Preparation of18F source for slow positron beam by proton bombardment of18O-water

Fluorine-18 produced by the¹⁸O(p,n)¹⁸F reaction on¹⁸O-water has proved to be highly useful as a source for a slow positron beam. About 70 GBq of¹⁸F is produced routinely by an ultra-compact cyclotron. The¹⁸F formed in H₂ ¹⁸O target is sent through a fine pipe to the site of positron slowing-down, fixed on a small spot by adsorption or drying, and then placed close to the moderator foil. An automatic apparatus has been set up for the entire process including the recovery of H₂ ¹⁸O.     

Synthesis and Bioimaging of Positron‐Emitting 15O‐Labeled 2‐Deoxy‐D‐glucose of Two‐Minute Half‐Life

In positron emission tomography (PET), which exploits the affinity of a radiopharmaceutical for the target organ, a systematic repertoire of oxygen‐15‐labeled PET tracers is expected to be useful for bioimaging owing to the ubiquity of oxygen atoms in organic compounds. However, because of the 2‐min half‐life of ¹⁵O, the synthesis of complex biologically active ¹⁵O‐labeled organic molecules has not yet been achieved. A state‐of‐the‐art synthesis now makes available an ¹⁵O‐labeled complex organic molecule, 6‐[¹⁵O]‐2‐deoxy‐D ‐glucose. Ultrarapid radical hydroxylation of 2,6‐dideoxy‐6‐iodo‐D ‐glucose with molecular oxygen labeled with ¹⁵O of two‐minute half‐life provided the target ¹⁵O‐labeled molecule. The labeling reaction with ¹⁵O was complete in 1.3 min, and the entire operation time starting from the generation of ¹⁵O‐containing dioxygen by a cyclotron to the purification of the labeled sugar was 7 min. The labeled sugar accumulated in the metabolically active organs as well as in the bladder of mice and rats. ¹⁵O‐labeling offers the possibility of repetitive scanning and the use of multiple PET tracers in the same body within a short time, and hence should significantly expand the scope of PET studies of small animals.     

Analysis of concrete labyrinth shielding and radiation dose for APF plasma focus neutron source by FLUKA Monte Carlo code

In this paper Monte Carlo simulations have been performed for the attenuation of neutrons radiation produced by a 4 kJ plasma focus device through labyrinth shielding design with various thicknesses. At the test site that will be fired with deuterium and deuterium fusion (D–D) resulting in a yield of about 10⁹ fusion neutrons of 2.45 MeV. This poses a radiological hazard to scientists and personnel operating the device. The goal of this study is to evaluate various shielding options under consideration for the plasma focus operating with D–D fusion. Shields of varying neutrons-shielding effectiveness were investigated using concrete materials. The most effective shield between labyrinth structure allowed almost 9.52E+6 shots per year while keeping personnel under 20 mSv of dose. The most expensive shield that is used labyrinth shield with 75 cm concrete thickness on the walls allowed almost 9E+8 shot per year.     

Renal blood volume vs. glomerular filtration rate: evaluation with C15O and 88Ga-ethylenediaminetetraacetic acid (EDTA) study

68Ga-EDTA (ethylenediaminetetraacetic acid) is simply and economically obtained without a cyclotron. We used renal blood volume (RBV) values obtained by C15O studies for blood activity subtraction on renal time activity curves using a positron emission tomography for the determination of the glomerular filtration rate (GFR) by intravenous 68Ga-EDTA administration. Positive correlation was revealed between the GFR and RBV values, where the ratio of blood activity in whole renal activity increased relatively as GFR value decreased. The estimation using a correction equation derived from the correlation curve was possible without a C15O study.     

