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Due to its mechanical properties circonia is an interesting implantation material. However, it may contain a certain amount of radioactive isotopes. The measurement of alpha-emission reveals varying amounts of radiation. As a result, a declaration of radioactivity should be required for circonia implants and only circonia with low emission levels should be used for implantation purposes.
Uranium and thorium daughters are ten times more concentrated in thyroids from some bovine animals than in the teeth of the same animals. These radioactive isotopes are believed to be from natural sources, but their resulting annual dosage of thyroid radiation has exceeded that from iodine-131 fallout.
Lead is unique among all the metals in having variations among mining districts in the relative abundances of its stable (non-radioactive) isotopes. Since first described in 1927, many applications have been reported, mostly for geological uses. More recently archeological, environmental, bio-kinetic and public health uses have been found. The abundances of the four stable isotopes are usually determined with specialized mass spectrometry using rapid mass scanning cycles or multiple collectors. The relative abundances are commonly expressed as 206/204, 206/207, and 206/208 atomic ratios. Precision of 0.5% for 206/204 and even better (0.03%) for the other pairs are obtainable. The three ratios co-vary strongly and depend on when the ore was formed. This provides a tracer for following a particular batch of lead, since the ratio can only change when the lead is mixed with a different lead. A major limitation of this method is that it is useful only to those problems where the potential sources are isotopically distinct and few in number. The covariance of the ratios usually allows for only two sources to be considered. Potential sources can often be ruled out.
The underlying principle of the two non-invasive radio-labelled urea breath tests is similar. Both are positive when the patient's stomach is colonised by Helicobacter pylori because the organism's urease enzyme splits the orally administered urea isotope to labelled CO2 which is then detected in the expired breath. The tests thus reflect active infection and are ideally suited to monitoring the success or failure of different eradication therapies as well as studying rates of acquisition and re-infection/late recrudescence post treatment. [13C]-urea should always be used in children since it is the stable non-radioactive isotope but the [14C]-urea breath test is suitable for most adults, since the dose of radioactivity is minimal.
Effective management of radioactive contamination requires comprehensive knowledge of pollutants' characteristics. The complicated character of the problem is due to a number of issues, such as the very wide range of contamination, the presence of a mixture of radioactive isotopes, the highly variable diffusion of radionuclides in soil, water, and air, and the effect of climatic conditions. The resultant field has an irregular mosaic structure, which restricts the choice of measurement methods and data processing. In view of this, application of classical statistics techniques is often inappropriate in modeling such an environment. Application of the tools of fractal and stochastic geometry provides a good insight and helps to distinguish between distribution characteristics of natural and man-made isotopes. Several techniques are implemented to determine scaling aspects of contaminated fields. The discovery of multifractal scaling leads to the hierarchical structure of contamination spots on different scales and intensity and places restrictions on the measurement net for detecting anomalies. The method of stochastic geometry further demonstrates that topological characteristics of contamination fields differ from those of the Gaussian fields and the topology of man-made isotopes differs from natural ones.
Skeletal isotopic exploration is fundamental in patients with prostatic cancer. Bone scintiscan is reliable. Its sensibility can be increased by using new radioactive isotopes and quantitative isotopic explorations. Bone marrow histologic study is indicated in case of a doubtful diagnosis, when there is a discordance between radiological and isotopic exploration.
Radio-ecological and cytogenetic assessments were made in the vicinity of Totsk nuclear explosion in the Orenburg Region. Increased contents of radioactive isotopes Cs and Pu were detected in the soil. A comparative cytogenetic analysis indicated that the population continued to be exposed to radioactive agents.
There is a need for non-invasive tests of gastrointestinal and nutritional function. Clinical problems peculiar to infancy and childhood require prompt diagnosis, and methods that are invasive or involve the use of radioisotopes are often impractical or ethically unacceptable. What the pediatrician and clinical scientist seek are tests that are simple, repeatable, and unequivocal in their result for diagnosis, to assess the effects of treatment, and to measure the development of gastrointestinal function during early life. Stable isotope breath tests offer a ready and attractive answer to these needs. They involve the ingestion of substrates labeled with the non-radioactive isotope of carbon (13C), followed by the collection of serial breath samples for analysis of the enrichment of 13CO2, the end product of substrate metabolism. Their non-invasive nature recommends them for use in infancy and childhood, and they can be performed in the ward, clinic, laboratory, and home. In this article I discuss to what degree stable isotope breath tests fulfill the pediatrician's and scientist's needs. I have chosen two examples from the work of myself and my colleagues to illustrate the principles and use of 13C breath tests to detect Helicobacter pylori infection and to measure fat digestion in infancy and childhood.
