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PubMed1988

Effects of verapamil on left ventricular diastolic filling in children with hypertrophic cardiomyopathy.

The effects of oral verapamil on resting left ventricular (LV) diastolic filling were examined in 10 children and adolescents with hypertrophic cardiomyopathy. Measurements of diastolic filling were made from gated technetium-99m radionuclide angiograms with postbeat rejection of data outside a 5% RR-interval window. LV time-activity curves were generated and the rapid-filling phase fit with a 3 degrees polynomial to calculate the peak filling rate and the time from end-systole to the point of peak filling. All patients had a radionuclide angiogram performed before and after 0.25 to 3 years of oral verapamil therapy. Verapamil did not change the LV ejection fraction but increased the peak filling rate (3.24 +/- 0.15 to 4.62 +/- 1.05 end-diastolic volume/s,p less than 0.01) and reduced the time to peak filling (217 +/- 57 to 168 +/- 63 ms, p less than 0.01). An increase in exercise endurance as measured by exercise treadmill test and subjective symptomatic improvement were also seen after verapamil therapy. Thus, in children with hypertrophic cardiomyopathy, symptomatic improvement and LV diastolic filling parameters improved with long-term oral verapamil.

Administration, Oral↗
PubMed2000

Endovascular brachytherapy for the prevention of restenosis after angioplasty.

Restenosis is an unsolved clinical and financial limitation of angioplasty. Local irradiation is a new approach for the reduction of restenosis. Several animal studies have demonstrated the effective inhibition of arterial neointimal proliferation by percutaneous or endovascular irradiation. High-dose-rate irradiation from gamma and beta sources can be applied from radioactive wires or seeds and from liquid beta-emitter-filled balloon catheters. Dosimetric calculations have been performed for all relevant radionuclides. An effective dose can be applied within 10 min to the treated arteries. Beta-emitters are characterized by a low tissue penetration, which simplifies radiation protection but complicates the achievement of a homogeneous dose distribution without centering of the irradiation source. Gamma-emitters are characterized by deep tissue penetration and delivery of almost the same dose to all vessel layers; however, considerable care with regard to radiation protection of the environment is required if gamma-emitters are used. The liquid-filled balloon ensures a homogeneous dose delivery due to the self-centring irradiation source but entails the possibility of radioactivity incorporation in the event of balloon rupture. The most attractive radionuclide for this purpose is rhenium-188, which is available from the 188W/188Re generator system. Radiation exposure after accidental incorporation can be limited by chelation with mercaptoacetyltriglycine or by subsequent oral administration of perchlorate. Initial clinical trials have demonstrated the feasibility of the various irradiation techniques and yielded encouraging results. The use of unsealed radioactivity in a balloon catheter involves the nuclear medicine physician in this new field of therapy. This review discusses the concepts, the radiotracers and the results of animal experiments and early clinical trials in the field of endovascular irradiation employed as a possible means to prevent restenosis after angioplasty.

Angioplasty, Balloon, Coronary↗
PubMed1976

Evaluation of perfusion with the 81Rb-81mKr generator.

The development of the 81Rb-81mKr generator-delivery system has made available an ultrashort (13-sec) half-life radionuclide for continuous, constant-rate delivery as a gas, or as an isotonic, nonionic solution in 5% dextrose and water. This system has been evaluated and applied to the scintigraphic imaging of various organs and anatomic regions by intravenous and intraarterial infusion and by inhalation and deglutition. This diffusible, noble gas is inert chemically and biologically. When the gas is administered intraarterially, the volume of tissue being perfused may be defined with the scintillation camera. The 13-sec half-life is of a similar magnitude to the rate of capillary exchange, producing a heterogeneous image with steady-state administration in which the intensity of detectable radioactivity is proprotional to the time of diffusion into the tissue. This system appears capable of defining the rate of capillary exchange and the moment-to-moment changes brought about by vasoactive stimuli in specific organs.

