[en] The present paper addresses the challenges faced in large-scaled biomonitoring surveys on trace element air pollution. Goals and set-ups of the survey are discussed, and criteria for the selection of the biomonitor species are considered. The local sampling site and the variances in local elemental concentrations are reviewed as key basic units of the survey, put in the context of a measurable quality concept, thereby also using the total survey variance. Factor analysis is discussed as a tool for data processing, both for straightforward source recognition and for data clean-up (e.g. removal of effects from soil dusts) or source-profile isolation. Practical examples are given which underline the importance of multi-elemental determinations for survey data interpretation; nuclear multi-elemental and non-destructive techniques such as NAA, PIXE or XRF are indicated as principally suited for the necessary (routine) analysis of the survey's solid samples. (author)

[en] Chromium-51 (⁵¹Cr) is an attractive radionuclide in the clinical application for labelling of red blood cells, diagnosis of gastrointestinal bleeding and assessing life span of red cells. This work reports that synthesis of two chromium-based metal-organic frameworks (MOFs) as radiation targets to produce high specific activity ⁵¹Cr production utilizing the Szilard-Chalmers effect. First, the radiation stability of two MOFs under high gamma doses was determined. The results showed that MIL-100 (Cr) and MIL-101 (Cr) exhibited excellent radiation stability after exposure to gamma radiation dose of 4 MGy. However, MIL-101 (Cr) started decomposing with increasing gamma dose, while MIL-100 (Cr) still kept a stable crystal structure at even higher radiation dose. Subsequently the Cr-MOFs were irradiated in the HOR reactor of the Reactor Institute Delft. The ⁵¹Cr yield and specific activity was determined at different irradiation time, extracting agents, extraction time and temperature. The best results show that high enrichment factor (>500) and yield (>40%) can be achieved, appearing a promising ⁵¹Cr production routes for nuclear medicine.

[en] Since the 2008 worldwide shortages in ⁹⁹Mo (the precursor for the medical imaging radionuclide ^99mTc), much attention and effort has been devoted to the exploration of possibilities to ensure ⁹⁹Mo production and delivery to hospitals. This attention comprised the whole production chain, from basic irradiation of targets and the availability of production facilities to a more effective use of produced ⁹⁹Mo by end-users. The present talk reviews the production possibilities, thereby focusing on various radiation sources (photons, neutrons, protons etc), the quality of the produced ⁹⁹Mo (in terms of specific activity SA), and also the yield per target. The adopted approach is a 'quick-and-dirty' calculation of the heat that is generated in targets, which in turn is used in a 'threshold' upper limit cut-off approach to arrive at maximal target mass: the results are used to examine the options for the routine and large-scaled production of ⁹⁹Mo. (author)

[en] The history of proton therapy began in 1946 with the Robert Wilson paper in which accelerator produced proton beams were suggested to treat tumors in humans. Since then, insight in the physics of proton therapy has advanced considerably, as shown in a topical review by Newhauser and Zhang. During the same time span, several nuclear reactions have been considered as potential reactions for controlled thermonuclear fusion for energy production. Aneutronic fusion, as a form of fusion power in which neutrons carry no more than 1 % of the total released energy, could reduce problems with neutron radiation such as ionizing damage, neutron activation, and biological shielding, and one of the promising fusion reactions discussed in that context is the proton-boron fusion reaction, the fusion of a boron nucleus with a proton produces slow-moving alpha particles but hardly any neutrons. We used MCNP6.2 for modelling, after we extended its cross-section library by adding the TENDL-2017 proton cross-section files, needed because the default cross-section database did not contain the proton-boron reaction. The presentation will go into details of all foregoing data, discussions and points of view, and will give the latest results of our current modelling efforts

[en] We have proposed the idea of a ^177mLu/¹⁷⁷Lu radionuclide generator for ¹⁷⁷Lu production based on the separation of the daughter nuclei, ¹⁷⁷Lu from its parent nuclei, ^177mLu. In our work, ^177mLu-DOTA-(Tyr3)-octreotate (DOTATATE) complex was retained on tC-18 silica and the bond ruptured ¹⁷⁷Lu ions was collected using a mobile phase flow. Using this method of separation, ¹⁷⁷Lu/ ^177mLu activity ratios were increased from 0.25 (in equilibrium) to values around 250. The ¹⁷⁷Lu was collected with efficiencies of about 65%. However in order to meet the clinical demands ¹⁷⁷Lu/^177mLu activity ratios close to 10,000 is needed. In our current research we are exploiting the potential of solvent extraction in separating the two isomers. ^177mLu is complexed with different chelating agents such as 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), DOTA-(Tyr3)-octreotate (DOTATATE) and others. The aqueous solution of complexed ^177mLu is left at a fixed temperature for a fixed interval of time to allow the accumulation of ¹⁷⁷Lu. After the fixed accumulation period, it is stirred with an immiscible organic phase (dihexyl ether) containing an extracting agent, Di-(2-ethylhexyl)phosphoric acid (DEHPA) serves to collect the free ¹⁷⁷Lu. Using this method of separation we are able to achieve ¹⁷⁷Lu/^177mLu activity ratios close to 3000, with a ¹⁷⁷Lu collection efficiency close to 50%. By optimizing the extraction process and by utilizing a microfluidic device we aim to deliver a system able to reach the quality needed for medical applications and to provide with a generator with ease of use that can provide with ¹⁷⁷Lu for long periods of time on location.

