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PubMed1981

Radionuclide angiography of the liver and spleen. Noninvasive method for assessing the ratio of portal venous to total hepatic blood flow and portasystemic shunt patency.

Radioactivity verus time curves were generated for the first pass of technetium-99m pertechnetate through the left ventricle, kidneys, spleen and liver, after a 20 mCi peripheral intravenous bolus injection. The rate of change of radioactivity in these organs before recirculation is proportional to blood flow through the organ. The hepatic perfusion index, defined as the ratio of portal flow to total hepatic blood flow, was correlated with the angiographic grade of portal perfusion. The hepatic perfusion index in seven normal subjects was 66.0 +/- 3.4 percent (mean +/- standard error of the mean), and in 22 cirrhotic patients with decreasing angiographic perfusion of grades 1 to 4 the index was 54 +/- 4.6, 37 +/- 2.6, 17 +/- 4.7 and 3 +/- 1.1 percent, respectively. The correlation between the calculated perfusion index and the angiographic grade of portal flow was highly significant (p less than 0.001). The passage of radionuclide through the spleen differed before and after shunt surgery in patients with portal hypertension. The slope to height ratio, based on the downslope of the splenic curve, was significantly greater (p less than 0.01) in the shunted patients and provided a simple index for assessing shunt patency.

Adult↗
PubMedDate not supplied

[Effect of some natural processes on the formation and characteristics of aerosols in regions polluted with radionuclides].

The formation of aerosols over the radioactive polluted areas results from some natural and industrial factors. In this paper physico-chemical characteristics of secondary aerosols generated by the Chernobyl accident are presented. The results of monitoring of the aerosol from traffic, dust storms and forest fires in 30-km zone of the Chernobyl nuclear power plant and other regions are compared. Some methodical aspects of the sampling and analyses of aerosols are considered. The recommendations for choice of the personal respirators are given.

Aerosols↗
PubMed2005

Modelling and experimental studies on the transfer of radionuclides to fruit.

Although fruit is an important component of the diet, the extent to which it contributes to radiological exposure remains unclear, partially as a consequence of uncertainties in models and data used to assess transfer of radionuclides in the food chain. A Fruits Working Group operated as part of the IAEA BIOMASS (BIOsphere Modelling and ASSessment) programme from 1997 to 2000, with the aim of improving the robustness of the models that are used for radiological assessment. The Group completed a number of modelling and experimental activities including: (i) a review of experimental, field and modelling information on the transfer of radionuclides to fruit; (ii) discussion of recently completed or ongoing experimental studies; (iii) development of a database on the transfer of radionuclides to fruit; (iv) development of a conceptual model for fruit and (v) two model intercomparison studies and a model validation study. The Group achieved significant advances in understanding the processes involved in transfer of radionuclides to fruit. The work demonstrated that further experimental and modelling studies are required to ensure that the current generation of models can be applied to a wide range of scenarios.

Fruit↗
PubMed2005

Generation of polluted waters from mining wastes in a uranium deposit.

Dump consisting of 9500 tons of rich-in-pyrite mining wastes located in the uranium deposit Curilo, Western Bulgaria, was, after rainfall, an intensive source of acid drainage waters. These waters had a pH in the range of about 1.7-4.5 and contained radionuclides (uranium, radium), heavy metals (copper, zinc, cadmium, lead, nickel, cobalt, iron, and manganese), arsenic and sulphates in concentrations usually much higher than the relevant permissible levels for waters intended for use in the agriculture and/or industry. The generation of these polluted waters was studied under real field conditions for a period of about seven years during different climatic seasons. It was found that the dump was inhabited by a diverse microflora in which some acidophilic chemolithotrophic bacteria were the prevalent microorganisms. The solubilization of the above-mentioned pollutants from the dump material was connected mainly with the oxidation of pyrite and other sulphide minerals by these bacteria. Their activity depended on some essential environmental factors such as temperature, pH, and water, oxygen and nutrient contents in the dump.

