Distribution of 201Tl in the blood

Thallium-201 distribution in the blood was investigated both in vivo and in vitro. Thallium-201 was distributed into the erythrocytes and plasma with the ratio of 1.4 +/- 0.3 to 1.0, immediately after its administration. The uptake of 201Tl into the erythrocytes in vitro were affected by the incubation temperature and the presence of ouabain and KCl; indicating that the 201Tl was uptaken into cells partly through their membranes Na, K-ATPase. Erythrocytes could retain 201Tl in it, whereas 201Tl was present as free ion in the plasma. Thallium-201 was flew out of erythrocytes into the plasma, keeping the ratio of 201Tl in erythrocytes/plasma to be 1.9 +/- 0.2/1.0.     

Whole body autoradiography with 201Tl and clinical results

Thallium-201 has been suggested as a useful diagnostic agent for myocardial scanning. We report herewith the clinical usefulness of Tl-201 as a result of our animal studies with rats as well as clinical trial for human being. After intravenous injection, we killed rats at regular intervals, then measured the activity in each anatomized organ by gamma-well counter and observed the internal distribution and examined autoradiograms with the naked eye. As a result, the accumulation of Tl=201 in the myocardium observed in 5 min after injection, reaching the maximum level in 30 min and gradually decreased hereafter. We performed 22 myocardial clinical scans. In adults we could clearly detect the lesion of myocardial infarction, but in children found it difficult to obtain full sufficient information due to small heart size and high pulse rate. Judging from the foregoing we think it possible to obtain much clearer images by using a data analyzer.     

Thallium-201 radioactive implant induced X-ray emission scanning of stable iodine distribution in thyroid--phantom experiment

A new method has been developed for imaging the thyroid gland by the use of 201Tl radioactive implant induced X-ray emission (RIXE). The thyroid phantom was made from two cylindrical tubes embedded in plastic neck phantom. Each tube consisted of stable iodine and 201Tl radioactive source in 10 ml water solution. Some photopeaks in the energy range from 20 to 200 ke V were scanned along a horizontal axis by the collimated Ge detector with high energy resolution. The distribution on the horizontal axis was obtained for the generated I K alpha-ray and some primary 201Tl radiations. The 201Tl RIXE scanning can provide information about the distribution of iodine with 201Tl as well as 201Tl distribution in the thyroid gland. The effectiveness of the 201Tl RIXE technique as a thyroid scanning method is discussed.     

Evaluation of 1 cm dose equivalent rate using a NaI(Tl) scintillation spectrometer

A method for evaluating 1 cm dose equivalent rates from a pulse height distribution obtained by a 76.2 mm phi spherical NaI(Tl) scintillation spectrometer was described. Weak leakage radiation from nuclear facilities were also measured and dose equivalent conversion factor and effective energy of leakage radiation were evaluated from 1 cm dose equivalent rate and exposure rate.     

Energy resolution improvement of NaI(Tl) scintillation detectors by means of a timing discrimination method

Gamma-ray energy spectrum of a ¹³⁷Cs radioisotope was obtained by using a NaI(Tl) scintillation detector. Improvement of the energy resolution of the detector was aimed. To achieve this, constant fraction timing method was used. Energy resolution of the photopeak of the isotope was improved from 7.1 to 6.7% through the timing application.     

Evaluation of the visualized left atrium by 201Tl myocardial scintigraphy

201Tl myocardial scintigraphy was evaluated in patients with 18 mitral stenosis cases. Left atrium was to be seen in ANT (16.7%), LAO (16.7%), MLAO (16.7%) and L-LAT (11.1%), respectively. Furthermore, 201Tl uptake ratio of left atrium, right ventricle, pulmonary area tended significantly to increase in visible group compared with invisible group. PCW pressure was correlated with left atrial Tl uptake (r = 0.51, p less than 0.005), and it indicated some correlation between left atrial pressure and 201Tl uptake.     

A case of parathyroid carcinoma visualized by 67Ga citrate and 201Tl chloride scintigraphy

Both 67Ga citrate and 201Tl chloride accumulated in a parathyroid tumor of a 62 year-old woman with primary hyperparathyroidism. Histological studies disclosed that the tumor was a parathyroid carcinoma. The use of both tumor scanning agents, 67Ga citrate and 201Tl chloride to visualize parathyroid carcinoma in a patient with primary hyperparathyroidism has not been reported as far as we could determine.     

