The quantification of Tl and Cu concentrations in 201Tl solutions using anodic stripping voltammetry

Thallium-201 is a cyclotron produced isotope which is used in nuclear medicine for myocardial function studies. Thallium-201 is prepared by the (p, 3n) reaction on ²⁰³Tl to form ²⁰¹Pb which decays by positron emission to ²⁰¹Tl. Prior to irradiation the thallium target is electro-deposited onto a copper cathode. After irradiation the target is processed by leaching the cathode with dilute acid and passing the leachate through ion exchange resins.Pharmocopoeia monographs on pharmaceutical grade ²⁰¹Tl define limits on the concentrations of Tl and Cu which may be present in solutions of ²⁰¹Tl. It is therefore important from a quality control viewpoint to have a rapid, accurate means of analysis of quantify levels of these metals in radioactive solutions of ²⁰¹Tl.We have developed a procedure utilizing anodic stripping voltammetry to quantify concentrations of Tl and Cu in solutions of ²⁰¹Tl.     

Degradation of myocardial perfusion SPECT images caused by contaminants in thallous (<Superscript>201</Superscript>Tl) chloride

Purpose Thallous (²⁰¹Tl) chloride is a single-photon emission computed tomography (SPECT) tracer mainly used for assessing perfusion and viability of myocardial tissue. ²⁰¹Tl emits X-rays around 72 keV and gammas at 167 keV, and has a half-life of 73 h. Regulations allow an intrinsic contamination up to 3–5%, which is mainly caused by ²⁰⁰Tl (368 keV; 26 h) and by ²⁰²Tl (439 keV; 12.2 days). Contra-intuitive to the low-level percentages in which these contaminants are present, their impact may be significant because of much higher gamma camera sensitivity for these high-energy photon emissions. Therefore, we investigate the effects of the contaminants in terms of detected fractions of photons in projections and contrast degradation in reconstructed images. Methods Acquisitions of a digital thorax phantom filled with thallous (²⁰¹Tl) chloride were simulated with a validated Monte Carlo tool, thereby, modelling 1% of contamination by ²⁰⁰Tl and ²⁰²Tl each. In addition, measurements of a thorax phantom on a dual-headed gamma camera were performed. The product used was contaminated by 0.17% of ²⁰⁰Tl and 0.24% of ²⁰²Tl at activity reference time (ART). This ART is specified by the manufacturer, thereby, accounting for the difference in half-lives of ²⁰¹Tl and its contaminants. These measurements were repeated at different dates associated with various contamination levels. Results Simulations showed that, with 1% of ²⁰⁰Tl and ²⁰²Tl, the total contamination in the 72 keV window can rise up to one out of three detected photons. For the 167keV window, the contamination is even more pronounced: more than four out of five detections in this photopeak window originate from contaminants. Measurements indicate that cold lesion contrast in myocardial perfusion SPECT imaging is at maximum close to ART. In addition to a higher noise level, relative contrast decreases 15% 2 days early to ART, which is explained by an increase in ²⁰⁰Tl contamination. After ART, contrast decreased by 16% when the ²⁰²Tl contamination increased to the maximal allowed limit. Conclusions Contra-intuitive to the low-level percentages in which they are typically present, penetration and downscatter of high-energy photons from ²⁰⁰Tl and ²⁰²Tl significantly contribute to thallous (²⁰¹Tl) chloride images, thereby, reducing contrast and adding noise. These findings may prompt for improved production methods, for updated policies with regard to timing of usage, and they also render the usefulness of adding the high photopeak window (167 keV) questionable. A window-based correction method for this contamination is advisable.     

