Zeitschrift fur Medizinische Physik最新文献

{"title":"Enhanced direct joint attenuation and scatter correction of whole-body PET images via context-aware deep networks","authors":"Saeed Izadi, Isaac Shiri, Carlos F. Uribe, Parham Geramifar, Habib Zaidi, Arman Rahmim, Ghassan Hamarneh","doi":"10.1016/j.zemedi.2024.01.002","DOIUrl":"https://doi.org/10.1016/j.zemedi.2024.01.002","url":null,"abstract":"<p>In positron emission tomography (PET), attenuation and scatter corrections are necessary steps toward accurate quantitative reconstruction of the radiopharmaceutical distribution. Inspired by recent advances in deep learning, many algorithms based on convolutional neural networks have been proposed for automatic attenuation and scatter correction, enabling applications to CT-less or MR-less PET scanners to improve performance in the presence of CT-related artifacts. A known characteristic of PET imaging is to have varying tracer uptakes for various patients and/or anatomical regions. However, existing deep learning-based algorithms utilize a fixed model across different subjects and/or anatomical regions during inference, which could result in spurious outputs. In this work, we present a novel deep learning-based framework for the direct reconstruction of attenuation and scatter-corrected PET from non-attenuation-corrected images in the absence of structural information in the inference. To deal with inter-subject and intra-subject uptake variations in PET imaging, we propose a novel model to perform subject- and region-specific filtering through modulating the convolution kernels in accordance to the contextual coherency within the neighboring slices. This way, the context-aware convolution can guide the composition of intermediate features in favor of regressing input-conditioned and/or region-specific tracer uptakes. We also utilized a large cohort of 910 whole-body studies for training and evaluation purposes, which is more than one order of magnitude larger than previous works. In our experimental studies, qualitative assessments showed that our proposed CT-free method is capable of producing corrected PET images that accurately resemble ground truth images corrected with the aid of CT scans. For quantitative assessments, we evaluated our proposed method over 112 held-out subjects and achieved an absolute relative error of <span><math><mrow is=\"true\"><mn is=\"true\">14.30</mn><mo is=\"true\">±</mo><mn is=\"true\">3.88</mn></mrow></math></span>% and a relative error of <span><math><mrow is=\"true\"><mo is=\"true\" linebreak=\"badbreak\">-</mo><mn is=\"true\">2.11</mn><mo is=\"true\">%</mo><mo is=\"true\">±</mo><mn is=\"true\">2.73</mn></mrow></math></span>% in whole-body.</p>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139661196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Radium deposition in human brain tissue: A Geant4-DNA Monte Carlo toolkit study","authors":"S.M.J. Mortazavi ,&nbsp;Payman Rafiepour ,&nbsp;S.A.R. Mortazavi ,&nbsp;S.M.T. Razavi Toosi ,&nbsp;Parya Roshan Shomal ,&nbsp;Lembit Sihver","doi":"10.1016/j.zemedi.2023.09.004","DOIUrl":"10.1016/j.zemedi.2023.09.004","url":null,"abstract":"<div><p>NASA has encouraged studies on ²²⁶Ra deposition in the human brain to investigate the effects of exposure to alpha particles with high linear energy transfer, which could mimic some of the exposure astronauts face during space travel. However, this approach was criticized, noting that radium is a bone-seeker and accumulates in the skull, which means that the radiation dose from alpha particles emitted by ²²⁶Ra would be heavily concentrated in areas close to cranial bones rather than uniformly distributed throughout the brain. In the high background radiation areas of Ramsar, Iran, extremely high levels of ²²⁶Ra in soil contribute to a large proportion of the inhabitants' radiation exposure. A prospective study on Ramsar residents with a calcium-rich diet was conducted to improve the dose uniformity due to ²²⁶Ra throughout the cerebral and cerebellar parenchyma. The study found that exposure of the human brain to alpha particles did not significantly affect working memory but was significantly associated with increased reaction times. This finding is crucial because astronauts on deep space missions may face similar cognitive impairments due to exposure to high charge and energy particles. The current study was aimed to evaluate the validity of the terrestrial model using the Geant4 Monte Carlo toolkit to simulate the interactions of alpha particles and representative cosmic ray particles, acknowledging that these radiation types are only a subset of the complete space radiation environment.