Technetium Tracer Research Articles

A synchronous papillary and follicular thyroid carcinoma presenting as a large toxic nodule in a female adolescent

Case presentationWe report for the first time a synchronous papillary and follicular thyroid carcinoma in a 12-year-old girl presenting with a large (5 cm diameter) left thyroid nodule, an increased left and right upper pole technetium tracer uptake at scintigraphy and hyperthyroidism. The uptake at the right lobe was explained by the crossing of the left nodule to the right site of the neck at Computed Tomography (CT) scanning.BackgroundAlthough thyroid nodules are less common in children than in adults, there is more vigilance required in children because of the higher risk of malignancy. According to literature, about 5% of the thyroid nodules in adults are malignant versus 20–26% in children. The characteristics of 9 other pediatric cases with a differentiated thyroid carcinoma presenting with a toxic nodule, which have been reported during the last 20 years, are summarized. A nodular size of more than 3.5 cm and female predominance was a common finding.ConclusionsThe presence of hyperthyroidism in association with a hyperfunctioning thyroid nodule does not rule out thyroid cancer and warrants careful evaluation, even in the absence of cervical lymph node invasion.

Arrêt de production du chrome-51 (51Cr) a usage clinique : quelles alternatives possibles pour les services de radiopharmacie et de médecine nucléaire ?

Last October, the nuclear medicine departments were informed of the closure of the chromium-51 production line for clinical use. This radionuclide has different diagnostic indications in nephrology and hematology. It was therefore essential to set up alternative exploration protocols to overcome this production stoppage. Chromium-51 EDTA has been replaced by technetium-99m DTPA for the determination of glomerular filtration rates. Sodium chromate was substituted by sodium pertechnetate for the determination of globular volumes. A retrospective analysis of the chromium-51 data was performed followed by a prospective study, from January to December 2019 for technetium tracers. One hundred and forty-four patients were included in the study. Forty-two EDTA-51Cr and 30 DTPA-99mTc exams were conducted and compared. There were no significant differences between the methods used to assess renal function (P=0.355). For the determination of blood cell and plasma volumes, 47 tests with 51Cr and 125I and 25 tests with 99mTc and 125I were performed and compared. There were no significant differences in the determination of total (P=0.325) and globular (P=0.148) volumes. The study carried out shows that there is no significant difference between the results obtained with chromium-51 and technetium tracers. As a result, clinical activity was maintained in good conditions.

Tumour Hypoxia and Technetium Tracers: In Vivo Studies

Hypoxia is a biochemical condition where reduced oxygen partial pressure at tissue level occurs. This metabolic situation can lead to resistance to radio and chemotherapy. In malignant solid tumours, hypoxia is a common characteristic, having a great impact at biological level, being of tremendous importance for complete understanding of tumour progression. We studied the behavior of 99mTc-HL91 in vivo, using an animal model based on Balb-c nu/nu mice with a xenotransplant of the human colorectal adenocarcinoma cell line, WiDr. In vivo studies using an animal model of xenograft on Balb/c nu/nu nude mice were carried out. This model, allowed us to evaluate the radiopharmaceutical biodistribution and to calculate tumour/muscle ratio, acquired after 99mTc-HL91 injection. We also performed ex vivo studies, using the excised tumours to access viability and to characterize the intracellular production of reactive oxygen species and the status of mitochondrial membrane potential through flow cytometry. The biodistribution after 99mTc-HL91 injection showed urinary and hepatobilliary excretion in similar proportions and tumour uptake around 4.4% of administered activity. This uptake was higher at the bigger tumours. Through flow cytometry we observed that larger tumours have a higher amount of reactive oxygen species and a decrease in mitochondrial membrane potential. 99mTc-HL91 allowed a non-invasive evaluation of the solid tumours oxidative state by nuclear medicine functional imaging. This information can be of high importance at the pre-treatment estimation of this type of tumours.