Acid Rain↗
PubMedDate not supplied

Effects of off-centering on dose uniformity along and around blood vessels undergoing catheter-based intravascular brachytherapy.

PURPOSE: In intravascular brachytherapy, either photon or beta emitters are often used in a linear arrangement so that blood vessels of lengths in the range of several centimeters can be treated. With a line source, the dose uniformity and the range of doses that various components of the blood vessels receive depend not only on the type of radionuclides used in the treatment but also on the geometric position of radioactive source relative to the blood vessel walls. The aim of this study is to investigate the dose uniformity around the blood vessel and the effects on the uniformity due to the changes of the off-centering of different photon and beta emitters within the lumen. MATERIALS AND METHODS: Dose distributions were calculated on a cylindrical blood vessel of various radii. The radioactive sources of (192)Ir, (125)I, (103)Pd, (188)Re, (32)P, and (90)Y/Sr were studied. All the sources were assumed to be in the form of a line and had a length of 2 cm. The dose rate at a point in space produced by a radioactive source was computed by integrating the point dose rate kernel of the corresponding radionuclide over the 2-cm-long radioactive line. The point dose rate kernel was computed with Monte Carlo simulation of radiation transport. Dosimetric calculations were performed for both concentric and nonconcentric radioactive line source locations. Off-centering effects on the dosimetry were characterized with two newly defined quantities LDU and ADU: LDU describes the longitudinal dose uniformity along blood vessels and ADU describes the azimuthal dose uniformity, i.e., the dose deviation from the expected delivery dose around blood vessels. RESULTS: The longitudinal dose uniformity did not change significantly with the off-center distance. The azimuthal dose uniformity around the blood vessel deteriorated as the off-center distance increased. The ADU was worse for nonconcentric beta emitters than the photon emitters. For example, if the off-center distance was 1 mm and the radial distance was 1.5 mm, the range of dose around the blood vessel on the central transverse plane (normalized to the corresponding dose under the concentric condition) was from 0.55 to 3.3, 0.56 to 3.3, 0.53 to 3.4, 0.43 to 6.0, 0.38 to 4.3, and 0.31 to 4.7 for (192)Ir, (125)I, (103)Pd, (90)Y/Sr, (188)Re, and (32)P sources, respectively. However, it appeared that there existed a lower limit of underdosing (about 40% of desired delivery dose) caused by the off-centering for the photon emitters. It was also found that both ADU and LDU became almost independent of source length when the length was longer than or equal to 20 mm. CONCLUSIONS: A generalized formalism for expressing the dose uniformity along and around blood vessels generated with a linear source was developed and used to study the longitudinal and azimuthal dose uniformity for different types of radionuclides. Although concentric beta emitters provide uniform dose coverage along blood vessels, nonconcentric beta emitters produced larger dose deviations and worse dose uniformity around the blood vessels than photon emitters. The off-centering introduced significantly higher dose on proximal vessel walls for both beta and photon emitters; however, the underdosing at distal points due to off-centering was somewhat limited for the high-energy photon emitters. The magnitude of off-centering effects for the low-energy photon emitters ((103)Pd) was less than that for beta emitters but more than that for higher energy photon emitters ((125)I and (192)Ir).

Beta Particles↗
PubMedDate not supplied

Assessment of left ventricular diastolic function with electrocardiography-gated myocardial perfusion SPECT: comparison with multigated equilibrium radionuclide angiography.