Tritium half-life measured by helium-3 growth

Determinations of the tritium half life have been made by measuring the rate of ³He buildup in neutron-irradiated natural lithium. The measurement method, which is substantially different from those used previously, consisted of mass spectrometric measurements of the ⁴He/³He isotopic ratio in samples of lithium metal that had been irradiated in the core of a Triga reactor. Almost all of the ³He in the samples resulted from the decay of tritium produced by the ⁶Li(n, t)⁴He and the ⁷Li(n n′t)⁴He reactions, both of which yielded equal amounts of tritium and ⁴He. The helium isotopic ratio measurements, combined with the known decay times between irradiation and analysis, yielded an average tritium half life of 12.38 ± 0.03 mean solar years (1 solar year = 365.2422 days). This value is higher than several earlier half life measurements, but is consistent with a recent determination by the U.S. National Bureau of Standard.     

A method for optimum PSA setting in the absence of a pure α or β emitter and its application in the determination of 237Np/233Pa

In the application of liquid scintillation counting (LSC), the α/β discrimination is carried out with the function of pulse shape analysis (PSA), which requires the setting of the optimum PSA level. The optimum PSA are usually determined by the generation of cross-over plots, whereby a pair of vials, one containing a pure α emitter and the other a pure β emitter, is counted. However, in some cases such as the determination of ²³⁷Np/²³³Pa, a pure α emitter or a pure β emitter is not available. Therefore, we have developed a new approach to set the optimum PSA by measuring the sample itself of mixed α/β emitters. The count rate of the sample in the α-multi-channel analyzer changes monotonically with the increase of the PSA, and there is always an inflection point which is related to the optimum PSA. By fitting the data near the inflection point with the function y=ax³+bx²+cx+d, we can obtain the optimum PSA as −b/(3a), which can be used to determine the radioactivity of ²³⁷Np/²³³Pa. The results obtained with this new approach were in good agreement with those obtained by HPGe γ spectrometry that was calibrated with an LSC sample of ²³⁷Np/²³³Pa under a radioactive secular equilibrium. The new approach is promising to be used in simultaneous determination of gross α and β emitters, especially in the absence of a pure α or β emitter.     

Concentration of 68Ga via solvent extraction

The metallic cation, ⁶⁸Ga (III) is suitable for complexation with chelators either naked or conjugated with biological macromolecules, however, such labeling procedure requires high chemical purity and concentrated solutions of ⁶⁸Ga (III), which cannot be sufficiently fulfilled by the presently available ⁶⁸Ge/⁶⁸Ga generator eluate. A method to increase the concentration and purity of ⁶⁸Ga obtained from a commercial ⁶⁸Ge/⁶⁸Ga generator has been developed. The ⁶⁸Ga eluate (1 M HCl) is extracted in methyl ethyl ketone, which is evaporated and taken in a small volume of buffer.     

Radioiodination of myoglobin with 125I using an on-line solid phase HPLC-coupled procedure

A new procedure is described for the radioiodination of proteins, such as myoglobin, which carry sensitive moieties, such as thiols or porphyrins. Myoglobin has been iodinated with ¹²⁵I by using the iodinating reagent, IODO-GEN^R, which has been adsorbed onto polyol silica and packed in a reactor pre-column coupled in tandem to a gel permeation chromatography column.     

Particle size distribution of 7Be-aerosols formed in high energy accelerator tunnels

The ⁷Be, produced by nuclear spallation reactions in the air of high energy accelerator tunnels, is present in the form of an aerosol. The size distribution of the ⁷Be-aerosols was measured with a parallel plate diffusion battery and was found to be a log-normal distribution with a geometric mean radii of 27 nm and a logarithmic standard deviation of 0.36. The formation of the ⁷Be-aerosol is adequately explained by the attachment of ⁷Be to non-radioactive aerosols containing sulfates, which are produced by radiation induced oxidation reactions of SO₂ present in the air.     

