. We concentrated on the study of an off-the-shelf CMOS imager tested in Interventional Radiology conditions. Two dosimetric quantities have been studied, the number of detected photons and the measured energy deposition. Both observables have a linear dependence with the dose measured by standard passive dosimeters (TLDs). The uncertainties in the measurement are dominated by statistic and can be pushed below 5%. The acquisition frequency can be kept at 1 Hz thus allowing a fast and precise dose rate measurement. The sensitivity to low energy photons (down to few keV) considerably lower than thecommercially available dosimeters, allowing to measure this radiation component, important for the evaluation of epidermis damages. We conclude that Active Pixel Devices could be used as sensitive element for X-ray dosimeter in the energy range characteristic of IR procedures. Acknowledgments: The research has been partially supported by: Fondazione Cassa di Risparmio di Perugia, (Research Grants 2010.011.0421, 2010.011.0474) and P.O.R. Umbria FSE 2007-2013. 115 DESIGN, DOSIMETRY CHARACTERISTICS AND SHIELDING ASSESSMENT OF A NEW MOBILE ELECTRON ACCELERATOR FOR INTRAOPERATIVE RADIATION THERAPY (IORT) DEVELOPED USING MONTE CARLO METHODS A. Wysocka-Rabin, P. Adrich, A. Wasilewski NCBJ, Otwock, Poland Purpose: Intraoperative radiation therapy (IORT) delivers a large, single fraction dose of radiation to a surgically exposed tumor or tumor bed. This work presents the design concept and dosimetry characteristics of an electron beam forming system for an IORT accelerator, with special emphasis on beam flatness, X-ray contamination and dose delivered outside the treatment field. Methods: The Monte Carlo code, BEAMnrc/EGSnrc, was used to build and test the electron beam forming system for two different docking systems (soft and hard) using circular metallic applicators. Calculations of therapeutic beam characteristics were performed at the patient surface. FLUKA code was used for beamstopper and shielding calculation. Results: Findings were obtained for initially monoenergetic electron beams with an energy range from 4 to 12 MeV, SSD equal to 60 cm., and circular applicators with diameters from 3 to 12 cm. Two-D distribution of dose equivalents inside and outside the operating room were calculated for a maximum energy of 12 MeV, with and without specially-designed halfbarrel metal shielding. Conclusions: An electron beam forming system for a new mobile electron accelerator for IORT, with two different docking systems of circular applicators, has been designed, verified and optimized based on Monte Carlo calculations. The electron beam forming system (collimators, scattering-flattening foils) is universal for every beam energy and every field diameter described above. Dose distribution in the patient plane, inside
ICTR-PHE 2012 and outside operating room, meets all regulatory requirements for radiation protection. A prototype will now be constructed and tested in the laboratory. This work was funded by the Polish Ministry of Science and Higher Education and the EU in frame of Operational Programme -) Innovative Economy, project no. POIG 1.1-21 116 FRAGMENTATION MEASUREMENT OF 12C IONS ON C AND AU TARGET WITH THE FIRST EXPERIMENT AT GSI V. Patera Universita' di Roma "Sapienza", Rome, Italy The study of nuclear fragmentation processes of 12C ions plays a key role in several different fields of basic and applied physics. An international collaboration of institutions from France, Germany, Italy and Spain designed and built the FIRST experiment at GSI. The scientific program foresees to collect high quality data of the fragmentation of ion beams on different targets, relevant for space radiation protection and tumor therapy applications. The experimental setup is made of a thin fast scintillator (Start Counter) and a large area Time of Flight system (TOFWALL), a Drift Chamber beam monitor, a Silicon Vertex detector integrated with the target system, a large angle proton tagger (KENTROS), a large dipolar magnet (ALADiN) and a Neutron detector (LAND2). During the first data taking in summer 2011 about 18M (carbon on carbon) and 2M (carbon on gold) events have been collected using 12C ions projectiles accelerated by the SIS at the energy of 400 A·MeV. We review in this presentation the performance of the different FIRST sub-detectors and the status of full event reconstruction and differential cross section measurements. 