粒子微束辐射生物学效应研究进展；Advances in Radiobiological Effect Studies Using a Particle Microbeam

粒子微束能够将单个或精确数目的粒子定点、定位射入靶目标,使得辐射生物学效应的研究由定性走向了定量。本文介绍了辐射目标靶研究,以及低剂量辐射生物学效应、低剂量辐射旁效应和重离子微束辐射生物学效应的研究进展。现代精确粒子微束的建立,有助于进一步研究低剂量辐射和空间辐射等生物学效应。

HIRFL－CSR辐射防护设计

本报告介绍了在兰州重离子加速器冷却储存环的辐射防护中所作的一些工作，重点讨论了重离子核反应次级中子辐射场的确定，辐射屏蔽计算、设计，安全联锁系统、辐射监测系统的设计等。对能量不是很高的重离子加速器来说，辐射防护的主要问题来自于重离子核反应产生的中子，其它如γ射线、μ子等与中子相比均可忽略不计。然而由于种种原因，重离子核反应出射中子的实验数据还很缺乏，很难找到现成的数据用于辐射防护设计。在本报告中，采用了不同的方法来估算CSR的次级中子辐射场，并采用偏保守的数据作为辐射防护设计与环境影响分析的基础。实验和理论计算均表明，重离子核反应产生的中子包括两种成分，一种是具有强烈前冲分布的高能中子，另一种是更趋向于各向同性分布的低能中子。屏蔽体外的剂量主要取决于前者，而后者是造成空气、冷却水和屏蔽体活化的主要因素。根据重离子核反应的这种特点，在屏蔽设计中采用整体屏蔽和局部屏蔽相结合的方式，用尽可能少的经费来达到辐射防护的要求。重离子加速器产生的感生放射性除了受到初级束直接照射的靶、加速器部件外，其比放射性一般都是很低的。对于象CSR这样高能量的重离子加速器来说，产生的放射性核素种类是非常多的。然而，考虑到反应截面、半衰期、母核丰度等种种因索，只有几种核素需要特别重视。计算表明，CSR的感生放射性问题并不严重，它对工作人员和环境的影响是很小的。对靶、法拉第筒等受到初级束直接照射的高比放射性物质，由于其量很少，可以严密封装后妥善处置。从已有的加速器运行经验来看，加速器产生的辐射事故主要是工作人员在加速器开机时误入高辐射区内，或是操作人员在加速器区内尚有人时就开机。为了杜绝这类事故，除了建立健全规章制度外，还必须采取安全联锁的办法，使得工作人员在加速器运行时“不能”而不是“不许”进入高辐射区内。为了达到这一目的，在安全联锁中采用了“冗余”、多重联锁的设计思想，来保证工作人员的安全。辐射防护是一项关系到工作人员人身安全，减少射线对环境造成危害的工作，它在放射性装置的设计中是必不可少的。然而，仅仅依靠合理的辐射防护设计是不够的，必须对员工进行安全培训，牢牢竖立安全第一的思想，才能彻底杜绝辐射事故的发生，保障工作人员生命财产的安全。

Estudo do comportamento no âmbito da radioprotecção de uma população trabalhadora na área da medicina dentária

Monografia apresentada à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Licenciada em Medicina Dentária

Spectrotemporal CT data acquisition and reconstruction at low dose.

