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At least 217 records · Page 12Linked to original sources
PubMed1984

The transfer of strontium-90 and caesium-137 to milk in a dairy herd grazing near a major nuclear installation.

A field investigation of the transfer of artificially produced radionuclides in the pasture--cow--milk pathway has been made at a farm close to the nuclear fuel reprocessing installation at Sellafield on the north-west coast of England. This paper reports results from analyses of samples collected during 1981, reports transfers coefficients for 90Sr and 137Cs from various types of feed to milk, and discusses factors that affect the transfer of these radionuclides. It is shown that during 1981 a large proportion of the 90Sr and 137Cs consumed by cattle grazing near Sellafield was derived from activity deposited in previous years. Transfer coefficients to milk, Fm, have been derived which are within the ranges of those observed in tracer and fallout studies. There are significant seasonal changes in transfer. For 90Sr, values of Fm between 9 X 10(-4)d 1(-1) and 4 X 10(-3)d 1(-1) have been obtained. It is concluded that this large range arises because daily intakes of 90Sr by the herd during the winter months are lower (by a factor of about 3) than intakes during the summer months and that the concentration of 90Sr in milk is not in equilibrium with intake, that is, the concentration of 90Sr in milk is maintained both by recent intakes and by remobilisation of activity that has been accumulated in bone from earlier intakes. For 137Cs, values of Fm between 3 X 10(-3)d 1(-1) and 9 X 10(-3)d 1(-1) have been obtained. It is concluded that this range most probably occurs because during the summer months, when the cows are grazing, a substantial proportion of the 137Cs intake is associated with soil on the surface of herbage and that, in this form, the 137Cs is less available for uptake from the digestive tract of the cows.

Animals↗
PubMed1985

Pelvic lymphadenectomy combined with transperineal interstitial implantation of iridium-192 and external beam radiotherapy for locally advanced prostatic carcinoma: technical description.

Regardless of the treatment modality, control of locally advanced extracapsular prostatic cancer remains a therapeutic challenge. At the Mayo Clinic, we have recently developed a combined approach for surgically staged patients employing interstitial irradiation with 192 Iridium via a transperineal template. The Martinez Universal Perineal Interstitial Template (MUPIT-II) and moderate doses of external beam irradiation. The procedure consists of: 1) preoperative single dose external beam irradiation to decrease potential for tumor seeding or showering of malignant cells during MUPIT-II placement; 2) adequate surgical staging through a bilateral retroperitoneal lymphadenectomy; 3) transperineal interstitial implantation of the tumor and retropubic palpation of the needles to verify proper position; 4) intraoperative X rays are taken and used for documentation of needle position as well as for calculation and optimization of the implant dose distribution with the aid of a computerized system; 5) moderate doses of external beam irradiation postoperatively to the prostate with adequate margins. Our favorable preliminary results obtained in 18 patients treated with the above approach warrant the continuation of this trial. Details of this technique are presented.

Adenocarcinoma↗
PubMed1985

Measurements of radiation dose distributions for shielded cervical applicators.

Cervical applicators with shielded ovoids are employed to reduce dose to the rectum and bladder. Because of asymmetries introduced by the shields, dose distribution calculations for individual patients will require extensive computer reference data for the ovoid sources. Requisite 3-D dose distributions were measured for an unshielded and a shielded ovoid containing a Cs-137 source, using a computerized system employing a diode in a water phantom. The probe stops at each measurement point and accumulates dose for several seconds. The system automates horizontal positioning of the detector and angular motion of the ovoid to obtain dose in one plane. The detector is moved manually to other planes for a complete three dimensional set of measurements. In order to suppress the energy and directional dependence of the diode, final dose distributions are calculated from ratios of shielded to unshielded data in conjunction with independently measured TLD data for unshielded sources.

Brachytherapy↗
PubMed1987

Chemical and physical properties of radionuclides.

There are many radionuclides with a wide range of energies and half-lives available for use as non-sealed radiotherapeutic agents. To date, no single radionuclide has emerged as being clearly superior to all others, in the way that 99mTc predominates in diagnostic imaging. It is unlikely that one will emerge. Instead, if a particular application demands certain decay properties, the radionuclide which will be used will be the one for which appropriate chemistry can be developed and which can be produced and distributed most economically.

Chemical Phenomena↗
PubMed2005

An overview of copper radionuclides and production of 61Cu by proton irradiation of (nat)Zn at a medical cyclotron.