Animals↗
PubMed1964

RADIOACTIVITY IN THE ATMOSPHERIC EFFLUENTS OF POWER PLANTS THAT USE FOSSIL FUELS.

Analysis of the fly ash produced by combustion of pulverized Appalachian coal has shown that a 1000-megawatt coal-burning power plant will discharge into the atmosphere from about 28 millicuries to nearly 1 curie per year of radium-226 and radium-228. An oil-burning plant of similar size will discharge about 0.5 millicurie of radium per year. Comparison of these data with data on the release of fission products from nuclear-powered generating stations shows that when the physical and biological properties of the various radionuclides are taken into consideration, the conventional fossil-fueled plants discharge relatively greater quantities of radioactive materials into the atmosphere than nuclearpowered plants of comparable size.

Air Pollution↗
PubMed2002

Positron emission tomography and brain monoamine neurotransmission -- entries for study of drug interactions.

Monoamine neurotransmission is a complicated process with interactions between individual neurotransmitter pathways, multiple receptors with different responses and a variety of feedback loops regulating neurotransmitter synthesis, release, reuptake and effect on receptors. The system is further affected by a range of enzymes with co-factors controlling synthesis and degradation of monoamines. Positron emission tomography (PET) has evolved to a very versatile tool for the in vivo imaging and characterisation of physiology and biochemistry. The basis for its expansion during the last years has been a rapid development of labelling methods, allowing a range of tracer molecules to be generated and used in human and research animal studies. The most important PET radionuclide is (11)C with a short half-life of approximately 20 minutes. This radionuclide is ideal for the labelling of organic molecules and for multi-tracer applications in research and drug development studies. PET has been used for a range of explorative studies on the monoamine neurotransmission, as exemplified by studies on the expression of dopamine and serotonin receptors as well as the rate of dopamine and serotonin synthesis. The present article gives examples of studies where PET has been used for the characterization of monoamine transmitter systems in experimental animals and in humans, both in healthy individuals and in patients with diseases affecting neurotransmission.

Animals↗
PubMed1989

Economic analysis of clinical positron emission tomography of the heart with rubidium-82.

This report describes a cost analysis for clinical positron emission tomography (PET) of the heart using generator produced rubidium-82 (82Rb). Considered sequentially are the clinical problem, current noninvasive radionuclide methods, positron emission tomograph, and the cost of PET per study. Also analyzed are the costs of PET versus thallium imaging in the management of chest pain, for screening asymptomatic men at high risk for coronary artery disease and for evaluating myocardial viability after myocardial infarction or thrombolytic therapy. Noninvasive assessment of coronary artery stenosis and myocardial ischemia/viability in symptomatic or asymptomatic subjects remains a major medical problem because the sensitivity and specificity of thallium imaging are only 70-85% and 50-70%, respectively, in recent studies. Cardiac positron imaging has an accuracy for noninvasive diagnosis of coronary artery disease in symptomatic or asymptomatic patients with a sensitivity and specificity of 95-98%. It can also be used for assessing physiologic stenosis severity, for imaging myocardial infarction and viability, for assessing effects of interventions such as thrombolysis, percutaneous transluminal coronary angioplasty (PTCA) or bypass surgery on myocardial perfusion, metabolism or coronary flow reserve, for assessing collateral function noninvasively in man, and for diagnosing cardiomyopathy not due to coronary artery disease. Although the cost for cardiac PET with 82Rb may be modestly higher than for 201Tl, the greater diagnostic yield of PET results in comparable or lower overall medical management costs than no diagnostic tests/interventions and lower overall costs compared to thallium imaging for evaluating patients with chest pain, asymptomatic high risk males, and patients after acute myocardial infarction/thrombolysis for myocardial viability.

Adult↗
PubMed1985

Clinical use of ultrashort-lived radionuclide krypton-81m for noninvasive analysis of right ventricular performance in normal subjects and patients with right ventricular dysfunction.