The urea breath test (UBT) is one of the most important non-invasive methods for detecting Helicobacter pylori infection. The test exploits the hydrolysis of orally administered urea by the enzyme urease, which H pylori produces in large quantities. Urea is hydrolysed to ammonia and carbon dioxide, which diffuses into the blood and is excreted by the lungs. Isotopically labelled CO2 can be detected in breath using various methods. Labelling urea with 13C is becoming increasingly popular because this non-radioactive isotope is innocuous and can be safely used in children and women of childbearing age. Breath samples can also be sent by post or courier to remote analysis centres. The test is easy to perform and can be repeated as often as required in the same patient. A meal must be given to increase the contact time between the tracer and the H pylori urease inside the stomach. The test has been simplified to the point that two breath samples collected before and 30 minutes after the ingestion of urea in a liquid form suffice to provide reliable diagnostic information. The cost of producing 13C-urea is high, but it may be possible to reduce the dosage further by administering it in capsule form. An isotope ratio mass spectrometer (IRMS) is generally used to measure 13C enrichment in breath samples, but this machine is expensive. In order to reduce this cost, new and cheaper equipment based on non-dispersive, isotope selective, infrared spectroscopy (NDIRS) and laser assisted ratio analysis (LARA) have recently been developed. These are valid alternatives to IRMS although they cannot process the same large number of breath samples simultaneously. These promising advances will certainly promote the wider use of the 13C-UBT, which is especially useful for epidemiological studies in children and adults, for screening patients before endoscopy, and for assessing the efficacy of eradication regimens.
The increased availability of an extensive range of stable isotope-labelled substrates and their ever decreasing cost, as well as the availability of sensitive analytical instruments, suggests that stable isotopes will increasingly be employed in all branches of medical research. It seems likely that within the near future they will totally replace radioactive isotopes in quantitative metabolic studies involving human subjects.
OBJECTIVE: The experiment was to investigate the role of the pedicle of the subdermal vascular network skin flap. METHODS: Ten healthy white pigs, weighting from 20 to 25 kg were used. The subdermal vascular network skin flap and the traditional skin flap were designed and created on each side of the animal's flank. The traditional skin flap on the contralateral side of the flank was used as control. Flap survival was studied by gross observation and ECT examination of isotope distribution. RESULTS: There were significant differences between the two groups in mean survival length and area (P < 0.05). In both groups the radioactive isotope gathering is restricted proximally with a ratio of length to width of (1-1.5):1. CONCLUSION: The presence of the pedicle of the subdermal vascular network skin flap makes no difference compared the traditional skin flap.
Dietary cholesterol restriction is a general recommendation for the medical community and emphasizes the importance of intestinal cholesterol absorption and metabolism in humans. However, several methods that may accurately quantify cholesterol absorption utilize radioactive isotopes that are undesirable for younger individuals, women, children, and normal subjects. To eliminate this hazard, we have developed a procedure for measurement of percent cholesterol absorption, based on that of Zilversmit (1972. Proc. Soc. Exp. Med. Biol. 140: 862-865), using stable nonradioactive isotopic tracers of cholesterol. [26,26,26,27,27,27-2H]cholesterol (30 mg) was administered orally and [23,24,25,26,27-13C]cholesterol (15 mg) was administered intravenously on day 0 and percent cholesterol absorption was calculated as the plasma ratio of oral/intravenous isotopic tracer on day 3 as determined by gas chromatography-mass spectrometry with selected ion monitoring. Tracer cholesterol given orally peaked in plasma on day 2 and then slowly declined in parallel with the intravenous tracer. Cholesterol absorption in 16 healthy subjects (on no medication and not ingesting alcohol) consuming a Step One Diet was 53.5% +/- 8.5 SD%. Five subjects underwent repeat testing after 4-6 weeks with excellent replication (SD of difference between tests = 2.8%). No differences in the metabolism of [13C5]cholesterol, [2H6]cholesterol, and [14C]cholesterol were observed. The use of stable isotopes for the study of percent cholesterol absorption is precise and safe, allowing repeated measurements in normal individuals and thus facilitating clinical investigation of this key component of human cholesterol metabolism.