In this article, production methods and applications of copper radionuclides are overviewed with special attention toward (61)Cu, due to its interesting nuclear properties. Selection of production parameters for (61)Cu including: appropriate nuclear reaction, proton beam energy, target thickness and targetry method are discussed for NRCAM 30MeV medical cyclotron. (64)Zn(p,alpha)(61)Cu was selected as the best reaction and (61)Cu was produced by 22MeV proton bombardment of a 80 microm thick natural zinc target. After 180microAh irradiation, the resultant activity of (61)Cu was 6.006Ci (12.015mCi/microAh). The chemical separation method was easy, quick and efficient (>95%) and yielded a no carrier added product with high chemical and radionuclidic purity (>99%). Detailed comparison with previous production methods confirms that our results are superior to other reports published to date.

Copper Radioisotopes↗
PubMed2006

Optimization of 124I production via 124Te(p,n)124I reaction.

(124)I was produced, via (124)Te(p,n)(124)I reaction, in greater than 3.7GBq (100 mCi, EOB) amount by bombarding (124)TeO(2) targets at 24 microA current for about 8h. This was achieved by keeping the target at 37 degrees relative to the beam during irradiation, by sweeping the beam across the target and by keeping the incident energy of the proton at 14.1MeV. The time-averaged yield of our 8h run was 21.1 MBq/microAh (0.57 mCi/microAh), which was 90% of the theoretical yield calculated using thick target yield data obtained from the reported excitation function for the reaction. At the end of bombardment, the level of (125)I and (126)I impurities, co-produced with (124)I, were 0.03% and 0.007%, respectively.

Iodine Radioisotopes↗
PubMed2006

A new binary compound for the production of 124I via the 124Te(p,n)124I reaction.

The binary compound, aluminum telluride (Al(2)Te(3)), was investigated as a target material for the production of (124)I by way of the (124)Te(p,n)(124)I reaction on a low-energy cyclotron. The high melting point and formation of a glassy matrix upon heating provided a stable target material at irradiations up to 20 microA of 11 MeV protons. The 87% tellurium mass fraction and 95% iodine separation yield led to significantly higher quantities of iodine compared to traditional TeO(2)/6%Al(2)O(3) admixtures. Radiochemical analysis of distilled samples using ion chromatography showed that the product remained in the iodide form while supported in weak buffer solutions. Stable Te impurities in the radioiodine product were less than 0.5 microg following purification by ion exchange chromatography. Average thick target yields of 229+/-18 microCi/microAh were achieved, and typical production runs at 18 microA for three hours yielded 12 mCi at the end-of-bombardment. Total losses of the target material after each irradiation and distillation cycle were approximately 2%.

Aluminum Compounds↗
PubMed1998

A new look at the cyclotron for making short-lived isotopes. 1966 -classical article-.

This reprint of an article that first appeared in Nucleonics in 1966 provides a unique perspective of the introduction of the cyclotron into clinical medicine and medical research. The cyclotron offers a potentially powerful tool to biomedical centers. With this accelerator one can produce a variety of short-lived nuclides that are unavailable from other sources.

Cyclotrons↗
PubMed1998

The state of positron emitting radionuclide production in 1997.

Thirty years ago Michel M. Ter-Pogossian and Henry N. Wagner, Jr. wrote an article that was published in Nucleonics on the cyclotron production of isotopes for biomedical research. In this report we use the Nucleonics paper as the framework to relate their predictions to the current state of the art, we have broken this into four key areas; commercially available cyclotrons, costs of operating cyclotron facilities, the emergence of compact accelerators, and the cyclotron production of long-lived radionuclides for therapeutic applications. Companies producing cyclotrons commercially are; General Electric Medical Systems, CTI Cyclotron Systems, EBCO, IBA, NNK/Oxford Instruments, and Japan Steel Works. The majority of these machines are now negative ion systems, which allows the option of dual irradiation of two targets. All have a modular design, which allows the system to be customed to a particular facility's need. Cyclotron facility costs have increased dramatically since 1966. We have determined that the bulk of the increase lies in the costs to establish and staff the facility. Increased regulation by Federal and State organizations has severely impacted operational expenses. The growing demand for PET radiopharmaceuticals in the clinical arena has increased the staffing requirements of the facility. Surprisingly, the costs of cyclotrons have not increased (in terms of real dollars) especially when one considers the much greater sophistication in target design, automation, and computer control that has occurred during this time. Innovative approaches are being taken to develop low energy accelerators that are capable of producing PET isotopes. These are easier to operate and less expensive than commercially available cyclotrons. Although many of these systems have been developed, none have as yet gained commercial recognition. A number of groups have begun to address the production of longer lived isotopes on biomedical cyclotrons. Development of this technology may well help to further progress in targeted radiotherapy. We present an overview of potentially useful isotopes.