The use of alumina “SepPaks®” as a simple method for the removal and determination of tungsten-188 breakthrough from tungsten-188/rhenium-188 generators

A simple method using an alumina SepPak^® has been developed to determine the breakthrough levels of ¹⁸⁸W from ¹⁸⁸W/¹⁸⁸Re generator systems. Detection of low levels of ¹⁸⁸W in the presence of high levels of ¹⁸⁸Re (155 keV, 15%) by traditional counting techniques is not possible because the ¹⁸⁸W parent emits gamma photons of only very low intensity at 227 keV (0.22%) and 290 keV (0.40%). In order to remove and quantitate levels of ¹⁸⁸W in “real time” without having to wait several days for decay of the ¹⁸⁸Re caughter, the use of an alumina SepPak^® in tandem with the alumina generator is an effective technique to trap the ¹⁸⁸W breakthrough. The efficiency of this technique was demonstrated by doping 2 mCi of ¹⁸⁸Re with 2 μCi of ¹⁸⁸W. This doped sample provided a control which would correspond to a very high breakthrough value (0.1%), which is 10³ times greater than the usual breakthrough of the alumina system (<10⁻⁴%). Even these very high levels of ¹⁸⁸W could not be detected by gamma-ray spectroscopy in the presence of the ¹⁸⁸Re. When the eluant was subsequently passed through an acid-washed alumina SepPak^® followed by thorough washing (20 mL) with 0.9% NaCl, however, the 227 and 290 keV gamma lines were clearly detected, which facilitated quantification of the ¹⁸⁸W breakthrough levels. Breakthrough levels 1000 times lower could still be detected by this method, making it a useful quality control tool in assessing ¹⁸⁸W/¹⁸⁸Re generator performance.     

Finding an optimal method for imaging lymphatic vessels of the upper limb

Lymphoscintigraphy involves interstitial injection of radiolabelled particulate materials or radioproteins. Although several variations in the technique have been described, their place in clinical practice remains controversial. Traditional diagnostic criteria are based primarily on lymph node appearances but in situations such as breast cancer, where lymph nodes may have been excised, these criteria are of limited use. In these circumstances, lymphatic vessel morphology takes on greater importance as a clinical endpoint, so a method that gives good definition of lymphatic vessels would be useful. In patients with breast cancer, for example, such a method, used before and after lymph node resection, may assist in predicting the development of breast cancer-related lymphoedema. The aim of this study was to optimise a method for the visualisation of lymphatic vessels. Subcutaneous (sc) and intradermal (id) injection sites were compared, and technetium-99m nanocolloid, a particulate material, was compared with ^99mTc-human immunoglobulin (HIG), which is a soluble macromolecule. Twelve normal volunteers were each studied on two occasions. In three subjects, id ^99mTc-HIG was compared with sc ^99mTc-HIG, in three id ^99mTc-nanocolloid was compared with sc ^99mTc-nanocolloid, in three id ^99mTc-HIG was compared with id ^99mTc-nanocolloid and in three sc ^99mTc-HIG was compared with sc ^99mTc-nanocolloid. Endpoints were quality of lymphatic vessel definition, the time after injection at which vessels were most clearly visualised, the rate constant of depot disappearance (k) and the systemic blood accumulation rate as measured by gamma camera imaging over the liver or cardiac blood pool. Excellent definition of lymphatic vessels was obtained following id injection of either radiopharmaceutical, an injection route that was clearly superior to sc. Differences between radiopharmaceuticals were less clear, although after id injection, ^99mTc-HIG gave images that were marginally but significantly better than those given by ^99mTc-nanocolloid. Image quality correlated inversely with time after injection at which the best image was obtained, consistent with the notion that good vessel definition was dependent on a narrow bolus width. k was approximately three times higher after id injection than after sc injection but it was not significantly different between radiopharmaceuticals for either injection route. Intradermal ^99mTc-HIG gave a cardiac blood pool signal that, over the first 60 min, increased about five times faster than that with sc ^99mTc-HIG, but no clear difference was observed in the rate of increase in hepatic activity between id ^99mTc-nanocolloid and sc ^99mTc-nanocolloid. We conclude that id injection provides rapid access of radiotracers to lymphatic vessels, which is ideal for imaging lymphatic vessel morphology. ^99mTc-HIG is marginally superior to nanocolloid for this purpose and, in drainage basins from which lymph nodes have been excised, is not handicapped by a potentially inferior ability, compared with radiocolloid, to image lymph nodes.     