BACKGROUND: Technetium-labeled myocardial perfusion tracers allow the simultaneous assessment of myocardial perfusion and left ventricular function by electrocardiography (ECG)-gated myocardial perfusion single photon emission computed tomography (SPECT). This study evaluates left ventricular systolic and diastolic function by ECG-gated SPECT with the use of higher framing (32 frames per cardiac cycle) data acquisition. METHODS AND RESULTS: After receiving an injection of technetium 99m tetrofosmin, 48 patients with cardiac diseases were examined by ECG-gated myocardial perfusion SPECT with a 3-headed gamma camera. During gated data collection, 32 frames per cardiac cycle were acquired over 360 degrees in 60 steps, each of which consisted of 60 beats. Immediately thereafter, the 32 frames taken at each projection angle were combined into 16-frame and 8-frame data sets. Left ventricular end-diastolic volume (LVEDV, in milliliters), left ventricular end-systolic volume (LVESV, in milliliters), and left ventricular ejection fraction (LVEF, percentage) were automatically calculated from the 32-frame, 16-frame, and 8-frame gated data sets. Left ventricular time-volume curves from the 3 data sets were generated by Fourier curve fitting analysis with the use of 3 harmonics, and then peak filling rate (PFR, per second) was measured. Twenty-nine patients also underwent multigated equilibrium radionuclide angiography (ERNA) to determine the LVEF and PFR. Combining the 32-frame data into 16-frame and 8-frame data sets from the 48 patients generated a smaller LVEDV and a larger LVESV, and LVEF was significantly lower in accordance with the decreasing number of frames. Compared with ERNA studies (n = 29), the Bland-Altman method showed underestimated LVEFs and larger 95% limits of agreement in lower framing gated SPECT. CONCLUSIONS: Left ventricular functional parameters obtained from 32-frame gated SPECT correlated closely with those determined by ERNA studies. ECG-gated SPECT with 32-frame data can provide comprehensive information with which to evaluate many types of cardiac diseases.

Adult↗
PubMed1982

Applications of nuclear medicine in genitourinary imaging.

Major advances in nuclear medicine instrumentation and radiopharmaceuticals for renal studies have occurred during the last decade. Current nuclear medicine methodology can be applied for accurate evaluation of renal function and for renal imaging in a wide variety of clinical situations. Total renal function can be estimated from the plasma clearance of agents excreted by glomerular filtration or tubular secretion, and individual function can be estimated by imaging combined with renography. A major area of radionuclide application is in the evaluation of obstructive uropathy. The introduction of diuretic renography and the use of computer-generated regions of interest offer the clinician added useful data which may aid in diagnosis and management. Imaging is of proven value also in trauma, renovascular hypertension, and acute and chronic renal failure. Methods for the evaluation of residual urine, vesicoureteral reflux, and testicular torsion have achieved increasing clinical use. These many procedures assure a meaningful and useful role for the application of nuclear medicine in genitourinary imaging.

Adult↗
PubMedDate not supplied

Influence of small-scale heterogeneities on contaminant transport in fractured crystalline rock.

We present a sequence of purely advective transport models that demonstrate the influence of small-scale geometric inhomogeneities on contaminant transport in fractured crystalline rock. Special weight is placed on the role of statistically generated variable fracture apertures. The fracture network geometry and the aperture distribution are based on information from an in situ radionuclide retardation experiment performed at Grimsel test site (Swiss Alps). The obtained breakthrough curves are fitted with the advection dispersion equation and continuous-time random walks (CTRW). CTRW is found to provide superior fits to the late-arrival tailing and is also found to show a good correlation with the velocity distributions obtained from the hydraulic models. The impact of small-scale heterogeneities, both in fracture geometry and aperture, on transport is shown to be considerable.

Computer Simulation↗
PubMed1978

Design of a three-dimensional positron camera for nuclear medicine.

A positron camera is proposed for nuclear medical imaging of radionuclide distributions in a series of isolated planes. This three-dimensional localisation is achieved through analysis of four time signals, whose differences directly measure the position (x, y, z) of individual positron annihilation events. A tetrahedronal symmetry is exploited, with two skewed plastic scintillator bars spanning a large sensitive volume. Phototubes on each end of both bars generate fast timing pulses uniquely determining the decay position through a time-of-flight technique. The mathematical properties of the transformation from the observed quantities to the spatial distribution of the radionuclide are investigated. A discussion of the efficiency of the system and the effects of Compton scattering in tissue is given. A one-dimensional pilot study encourages the development of the prototype three-dimensional positron camera.