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388923001162/pdfft?md5=4a37c050de1ea682a73d9bbaecce0fac&pid=1-s2.0-S0939388923001162-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136160957","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The ESA Active Dosimeter (EAD) system onboard the International Space Station (ISS)","authors":"Ulrich Straube ,&nbsp;Thomas Berger ,&nbsp;Matthias Dieckmann","doi":"10.1016/j.zemedi.2023.03.001","DOIUrl":"10.1016/j.zemedi.2023.03.001","url":null,"abstract":"<div><p>Ionizing radiation in general and mixed fields of space radiation in particular pose a risk of serious harm to human health. The risk of such adverse effects increases with the duration of the mission, and for all missions outside the protective properties of the Earth’s magnetic field and atmosphere. Accordingly, radiation protection is of central importance for all human spaceflight, which is recognized by all international space agencies. To date various systems, analyze and determine the exposure to ionizing radiation within the environment and to the crew onboard the International Space Station (ISS). In addition to this operational monitoring, experiments and technology demonstrations are carried out. This to further enhance systems capabilities, to prepare for exploratory missions, to the Deep Space Gateway and/or to enable for human presence at other celestial bodies. Subsequently the European Space Agency (ESA) decided early to support the development of an active personal dosimeter. Under the auspices of the European Space Research and Technology Center (ESTEC) together with the European Astronaut Center's (EAC) Medical Operations and Space Medicine (HRE-OM) team, a European industrial consortium was formed to develop, build, and test this system. To complete the ESA Active Dosimeter (EAD) Technology Demonstration in space, EAD components were delivered to ISS with the ESA’s space missions ‘iriss’ and ‘proxima’ in 2015 and 2016. This marked Phase 1 (2015) and 2 (2016–2017) of the EAD Technology Demonstration to which focus is given in this publication. All EAD systems and their functionalities, the different radiation detector, their properties, and calibrations procedures are described. Emphasis is first on the “iriss” mission of September 2015, that provided a complete set of data for an entire space mission from launch to landing, for the first time. Data obtained during Phase 2 in 2016–2017 are discussed thereafter. Measurements with the active radiation detectors of the EAD system provided data of the absorbed dose, dose equivalent, quality factor as well as the various dose contributions during the crossings of the South Atlantic Anomaly (SAA) and/or resulting from galactic cosmic radiation (GCR). Results of the in-flight cross-calibrations among the internal sensors of the EAD systems are discussed and alternative usage of the EAD Mobile Units as area monitors at various different locations inside the ISS is described.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388923000387/pdfft?md5=ef09aeea57095d3cbb83b301a7bcb7a2&pid=1-s2.0-S0939388923000387-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9516756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Light flashes and other sensory illusions perceived in space travel and on ground, including proton and heavy ion therapies","authors":"Livio Narici","doi":"10.1016/j.zemedi.2023.06.004","DOIUrl":"10.1016/j.zemedi.2023.06.004","url":null,"abstract":"<div><p>Most of the astronauts experience visual illusions, apparent flashes of light (LF) in absence of light. The first reported observation of this phenomenon was in July 1969 by Buzz Aldrin, in the debriefing following the Apollo 11 mission. Several ground-based experiments in the 1970s tried to clarify the mechanisms behind these light flashes and to evaluate possible related risks. These works were supported by dedicated experiments in space on the following Apollo flights and in Low Earth Orbit (LEO). It was soon demonstrated that the LF could be caused by charged particles (present in the space radiation) traveling through the eye, and, possibly, some other visual cortical areas. In the 1990s the interest in these phenomena increased again and additional experiments in Low Earth Orbit and others ground-based were started. Recently patients undergoing proton and heavy ion therapy for eye or head and neck tumors have reported the perception of light flashes, opening a new channel to investigate these phenomena.</p><p>In this paper the many LF studies will be reviewed, presenting an historical and scientific perspective consistent with the combined set of observations, offering a single comprehensive summary aimed to provide further insights on these phenomena.