Phase and structural transformations in metallic iron under the action of heavy ions and recoil nuclei

By the use of various modes of Mössbauer spectroscopy after effects of irradiation of metal iron with ¹²C⁴⁺ and ¹⁴N⁵⁺ ions of medium energies, and alpha-particles and the ²⁰⁸Tl, ^208,212Pb, and ²¹⁶Po recoil from a ²²⁸Th-source have been studied. The experimental data obtained in the study enabled various types of external and internal radiation to be compared in regard to the damage they cause, as well as to their effect on the structure-, phase composition- and corrosion resistance properties of metallic iron. Irradiation with ¹²C⁴⁺ and ¹⁴N⁵⁺ ions is accompanied by both structural disordering of the α-Fe lattice, and the appearance of γ-phase in the bulk metal. This is indicated by a single line which is 2 to 3-fold broadened (as compared to the lines of the magnetic sextet). This is a result of a strong local heating of the lattice in the thermal spike area with a subsequent instant cooling-down and recrystallization of this “molted” area. Irradiation of iron foils with ¹²C⁴⁺- and ¹⁴N⁵⁺ ions and with recoil nuclei does provoke corrosion processes (the formation of γ-FeOOH) and is accompanied by an intensive oxidation of the metal.     

Whole-body iodine-131 metaiodobenzylguanidine imaging for detection of bone metastases in patients with paraganglioma: comparison with bone scintigraphy

Iodine-131 metaiodobenzylguanidine (¹³¹I-MIBG) therapy is an effective treatment for patients with malignant paraganglioma for which surgical resection is not indicated. We performed high-dose ¹³¹I-MIBG therapy on two patients with malignant paraganglioma and multiple bone metastases. The bone metastases were diagnosed by magnetic resonance imaging (MRI). Metastatic bone lesions were evaluated by whole-body ¹³¹I-MIBG imaging and bone scintigraphy. Whole-body ¹³¹I-MIBG imaging showed extensive metastatic bone lesions, whereas conventional bone scintigraphy did not. There was a remarkable discrepancy between ¹³¹I-MIBG imaging and bone scintigraphy in the diagnosis of metastatic bone lesions of malignant paraganglioma in our two patients. High-dose ¹³¹I-MIBG imaging may detect early stages of bone metastases, compared with bone scintigraphy, in patients with malignant paraganglioma.     

A kinetic model for99mTc-DMSA in the rat

A pharmacokinetic model was developed for the renal imaging agent^9mTc-DMSA in anesthetized rats, which incorporated data from serial measurements of blood and urine simultaneously with dynamic images obtained over an 8-h period. Animals which received a 10 mg/kg dose of unlabeled DMSA immediately before^99mTc-DMSA injection had a significantly reduced kidney accumulation and greater urinary elimination of^99mTc than animals which received the radiopharmaceutical alone. The kidney clearance was also significantly lower in rats receiving unlabeled DMSA, but no significant difference was determined between the urine clearance estimates of the two animal groups. Because the increase in the amount eliminated in the urine was not coupled with a significant change in urine clearance, it would appear that unlabeled DMSA saturated the kidney uptake mechanism(s) of^99mTc-DMSA without modifying the urinary clearance process. This interpretation is consistent with the hypothesis that renal handling of^99m'Tc-DMSA is governed by both glomerular filtration and peritubular capillary uptake. The simultaneous acquisition of blood, urine and non invasive image data allows for a comprehensive and informative model of the physiological disposition of^99mTc-DMSA.     

