Korichi, A., Lauritsen, T., Wilson, A. N., Dudouet, J., Clement, E., Lalovic, N., et al. (2017). Performance of a gamma-ray tracking array: Characterizing the AGATA array using a Co-60 source. Nucl. Instrum. Methods Phys. Res. A, 872, 80–86.
Abstract: The AGATA (Advanced GAmma Tracking Array) tracking detector is being designed to far surpass the performance of the previous generation, Compton-suppressed arrays. In this paper, a characterization of AGATA is provided based on data from the second GSI campaign. Emphasis is placed on the proper corrections required to extract the absolute photopeak efficiency and peak-to-total ratio. The performance after tracking is extracted and GEANT4 simulations are used both to understand the results and to scale the measurements up to predicted values for the full 4 pi implementation of the device.
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Garcia, A. R., Mendoza, E., Cano-Ott, D., Nolte, R., Martinez, T., Algora, A., et al. (2017). New physics model in GEANT4 for the simulation of neutron interactions with organic scintillation detectors. Nucl. Instrum. Methods Phys. Res. A, 868, 73–81.
Abstract: The accurate determination of the response function of organic scintillation neutron detectors complements their experimental characterization. Monte Carlo simulations with GEANT4 can reduce the effort and cost implied, especially for complex detection systems for which the characterization is more challenging. Previous studies have reported on the inaccuracy of GEANT4 in the calculation of the neutron response of organic scintillation detectors above 6 MeV, due to an incomplete description of the neutron-induced alpha production reactions on carbon. We have improved GEANT4 in this direction by incorporating models and data from NRESP, an excellent Monte Carlo simulation tool developed at the Physikalisch-Technische Bundesanstalt (PTB), Germany, for the specific purpose of calculating the neutron response function of organic scintillation detectors. The results have been verified against simulations with NRESP and validated against Time-Of-Flight measurements with an NE213 detector at PTB. This work has potential applications beyond organic scintillation detectors, to other types of detectors where reactions induced by fast neutrons on carbon require an accurate description.
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Doncel, M., Cederwall, B., Gadea, A., Gerl, J., Kojouharov, I., Martin, S., et al. (2017). Performance and imaging capabilities of the DEGAS high-resolution gamma-ray detector array for the DESPEC experiment at FAIR. Nucl. Instrum. Methods Phys. Res. A, 873, 36–38.
Abstract: Monte Carlo simulations of one of the possible configurations of the imaging phase for the DEGAS spectrometer situated at the DESPEC/NUSTAR experiment have been performed. The geometry consists of the coupling of the high-resolution gamma spectroscopy array, AGATA, with a high-resolution segmented planar detector utilized as an implantation detector in a compact configuration. The sensitivity and performance of the array in terms of efficiency and imaging capability is deduced.
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AGATA Collaboration(Clement, E. et al), Domingo-Pardo, C., Gadea, A., Perez-Vidal, R. M., & Civera, J. V. (2017). Conceptual design of the AGATA 1 pi array at GANIL. Nucl. Instrum. Methods Phys. Res. A, 855, 1–12.
Abstract: The Advanced GAmma Tracking Array (AGATA) has been installed at the GANIL facility, Caen-France. This setup exploits the stable and radioactive heavy-ions beams delivered by the cyclotron accelerator complex of GANIL. Additionally, it benefits from a large palette of ancillary detectors and spectrometers to address in-beam gamma-ray spectroscopy of exotic nuclei. The set-up has been designed to couple AGATA with a magnetic spectrometer, charged-particle and neutron detectors, scintillators for the detection of high-energy gamma rays and other devices such as a plunger to measure nuclear lifetimes. In this paper, the design and the mechanical characteristics of the set-up are described. Based on simulations, expected performances of the AGATA l pi array are presented.
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Becker, R., Buck, A., Casella, C., Dissertori, G., Fischer, J., Howard, A., et al. (2017). The SAFIR experiment: Concept, status and perspectives. Nucl. Instrum. Methods Phys. Res. A, 845, 648–651.
