Sources of single event effects in the NVIDIA Xavier SoC family under proton irradiation

In this paper we characterise two embedded GPU devices from the NVIDIA Xavier family System-on-Chip (SoC) using a proton beam. We compare the NVIDIA Xavier NX and Industrial devices, that respectively target commercial and automotive applications. We evaluate the Single-Event Effect (SEE) rate of both modules and their sub-components, both the CPU and GPU, using different power modes, and we try for the first time to identify their exact sources using the on-line testing facilities included in their ARM based system. Our conclusion is that the most sensitive part of the CPU complex of the SoC is the tag array of the various cache structures, while no errors were observed in the GPU, probably because of its fast execution compared to the CPU part of the application during the radiation campaign.This work was supported by ESA through the 4000136514/21/NL/GLC/my co-funded PhD activity ”Mixed Software/Hardware-based Fault-tolerance Techniques for Complex COTS System-on-Chip in Radiation Environments” and the GPU4S (GPU for Space) project. Moreover, it was partially supported by the Spanish Ministry of Economy and Competitiveness under grants PID2019-107255GB-C21 and IJC2020-045931-I (Spanish State Research Agency / http://dx.doi.org/10.13039/501100011033) and the HiPEAC Network of Excellence.Peer ReviewedPostprint (author's final draft

A hybrid multi-particle approach to range assessment-based treatment verification in particle therapy

Particle therapy (PT) used for cancer treatment can spare healthy tissue and reduce treatment toxicity. However, full exploitation of the dosimetric advantages of PT is not yet possible due to range uncertainties, warranting development of range-monitoring techniques. This study proposes a novel range-monitoring technique introducing the yet unexplored concept of simultaneous detection and imaging of fast neutrons and prompt-gamma rays produced in beam-tissue interactions. A quasimonolithic organic detector array is proposed, and its feasibility for detecting range shifts in the context of proton therapy is explored through Monte Carlo simulations of realistic patient models and detector resolution efects. The results indicate that range shifts of 1 mm can be detected at relatively low proton intensities (22.30(13) × 107 protons/spot) when spatial information obtained through imaging of both particle species are used simultaneously. This study lays the foundation for multiparticle detection and imaging systems in the context of range verifcation in PTpublishedVersio

Helium ions for radiotherapy? Physical and biological verifications of a novel treatment modality

Purpose: Modern facilities for actively scanned ion beam radiotherapy allow in principle the use of helium beams, which could present specific advantages, especially for pediatric tumors. In order to assess the potential use of these beams for radiotherapy, i.e., to create realistic treatment plans, the authors set up a dedicated He-4 beam model, providing base data for their treatment planning system TRiP98, and they have reported that in this work together with its physical and biological validations. Methods: A semiempirical beam model for the physical depth dose deposition and the production of nuclear fragments was developed and introduced in TRiP98. For the biological effect calculations the last version of the local effect model was used. The model predictions were experimentally verified at the HIT facility. The primary beam attenuation and the characteristics of secondary charged particles at various depth in water were investigated using He-4 ion beams of 200 MeV/u. The nuclear charge of secondary fragments was identified using a Delta E/E telescope. 3D absorbed dose distributions were measured with pin point ionization chambers and the biological dosimetry experiments were realized irradiating a Chinese hamster ovary cells stack arranged in an extended target. Results: The few experimental data available on basic physical processes are reproduced by their beam model. The experimental verification of absorbed dose distributions in extended target volumes yields an overall agreement, with a slight underestimation of the lateral spread. Cell survival along a 4 cm extended target is reproduced with remarkable accuracy. Conclusions: The authors presented a simple simulation model for therapeutical He-4 beams which they introduced in TRiP98, and which is validated experimentally by means of physical and biological dosimetries. Thus, it is now possible to perform detailed treatment planning studies with He-4 beams, either exclusively or in combination with other ion modalities. (C) 2016 Author(s)

CD20 therapies in multiple sclerosis and experimental autoimmune encephalomyelitis - Targeting T or B cells?