Gamma Rays↗
PubMed1984

Relation between left ventricular gradient and relative stroke volume ejected in early and late systole in hypertrophic cardiomyopathy. Assessment with radionuclide cineangiography.

Hypertrophic cardiomyopathy is characterised by hyperkinetic left ventricular function, but the effect of an outflow tract gradient on the haemodynamics of ejection remains controversial. To determine the functional importance of left ventricular gradients in hypertrophic cardiomyopathy technetium-99m gated equilibrium radionuclide angiography was performed in 18 normal subjects and 57 patients, 26 with and 31 without left ventricular gradients. Time activity curves were generated from list mode data, and the proportion of stroke volume ejected during various phases of systole was computed. The proportion of stroke volume ejected during the initial third, the initial 50%, and the initial 80% of systole was greater in patients with hypertrophic cardiomyopathy than in normal subjects but was identical in patients with and without left ventricular gradients. The duration of systole was similar in the three groups. These findings favour the interpretation that a left ventricular gradient does not represent true obstruction and are consistent with previous observations that clinical features and prognostic indicators do not relate to gradients in this disease.

Adolescent↗
PubMed1979

Left ventricular volumes by gated equilibrium radionuclide angiography: a new method.

To compare radionuclide end-diastolic (EDV) and end-systolic (ESV) volumes with angiographic volume, we studied 52 patients with equilibrium radionuclide angiography using 99mTc-human serum albumin within 48 hours of contrast angiography. Each RR interval was divided into 20--28 equally timed frames and a time-activity curve generated. End-diastolic counts were taken at the early peak of the curve and end-systolic counts at its nadir. Counts were divided by the total number of processed heart beats and normalized for: 1) dose per body surface area; 2) plasma volume; and 3) counts/ml of plasma. A cardiac phantom was developed and serial volumes were studied using a normalization factor. Radionuclide values were expressed as dimensionless units and compared with either biplane angiographic volumes (in the patient studies) or known phantom volumes. Good correlations were obtained with methods 1 and 2 in 35 patients (r greater than 0.84), but the best correlation was obtained in 17 patients when normalization for counts/ml of plasma was used (r = 0.98; y = 0.255 x -0.121). The standard error of the estimate (SEE) was +/- 11.5 ml for EDV and +/- 7.3 ml for ESV. The phantom study also showed an excellent correlation (r = 0.99), with a SEE of +/- 6.5 ml. We conclude that a radionuclide method independent of geometric assumptions can be used to estimate left ventricular volume in man.

Adult↗
PubMed1986

Krypton-79m: a new radionuclide for applications in nuclear medicine.

Krypton-79m emits 130-keV gamma rays in 27 +/- 1% of its disintegrations and decays with a half-life of 50 +/- 3 sec. It is generated readily by bombarding nearly saturated aqueous solutions of bromide salts, or bromoform, with 14-MeV protons. The 79mKr is swept out continuously as it is produced by bubbling helium upward through the liquids. Up to 200 mCi per I are obtained of the resulting mixture of gases. The 79mKr + helium is mixed with about five volumes of air and then driven continuously through a small-bore tube to an Anger scintillation camera located approximately 200 yards away. The rate of flow is adjusted so that the amounts of 13-sec 81mKr and of 35-hr 79Kr are inconsequential at the time and point of use. When the gases are inhaled, good images of the lungs are obtained with an Anger scintillation camera. The trachea and bronchi commonly are revealed also.

Humans↗
PubMed1994

New method for mechanistic studies of cardiomyoplasty: three-dimensional MRI reconstructions.