Time-resolved SAXS studies of morphological changes in cold crystallized poly(ethylene terephthalate) during annealing and heating

Structural changes occurring during crystallization of quenched amorphous poly(ethylene terephthalate) (PET) and subsequent cooling/heating cycles have been studied by real-time small-angle x-ray scattering (SAXS), using synchrotron radiation. Initial crystallization is found to occur by insertion of new lamellae between the existing ones, while rapid continuous melting/recrystallization happens when the cold-crystallized PET samples are heated above the previous highest annealing temperature. Such melting/recrystalization results in irreversible increases in the lamellar long period, the crystal thickness and the density difference between the crystalline and amorphous regions; in contrast, at temperatures below the prior highest crystallization temperature, the structural changes are dominated by reversible effects such as thermal expansion. However, throughout the entire temperature range up to the melting point around 250 °C, the crystal core thickness remains quite small, less than ca. 50 Å, and the linear crystallinity of lamellar stacks remains nearly constant around 0.3. Such a low crystallinity indicates the presence of thick order-disorder interfacial layers on the lamellar surface, whose thickness increases with temperature.Dedicated to Prof. E. W. Fischer on the occasion of his 65th birthday.     

Rapid synthesis of C-labeled FK506 for positron emission tomography

The present study describes a rapid synthesis method for labeled [¹¹C]FK506 for positron emission tomography (PET). A one-pot reaction from [¹¹C]CH₃I, involving a Wittig reaction as the key carboncarbon bond formation was developed. The chemical process was accomplished using a designed, fully automated synthetic apparatus, and an injectable solution of [¹¹C]FK506 was obtained in only 34 min from [¹¹C]CH₃I. The decay-corrected radiochemical yield based on [¹¹C]CH₃I was 11.9%, and the specific activity was 39.8 GBq/μmol.     

Shielding ability of lead loaded radiation resistant gloves

The shielding ability of radiation resistant gloves was examined. The gloves are made of lead loaded (as PbO2) polyvinyl chloride resin and are about 0.4 mm in thickness (70 mg/cm2). Eleven test pieces were sampled from each of three gloves (total 33) and the transmission rates for radiations (X-ray or gamma-ray) through the test pieces were measured with radiation sources, 99mTc, 57Co, 133Ba, 133Xe and 241Am. The differences of the transmission rates for radiations by the positions of the gloves were smaller than 15%, and the differences by three gloves were smaller than 5% in the case of 60 keV and 141 keV radiations. The average transmission rates for radiations in the 33 test pieces were about 40% for 30 keV radiation, about 90% for 80 keV and 140 keV radiations. The shielding characteristic of the gloves is equivalent to about 0.026 mm thick lead plate.     

Formation of High-quality Advanced High-k Oxide Layers at Low Temperature by Excimer UV Lamp-assisted Photo-CVD and Sol-gel Processing

IntroductionOne of the most critical challenges for deepsubmicron silicon researches is the technologicallimit to the use of silicon dioxide as the gate dielec-tric. For sub- 0 .1μm CMOS technology roadmapspredict the need for a sub- 2 nm Si- oxide gate di-electric[1,2 ] . Off- state tunnelling effects for transis-tors with gate oxide thickness below 2 nm lead tohigh leakage current densities of1 _ 1 0 A/cm2 [3 ] ,which become a serious obstacle for transistors,particularly for the rapidly …     

Automatic F positron source supply system for a monoenergetic positron beam

A system which supplies an intense ¹⁸F (half life 110 min) positron source produced by an AVF cyclotron through ¹⁸O(p,n)¹⁸F reaction has been constructed. Produced ¹⁸F is transferred to a low background experiment hall through a capillary. It is electro-deposited on a graphite rod and used for a source of a slow positron beam. In the meantime the next batch of target ¹⁸O water is loaded and proton irradiation proceeds. This system makes it possible to perform continuous positron beam experiments using the ¹⁸F positron source.     

Chemistry for Positron Emission Tomography: Recent Advances in 11C‐, 18F‐, 13N‐, and 15O‐Labeling Reactions

Positron emission tomography (PET) is a molecular imaging technology that provides quantitative information about function and metabolism in biological processes in vivo for disease diagnosis and therapy assessment. The broad application and rapid advances of PET has led to an increased demand for new radiochemical methods to synthesize highly specific molecules bearing positron‐emitting radionuclides. This Review provides an overview of commonly used labeling reactions through examples of clinically relevant PET tracers and highlights the most recent developments and breakthroughs over the past decade, with a focus on ¹¹C, ¹⁸F, ¹³N, and ¹⁵O.     