</p><p>While the light flashes appear not to be a risk by themselves, they might provide information on the amount of radiation induced radicals in the astronauts’ eyes. Understanding their generation mechanisms might also support radiation countermeasures development. However, even given the substantial progress outlined in this paper, many questions related to their generation are still under debate, so additional studies are suggested. Finally, it is also conceivable that further LF investigations could provide evidence about the possible interaction of single particles in space with brain function, impacting with the crew ability to optimally perform a mission.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388923000818/pdfft?md5=6fee664558ca86ac12cabfee7b9ee0d4&pid=1-s2.0-S0939388923000818-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9783877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Monte Carlo model for ion mobility and diffusion for characteristic electric fields in nanodosimetry","authors":"Irina Kempf ,&nbsp;Uwe Schneider","doi":"10.1016/j.zemedi.2022.12.006","DOIUrl":"10.1016/j.zemedi.2022.12.006","url":null,"abstract":"<div><p>The quantification of the effects of space radiation for manned spaceflight can be approximated by nanodosimetric measurements. For the development of nanodosimetric detectors, a Monte Carlo model for ion mobility and diffusion for characteristic electric fields is presented.</p><p>This model can be used to describe the interactions of ions in their parent gas based solely on commonly known input parameters, such as the ionization potential, kinetic diameter, molar mass, and polarizability of the gas. A model for approximating the resonant charge exchange cross section has been proposed, requiring only the ionization energy and mass of the parent gas as input parameters. The method proposed in this work was tested against experimental drift velocity data for a wide range of gases (helium, neon, nitrogen, argon, krypton, carbon monoxide, carbon dioxide, oxygen, propane). The transverse diffusion coefficients were compared to experimental values for helium, nitrogen, neon, argon, and propane gas.</p><p>With the Monte Carlo code and resonant charge exchange cross section approximation model presented in this work, it is now possible to calculate an estimate of the drift velocities, transverse diffusion, and thus the ion mobility of ions in their parent gas. This is essential for further nanodosimetric detector development, as those parameters are often not well known for the gas mixtures used in nanodosimetry.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922001398/pdfft?md5=da9a5e516b9b172c1f85166490be2157&pid=1-s2.0-S0939388922001398-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10757881","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Back to the future: Spaceflight – Radiation and new horizons","authors":"Ulrich Straube,&nbsp;Matthias Maurer","doi":"10.1016/j.zemedi.2024.01.003","DOIUrl":"10.1016/j.zemedi.2024.01.003","url":null,"abstract":"","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388924000035/pdfft?md5=2731ac532c9fb6f6b71c85abfad52665&pid=1-s2.0-S0939388924000035-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139543950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"System of radiological protection: Towards a consistent framework on Earth and in space","authors":"Werner Rühm,&nbsp;Nobuhiko Ban,&nbsp;Jing Chen,&nbsp;Chunsheng Li,&nbsp;Mikhail Dobynde,&nbsp;Marco Durante,&nbsp;Samy El-Jaby,&nbsp;Tatsuto Komiyama,&nbsp;Kotaro Ozasa,&nbsp;Tatsuhiko Sato,&nbsp;Edward J Semones,&nbsp;Mark Shavers,&nbsp;Vyacheslav Shurshakov,&nbsp;Ulrich Straube,&nbsp;Leena Tomi,&nbsp;Alexander Ulanowski,&nbsp;Ludovic Vaillant,&nbsp;Zhenhua Xu,&nbsp;Constantinos Zervides,&nbsp;Guangming Zhou","doi":"10.1016/j.zemedi.2024.01.004","DOIUrl":"10.1016/j.zemedi.2024.01.004","url":null,"abstract":"","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388924000047/pdfft?md5=93e6563edd0a99b0f35e11f600e1771c&pid=1-s2.0-S0939388924000047-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139543953","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Moon, Mars and Minds: Evaluating Parkinson’s disease mortality among U.S. radiation workers and veterans in the million person study of low-dose effects","authors":"Lawrence T. Dauer ,&nbsp;Linda Walsh ,&nbsp;Michael T. Mumma ,&nbsp;Sarah S. Cohen ,&nbsp;Ashley P. Golden ,&nbsp;Sara C. Howard ,&nbsp;Grace E. Roemer ,&nbsp;John D. Boice Jr","doi":"10.1016/j.zemedi.2023.07.002","DOIUrl":"10.1016/j.zemedi.2023.07.002","url":null,"abstract":"<div><h3>Background</h3><p>Radiation is one of the most important stressors related to missions in space beyond Earth’s orbit. Epidemiologic studies of exposed workers have reported elevated rates of Parkinson’s disease. The importance of cognitive dysfunction related to low-dose rate radiation in humans is not defined. A meta-analysis was conducted of six cohorts in the Million Person Study (MPS) of low-dose health effects to learn whether there is consistent evidence that Parkinson’s disease is associated with radiation dose to brain.