The ultrashort-lived radionuclide krypton-81m, eluted in 5% dextrose from a bedside rubidium-81m generator, was intravenously infused for rapid imaging of the right-sided heart chambers in the right anterior oblique projection adjusted for optimal right atrioventricular separation. Left-sided heart and lung background was minimized by rapid decay and efficient exhalation of krypton-81m, requiring no algorithm for background correction. A double region of interest method decreased the variability in the assessment of ejection fraction to 5%. In 10 normal subjects, 11 patients with pulmonary hypertension, 4 patients with right ventricular outflow tract obstruction and 4 patients with right ventricular infarction, right ventricular ejection fraction determined by krypton-81m equilibrium blood pool imaging ranged from 14 to 76%. The correlation between these values and those determined by cineangiography according to Simpson's rule was close: r = 0.93 for all data points (p less than 0.001), r = 0.92 for studies at rest (p less than 0.001) and r = 0.93 for exercise studies (p less than 0.001). Exercise-related changes in right ventricular function revealed a disturbed functional reserve with pulmonary hypertension and right ventricular infarction, whereas in compensated right ventricular outflow tract obstruction there was a physiologic increase in ejection fraction with exercise (p less than 0.001). Thus, equilibrium-gated right ventricular imaging using ultrashort-lived krypton-81m is a simple, accurate and reproducible method with potential for serial assessment of right ventricular ejection fraction in a variety of right ventricular anatomic and functional abnormalities, both at rest and during exercise. Advantages of this method include an extremely low radiation dose to patients and clear right atrioventricular separation without the need to correct for background activity.

Adult↗
PubMed1990

Assessment of regional myocardial and renal blood flow with copper-PTSM and positron emission tomography.

We recently demonstrated in isolated, perfused hearts that radiolabeled pyruvaldehyde bis(N4-methylthiosemicarbazonato)copper(II) (Cu-PTSM) is well extracted throughout a range of conditions including ischemia, hypoxia, and hyperemia. Once extracted, binding of radioactivity by the isolated heart was essentially irreversible, giving this tracer microspherelike qualities. Because Cu-PTSM can be readily prepared with the generator-produced positron-emitting copper 62 and other gamma- or positron-emitting copper radionuclides, we evaluated its usefulness for measuring regional myocardial and renal blood flow in vivo in intact dogs at rest, after ischemia, or after coronary hyperemia was induced by intravenous administration of dipyridamole. After intravenous administration of radiolabeled Cu-PTSM, the tracer cleared rapidly from the blood. Myocardial uptake of single photon-emitting 67Cu-labeled Cu-PTSM was measured directly in myocardial samples 15 minutes after tracer administration, and it increased proportionally with blood flow throughout the flow range (estimated concomitantly with radiolabeled microspheres) of 0.0-6.0 ml/g/min (n = 340 samples from 17 dogs, r = 0.99, Ycopper radioactivity = 85Xmicrosphere flow -7 chi 2 + 17). Renal uptake of radiolabeled Cu-PTSM was also proportional to blood flow. Positron emission tomography was performed in four intact dogs after intravenous administration of 64Cu-labeled Cu-PTSM (19% positron decay, t1/2 = 12.8 hours). High-quality images of heart and kidney were obtained. Accordingly, radiolabeled Cu-PTSM should be a useful, generator-produced tracer for estimating regional myocardial and renal blood flow with positron emission tomography.

Animals↗
PubMedDate not supplied

Diuretic radionuclide renography in assessing Anderson-Hynes pyeloplasty in unilateral pelviureteric junction obstruction.