Charge compensation for XPS on polymers

Summary Line broadening, induced by differential charging under monochromated X-radiation, makes it difficult to separate adjacent chemical states in X-ray photoelectron spectroscopy (XPS) on insulators, particularly polymers. Electron flood guns, floating filaments, standard X-ray sources, UV lamps, grids and combinations of these have been used to eliminate or minimize the line broadening. Low dose, wide area X-ray irradiation before the measurement, plus a hot filament grounded at its positive lead and shielded by an LN₂-cooled copper foil, yields excellent results. Once the optimum geometrical arrangement has been found for sample surface, shield and filament, no bias voltage on the shield or other electrode is required. The same filament emission current, plus the same cooling power, reproduces routinely a FWHM (full-width-at-half-maximum) of 0.9 eV on solid PMMA [poly(methyl methyl-acrylate)] or PET [poly(ethylene terephthalate)]; this has been shown to be optimum for all other insulators investigated so far. More than 6 h of continuous filament operation does not result in any alteration of the sample by radiation or contamination. There are indications that the system also works for nonmonochromated XPS and for tilt experiments.     

Contribution to the cyclotron targetry

The radionuclide¹⁸F is of considerable interest for biochemical and physiological studies using positron emission tomography (PET). Of all methods used for its production only two have found wide application since their yield is high enough and the chemical form of the product is suitable for fluorination of organic compounds. Proton irradiation of enriched water using¹⁸O(p,n)¹⁸F reaction and deuteron bombardment of gaseous neon²⁰Ne(d,)¹⁸F process are the commonly used effective cyclotron production procedures. In our previous papers^1,2 the different reactions and target parameters of the deuteron irradiation of neon gas were reported. In the present work, the production yields for the (d,), (d,n) and (d,p) reactions were determined.     

羟基磷灰石负载放射性18F作为分子影像纳米探针在生物医学中的应用

采用简便有效的方法,制备了生物兼容性强、放射性标记羟基磷灰石(HAp)纳米粒子的正电子发射计算机断层显像(PET)纳米探针。在合成HAp纳米粒子的过程中,放射性的~(18)F作为掺杂剂,占据HAp晶格中羟基位置,在短时间内牢固地标记到HAp上。~(18)F不仅标记在纳米粒子的表面,而且还通过强的化学键标记在纳米颗粒的内部。以达到提高标记量并防止辐射泄漏的目的。设计的高标记量的放射性纳米探针应用于动物实验并靶向到达脏器器官。     

Efficient synthesis of [¹¹C]ramelteon as a positron emission tomography probe for imaging melatonin receptors involved in circadian rhythms

Ramelteon (TAK-375) is a novel melatonin receptor agonist that is used for clinical treatment of insomnia. The present report describes radiolabeling of ramelteon with the short-lived positron-emitter 11C (T(1/2)=20.4 min) by 2 methods. One method was [11C]methylation of an acetoamide precursor and the other was [11C]acylation of the corresponding amine precursor. First, [11C]methylation method showed the low reproducibility together with the production of many kinds of side products from which the [11C-methyl]Ramelteon was separated with chemical purity of <28% and radiochemical purity of >98%. Whereas, the [11C]acylation method showed high efficiency and reproducibility with a good radiochemical yield (22-43%, decay corrected), high chemical and radiochemical purities (>99% each), and high specific activity (43-162 GBq/μmol) (n=5) after HPLC purification. [11C]Ramelteon is a potential positron emission tomography (PET) probe for imaging the melatonin receptor.     

Methods and applications of positron-based medical imaging

Positron emission tomography (PET) is a diagnostic imaging method to examine metabolic functions and their disorders. Dedicated ring systems of scintillation detectors measure the 511 keV γ-radiation produced in the course of the positron emission from radiolabelled metabolically active molecules. A great number of radiopharmaceuticals labelled with ¹¹C, ¹³N, ¹⁵O, or ¹⁸F positron emitters have been applied both for research and clinical purposes in neurology, cardiology and oncology. The recent success of PET with rapidly increasing installations is mainly based on the use of [¹⁸F]fluorodeoxyglucose (FDG) in oncology where it is most useful to localize primary tumours and their metastases.     