New oxorhenium (V) complex with an imidazol [NN] /hydantoin [SN] mixed ligand system, and radiochemical behavior of its oxotechnetium (V) complex analog

A [ReO(Imz)(Hyd)(H2O)2OH] complex was successfully synthesized by the ligand exchange method using oxorhenuim citrate and an imidazole /Hydanton mixed ligand system. Geometry optimization of complex has been carried out using DFT at the B3LYP/LANL2DZ functional in singlet state. B3LYP predicated infrared spectrum of the geometrically optimized structure using the same level of the theory and the same base set showed good agreement with experimentally observed values. The spin allowed singlet-singlet electronic transition of the [ReO(Imz)(Hyd) (H2O)2OH] complex was calculated with time dependent density function theory (TD-DFT) and the UV-Vis spectra has been discussed on this basis. The complex was characterized using microanalysis and IR, UV-Vis, NMR and mass spectroscopic. The technetium tracer [99mTcO(Imz)(Hyd) (H2O)2OH] has also been synthesized by two methods using 99mTc-gluconate as a precursor or; by direct reduction. The radiochemical purity of the complex was over 95% as measured by thin layer chromatography. In vitro studies showed that the complex possessed good stability under physiological conditions. The partition coefficient indicated that the complex hydrophilic and the electrophoresis results showed that the complex cationic. Biodistrbution in mice showed that the complex accumulated in heart uptake of 9.53±3.87 % ID/gm at 5 min and good retention (6.37±1.21) % ID/gm at 60 min. One hour after the injection, the heart/liver, heart/lung and heart/blood radioactivity ratios were 0.46, 1.04 and 0.56, respectively. These findings indicate that the complex might be suitable for myocardial imaging.

Relevancia de la hipocinesia septal como hallazgo en la gated-SPECT de perfusión miocárdica

ObjectiveTo identify septal hypokinesia (SH) with signs of right ventricular (RV) overload. Materials and methodsProspective study of consecutive patients divided into cases with SH (n=39) and controls without SH (n=27). Subjects with septal perfusion defects and alterations in conduction were excluded. Images were obtained after injection of 20 mCi (740 MBq) of technetium tracer. The perfusion and septal mobility, RV and left ventricle values were quantified and other clinical parameters were obtained. Multivariate non-parametric tests and Pearson's correlation tests were applied. ResultsRV perfusion was higher in the case group (31.7% vs 27.5 %, p=0.012). 35.9 % of cases had undergone cardiac surgery (CS) in the past. A higher number of subjects with valve diseases (VD) was found in the case group (23.1 % vs 3.7 %, p=0.031); the same occurred with smoking (46.2 % in cases vs. 11.1% in controls, p=0.05). Correlation was obtained between septal mobility and RV perfusion (−0.374, p=0.015 bilateral), and between mobility of the septum and the RV (0.299, p=0.015 unilateral). DiscussionThis test has been scarcely applied in RV pathology; this entity has great repercussion on the prognosis of patients with heart failure. These findings may clarify certain aspects of its physiopathology. ConclusionsAccording to our study, SH is associated with the degree of RV perfusion and mobility, as well as the presence of history of CS, VD and smoking.

Relevance of septal hypokinesia as a finding in myocardial perfusion gated-SPECT

Objective To identify septal hypokinesia (SH) with signs of right ventricular (RV) overload. Materials and methods. Prospective study of consecutive patients divided into cases with SH (n = 39) and controls without SH (n = 27). Subjects with septal perfusion defects and alterations in conduction were excluded. Images were obtained after injection of 20 mCi (740 MBq) of technetium tracer. The perfusion and septal mobility, RV and left ventricle values were quantified and other clinical parameters were obtained. Multivariate non-parametric tests and Pearson's correlation tests were applied. Results RV perfusion was higher in the case group (31.7% vs 27.5%, p = 0.012). 35.9% of cases had undergone cardiac surgery (CS) in the past. A higher number of subjects with valve diseases (VD) was found in the case group (23.1% vs 3.7%, p = 0.031); the same occurred with smoking (46.2% in cases vs. 11.1% in controls, p = 0.05). Correlation was obtained between septal motion and RV perfusion (-0.374, p = 0.015 bilateral), and between septal and RV wall motion (0.299, p = 0.015 one-sided). Discussion This test has been scarcely applied in RV pathology; this entity has great repercussion on the prognosis of patients with heart failure. These findings may clarify certain aspects of its physiopathology. Conclusions According to our study, SH is associated with the degree of RV perfusion and wall motion, as well as the presence of history of CS, VD and smoking.