The topic of whether improvement can be expected after pyeloplasty in patients with pelvi-ureteric junction obstruction (PUJO) continues to generate debate. The aim of this study was to analyse the functional outcome of unilateral Anderson-Hynes (A-H) pyeloplasty using differential renal function (DRF) and drainage patterns determined by diuretic radionuclide renography (DRR). A retrospective study was carried out by evaluation of the records of patients who underwent A-H pyeloplasty for unilateral PUJO and reported for a follow up renal dynamic scan between the years 2000 and 2003. A total of 126 patients (93 males and 33 females) aged three months to 40 years had undergone pre-operative and post-operative DRR and were followed for at least six months after operation. For comparison, the renal function prior to and after pyeloplasty was classified into three Groups based on the DRF: Group A: > or = 40% DRF 52 patients, Group B: 20%-39% DRF 65 patients and Group C: < 20% DRF 9 patients. The difference between pre-operative and post-operative DRF in the last follow up study, which ranged from six months to 144 months after operation, was calculated for each patient. To account for an accepted error of measurement, an absolute difference in DRF of more than 5% was considered significant. Improvement in drainage was assessed by the time Tmax 1/2 of the renographic curve. Unpaired t test was applied between Group A and Group B patients. Chi square analysis was applied to estimate the proportion of improvement between Groups A and B. Post-pyeloplasty scans revealed stable renal function in 102 (81%) subjects, while improvement was noticed in 14 (11%) subjects. The remaining 10 (8%) subjects had deterioration in renal function. No improvement in renal function was seen in Group C patients. Our results have shown that in the majority of cases studied, after A-H pyeloplasty renal function remains stable. A-H pyeloplasty applied in patients with preserved DRF and obstruction will result in long term preservation of renal function.

Adolescent↗
PubMed1983

Radionuclide evaluation of circulatory shunts.

With first-pass radionuclide angiography, it is possible to visualize sequentially the cardiovascular structures and to obtain computer-generated time-activity curves for regions of interest over these structures. Analysis of these curves permits the detection, localization, and quantitation of intracardiac shunts and shunts between the great arteries. The authors present the formulae used for the quantitative analysis and discuss clinical applications.

Ductus Arteriosus, Patent↗
PubMed2005

Radioactivity concentration in liquid and solid phases of scale and sludge generated in the petroleum industry.

Scales and sludge generated during oil extraction and production can contain uranium, thorium, radium and other natural radionuclides, which can cause exposure of maintenance personnel. This work shows how the oil content can influence the results of measurements of radionuclide concentration in scale and sludge. Samples were taken from a PETROBRAS unit in Northeast Brazil. They were collected directly from the inner surface of water pipes or from barrels stored in the waste storage area of the E&P unit. The oil was separated from the solids with a Soxhlet extractor by using aguarras at 90+/-5 degrees C as solvent. Concentrations of 226Ra and 228Ra in the samples were determined before and after oil extraction by using an HPGe gamma spectrometric system. The results showed an increase in the radionuclide concentration in the solid (dry) phase, indicating that the above radionuclides concentrate mostly in the solid material.

Background Radiation↗
PubMed1991

The effect of combined hypoxemia and cephalic hypotension on fetal cerebral blood flow and metabolism.