[en] This paper introduces reversed phase free ion selective radiotracer extraction (RP-FISRE) as a new tool to assess the stability of metal complexes, as illustrated by the assessment of the stability of [¹⁷⁷Lu]Lu-DOTA-octreotate. To this end, the TUDelft-developed FISRE, where the released metal is column-retained and the complex eluted, was changed into RP-FISRE, where the complex is column-retained and the released metal is eluted. This change in the approach allows for studies to be performed with high stability complexes. This paper presents RP-FISRE, the strength of the radiotracer approach, and the first-ever k_d data on the release of ¹⁷⁷Lu from [¹⁷⁷Lu]Lu-DOTA-octreotate. - Highlights: • A new Radiotracer-based RP-FISRE technique developed. • First-ever data on k_d's for ¹⁷⁷Lu-DOTAtate. • Rate constants k_d of the dissociation of Lu-DOTA-Octreotate (ML, MHL, MH₂L forms) determined as k_ML=1.1 10^–8 s⁻¹, k_MHL=7.4 10⁻⁶ s⁻¹, k_MH2L=1.1×10^–4 s⁻¹

[en] We have developed polymeric nanocarriers capable of retaining the recoiling daughters of the alpha-emitting radionuclide ²²⁵Ac and thus limit healthy tissue toxicity. Using a Monte Carlo-based simulation tool, a number of different polymersome designs have been simulated to optimize the recoil retention. Subsequently, polymersomes have been prepared with ²²⁵Ac co-precipitated with an InPO₄ nanoparticle inside the vesicle, as the use of high-Z materials results in a much-reduced recoil range as compared to an aqueous environment. Using this new formulation, recoil retentions have improved significantly as compared to earlier published results by Wang et al., where ²²⁵Ac was encapsulated using a hydrophilic chelate. Excellent results have been obtained in vitro, where the potential of ²²⁵Ac-loaded polymersomes has been evaluated in U87 glioblastoma multicellular spheroids. We have found that polymersomes distribute themselves throughout the spheroid after 4 days which, considering the long half-life of ²²⁵Ac (9.9 d), allows for irradiation of the entire spheroid. Our studies indicated that even at low radionuclide activity the ²²⁵Ac polymersomes deliver a very high dose, with spheroid growth inhibition was already observed at just 0.1 kBq of ²²⁵Ac added. The therapeutic efficacy upon intratumoral administration of ²²⁵Ac-polymersomes has been tested in vivo in BALB/c mice bearing an MDA-MB-231 tumour. The retention of the vesicles upon intratumoral administration has been shown to be very high (46.0 ± 21.5% and 37.0 ± 23.9% at 1 day and 7 day p.i. respectively), whereas the tumours which have been injected with ²²⁵Ac-DOTA retained less than 1% (1 day p.i.), demonstrating the advantage of using the vesicles intratumorally. The accumulation of recoiled ²¹³Bi in the kidneys was limited, with a kidney to tumour ratio of only 1:30. Immuno-histochemical analysis of the tumours has shown an increase in double-stranded breaks in the group treated with ²²⁵Ac-polymersomes, indicating their suitability for tumour irradiation. Large strides have thus been made towards the clinical implementation of polymersomes in ART. The incorporation of nanoparticles in polymersomes has allowed for high retention of the ²²⁵Ac mother and daughter nuclides, and both in vitro as well as in vivo their potential in destroying tumours has been demonstrated.

[en] Expanding the exponential relations found for collimated beams yields new relations applicable in planar geometry including covering foils. These relations predict that in planar geometry the transmission curve falls off much faster than the one observed experimentally for a collimated beam. When the top angle of the detector decreases, the transmission curves converge to the exponential decay for collimated transmission although the apparent attenuation coefficient can differ considerably from the true one. Our predictions agree with experiments and Monte Carlo prediction in 2π geometry up to ∼10 mg/m² and good agreement with experimental results is found up to 300 mg/m² aluminium when the top angle is 38^o. Therefore, it is concluded that the derived relations give a good approximation of the attenuation in thin, low Z, absorbers

[en] Two types of liposomes, commonly used in drug delivery studies, and E. coli bacteria, all prepared in H₂O, were resuspended in D₂O and measured with Small Angle Spin-Echo Neutron Scattering (SESANS). Modeling was performed using correlation functions for solid spheres and hollow spheres. The signal strength and curve shape were more indicative of hollow particles, indicating that the H₂O-D₂O exchange occurred too fast to be observed with the available time resolution. Fitting the particle diameter and membrane thickness of the hollow sphere model to the data, gave results which were in good agreement with Dynamic Light Scattering (DLS) data and literature, showing as a proof-of-principle that SESANS is able to investigate such systems. SESANS may become a good alternative to conventional tritium studies or a tool with which to study intracellular vesicle transport phenomena, with possible in vivo applications. Calculations show that a substantial change in numbers of a mixed system of small and large biological particles should be observable. A possible application is the destruction by external means of great numbers of liposomes in the presence of tumor cells for triggered drug release in cancer treatment. Since SESANS is both non-invasive and non-destructive and can handle relatively thick samples, it could be a useful addition to more conventional techniques.