Study of the nuclear recoil response of a NaI(Tl) scintillator detector with a Cf neutron source

This paper describes the behavior of the scintillation pulses induced in a NaI(Tl) crystal scintillator under excitation of a ²⁵²Cf neutron source and a ¹³⁷Cs gamma source and the possible identification of the incident particle by the study of the pulse shape. Furthermore, the energy dependence of the mean decay time is presented.     

Separation of Tl(I)-Pb(II) by liquid-liquid extraction with diethyldithiocarbamic acid isolation of201Tl

The production of²⁰¹ Tl is described. Natural thallium is irradiated with protons and the induced²⁰¹Pb is separated from the target by liquid-liquid extraction with diethyldithiocarbamic acid in chloroform.²⁰¹Tl is separated from the mother activity (²⁰¹Pb) by liquid-liquid extraction with the same reagent. The decontamination of the final product (carrier free²⁰¹TlCl) is ≥5·10⁶ from the thallium of the target and>5×10⁴ from lead isotopes.     

Thallium-201 chloride dynamic analysis using thallium-201 chloride and sodium iodide-131 thyroid subtraction scintigraphy

The mechanism of 201Tl chloride accumulation is unclear in thyroid gland and thyroid tumor. This report examines 108 patients that received thyroid scintigraphy examinations with both 201Tl chloride and sodium 131I. The patients were diagnosed clinically and histologically whenever possible. The ROI were obtained by subtraction imaging with both isotopes and by subtraction positive and negative areas of imaging. Dynamic curves were obtained for 201Tl chloride per square unit of each ROI. The dynamic curve in the radioiodide-accumulated area was examined. The data indicate that the clearance rate of 201Tl chloride (T15) was correlated with the sodium 131I uptake rate at 24 h (r = 0.70).     

A compton-suppressed phoswich detector for gamma spectroscopy

A phoswich detector with two scintillation layers has been designed and assembled at Oregon State University. This detector is able to identify and reject Compton events and ultimately reduce the Compton continuum in gamma energy spectra. In this detector, CsI(Tl) crystal is used to primarily detect photoelectric events. The CsI(Tl) crystal is partially surrounded by a BGO crystal layer to capture and identify Compton-scattered photons. Both crystals are optically coupled to a single photomultiplier tube. A real-time, FPGA-based digital pulse shape analysis was developed to discriminate and reject Compton-induced pulses from the CsI(Tl) crystal. All the digital pulse processing functions including pulse shape discrimination analysis, pile-up rejection and energy measurement were implemented in an on-board FPGA device. In this paper, the results of recent measurements using radioactive lab sources will be presented and discussed.     

Quantitative measurement of 125I with NaI(Tl) scintillation survey meter

This paper describes a NaI(Tl) scintillation survey meter which can quantify 125I on a contaminated surface in situ. This survey meter has four inherent windows; 20-45 keV the singles photopeak region, 45-80 keV the sum photopeak region, 20-80 keV the total photopeak region, and 80 keV-. The activity was calculated based on the sum peak method. The calculated activity of a point source agreed with the standardized source activity within an uncertainty of about 10% both up to the distance of 3 cm from the detector surface along the axis of the detector and on the detector surface. The activity of a simulated plate source also agreed with the source activity within the same uncertainty.     

The effect of the housing material on the NaI(Tl) detector response function

In this study, a Monte Carlo program has been developed to simulate the response function of the NaI(Tl) detector with all features for ⁶⁰Co and ¹³⁷Cs and to investigate the effects of detector housing material on response function. The pulse height spectra in a 2???×?2?? NaI(Tl) detector due to these gamma ray sources have been measured. Comparison of the experimentally obtained and simulated spectra shows that there is good agreement between both spectra. Energy distributions of gamma photons that generate the backscattering peak in the response function were obtained and the contribution of single, double and multiple Compton scattering events to these distributions was investigated.     

Sequential changes of the cardiomyopathy in Duchenne muscular dystrophy by 201Tl myocardial SPECT

201Tl myocardial SPECT was performed to evaluate cardiomyopathy in Duchenne type of progressive muscular dystrophy (DMD). Follow up SPECT images of the same patients were also obtained about 1 year after the first scan. Cases subjected to study were 10 DMD. At the first study the hypoperfusion area of the left ventricular muscle was observed in 6 cases (60%) out of 10. At the second study the hypoperfusion areas became wider and lower in 4 out of 6 cases (66.7%). The new hypoperfusion area which was not demonstrated at the first study was observed at the second study in one case of these cases. These results suggested that the positive rate of cardiomyopathy in DMD by 201Tl myocardial SPECT was high, and 201Tl myocardial SPECT is a useful examination to detect the change of myocardial damage in DMD.     