PURPOSE: X-ray computed tomography (CT) is widely used, both clinically and preclinically, for fast, high-resolution anatomic imaging; however, compelling opportunities exist to expand its use in functional imaging applications. For instance, spectral information combined with nanoparticle contrast agents enables quantification of tissue perfusion levels, while temporal information details cardiac and respiratory dynamics. The authors propose and demonstrate a projection acquisition and reconstruction strategy for 5D CT (3D+dual energy+time) which recovers spectral and temporal information without substantially increasing radiation dose or sampling time relative to anatomic imaging protocols. METHODS: The authors approach the 5D reconstruction problem within the framework of low-rank and sparse matrix decomposition. Unlike previous work on rank-sparsity constrained CT reconstruction, the authors establish an explicit rank-sparse signal model to describe the spectral and temporal dimensions. The spectral dimension is represented as a well-sampled time and energy averaged image plus regularly undersampled principal components describing the spectral contrast. The temporal dimension is represented as the same time and energy averaged reconstruction plus contiguous, spatially sparse, and irregularly sampled temporal contrast images. Using a nonlinear, image domain filtration approach, the authors refer to as rank-sparse kernel regression, the authors transfer image structure from the well-sampled time and energy averaged reconstruction to the spectral and temporal contrast images. This regularization strategy strictly constrains the reconstruction problem while approximately separating the temporal and spectral dimensions. Separability results in a highly compressed representation for the 5D data in which projections are shared between the temporal and spectral reconstruction subproblems, enabling substantial undersampling. The authors solved the 5D reconstruction problem using the split Bregman method and GPU-based implementations of backprojection, reprojection, and kernel regression. Using a preclinical mouse model, the authors apply the proposed algorithm to study myocardial injury following radiation treatment of breast cancer. RESULTS: Quantitative 5D simulations are performed using the MOBY mouse phantom. Twenty data sets (ten cardiac phases, two energies) are reconstructed with 88 μm, isotropic voxels from 450 total projections acquired over a single 360° rotation. In vivo 5D myocardial injury data sets acquired in two mice injected with gold and iodine nanoparticles are also reconstructed with 20 data sets per mouse using the same acquisition parameters (dose: ∼60 mGy). For both the simulations and the in vivo data, the reconstruction quality is sufficient to perform material decomposition into gold and iodine maps to localize the extent of myocardial injury (gold accumulation) and to measure cardiac functional metrics (vascular iodine). Their 5D CT imaging protocol represents a 95% reduction in radiation dose per cardiac phase and energy and a 40-fold decrease in projection sampling time relative to their standard imaging protocol. CONCLUSIONS: Their 5D CT data acquisition and reconstruction protocol efficiently exploits the rank-sparse nature of spectral and temporal CT data to provide high-fidelity reconstruction results without increased radiation dose or sampling time.

Gamma ray-induced bystander effect in tumour glioblastoma cells: a specific study on cell survival, cytokine release and cytokine receptors.

Recent experimental evidence has challenged the paradigm according to which radiation traversal through the nucleus of a cell is a prerequisite for producing genetic changes or biological responses. Thus, unexposed cells in the vicinity of directly irradiated cells or recipient cells of medium from irradiated cultures can also be affected. The aim of the present study was to evaluate, by means of the medium transfer technique, whether interleukin-8 and its receptor (CXCR1) may play a role in the bystander effect after gamma irradiation of T98G cells in vitro. In fact the cell specificity in inducing the bystander effect and in receiving the secreted signals that has been described suggests that not only the ability to release the cytokines but also the receptor profiles are likely to modulate the cell responses and the final outcome. The dose and time dependence of the cytokine release into the medium, quantified using an enzyme linked immunosorbent assay, showed that radiation causes alteration in the release of interleukin-8 from exposed cells in a dose-independent but time-dependent manner. The relative receptor expression was also affected in exposed and bystander cells.

Radioprotection of targeted and bystander cells by methylproamine

INTRODUCTION: Radioprotective agents are of interest for application in radiotherapy for cancer and in public health medicine in the context of accidental radiation exposure. Methylproamine is the lead compound of a class of radioprotectors which act as DNA binding anti-oxidants, enabling the repair of transient radiation-induced oxidative DNA lesions. This study tested methylproamine for the radioprotection of both directly targeted and bystander cells.

METHODS: T98G glioma cells were treated with 15 μM methylproamine and exposed to (137)Cs γ-ray/X-ray irradiation and He(2+) microbeam irradiation. Radioprotection of directly targeted cells and bystander cells was measured by clonogenic survival or γH2AX assay.

RESULTS: Radioprotection of directly targeted T98G cells by methylproamine was observed for (137)Cs γ-rays and X-rays but not for He(2+) charged particle irradiation. The effect of methylproamine on the bystander cell population was tested for both X-ray irradiation and He(2+) ion microbeam irradiation. The X-ray bystander experiments were carried out by medium transfer from irradiated to non-irradiated cultures and three experimental designs were tested. Radioprotection was only observed when recipient cells were pretreated with the drug prior to exposure to the conditioned medium. In microbeam bystander experiments targeted and nontargeted cells were co-cultured with continuous methylproamine treatment during irradiation and postradiation incubation; radioprotection of bystander cells was observed.

DISCUSSION AND CONCLUSION: Methylproamine protected targeted cells from DNA damage caused by γ-ray or X-ray radiation but not He(2+) ion radiation. Protection of bystander cells was independent of the type of radiation which the donor population received.