Costs and Cost Analysis↗
PubMed1983

Spectrum of global left ventricular responses to supine exercise. Limitation in the use of ejection fraction in identifying patients with coronary artery disease.

Left ventricular function was evaluated with rest and supine bicycle exercise-multigated blood pool scans in 53 patients who had previously undergone coronary angiography for evaluation of a chest pain syndrome. There were 21 normal patients (less than 25% stenosis in any coronary artery, left ventricular end-diastolic pressure less than or equal to 12 mm Hg, and normal left ventriculography) and 32 patients with coronary artery disease (CAD) (greater than 50% narrowing in 1 or more major coronary arteries). Thirty-two (60%) were receiving propranolol at the time of the study. The normal patient group had a significant increase in mean ejection fraction (EF) during exercise (+0.08 +/- 0.09), while the CAD group had no increase (0 +/- 0.11; p less than 0.05). Mean end-systolic volume decreased significantly in the normal group (-5 +/- 8 ml/m2) but demonstrated no significant change in the CAD group (1 +/- 12 ml/m2; p less than 0.05 compared with normal patients). There was no significant change in mean end-diastolic volume in either group. Mean ejection rate, mean peak systolic pressure/end-systolic volume ratio, and mean pulmonary blood volume ratio also differed in the normal versus CAD patients. Despite mean differences, there was considerable overlap in both groups of individual EF responses: 8 of 21 (38%) of the normal group did not have an increase in EF of 0.05 with exercise, while 15 of 32 (47%) of the CAD group did have an increase in EF of 0.05 with exercise. However, the addition of peak systolic pressure/end-systolic volume ratio and pulmonary blood volume (exercise/rest) ratio improved the sensitivity for detecting CAD from 53 to 84% without adversely affecting specificity. Thus, there is a wide spectrum of left ventricular EF responses to supine exercise. In our patient population, EF alone was an insensitive and nonspecific marker of CAD. The addition of other parameters of global left ventricular function, which may be generated using radionuclide angiography, helps distinguish patients with CAD from normal subjects.

Adult↗
PubMed2000

Human lung deposition data: the bridge between in vitro and clinical evaluations for inhaled drug products?

Regulatory dossiers for new inhaled drug products generally contain in vitro data, which assess delivered dose and particle size distribution, together with clinical efficacy and safety data. Human lung deposition data may be generated using radionuclide imaging techniques or appropriate pharmacokinetic methods, and can act as a 'bridge' via which a seamless transition can be made between in vitro testing in the laboratory and efficacy/safety testing in the clinic. By enabling informed decisions to be made about the evaluation of new devices or formulations in man, lung deposition data permit a long and expensive clinical trials programme to be commenced with much greater certainty of a successful outcome. Human lung deposition data should be considered for supplementing the information required for regulatory dossiers.

Administration, Inhalation↗
PubMed1999

Development of a lyophilized kit formulation for labeling of DNA probes with 99mTc.

DNA fragments such as oligodeoxynucleotides (ODNs) are under investigation for a possible utilization in nuclear medicine. Until now, experiments on 99mTc-labeled ODNs in vitro or in vivo have required the application of time-consuming procedures to obtain and control the purity of the radiolabeled compound. A lyophilized labeling kit would ease and improve the reproducibility in further investigations with this class of promising biomolecules; therefore a study was initiated to evaluate the suitability of conjugates of ODNs and a bifunctional chelating agent to be part of lyophilized kit formulations. We report here the development of the first kit for one-step labeling of oligonucleotides with 99mTc. The formulation comprises 250-500 pmol S-benzoyl-mercaptoacetyldiglycine (MAG2)-ODN phosphorothioate conjugate, 5 mg potassium sodium tartrate tetrahydrate and 100 microg stannous chloride dihydrate in a lyophilized kit. Labeling yields above 90% were reproducibly achieved after addition of 0.1-1 GBq pertechnetate and subsequent heating in a boiling water bath. Once formed, the 99mTc-MAG2-ODN complexes were stable for at least 24 h. The shelf life of the kits is at least 10 weeks when stored protected from light at room temperature, but even kits stored at 40 degrees C gave labeling yields above 90% after 10 weeks.