Abstract: The SAFIR development represents a novel Positron Emission Tomography (PET) detector, conceived for preclinical fast acquisitions inside the bore of a Magnetic Resonance Imaging (MRI) scanner. The goal is hybrid and simultaneous PET/MRI dynamic studies at unprecedented temporal resolutions of a few seconds. The detector relies on matrices of scintillating LSO-based crystals coupled one-to-one with SiPM arrays and readout by fast ASIC5 with excellent timing resolution and high rate capabilities. The paper describes the detector concept and the initial results in terms of simulations and characterisation measurements.
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Albiol, F., Corbi, A., & Albiol, A. (2017). 3D measurements in conventional X-ray imaging with RGB-D sensors. Med. Eng. Phys., 42, 73–79.
Abstract: A method for deriving 3D internal information in conventional X-ray settings is presented. It is based on the combination of a pair of radiographs from a patient and it avoids the use of X-ray-opaque fiducials and external reference structures. To achieve this goal, we augment an ordinary X-ray device with a consumer RGB-D camera. The patient' s rotation around the craniocaudal axis is tracked relative to this camera thanks to the depth information provided and the application of a modern surface-mapping algorithm. The measured spatial information is then translated to the reference frame of the X-ray imaging system. By using the intrinsic parameters of the diagnostic equipment, epipolar geometry, and X-ray images of the patient at different angles, 3D internal positions can be obtained. Both the RGB-D and Xray instruments are first geometrically calibrated to find their joint spatial transformation. The proposed method is applied to three rotating phantoms. The first two consist of an anthropomorphic head and a torso, which are filled with spherical lead bearings at precise locations. The third one is made of simple foam and has metal needles of several known lengths embedded in it. The results show that it is possible to resolve anatomical positions and lengths with a millimetric level of precision. With the proposed approach, internal 3D reconstructed coordinates and distances can be provided to the physician. It also contributes to reducing the invasiveness of ordinary X-ray environments and can replace other types of clinical explorations that are mainly aimed at measuring or geometrically relating elements that are present inside the patient's body.
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Hueso-Gonzalez, F., Ballester, F., Perez-Calatayud, J., Siebert, F. A., & Vijande, J. (2017). Towards clinical application of RayStretch for heterogeneity corrections in LDR permanent I-125 prostate brachytherapy. Brachytherapy, 16(3), 616–623.
Abstract: PURPOSE: RayStretch is a simple algorithm proposed for heterogeneity corrections in low-dose-rate brachytherapy. It is built on top of TG-43 consensus data, and it has been validated with Monte Carlo (MC) simulations. In this study, we take a real clinical prostate implant with 71 1251 seeds as reference and we apply RayStretch to analyze its performance in worst-case scenarios. METHODS AND MATERIALS: To do so, we design two cases where large calcifications are located in the prostate lobules. RayStretch resilience under various calcification density values is also explored. Comparisons against MC calculations are performed. RESULTS: Dose volume histogram related parameters like prostate D-90, rectum D-2cc, or urethra D-10 obtained with RayStretch agree within a few percent with the detailed MC results for all cases considered. CONCLUSIONS: The robustness and compatibility of RayStretch with commercial treatment planning systems indicate its applicability in clinical practice for dosimetric corrections in prostate calcifications. Its use during intraoperative ultrasound planning is foreseen.
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Molina, F., Aguilera, P., Romero-Barrientos, J., Arellano, H. F., Agramunt, J., Medel, J., et al. (2017). Energy distribution of the neutron flux measurements at the Chilean Reactor RECH-1 using multi-foil neutron activation and the Expectation Maximization unfolding algorithm. Appl. Radiat. Isot., 129, 28–34.
Abstract: We present a methodology to obtain the energy distribution of the neutron flux of an experimental nuclear reactor, using multi-foil activation measurements and the Expectation Maximization unfolding algorithm, which is presented as an alternative to well known unfolding methods such as GRAVEL. Self-shielding flux corrections for energy bin groups were obtained using MCNP6 Monte Carlo simulations. We have made studies at the at the Dry Tube of RECH-1 obtaining fluxes of 1.5(4) x 10(13) cm(-2) s(-1) for the thermal neutron energy region, 1.9(5) x 10(12) cm(-2) s(-1) for the epithermal neutron energy region, and 4.3(11) x 10(11) cm(-2) s(-1) for the fast neutron energy region.