Patient gender and radiopharmaceutical tracer is of minor importance for the interpretation of myocardial perfusion images using an artificial neural network

The purpose of this study was to assess the influence of patient gender and choice of perfusion tracer on computer-based interpretation of myocardial perfusion images. For the image interpretation, an automated method was used based on image processing and artificial neural network techniques. A total of 1000 patients were studied, all referred to the Royal Brompton Hospital in London for myocardial perfusion scintigraphy over a period of 1 year. The patients were randomized to receive either thallium or one of the two technetium tracers, methoxyisobutylisonitrile or tetrofosmin. Artificial neural networks were trained with either mixed gender or gender-specific and mixed tracer or tracer-specific training sets of different sizes. The performance of the networks was assessed in separate test sets, with the interpretation of experienced physicians regarding the presence or absence of fixed or reversible defects in the images as the gold standard. The neural networks trained with large mixed gender training sets were as good as the networks trained with gender-specific data sets. In addition, the neural networks trained with large mixed tracer training sets were as good as or better than the networks trained with tracer-specific data sets. Our results indicate that the influence of patient gender and perfusion tracer are of minor importance for the computer-based interpretation of the myocardial perfusion images. The differences that occur can be compensated for by larger training sets.

Assessment of left ventricular function during treadmill exercise with a new method of motion correction of first-pass radionuclide angiography using a multiwire gamma camera

Background: Earlier studies with first-pass radionuclide angiography during treadmill exercise used Anger(single-crystal) or multi-crystal gamma camera, a technetium tracer and either did not correct for motion or used external point sources. Motion correction by such dual-isotope method is limited to plane movement corrections and inherently assumes that the patient is rotationally fixed. Method: In this study we used a Multiwire gamma camera (MWGC), a generator-produced Ta-178, which has a low energy and a short half-life (9.3 min) and a novel method of motion correction during treadmill exercise testing. Motion correction was achieved by incorporating an electromagnetic tracking device to track the movement of left ventricle (LV) center, based on real-time six-dimensional position and orientation of a sensor attached to the patient's back, and LV center rotation in patient's chest contour. Result: We studied 72 patients who had normal rest and stress gated single-photon emission tomography (SPECT) myocardial perfusion images. There were 42 men and 30 women, aged 51±12 years. The resting gated SPECT LV ejection fraction (EF) was 61±10% (range 26 to 87%). The resting EF in the upright position by MWGC was 58±11% ( r = 0.33, p = 0.005 vs gated SPECT). At peak exercise the EF by MWGC was 62±24% if uncorrected for motion and 70±11% when motion corrected. A normal response to exercise , defined as resting EF>50%, and an increase in EF from rest to exercise of 5% or more, was seen in 22 patients (30%) with the uncorrected method and 42 patients (58%) with the corrected method (p < 0.05). Abnormal EF response despite normal perfusion is not unexpected in patients with hypertension or other conditions. Conclusion: Thus, assessment of LV function at rest or peak treadmill exercise is feasible with a MWGC and a novel motion correction algorithm. The method may offer a cost-effective and rapid screening strategy to identify low- and high-risk patients with suspected or known CAD.

Myocardial perfusion imaging in Denmark: activity from 1997 to 2001 and current practice.