Hypoxia-induced redox alterations and their correlation with 99mTc-MIBI and 99mTc-HL-91 uptake in colon cancer cells

Colorectal cancer is one of the most common malignancies in the Western world and is an example of a solid tumour in which hypoxia is a common feature and develops because of the inability of the vascular system to supply adequate amounts of oxygen to growing tumours. Hypoxia effects on tumour cell biology can be detected and characterized using different methods. The use of imaging with γ-emitting radionuclides to detect hypoxic tissue was first suggested by Chapman in 1979 [N Engl J Med 301 (1979) 1429–1432]. ^99mTc-4,9-diaza-3,3,10,10-tetramethyldodecan-2,11-dione dioxime, also known as ^99mTc-HL-91, has been among the most studied hypoxia markers.The objective of this study was to correlate the uptake of ^99mTc-HL-91 and ^99mTc-MIBI in colon cancer cells under normoxic and hypoxic conditions and to compare this information with some parameters such as oxidative stress and mitochondrial dysfunction of the cells analyzed by flow cytometry.Our results show that the in vitro ^99mTc-HL-91 uptake is higher in hypoxic conditions, which is confirmed by the decreased uptake of ^99mTc-MIBI. Flow cytometry results demonstrate that hypoxic conditions used are not enough to induce cellular death, but are responsible for the alterations in the intracellular redox environment, namely, increase of ROS production, proteic pimonidazol-derived adduct formation and alteration in the mitochondrial membrane permeability. Therefore, these results confirm that ^99mTc-HL-91 is a radiopharmaceutical with favourable characteristics for detecting hypoxia.     

3D dose distribution calculation in a voxelized human phantom by means of Monte Carlo method

The aim of this work is to provide the reconstruction of a real human voxelized phantom by means of a MatLab^® program and the simulation of the irradiation of such phantom with the photon beam generated in a Theratron 780^® (MDS Nordion) ⁶⁰Co radiotherapy unit, by using the Monte Carlo transport code MCNP (Monte Carlo N-Particle), version 5. The project results in 3D dose mapping calculations inside the voxelized antropomorphic head phantom.The program provides the voxelization by first processing the CT slices; the process follows a two-dimensional pixel and material identification algorithm on each slice and three-dimensional interpolation in order to describe the phantom geometry via small cubic cells, resulting in an MCNP input deck format output. Dose rates are calculated by using the MCNP5 tool FMESH, superimposed mesh tally, which gives the track length estimation of the particle flux in units of particles/cm². Furthermore, the particle flux is converted into dose by using the conversion coefficients extracted from the NIST Physical Reference Data.The voxelization using a three-dimensional interpolation technique in combination with the use of the FMESH tool of the MCNP Monte Carlo code offers an optimal simulation which results in 3D dose mapping calculations inside anthropomorphic phantoms. This tool is very useful in radiation treatment assessments, in which voxelized phantoms are widely utilized.     

Development of monitoring method of spatial neutron distribution in neutrons–gamma rays mixed field using imaging plate for NCT—Depression of the field

The degree of depression in the neutron field caused by neutron absorption in the materials of an imaging plate (IP) was investigated using MCNP-4C. Consequently, the IP doped with Gd, which reproduced the distribution of ¹⁵⁷Gd(n,γ)¹⁵⁸Gd reaction rate in the previous study, depresses the relative distribution by about 50%. The depression for the IP in which Gd is replaced with similar amount of B atoms was estimated to be about 10%. The signal intensity for this IP is estimated to be at a similar level with that for Gd-doped IP.     

Detection of 32P scintillating plastic vials

This paper describes a novel technique for the detection of ³²P using a liquid scintillation counter. In this technique ³²P is detected in plastic vials which have been given scintillation properties through impregnation with a scintillating liquid. Beta particles emitted by the ³²P are detected when they interact with the scintillating walls of the vials.Measurements show much better repeatability than those using the Cerenkov effect in the walls of glass or plastic vials; counting efficiency is very close to that obtained with the liquid scintillation method.     

λ-prophage Induction in Repair-deficient and Wild Type E. Coli Strains by γ-rays and Heavy Ions

Summary

λ-prophage induction in repair-deficient and wild-type E. coli strains by heavy ions and γ-rays has been investigated. The dose dependence of the fraction of induced cells has been measured and its initial slope (λ-induction potency) determined. The induction by γ-rays was found to be more efficient in a polA-repair-deficient strain; the value of λ-induction potency is zero in lexA^? and recA^? strains. The λ-induction potency increased with LET for wild-type cells but remained constant in the case of polA^? mutant cells. It is suggested that the DNA damage triggering the λ-prophage induction in the case of ionizing radiation could be a type of DNA single-strand break with complex structure which cannot be repaired by fast repair processes, and which requires a substantial level of energy deposition for induction in a DNA molecule.     