Desorption behavior of carrier free tritium from the inner surface of a glass ampoule

The desorption behavior of tritium from the glass ampoule which originally contained 37 GBq of carrier free tritium gas was studied by etching the surface with a diluted hydrofluoric acid solution or by heating at the constant rate up to 800 degrees C. The total amount of tritium sorbed on the inner surface of the ampoule was found to be 3.9 +/- 0.7 GBq. This value corresponded to more than 10% of tritium contained in the ampoule. The release rate of tritiated water (HTO) was 2.3 kBq/cm2.min, and the amount of HTO desorbed was strongly depended on the atmosphere. Thus, special precaution should be paid to the processing of a vessel once containing such an amount of tritium.     

A Localized Tolerance in the Substrate Specificity of the Fluorinase Enzyme enables “Last‐Step” 18F Fluorination of a RGD Peptide under Ambient Aqueous Conditions

A strategy for last‐step ¹⁸F fluorination of bioconjugated peptides is reported that exploits an “Achilles heel” in the substrate specificity of the fluorinase enzyme. An acetylene functionality at the C‐2 position of the adenosine substrate projects from the active site into the solvent. The fluorinase catalyzes a transhalogenation of 5′‐chlorodeoxy‐2‐ethynyladenosine (ClDEA) to 5′‐fluorodeoxy‐2‐ethynyladenosine (FDEA). Extending a polyethylene glycol linker from the terminus of the acetylene allows the presentation of bioconjugation cargo to the enzyme for ¹⁸F labelling. The method uses an aqueous solution (H₂¹⁸O) of [¹⁸F]fluoride generated by the cyclotron and has the capacity to isotopically label peptides of choice for positron emission tomography (PET).     

Preparation and Characterization of Sol-Gel Derived Y2O3 Thin Films

Sol-gel derived Y2O3 thin films have been prepared on platinum coated silicon wafers and fired to temperatures ranging from 400°C to 750°C. Multiple coats were used to obtain films up to 0.5 m thick with an intermediate firing of 400°C between coatings. Top Pt electrodes were sputtered to form monolithic capacitors. These films exhibited a dielectric constant of 18 and a leakage current of 10–11–10–7 A/cm2, making them attractive candidates for high dielectric constant dielectric films in high density DRAMs.     

Solvent-induced crystallization. I. Crystallization kinetics

The kinetics of crystallization of quenched poly(ethylene terephthalate) (PET) films during the imbibition of methylene chloride (MeCl₂) vapor is studied by density measurements. The effects of film thickness (0.0025–0.086 cm) and temperature (0–38°C) were examined. The data suggest that MeCl₂ transport controls the crystallization in thick films and at elevated temperatures, but that spherulite growth controls in thin films and at reduced temperatures. The application of a mathematical model developed previously supports this mechanistic interpretation of the data.     

Surface modifications of PET in argon atmospheric pressure plasma: Gas flow rate effect

The correlation between plasma optical properties and the treated polyethylene terephthalate (PET) surface characteristics have been studied at various Ar flow rate. The rotational T_rot and vibrational T_vib temperatures of APPJ were determined from SPS emission band. The pristine and plasma-treated PET surfaces were characterized by several techniques including X-ray photoelectrons spectroscopy (XPS), Raman spectroscopy, contact angle (CA), and atomic force microscope (AFM). The CA decreased rapidly in the flow rate range 1–3 L/min and weakly dependent as flow rate > 3 L/min. XPS results showed that C 1s % of plasma-treated PET surfaces decreases and has a minimum for samples treated at 3–4 L/min, while O 1s has a maximum at the same flow rate range. The carbon C 1s peak of pristine and plasma treated PET samples resolved into five subcomponents: C–C, C–O, C=O, O–C=O, and π–π bonds with variable percentage ratio accordance to the plasma gas flow rate. Raman data revealed a partial loss in the crystallinity of the treated PET samples and also confirm the incremental of C–O band at Ar flow rate of 3 L/min. AFM images showed that the surface roughness of treated PET films increases as Ar flow rate increases.