</p></div><div><h3>Materials and methods</h3><p>The MPS evaluates all causes of death among U.S. radiation workers and veterans, including Parkinson’s disease. Systematic and consistent methods are applied to study all categories of workers including medical radiation workers, industrial radiographers, nuclear power plant workers, atomic veterans, and Manhattan Projects workers at the Los Alamos National Laboratory and at Rocky Flats. Consistent methods for all cohorts are used to estimate organ-specific doses and to obtain vital status and cause of death.</p></div><div><h3>Results</h3><p>The meta-analysis include 6 cohorts within the MPS, consisting of 517,608 workers and 17,219,001 person-years of observation. The mean dose to brain ranged from 6.9 to 47.6 mGy and the maximum dose from 0.76 to 2.7 Gy. Five of the 6 cohorts revealed positive associations with Parkinson’s disease. The overall summary estimate from the meta-analysis was statistically significant based on 1573 deaths due to Parkinson’s disease. The summary excess relative risk at 100 mGy was 0.17 (95% CI: 0.05; 0.29).</p></div><div><h3>Conclusions</h3><p>Parkinson’s disease was positively associated with radiation in the MPS cohorts indicating the need for careful evaluation as to causality in other studies, delineation of possible mechanisms, and assessing possible implications for space travel as well as radiation protection guidance for terrestrial workers.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388923000843/pdfft?md5=55de90c157fa0c23b32bb59c61d5b42c&pid=1-s2.0-S0939388923000843-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9988165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Editorial Board + Consulting Editorial Board","authors":"","doi":"10.1016/S0939-3889(24)00010-2","DOIUrl":"https://doi.org/10.1016/S0939-3889(24)00010-2","url":null,"abstract":"","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388924000102/pdfft?md5=e0ecf1ae9419dfa32d47b77a07bf2bb6&pid=1-s2.0-S0939388924000102-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139986910","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Space agency-specific standards for crew dose and risk assessment of ionising radiation exposures for the International Space Station","authors":"Mark Shavers ,&nbsp;Edward Semones ,&nbsp;Leena Tomi ,&nbsp;Jing Chen ,&nbsp;Ulrich Straube ,&nbsp;Tatsuto Komiyama ,&nbsp;Vyacheslav Shurshakov ,&nbsp;Chunsheng Li ,&nbsp;Werner Rühm","doi":"10.1016/j.zemedi.2023.06.005","DOIUrl":"10.1016/j.zemedi.2023.06.005","url":null,"abstract":"<div><p>The Partner Agencies of the International Space Station (ISS) maintain separate career exposure limits and shared Flight Rules that control the ionising radiation exposures that crewmembers can experience due to ambient environments throughout their space missions. In low Earth orbit as well as further out in space, energetic ions referred to as galactic cosmic radiation (GCR) easily penetrate spacecraft and spacecraft contents and consequently are always present at low dose rates. Protons and electrons that are trapped in the Earth’s geomagnetic field are encountered intermittently, and a rare energetic solar particle event (SPE) may expose crew to (mostly) energetic protons. Space radiation protection goals are to optimize radiation exposures to maintain deleterious late effects at known and acceptable levels and to prevent any early effects that might compromise crew health and mission success. The conventional radiation protection metric <em>effective dose</em> provides a basic framework for limiting exposures associated with human spaceflight and can be communicated to all stakeholders. Additional metrics and uncertainty analyses are required to understand more completely and to convey nuanced information about potential impacts to an individual astronaut or to a space mission. Missions to remote destinations well beyond low Earth orbit (BLEO) are upcoming and bestow additional challenges that shape design and radiation protection needs. NASA has recently adopted a more permissive career exposure limit based upon effective dose and new restrictions on mission exposures imposed by nuclear technologies. This manuscript reviews the exposure limits that apply to the ISS crewmembers. This work was performed in collaboration with the advisory and guidance efforts of International Commission on Radiological Protection (ICRP) Task Group 115 and will be summarized in an upcoming ICRP Report.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S093938892300082X/pdfft?md5=dec577eed0f7d7f58dec908ed022eeef&pid=1-s2.0-S093938892300082X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9885508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}