The imaging modalities used to study the mechanism of cardiomyoplasty, such as echocardiography and radionuclide scintigraphy, are seriously limited by their two-dimensional format. Radiofrequency-pulse-tagged magnetic resonance imaging was used to generate three-dimensional reconstructions of the left ventricle throughout the cardiac cycle after cardiomyoplasty. In 2 dogs that had undergone conditioned, right anterior cardiomyoplasty, wrap stimulation with alternating heartbeats was found to produce marked translation of the left ventricle in the short-axis plane, rotation around the long axis, and displacement along the long axis with net long-axis compression; there was no augmentation of radial squeeze. The findings from this study suggest that any systolic augmentation produced by the right anterior wrap is due primarily to long-axis compression. Our study demonstrates a new, more accurate technique of assessing the mechanical effects of cardiomyoplasty in three dimensions, thus permitting a more rational optimization of wrap configurations, and emphasizes the perils of using standard two-dimensional imaging modalities in this setting of exaggerated three-dimensional motion.

Animals↗
PubMed2005

The legacy of monazite processing in Brazil.

The exploitation of natural resources containing naturally occurring radionuclides may lead to enhanced levels of radioactive isotope and enhanced potential for exposure to naturally occurring radionuclides in products, by-products, residues or wastes. Such resources include, for instance, monazite, the processing of which, in Brazil, generated a great amount of radioactive residues, being stored in buried concrete tanks, in temporary storage buildings and in sealed trenches. In addition, during the 1980s there were no radiological protection rules concerning the storage and transportation of these kinds of residues. Mineral radioactive residues were used as landfills and the residues of chemical processes contaminated floors and buildings. The decommissioning process and cleaning of old plants have generated tons of wastes that has been added to previously produced wastes. This paper reports and discusses the cycle of monazite in Brazil and its consequences in terms of site remediation and amount of wastes and residues generated and stored.

Brazil↗
PubMed2004

Stakeholder perspectives on radiation protection.

Standards for permissible exposure to radiation and the way they are established must incorporate a set of principles that uphold both health and democracy. When the science is uncertain, the burden of proof that risk is not being imposed should be on the source of the risk, not on the possibly affected public or workforce. Scientific processes must be transparent to the public, must address all relevant risk issues and endpoints (and not only cancer), and must be inclusive of the actual experience and opinion of the people who are exposed to radiation risks. Scientists are too often dismissive of public experience and interests, as for instance with worker illnesses or fallout, even though input from the public and workers has frequently proven to be valuable in the development of radiation protection principles. Incorporating the concerns, views, and experiences of workers and the public in a respectful way while maintaining a high standard of scientific work must be an essential part of the standard-setting process. Further, the clearly enunciated International Commission on Radiological Protection principle that the imposition of risk must be accompanied by a clear benefit needs to be a far more explicit part of standard-setting processes, which must also ensure that all known risks are disclosed and that suspected risks, such as possible synergisms between some radionuclides and hormone-disrupting chemicals, are carefully considered. Finally, given the long-lived nature of risks from many radionuclides and the large uncertainties about future physical, social, economic, and other conditions, the issue of how the interests of future generations can be included in standard setting is a difficult but vital matter.

Community Participation↗
PubMed1975

Application of annihilation coincidence detection to transaxial reconstruction tomography.

A study was carried out to investigate the use of annihilation coincidence detection (ACD) in emmision transaxial reconstruction tomography. The ACD was evaluated in terms of spatial resolution and sensitivity with depth, detection efficiency, effect of pulse-height analysis on resolution and efficiency, correction for attenuation, and cold spot contrast. A prototype positron emission transaxial tomograph (PETT) consisting of a hexagonal array of 24 Nal (Tl) detectors employing ACD was constructed. A fast Fourier transform algorithm was employed to generate the reconstructed image. Computer simulations and phantom and animal studies were carried out to demonstrate that this approach yields tomographic radionuclide images that have high resolution and contrast (hot and cold spot) and that are independent of activity above and below the plane examined. The ACD yields a quantitative nuclear medicine imaging device with high detection efficiency. Comparisons are presented between the ACD and the scintillation camera and scanner. Discussion of the possible applications of the PETT in nuclear medicine is included.

Animals↗