Chromatography, High Pressure Liquid↗
PubMed2001

Excitation functions of 125Te(p, xn)-reactions from their respective thresholds up to 100 MeV with special reference to the production of 124I.

Excitation functions of the nuclear reactions 125Te(p, xn) (119,120m, 120g, 121,122,123,124,125)I were measured for the first time from their respective thresholds up to 100 MeV using the stacked-foil technique. Thin samples were prepared by electrolytic deposition of 98.3% enriched 125Te on Ti-backing. In addition to experimental studies, excitation functions were calculated by the modified hybrid model code ALICE-IPPE. The experimental and theoretical data generally showed good agreement. From the measured cross section data, integral yields of (123,124,125)I were calculated. The energy range Ep 21 --> 15 MeV appears to be very suitable for the production of the medically interesting radionuclide 124I (T(1/2) = 4.18 d; I(beta)+ = 25%). The thick target yield of 124I amounts to 81 MBq/microA h and the level of 125I-impurity to 0.9%. The 125Te(p,2n)124I reaction gives 124I yield about four times higher than the commonly used 124Te(p,n)124I and 124Te(d,2n)124I reactions. The proposed production energy range is too high for small cyclotrons but large quantities of 124I can be produced with medium-sized commercial machines.

Cyclotrons↗
PubMed2003

Some optimisation studies relevant to the production of high-purity 124I and 120gI at a small-sized cyclotron.

Optimisation experiments on the production of the positron emitting radionuclides 124I(T(1/2) = 4.18d) and (120g)I (T(1/2) = 1.35 h) were carried out. The TeO(2)-target technology and dry distillation method of radioiodine separation were used. The removal of radioiodine was studied as a function of time and the loss of TeO(2) from the target as a function of oven temperature and time of distillation. A distillation time of 15 min at 750 degrees C was found to be ideal. Using a very pure source and comparing the intensities of the annihilation and X-ray radiation, a value of 22.0 +/- 0.5% for the beta(+) branching in 124I was obtained. Production of 124I was done using 200 mg/cm(2) targets of 99.8% enriched 124TeO(2) on Pt-backing, 16 MeV proton beam intensities of 10 microA, and irradiation times of about 8 h. The average yield of 124I at EOB was 470 MBq(12.7 mCi). At the time of application (about 70 h after EOB) the radionuclidic impurity 123I (T(1/2) = 13.2 h) was <1%. The levels of other impurities were negligible (126I < 0.0001%;125I = 0.01%). Special care was taken to determine the 125I impurity. For the production of (120g)I only a thin 30 mg target (on 0.5 cm(2) area) of 99.9% enriched 120TeO(2) was available. Irradiations were done with 16 MeV protons for 80 min at beam currents of 7 microA. The 120gI yield achieved at EOB was 700 MBq(19 mCi), and the only impurity detected was the isomeric state 120 mI(T(1/2) = 53 min) at a level of 4.0%. The radiochemical purity of both 124I and 120gI was checked via HPLC and TLC. The radioiodine collected in 0.02 M NaOH solution existed >98% as iodide. The amount of inactive Te found in radioiodine was <1 microg. High purity 124I and 120gI can thus be advantageously produced on a medium scale using the low-energy (p,n) reaction at a small-sized cyclotron.

Cyclotrons↗
PubMed2003

Neutron flux characterization of a peripheral target position in the High Flux Isotope Reactor.

The High Flux Isotope Reactor at the Oak Ridge National Laboratory provides the highest steady-state thermal neutron flux in the western world for a wide range of experiments and for isotope production. The highest available fluxes are located in a flux trap region created inside the nested fuel elements. The experimentally determined thermal and the empirically obtained epithermal flux values along the vertical axis of the peripheral target position were fit to cosine curves, with the thermal flux ranging from 1.1 x 10(15)ns(-1)cm(-2) at outer positions to 1.5 x 10(15)ns(-1)cm(-2) at the center. The corresponding epithermal flux ranged from 3.5 x 10(13) to 7.5 x 10(13)ns(-1)cm(-2), respectively. The fast neutron flux (En > or = 0.32 MeV in two positions and En > or = 1.5 MeV in two other positions) was approximately 6 x 10(14)ns(-1)cm(-2), corresponding to a fast to thermal ratio of approximately 0.4.

Gamma Rays↗