118 INBEAM SPECT BASED IN VIVO DOSIMETRY: FROM TREATMENT PLANNING TO MEASURED DOSE A. Müller1, F. Fiedler2, D. Georg3, J. Hopfgartner3, W. Enghardt1,2 1 TU Dresden, OncoRay – National Center for Radiation Research in Oncology, Fetscherstr. 74, D01307 Dresden, Germany 2 HelmholtzZentrum DresdenRossendorf, Postfach 51 01 19, D01314 Dresden, Germany AKHWien, 3 Universitätsklinik für Strahlentherapie, Währinger Gürtel 1820, A1090 Vienna, Austria To achieve the best possible treatment success, radiotherapy with protons and light ions for treating and curing cancer requires an accurate, reliable and especially tumour conformal dose deposition. Currently, positron emission tomography (PET) is the only feasible method to provide a qualitative in vivo dose estimation during particle therapy. An imaging system based on Compton scattering has been suggested as an alternative to PET. Inbeam single particle emission computed tomography (SPECT) with a Compton camera is expected to detect prompt gammarays, emitted during the irradiation, over a wide energy range. In contrast to PET, that relies on the
ICTR-PHE 2012 (1) Analysis of the efficiency in dependence of the geometry; (2) Study of background caused by backscattered photons and other secondary particles; (3) Development of filters for event selection; (4) Study parameters influencing the spatial resolution of the reconstructed image (multiple Compton-scattering inside a detector layer, escape of energy, intrinsic radioactivity of the detector material, Dopplerbroadening); (5) Creation of test data sets as input for the reconstruction. For photon energies above 7 MeV the pair production is the dominant electromagnetic process in CZT. To use these events the Compton-camera might be combined with a pair-conversion camera by adding thin silicon layers in between to track the path of the electron and the positron produced during pair conversion. Exploiting this information the direction of the incident photon can be deduced. Unfortunately, the angular resolution is heavily degraded especially for photons with rather low incident energies by small-angle scattering of the secondary particles and by the recoil of the nuclei when a pair production takes place [Gol11]. Both effects were studied whereas the latter is not included in the GEANT4 code version 9.3. This simulation serves as basis for the development of an iterative reconstruction algorithm dedicated to in-beam SPECT with a pair production camera. Apart from the analysis of efficiency, angular resolution and noise, the combination of a pair production and a Comptoncamera is a challenging task. Results on simulations for optimizing the setup and the refinement of the reconstruction algorithm for a clinical dose verification system will be presented. [Eng04] W. Enghardt et al., Nucl. Instr. and Meth. A 525 (2004) 284. [Fie11] F. Fiedler et al., Nucl. Sci. Symp. IEEE (2011), accepted. [Gol11] C. Golnik et al., Nucl. Sci. Symp. IEEE (2011), accepted. [Kor10] T. Kormoll et al., Nucl. Instr. Meth. A 626/627 (2011) 114. [Kor11] T. Kormoll et al., Nucl. Sci. Symp. IEEE (2011), accepted. [Ric10] M.-H. Richard et al., IEEE Transactions on Nuclear Science (2010) [Sch11] S. Schöne et al., Proc. Fully 3D Meeting (2011). [Zog04] A. Zoglauer et al., Nucl. Sci. Symp. Conf. Rec. IEEE (2004). 114 CMOS IMAGERS AS DOSIMETRIC DEVICES IN INTERVENTIONAL RADIOLOGY PROCEDURES. L. Servoli1, M. Biasini1, P. Placidi1, D. Passeri2, L. Fano1, B. Checcucci3, 1 Universita e INFN Perugia, Italy 2 University of Perugia, Italy 3 INFN Sez. Di Perugia c/o Dipt. Di Fisica (INFN), Italy Interventional Radiology (IR) is a subspecialty of radiology comprehensive of all minimally invasive diagnostic and therapeutic procedures performed using radiological devices to obtain image guidance. The interventional procedures are potentially harmful for interventional radiologists and medical staff due to the X-ray diffusion by the patient's body. The characteristic energy range of the diffused photons spans few tens of keV.