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Albiol, F., Corbi, A., & Albiol, A. (2017). Evaluation of modern camera calibration techniques for conventional diagnostic X-ray imaging settings. Radiol. Phys. Technol., 10(1), 68–81.
Abstract: We explore three different alternatives for obtaining intrinsic and extrinsic parameters in conventional diagnostic X-ray frameworks: the direct linear transform (DLT), the Zhang method, and the Tsai approach. We analyze and describe the computational, operational, and mathematical background differences for these algorithms when they are applied to ordinary radiograph acquisition. For our study, we developed an initial 3D calibration frame with tin cross-shaped fiducials at specific locations. The three studied methods enable the derivation of projection matrices from 3D to 2D point correlations. We propose a set of metrics to compare the efficiency of each technique. One of these metrics consists of the calculation of the detector pixel density, which can be also included as part of the quality control sequence in general X-ray settings. The results show a clear superiority of the DLT approach, both in accuracy and operational suitability. We paid special attention to the Zhang calibration method. Although this technique has been extensively implemented in the field of computer vision, it has rarely been tested in depth in common radiograph production scenarios. Zhang's approach can operate on much simpler and more affordable 2D calibration frames, which were also tested in our research. We experimentally confirm that even three or four plane-image correspondences achieve accurate focal lengths.
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Ma, Y. Z., Vijande, J., Ballester, F., Tedgren, A. C., Granero, D., Haworth, A., et al. (2017). A generic TG-186 shielded applicator for commissioning model-based dose calculation algorithms for high-dose-rate Ir-192 brachytherapy. Med. Phys., 44(11), 5961–5976.
Abstract: PurposeA joint working group was created by the American Association of Physicists in Medicine (AAPM), the European Society for Radiotherapy and Oncology (ESTRO), and the Australasian Brachytherapy Group (ABG) with the charge, among others, to develop a set of well-defined test case plans and perform calculations and comparisons with model-based dose calculation algorithms (MBDCAs). Its main goal is to facilitate a smooth transition from the AAPM Task Group No. 43 (TG-43) dose calculation formalism, widely being used in clinical practice for brachytherapy, to the one proposed by Task Group No. 186 (TG-186) for MBDCAs. To do so, in this work a hypothetical, generic high-dose rate (HDR) Ir-192 shielded applicator has been designed and benchmarked. MethodsA generic HDR Ir-192 shielded applicator was designed based on three commercially available gynecological applicators as well as a virtual cubic water phantom that can be imported into any DICOM-RT compatible treatment planning system (TPS). The absorbed dose distribution around the applicator with the TG-186 Ir-192 source located at one dwell position at its center was computed using two commercial TPSs incorporating MBDCAs (Oncentra((R)) Brachy with Advanced Collapsed-cone Engine, ACE, and BrachyVision ACUROS) and state-of-the-art Monte Carlo (MC) codes, including ALGEBRA, BrachyDose, egs_brachy, Geant4, MCNP6, and Penelope2008. TPS-based volumetric dose distributions for the previously reported source centered in water and source displaced test cases, and the new source centered in applicator test case, were analyzed here using the MCNP6 dose distribution as a reference. Volumetric dose comparisons of TPS results against results for the other MC codes were also performed. Distributions of local and global dose difference ratios are reported. ResultsThe local dose differences among MC codes are comparable to the statistical uncertainties of the reference datasets for the source centered in water and source displaced test cases and for the clinically relevant part of the unshielded volume in the source centered in applicator case. Larger local differences appear in the shielded volume or at large distances. Considering clinically relevant regions, global dose differences are smaller than the local ones. The most disadvantageous case for the MBDCAs is the one including the shielded applicator. In this case, ACUROS agrees with MC within [-4.2%, +4.2%] for the majority of voxels (95%) while presenting dose differences within [-0.12%, +0.12%] of the dose at a clinically relevant reference point. For ACE, 95% of the total volume presents differences with respect to MC in the range [-1.7%, +0.4%] of the dose at the reference point. ConclusionsThe combination of the generic source and generic shielded applicator, together with the previously developed test cases and reference datasets (available in the Brachytherapy Source Registry), lay a solid foundation in supporting uniform commissioning procedures and direct comparisons among treatment planning systems for HDR Ir-192 brachytherapy.
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