Nuclear disasters and health: lessons learned, challenges, and proposals

Past nuclear disasters, such as the atomic bombings in 1945 and major accidents at nuclear power plants, have highlighted similarities in potential public health effects of radiation in both circumstances, including health issues unrelated to radiation exposure. Although the rarity of nuclear disasters limits opportunities to undertake rigorous research of evidence-based interventions and strategies, identification of lessons learned and development of an effective plan to protect the public, minimise negative effects, and protect emergency workers from exposure to high-dose radiation is important. Additionally, research is needed to help decision makers to avoid premature deaths among patients already in hospitals and other vulnerable groups during evacuation. Since nuclear disasters can affect hundreds of thousands of people, a substantial number of people are at risk of physical and mental harm in each disaster. During the recovery period after a nuclear disaster, physicians might need to screen for psychological burdens and provide general physical and mental health care for many affected residents who might experience long-term displacement. Reliable communication of personalised risks has emerged as a challenge for health-care professionals beyond the need to explain radiation protection. To overcome difficulties of risk communication and provide decision aids to protect workers, vulnerable people, and residents after a nuclear disaster, physicians should receive training in nuclear disaster response. This training should include evidence-based interventions, support decisions to balance potential harms and benefits, and take account of scientific uncertainty in provision of community health care. An open and joint learning process is essential to prepare for, and minimise the effects of, future nuclear disasters.

virtX: ein Lehr- und Lernsystem für mobile Röntgengeräte zur Verbesserung der Ausbildung im Strahlenschutz

Hintergrund und Fragestellung: Die durch röntgentechnische Diagnoseverfahren in der Medizin entstehende Strahlenbelastung für Patient und Personal soll laut Strahlenschutzverordnung so gering wie möglich gehalten werden. Um dieses zu erreichen ist ein professioneller und bedachter Umgang mit den Röntgengeräten unabdingbar. Dieses Verhalten kann derzeit jedoch nur theoretisch vermittelt werden, da sich ein Üben mit realer Strahlung von selbst verbietet. Daher stellt sich die Frage wie man die Strahlenschutzausbildung durch eine verbesserte Vermittlung der komplexen Thematik unterstützen kann. Methoden: Das CBT-System (Computer Based Training) virtX, welches das Erlernen der korrekten Handhabung mobiler Röntgengeräte unterstützt, wurde um Aspekte aus dem Bereich des Strahlenschutzes erweitert. Es wurde eine prototypische Visualisierung der entstehenden Streustrahlung sowie die Darstellung des Nutzstrahlenganges integriert. Des Weiteren wurde die Berechnung und Anzeige der virtuellen Einfallsdosis für das durchstrahlte Volumen sowie für den Bereich des Bildverstärkers hinzugefügt. Für die Berechnung und Visualisierung all dieser Komponenten werden die in virtX parametrisierbaren C-Bogen-Einstellungen, z.B. Stellung der Blenden, Positionierung des Röntgengerätes zum durchstrahlten Volumen und Strahlenintensität, herangezogen. Das so erweiterte System wurde auf einem dreitägigen Kurs für OP-Personal mit über 120 Teilnehmern eingesetzt und auf der Basis von Fragebögen evaluiert. Ergebnisse: Von den Teilnehmern gaben 55 einen ausgefüllten Evaluations-Fragebogen ab (Responserate 82%). Das Durchschnittsalter der 39 weiblichen und 15 männlichen Teilnehmer (einer o.A.) lag bei 33±8 Jahren, die Berufserfahrung bei 9,37±7 Jahren. Die Erfahrung mit dem C-Bogen wurde von einem Teilnehmer (2%) mit „Keine oder bisher nur Einführung erhalten“, von acht Teilnehmern (14%) mit „bediene einen C-Bogen gelegentlich“ und von 46 (84%) mit „bediene einen C-Bogen regelmäßig“ angegeben. 45 (92%) der Teilnehmer gaben an, durch die Visualisierung der Streustrahlung etwas Neues zur Vermeidung unnötiger Strahlenbelastung dazugelernt zu haben. Schlussfolgerung: Trotz einer bislang nur prototypischen Visualisierung der Streustrahlung können mit virtX zentrale Aspekte und Verhaltensweisen zur Vermeidung unnötiger Strahlenbelastung erfolgreich vermittelt werden und so Lücken der traditionellen Strahlenschutzausbildung geschlossen werden.