S47 In this work we propose an active pixel device to be used as X-ray dosimeter for individual operators. APS have shown a good capability as ionizing radiation detectors for the X-ray energy range of interest. We concentrated on the study of an off-the-shelf CMOS imager tested in Interventional Radiology conditions. Two dosimetric quantities have been studied, the number of detected photons and the measured energy deposition. Both observables have a linear dependence with the dose measured by standard passive dosimeters (TLDs). The uncertainties in the measurement are dominated by statistic and can be pushed below 5%. The acquisition frequency can be kept at 1 Hz thus allowing a fast and precise dose rate measurement. The sensitivity to low energy photons (down to few keV) considerably lower than thecommercially available dosimeters, allowing to measure this radiation component, important for the evaluation of epidermis damages. We conclude that Active Pixel Devices could be used as sensitive element for X-ray dosimeter in the energy range characteristic of IR procedures. Acknowledgments: The research has been partially supported by: Fondazione Cassa di Risparmio di Perugia, (Research Grants 2010.011.0421, 2010.011.0474) and P.O.R. Umbria FSE 2007-2013. 115 DESIGN, DOSIMETRY CHARACTERISTICS AND SHIELDING ASSESSMENT OF A NEW MOBILE ELECTRON ACCELERATOR FOR INTRAOPERATIVE RADIATION THERAPY (IORT) DEVELOPED USING MONTE CARLO METHODS A. Wysocka-Rabin, P. Adrich, A. Wasilewski NCBJ, Otwock, Poland Purpose: Intraoperative radiation therapy (IORT) delivers a large, single fraction dose of radiation to a surgically exposed tumor or tumor bed. This work presents the design concept and dosimetry characteristics of an electron beam forming system for an IORT accelerator, with special emphasis on beam flatness, X-ray contamination and dose delivered outside the treatment field. Methods: The Monte Carlo code, BEAMnrc/EGSnrc, was used to build and test the electron beam forming system for two different docking systems (soft and hard) using circular metallic applicators. Calculations of therapeutic beam characteristics were performed at the patient surface. FLUKA code was used for beamstopper and shielding calculation. Results: Findings were obtained for initially monoenergetic electron beams with an energy range from 4 to 12 MeV, SSD equal to 60 cm., and circular applicators with diameters from 3 to 12 cm. Two-D distribution of dose equivalents inside and outside the operating room were calculated for a maximum energy of 12 MeV, with and without specially-designed halfbarrel metal shielding. Conclusions: An electron beam forming system for a new mobile electron accelerator for IORT, with two different docking systems of circular applicators, has been designed, verified and optimized based on Monte Carlo calculations. The electron beam forming system (collimators, scattering-flattening foils) is universal for every beam energy and every field diameter described above. Dose distribution in the patient plane, inside
ICTR-PHE 2012 and outside operating room, meets all regulatory requirements for radiation protection. A prototype will now be constructed and tested in the laboratory. This work was funded by the Polish Ministry of Science and Higher Education and the EU in frame of Operational Programme -) Innovative Economy, project no. POIG 1.1-21 116 FRAGMENTATION MEASUREMENT OF 12C IONS ON C AND AU TARGET WITH THE FIRST EXPERIMENT AT GSI V. Patera Universita' di Roma "Sapienza", Rome, Italy The study of nuclear fragmentation processes of 12C ions plays a key role in several different fields of basic and applied physics. An international collaboration of institutions from France, Germany, Italy and Spain designed and built the FIRST experiment at GSI. The scientific program foresees to collect high quality data of the fragmentation of ion beams on different targets, relevant for space radiation protection and tumor therapy applications. The experimental setup is made of a thin fast scintillator (Start Counter) and a large area Time of Flight system (TOFWALL), a Drift Chamber beam monitor, a Silicon Vertex detector integrated with the target system, a large angle proton tagger (KENTROS), a large dipolar magnet (ALADiN) and a Neutron detector (LAND2). During the first data taking in summer 2011 about 18M (carbon on carbon) and 2M (carbon on gold) events have been collected using 12C ions projectiles accelerated by the SIS at the energy of 400 A·MeV. We review in this presentation the performance of the different FIRST sub-detectors and the status of full event reconstruction and differential cross section measurements. 118 INBEAM SPECT BASED IN VIVO DOSIMETRY: FROM TREATMENT PLANNING TO MEASURED DOSE A. Müller1, F. Fiedler2, D. Georg3, J. Hopfgartner3, W. Enghardt1,2 1 TU Dresden, OncoRay – National Center for Radiation Research in Oncology, Fetscherstr. 74, D01307 Dresden, Germany 2 HelmholtzZentrum DresdenRossendorf, Postfach 51 01 19, D01314 Dresden, Germany AKHWien, 3 Universitätsklinik für Strahlentherapie, Währinger Gürtel 1820, A1090 Vienna, Austria To achieve the best possible treatment success, radiotherapy with protons and light ions for treating and curing cancer requires an accurate, reliable and especially tumour conformal dose deposition. Currently, positron emission tomography (PET) is the only feasible method to provide a qualitative in vivo dose estimation during particle therapy. An imaging system based on Compton scattering has been suggested as an alternative to PET. Inbeam single particle emission computed tomography (SPECT) with a Compton camera is expected to detect prompt gammarays, emitted during the irradiation, over a wide energy range. In contrast to PET, that relies on the