The effect of hypoxemia and cephalic hypotension, alone and in combination, on hemispherical CBF and metabolism was examined in seven chronically catheterized fetal sheep. Hypoxemia was induced by lowering the maternal inspired oxygen fraction and cephalic hypotension was generated by partial occlusion of the fetal brachiocephalic artery. CBF was measured with radionuclide-labeled microspheres. During control, the arterial blood oxygen content (CaO2) was 3.2 +/- 1.0 (SD) mM and CBF averaged 131 +/- 21 (SD) ml min-1 100 g-1. The cephalic perfusion pressure (PP, mean cephalic arterial-sagittal venous) was 40 +/- 4 mm Hg and cerebral vascular resistance (CVR, PP/CBF) was 0.31 +/- 0.06 mm Hg ml-1 min 100 g. During induced hypoxemia, CaO2 was 1.4 +/- 0.7 mM and CBF was elevated to 223 +/- 60 ml min-1 100 g-1. PP was not different from control and CVR was lower at 0.19 +/- 0.04 mm Hg ml-1 min 100 g, reflecting cerebral vasodilation. With cephalic hypotension alone (PP = 21 +/- 4 mm Hg; CaO2 = 3.4 +/- 0.9 mM), CBF fell to 83 +/- 23 ml min-1 100 g-1 and there was no significant change in CVR (0.26 +/- 0.05 mm Hg ml-1 min 100 g). During combined hypoxemia and hypotension (CaO2 = 1.5 +/- 0.8 mM and PP = 18 +/- 4 mm Hg), CBF was significantly greater than during hypotension alone (100 +/- 6 ml min-1 100 g). CVR was 0.19 +/- 0.05 mm Hg ml-1 min 100 g, identical to that measured in normotensive hypoxemia and significantly less than found during hypotension alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Beam dumps design and local radiation protection at TERA synchrotron.

The realisation of the National Center of Hadrontherapy was funded by the Italian Government in 2002. The Centre will be built in the area of Pavia (Italy). The synchrotron designed in the framework of this programme will accelerate protons and carbon ions up to 250 MeV and 400 MeV u(-1), respectively. Some of the main aspects which were taken into account in the design of the acceleration system are the patient's safety and the beam control. From this point of view an important role is played by the beam dumps in the synchrotron ring and upstream of the extraction system. In particular, an horizontal and a vertical beam dump will be installed in the synchrotron ring: the former will be used for lowering the beam intensity and the latter for beam abortion. The dump at the extraction will absorb the particles during the mounting and the falling ramps of the synchrotron magnetic cycle, thus extracting only the flat top of the ion spill. Beam dumps can produce intense fields of secondary radiation (neutrons, charged light-hadrons and photons) and high rates of induced activity, since they can absorb the beam completely. Usually they have to be shielded to protect the electronics during machine operation and to attenuate the radiation dose below the limits imposed by the law when the personnel access to the synchrotron hall. The part of the shielding design of the beam dumps concerning with the acceleration of protons was made using Monte Carlo simulations with the FLUKA code. Both induced activity and secondary radiation were taken into account. The shields against secondary radiation produced by carbon ions were designed, referring only to secondary neutrons, taking double-differential distributions from the literature as sources for the FLUKA simulations. The induced activity from carbon ions interactions was estimated analytically, using the data generated by the EPAX 2 code. The dose-equivalent rates from the induced radionuclides were calculated at 1 m from the shielded dumps, taking into account the contribution of activated components of the synchrotron ring.

Computer Simulation↗
PubMed2003

Estimate of the dose-increment due to outdoor exposure to gamma rays from uranium progeny deposited on the soil around a coal-fired power plant in Ajka Town, Hungary.

Brown coal unusually rich in uranium is burnt in a coal-fired power plant that lies inside the confines of a small industrial town named Ajka, Hungary, and has been operational since 1943. The 238U (226Ra) activity discharged to the atmosphere per unit electrical energy produced was about 330-400 GBq (GW y)(-1), which is 66-80 times more than that was estimated by UNSCEAR (1988) as a characteristic value for old type coal-fired power plants [5 GBq (GW y)(-1)]. The objective of this study was the experimentally established assessment of the artificial increment in the dose from external exposure to gamma rays of terrestrial radionuclides outdoors. Soil samples were collected in and near Ajka from 81 locations. The samples were investigated by Ge(Li) gamma spectrometry. Considerably elevated concentrations of uranium and its progeny have been measured in most of the samples that were collected near to the plant. Concentrations of 238U and 226Ra in the top (0-5 cm depth) layer of undisturbed soil at public areas inside town were 4.7 times higher, on average, than those in the uncontaminated deeper layers. Dose rate in air (air kerma) from external exposure to terrestrial gamma rays outdoors at a height of 1 m and effective doses were estimated from the measured activity concentrations using some relevant literature data. The estimated artificial increment in the dose rate in air was, on average, 32.8, 10.3, and 102.1 nGy h(-1) at public areas, vegetable gardens, and backyards, respectively. The mean artificial increment in the annual per caput effective dose from external exposure to terrestrial radionuclides outdoors is 21.8 microSv y(-1). The collective dose commitment per unit energy generated from outdoor exposure to the deposited uranium progeny is about 8.0-9.1 person Sv (GW y)(-1), which is 67-76 times more than that evaluated by UNSCEAR (1988) for a typical "old" coal-fired power plant [0.12 person Sv (GW y)(-1)]. Ajka is a suitable place for studying the dosimetric consequences of the utilization of coal for energy production experimentally.