A questionnaire was sent to all departments of nuclear medicine in Denmark (n=20) asking for details of myocardial perfusion imaging (MPI), including the number of patients examined each year from 1997 to 2001 and the current clinical and technical practice. All (100%) departments replied, and the survey thus covers all MPI performed in Denmark during the period in question. The number of MPI studies (examined patients) was 2,531 in 1997 (0.47 MPI/1,000/year) and 4,961 (0.93 MPI/1,000/year) in 2001, which is a doubling in activity in 5 years. Nineteen (95%) of the Danish departments performed MPI in 2001, and 14 (74%) of these reported that activity had increased over the past 5 years. MPI activity was unevenly distributed between hospitals and regions. In 2001, the university hospitals in the central Copenhagen region (capital) accounted for the highest MPI activity (2.00/1,000/year), while the non-university hospitals in general had the lowest activity rate (0.73/1,000/year). The most pronounced increment found in the period was observed in the university hospitals outside Copenhagen, where activity increased by 300% from 0.44/1,000/year in 1997 to 1.33/1,000/year in 2001. All departments providing MPI used tomographic acquisition technique and all departments used technetium tracers. The more sophisticated techniques of MPI - gated acquisition, attenuation correction and iterative reconstruction - were used in 74%, 32% and 42% of departments, respectively. The stress mode in perfusion studies was dipyridamole/adenosine in 76%, exercise in 18% and dobutamine in 6%. Despite these encouraging figures, MPI activity for 2001 remained well below what is recommended by other national and international societies. The anticipated further increase in nuclear cardiology is encouraging, but the nuclear medicine community needs to address the issues that prevent it from keeping up with demand. In general, the restricted camera time and the limited number of trained personnel explain the excessive waiting lists in Denmark.

Syntheses and First Crystal Structures of Rhenium Complexes Derived from ψ-Functionalized Fatty Acids as Model Compounds of Technetium Tracers for Myocardial Metabolism Imaging

In an attempt to develop new technetium-based radiopharmaceuticals for the noninvasive diagnosis of myocardial metabolism, we have synthesized three examples of novel metal-containing fatty acid derivatives according to the “3+1” mixed-ligand and the Schiff base/tricarbonyl design. The chelates contain the metal core in the oxidation states +5 and +1, respectively, and are attached to the end-position of a fatty acid chain. The complex formation was accomplished by ligand-exchange reactions with three different rhenium precursors, whereas the inactive rhenium metal was utilized as a surrogate of the technetium radionuclide. The molecular structures of the fatty acid complexes 7, 10 and 14 were determined by single-crystal X-ray diffraction analyses and impressively show a general problem in technetium tracer research, namely the significant structural alterations of bioactive molecules by coordination even to small metal chelates. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Novel oxorhenium and oxotechnetium complexes from an aminothiol[NS]/thiol[S] mixed-ligand system.

The simultaneous action of a bidentate aminothiol ligand, LnH, (n = 1: (CH3CH2)2NCH2CH2SH and n = 2: C5H10NCH2CH2SH) and a monodentate thiol ligand, LH (LH: p-methoxythiophenol) on a suitable MO (M = Re, 99gTc) precursor results in the formation of complexes of the general formula [MO(Ln)(L)3] (1, 2 for Re and 5. 6 for 99gTc). In solution these complexes gradually transform to [MO(Ln)(L)2] complexes (3, 4 for Re and 7, 8 for 99gTc). The transformation is much faster for oxotechnetium than for oxorhenium complexes. Complexes 1-4, 7, and 8 have been isolated and fully characterized by elemental analysis and spectroscopic methods. Detailed NMR assignments were made for complexes 3, 4, 7, and 8. X-ray studies have demonstrated that the coordination geometry around rhenium in complex 1 is square pyramidal (tau = 0.06), with four sulfur atoms (one from the L1H ligand and three from three molecules of p-methoxythiophenol) in the basal plane and the oxo group in the apical position. The L1H ligand acts as a monodentate ligand with the nitrogen atom being protonated and hydrogen bonded to the oxo group. The four thiols are deprotonated during complexation resulting in a complex with an overall charge of zero. The coordination geometry around rhenium in complex 4 is trigonally distorted square pyramidal (tau = 0.41), while in the oxotechnetium complex 7 it is square pyramidal (tau = 0.16). In both complexes LnH acts as a bidentate ligand. The NS donor atom set of the bidentate ligand and the two sulfur atoms of the two monodentate thiols define the basal plane, while the oxygen atom occupies the apical position. At the technetium tracer level (99mTc), both types of complexes, [99mTcO(Ln)(L)3] and [99mTcO(Ln)(L)2], are formed as indicated by HPLC. At high ligand concentrations the major complex is [99mTcO(Ln)(L)3], while at low concentrations the predominant complex is [99mTcO(Ln)(L)2]. The complexes [99mTcO(Ln)(L)3] transform to the stable complexes [99mTcO(Ln)(L)2]. This transformation is much faster in the absence of ligands. The complexes [99mTcO(Ln)(L)2] are stable, neutral, and also the predominant product of the reaction when low concentrations of ligands are used, a fact that is very important from the radiopharmaceutical point of view.