PCR inhibitor removal using the NucleoSpin® DNA Clean-Up XS kit

Forensic evidence samples are collected from an unlimited variety of substrates, which may contain compounds known to inhibit the polymerase chain reaction (PCR). These PCR inhibitors are co-extracted with the DNA sample and can negatively affect the DNA typing results, which can range from partial to complete inhibition of the short tandem repeat (STR) PCR. One potential solution is to remove the PCR inhibitors from the extracts prior to the STR PCR with the NucleoSpin^® DNA Clean-Up XS kit. The kit contains a NucleoSpin^® XS silica column that has a special funnel design of thrust rings along with a very small silica membrane, which allows for sample elution in a small volume that is appropriate for use with current STR typing kits. The NucleoSpin^® DNA Clean-Up XS kit was optimized for the best possible DNA recovery and then evaluated for its ability to remove eight commonly encountered PCR inhibitors including: bile salt, collagen, hematin, humic acid, indigo, melanin, tannic acid and urea. Each of these PCR inhibitors was effectively removed by the NucleoSpin^® DNA Clean-Up XS kit as demonstrated by generating more complete STR profiles from the cleaned up inhibitor samples than from the raw inhibitor samples.     

A flexible 32‐channel receive array combined with a homogeneous transmit coil for human lung imaging with hyperpolarized 3He at 1.5 T

Parallel imaging presents a promising approach for MRI of hyperpolarized nuclei, as the penalty in signal‐to‐noise ratio typically encountered with ¹H MRI due to a reduction in acquisition time can be offset by an increase in flip angle. The signal‐to‐noise ratio of hyperpolarized MRI generally exhibits a strong dependence on flip angle, which makes a homogeneous B₁⁺ transmit field desirable. This paper presents a flexible 32‐channel receive array for ³He human lung imaging at 1.5T designed for insertion into an asymmetric birdcage transmit coil. While the 32‐channel array allows parallel imaging at high acceleration factors, the birdcage transmit coil provides a homogeneous B₁⁺ field. Decoupling between array elements is achieved by using a concentric shielding approach together with preamplifier decoupling. Coupling between transmit coil and array elements is low by virtue of a low geometric coupling coefficient, which is reduced further by the concentric shields in the array. The combination of the 32‐channel array and birdcage transmit coil provides ³He ventilation images of excellent quality with similar signal‐to‐noise ratio at acceleration factors R = 2 and R = 4, while maintaining a homogeneous B₁⁺. Magn Reson Med, 2011. © 2011 Wiley Periodicals, Inc.     

Drug-induced pneumonitis detected earlier by 18F-FDG-PET than by high-resolution CT: a case report with non-Hodgkin’s lymphoma

Drug-induced pneumonitis is a serious and an unpredictable side effect of chemotherapy in patients with malignant lymphoma. We present the case of a 51-year-old man who developed drug-induced pneumonitis during chemotherapy for non-Hodgkin’s lymphoma in which pneumonitis was detected earlier by ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG-PET) than by high-resolution computed tomography (HRCT). After five courses of chemotherapy, ¹⁸F-FDG-PET was performed for assessing residual lesions, and diffuse lung uptake was incidentally observed. No symptoms were present, and HRCT performed immediately following PET revealed no abnormalities. Mild dyspnea appeared 3 days after PET, and additional HRCT revealed patchy ground-glass opacities disseminated with the appearance of interlobular septum thickening. Drug-induced pneumonitis was finally diagnosed, and treatment was initiated. ¹⁸F-FDG-PET can be an imaging modality for detecting drug-induced pneumonitis at an extremely early stage in which HRCT is incapable of revealing any abnormal changes.