Air Pollution, Indoor↗
PubMed2000

Methods to determine the fluorescence and Auger spectra due to decay of radionuclides or due to a single atomic-subshell ionization and comparisons with experiments.

The aim of this work is to describe methods of determining the fluorescence and Auger spectra due to decay of radionuclides or a single atomic-subshell ionization. First discussed is the electron vacancy generation in an atomic subshell by ionization, internal-conversion decay, or electron-capture decay. Later discussed is the status of electron vacancy following emission of fluorescence x rays and Auger electrons. Special attention is given to the relaxation probabilities and the procedures to calculate energies of released electrons. Also discussed are the Monte Carlo and deterministic methods to calculate vacancy cascades.

Electrons↗
PubMed1981

Fluorescent thyroid imaging. Physical evaluation of an alternative instrument.

The authors describe a rectilinear scanner-head assembly containing an x-ray tube and a Si(Li) detector developed to stimulate and detect fluorescence from intrinsic iodine in the thyroid. Various operational parameters were evaluated. Because of the abundant supply of photons, a scanning distance of 3 inches (7.62 cm) could be used. The full width at half maximum at this distance was 0.52 cm. Optimal exposure was obtained at 80 kVp, 0.5 mA with a copper-aluminum filter combination. The scanner with an x-ray generator appears to be a workable alternative to imaging devices using long-lived radionuclide sources.

Fluorescence↗
PubMed2005

Air kerma rate constants for gamma emitters used most often in practice.

It is often required to estimate the dose rate at a distance from radionuclides that are sources of X rays and gamma rays. Such calculations may be required for planning radiation protection measures in the vicinity of radioactive sources or patients containing radionuclides, calibrations of radiation instruments or for estimating the absorbed dose rate to patients receiving brachytherapy. The factor relating activity and air kerma rate is called air kerma rate constant--gamma(delta). In this paper, the results of recalculation of this quantity for unfiltered point sources of radionuclides in practice used most often are given. The calculations included corrections for internal conversion of X rays and gamma rays and detailed accounting of the generation of the K and L series X rays from internal conversion and electron capture. Particular air kerma rate constants were calculated for each discrete line in the photon spectrum of radionuclide with a yield per decay event >0.01% and the energy >20 keV. Since the energy structure of the photon spectra and accessible discrete numerical values of the mass energy-transfer coefficient for air are not the same, the cubic spline interpolation was used to obtained the coefficient, where the photon spectrum data are available. In the calculation, the latest gamma ray spectral data for all radionuclides and latest data for the mass energy-transfer coefficient for air are used. Air kerma rate constants for the following 35 radionuclides are calculated: 11C, 13N, 15O, 18F, 24Na, 42K, 43K, 51Cr, 52Fe, 59Fe, 57Co, 58Co, 60Co, 67Ga, 68Ga, 75Se, 99Mo, 99mTc, 111In, 113mIn, 123I, 125I, 131I, 127Xe, 133Xe, 137Cs, 152Eu, 154Eu, 170Tm, 182Ta, 192Ir, 197Hg, 198Au, 201Tl and 241Am.

Air↗