MS is widely considered to be a T cell-mediated disease although T cell immunotherapy has consistently failed, demonstrating distinct differences with experimental autoimmune encephalomyelitis (EAE), an animal model of MS in which T cell therapies are effective. Accumulating evidence has highlighted that B cells also play key role in MS pathogenesis. The high frequency of oligoclonal antibodies in the CSF, the localization of immunoglobulin in brain lesions and pathogenicity of antibodies originally pointed to the pathogenic role of B cells as autoantibody producing plasma cells. However, emerging evidence reveal that B cells also act as antigen presenting cells, T cell activators and cytokine producers suggesting that the strong efficacy of anti-CD20 antibody therapy observed in people with MS may reduce disease progression by several different mechanisms. Here we review the evidence and mechanisms by which B cells contribute to disease in MS compared to findings in the EAE model

Fragmentation and lateral scattering of 120 and 200 MeV/u 4He ions on water targets

Along with an increased popularity of heavy ions in cancer therapy, 4He ions have regained the interest of the medical community as a compromise between protons and 12C ions. Al- though 2054 patients have been treated with 4He beams at Lawrence Berkeley Laboratory (LBL) (Berkeley CA, US) between 1975 and 1992, a comprehensive database of biological and physics measurements in the therapeutic energy range is still missing. One of the first steps necessary for introducing 4He ions in particle therapy, is the develop- ment of a dedicated treatment planning system, for which basic physics information such as the characterization of the beam lateral scattering and fragmentation cross sections describing the loss of primary particles and the build up of secondary fragments are required. Examination of data found in the literature reveals a gap in the therapeutic energy range. These measurements are essential for benchmarking not only the new model developed for the in-house treatment planning code TRiP98 (Treatment Planning for Particles) [1], but also for already existing beam algorithms [2, 3] and for Monte Carlo codes like Geant4 [4] and Fluka [5]. The aim of this work is to provide fragmentation cross sections of 4He ions in the therapeutic energy range. The experimental data presented here were measured at Heidelberg Ion Beam Therapy Cen- ter (HIT) (Heidelberg, Germany) using 120 MeV/u and 200 MeV/u 4He beams. The attenuation of 200 MeV/u 4He beam in water was studied together with the build up of the secondary frag- ments produced by nuclear fragmentation processes. Target thicknesses between 1 and 25 cm H2O were chosen to investigate nuclear fragmentation also beyond the maximum penetration depth of the 4He ions. The mixed radiation field produced by the interaction of 120 and 200 4He ions with wa- ter targets (4.28 and 13.96 cm thick, respectively) has also been investigated in this work by measuring double differential cross sections. A combination of energy deposition and Time of Flight (TOF) acquired with a ∆E-E telescope system provided yields and kinetic energy spectra of all particle species emitted between 0◦ and 23◦ with respect to the primary beam direction. Coupling the angular distributions and the kinetic energy spectra gave an estimate of the dose contribution from all particles types. A direct measurement of the beam dose profile was per- formed independently. For this purpose, a two dimensional (2D) Ionization Chamber (IC) array and radiographic films were used to get information not only on the core of the radial dose distribution but also on its halo. The two datasets have been compared and showed consistent results. As a good parametrization of the beam lateral dose profile is a crucial element in a treatment planning systems, a fit of the measured distribution was performed and compared to the simple Gaussian approach still used by some treatment planning systems. The gap of experimental data in the energy range between 100 and 300 MeV/u proves the significance of this work not only for therapeutic applications but also for any other applications where the benchmark of Monte Carlo codes in simulating 4He fragmentation is required

Acoustic Modulation Enables Proton Detection With Nanodroplets at Body Temperature

Superheated nanodroplet (ND) vaporization by proton radiation was recently demonstrated, opening the door to ultrasound-based in vivo proton range verification. However, at body temperature and physiological pressures, perfluorobutane nanodroplets (PFB-NDs), which offer a good compromise between stability and radiation sensitivity, are not directly sensitive to primary protons. Instead, they are vaporized by infrequent secondary particles, which limits the precision for range verification. The radiation-induced vaporization threshold (i.e., sensitization threshold) can be reduced by lowering the pressure in the droplet such that ND vaporization by primary protons can occur. Here, we propose to use an acoustic field to modulate the pressure, intermittently lowering the proton sensitization threshold of PFB-NDs during the rarefactional phase of the ultrasound wave. Simultaneous proton irradiation and sonication with a 1.1 MHz focused transducer, using increasing peak negative pressures (PNPs), were applied on a dilution of PFB-NDs flowing in a tube, while vaporization was acoustically monitored with a linear array. Sensitization to primary protons was achieved at temperatures between 29 °C and 40 °C using acoustic PNPs of relatively low amplitude (from 800 to 200 kPa, respectively), while sonication alone did not lead to ND vaporization at those PNPs. Sensitization was also measured at the clinically relevant body temperature (i.e., 37 °C) using a PNP of 400 kPa. These findings confirm that acoustic modulation lowers the sensitization threshold of superheated NDs, enabling a direct proton response at body temperature