201Tl production through light charged-particle induced reactions on Tl and Hg isotopes: theoretical and simulation approaches

Investigation of the significant ²⁰¹Tl diagnostic radionuclide production via protons and deuterons induced reactions by using the ²⁰³Tl, ²⁰¹Hg and ²⁰²Hg isotope targets is the main goal of this study. The effect of three phenomenological and microscopic level density models utilizing the TALYS-1.8 code along with TENDL-2017 data were applied to excitation functions evaluations. Furthermore, simulation code was used for the above production processes. Subsequently the prediction of the production yield in each reaction was done. Finally, the comparison between EXFOR database experimental data and the theoretical and simulation-based calculations was implemented.

     

Analytical investigation of energy spectrums of beta rays emitted from <Superscript>90</Superscript>Sr and <Superscript>204</Superscript>Tl radioisotopes

The energy spectra of beta rays emitted from ⁹⁰Sr and ²⁰⁴Tl radioisotopes were obtained by using a silicon surface barrier detector with a 1000 μm depleted layer and 50 mm² effective area. The detector response function is interpreted by making use of range distributions of mono-energetic electrons in matter and by assuming a linear energy loss along the range in the depleted layer of the detector. An analytical expression is given for pulse height distribution obtained in the surface barrier detector. A good agreement is observed between the experimental results and theoretical interpretation.     

Pulse rise-time characterization of a high pressure xenon gamma detector for use in resolution enhancement

High pressure xenon ionization chamber detectors are possible alternatives to traditional thallium doped sodium iodide [NaI(Tl)] and hyperpure germanium as gamma-spectrometers in certain applications. Xenon detectors incorporating a Frisch grid exhibit energy resolutions comparable to cadmium/zinc/telluride (CZT) (e.g., 2% @ 662 keV) but with far greater sensitive volumes. The Frisch grid reduces the position dependence of the anode pulse rise-times, but it also increases the detector vibration sensitivity, anode capacitance, voltage requirements and mechanical complexity. We have been investigating the possibility of eliminating the grid electrode in high-pressure xenon detectors and preserving the high energy resolution using electronic rise-time compensation methods. A two-electrode cylindrical high pressure xenon gamma-detector coupled to time-to-amplitude conversion electronics was used to characterize the pulse rise-time of deposited gamma-photons. Time discrimination was used to characterize the pulse rise-time versus photo peak position and resolution. These data were collected to investigate the effect of pulse rise-time compensation on resolution and efficiency.     

Sterilization of foods with low-energy electrons (“soft-electrons”)

Electrons with an energy of 300 keV or lower were defined as “Soft-electrons”, which showed several advantages over conventional irradiation with gamma-rays or high-energy electrons in decontamination of grains and spices. Energies of electrons necessary to reduce microbial loads to levels lower than 10 CFU/g were 60 keV for brown rice, 75 keV for wheat, 100 keV for white pepper, coriander and basil, 130 keV for buckwheat, 160 keV for rough rice, and 210 keV for black pepper. Electrons with such energies did not significantly influence the quality.     

A new production method for carrier-free201Tl using IEN'S cyclotron in Rio De Janeiro

A new and simplified method was developed for the separation of thallium 201 which will allow the shipment of a “one shot generator” to distant places and easy elution at the destination. Thallium is produced as usually, through the reaction $${}^{nat}Tl/p,xn/^{201} pb\xrightarrow{{\beta ^ + }}{}^{201}Tl$$ with 24-MeV protons from IEN'S CV-28 cyclotron. The separation is based on the properties of a chelating carboxylic acid cation exchange resin column which at pH 4.5 retains lead while thallim is easily eluted. This column can also be used as a regular generator to produced greater quantities of²⁰¹Tl but at the expense of more elutions.     

Characterization of LaBr<Subscript>3</Subscript>: Ce and LaCl<Subscript>3</Subscript>: Ce scintillators for gamma-ray spectroscopy

This study aims to investigate the performance of relatively new cerium-doped scintillators, LaCl₃ and LaBr₃, for gamma-ray spectroscopy. The study involved recording of detected spectra and measurement of energy resolution, as well as photo-fraction. The Monte Carlo package, GATE, was used to validate the experiments. In general, the energy resolution figures achieved were twice as good as that of NaI(Tl). In conclusion, LaBr₃: Ce and LaCl₃: Ce crystals have excellent energy resolution, (2.13±0.03)% and (2.92±0.04)% at 1332 keV, respectively, and comparable photo-fraction to NaI(Tl). Hence, these crystals, particularly LaBr₃: Ce, have the potential to replace NaI(Tl) as the scintillator of choice for γ-ray spectroscopy.