Transfer of technetium from soil to paddy and upland rice.

Soil-plant transfer factors (concentration ratio between the plant and soil) of technetium in paddy and upland rice plants were obtained from laboratory experiments. The transfer factor is one of the most important parameters for environmental radiation dose assessment. Technetim tracer (95mTcO4-) was added to the soil prior to rice cultivation. The transfer factor of technetium for the hulled grains (brown rice) of paddy rice (< or = 0.0002) was much lower than for that of upland (0.021). The transfer factors for both types of hulled grains were much lower than in the leaves. The technetium decontamination rate from hulled grains by polishing was 34%, the percentage of the weight decrease being 12%. The concentration of technetium in the soil solution collected from the paddy rice soil (flooded conditions) decreased rapidly with time due to its adsorption on the soil. In the upland rice soil (non-flooded) solution, the decrease in the technetium concentration was fairly slow. The low transfer factors for the paddy rice plants could be explained by the immobilization of technetium in the flooded soil. The oxidation-reduction potentials (Eh) in the flooded soil decreased rapidly with time. We conclude that technetium tracer added as TcO4- to flooded soil is readily transformed to an insoluble form (e.g. TcO2) under the reducing conditions provided by flooding.

Production of96Tc and95mTc via the93Nb(α, xn) Reactions

Relatively longer liver technetium tracers such as95mTc (61 d) are useful for the development, evaluation and comparison of new technetium complexes for eventual development of99mTc radiopharmaceuticals. The feasibility of producing96Tc (4.35 d) and95mTc (61 d) was studied by the alpha bombardment of pure Nb targets (93Nb-100%).96Tc was obtained in a yield of 30 μCi/μAh using 16 MeV alphas, but it contained significant activity of95Tc (20 h) Relatively pure96Tc and95mTc was produced in yields of 18 μCi/μAh and about 1 μCi/μAh respectively with alphas of suitable energy and after allowing for suitable cooling periods after the end of bombardment (EOB).

Isolation of Milligram Quantities of Long-lived Technetium from Neutron Irradiated Molybdenum

The method employed for the isolation of milligram quantities of long- lived Tc/sup 99/ formed in molybdenum metal by prolonged neutron irradiation in the Oak Ridge graphitenatural uranium pile is described. The identity of the element Isolated was established by measurements of its x ray and its optical emission spectra. Careful specific activity determinations using 4 pi beta counting techniques yielded a value of 2.15 plus or minus 0.05 x 10/sup 5/ years for the half-life of Tc/sup 99/g while measurements of the absorption of its radiations in aluminum gave 0.29 plus or minus 0.01 Mev as its maximum beta -ray energy. Collateral observations on the wet volatility, solvent extraction, reduction by metals in acid and alkaline solutions and on the coprecipitation of tracer quantities of technetium were made. A convenient method for the preparation of high specific activity technetium tracer from cyclotron irradiated molybdenum metal targets is outlined. (auth)