Lymphoscintigraphy has been very useful in determination of lymphatic abnormalities. However, the radioactive isotopes used have been investigational and difficult obtain. The purpose of this study was to examine patients with extremity edema by lymphoscintigraphy using a radioactive colloid readily available in our nuclear pharmacy, Technetium 99m sulfur minicolloid. Forty limbs in 20 patients were evaluated using Technetium 99m sulfur minicolloid lymphoscintigraphy. All patients had lower extremity edema initially attributed to a venous or lymphatic etiology. There were 12 patients with normal bilateral studies. Seven patients exhibited unilateral obstruction to lymphatic flow, and one had unilateral enhanced flow of lymph. Those with normal studies included five patients with nonspecific edema, four with varicosities, and one patient each with acute deep vein thrombosis, chylous ascites, and excision of the greater saphenous vein for arterial bypass grafting. Five patients with obstructed patterns had previous arterial bypass procedures, one had trauma to the extremity, and one had lymphedema tarda. The one enhanced lymphoscintigraphic pattern was seen in a patient with acute cellulitis. All patients had Doppler venous examinations and other studies included strain gauge phlethysmography, venograms, computed tomography, magnetic resonance imaging, and ultrasound. As with other scintigraphic imaging agents used to study lymphatic flow, Technetium 99m provides clinically useful information in evaluating the swollen extremity noninvasively.
The uptake by, and distribution and retention of radioactive isotopes in various organs of Wistar rats were examined using the multitracer technique. A hydrocholoric acid solution (pH 3) of a carrier-free radioactive multitracer was prepared from gold foil irradiated with a 14N beam of 135 MeV nucleon. The solution was administered orally to 12 7-week-old male rats. Urine and faeces were collected and each group of three rats was killed at 1, 2, 3 or 6 days after administration. The percentage of administered dose of the 17 elements, Mn, Co, Zn, As, Rb, Sr, Y, Eu, Gd, Er, Tm, Yb, Lu, W, Re, Ir and Pt in the organs blood and excreta were determined using gamma-ray spectrometry. Each element revealed its characteristic distribution among the different organs, including the blood. These results are discussed and compared with those of single-tracer experiments, and the advantages of the multitracer technique are presented.
The synthesis of various volatile and thermally stable derivatives of metals ions has permitted the use of conventional mass spectrometry for trace metal analysis. This paper reviews the development of the field using electron impact and chemical ionization mass spectrometry. This latter methodology produces simple mass spectra that enable complex mixtures to be analyzed. In addition the use of negative ion detection has produced selective ionization since many metal chelates contain heteroatoms which are electronegative. A discussion of the use of this general methodology for trace metal analysis is included, together with its applications to the analysis of ruthenium in automobile exhaust emissions and iron in red blood cells from laboratory rats. The future use of this methodology is expected to be for the monitoring of stable metal isotopes. This procedure could be used to follow these tracers in clinical and environmental studies and it is expected that their use will replace radioactive isotopes in most studies.
Magnesium (Mg) is a biologically essential mineral and Mg deficiency is known to lead to severe biochemical and symptomatic disorders. Radioactive isotopes and, more recently, stable isotopes have been used as research tools to determine intestinal Mg absorption in humans and animals under different nutritional and physiological conditions. Mg isotopes are given orally or orally plus intravenously and analysed in faeces and/or in plasma and urine in order to calculate intestinal Mg absorption and possibly endogenous Mg excretion. Mg isotopes have been used to assess exchangeable pools of Mg under nutritional and physiopathological conditions. Mg isotopes are given intravenously and are analysed in plasma and urine to calculate the size and half-life of the various Mg exchangeable pools. More recently, in vitro isotopic tests have been developed to study the need of cells for Mg in different nutritional and genetic conditions. Whole blood is incubated with Mg isotopes and isotopic blood cell enrichment is measured, which reflects the avidity of cells for Mg and thus its initial status. This paper is a report on the use of stable Mg isotopes and their advantages in these different fields of Mg absorption and metabolism. The studies available have clearly demonstrated that stable isotopes provide a useful research tool for determining intestinal Mg absorption, and represent a precious research tool for the study of Mg metabolism and the assessment of Mg status.
Saline waters from underground coal mines in Poland often contain natural radioactive isotopes, mainly 226Ra from the uranium decay series and 228Ra from the thorium series. Approximately 40% of the total amount of radium remains underground as radioactive deposits, but 225 MBq of 226Ra and 400 MBq of 228Ra are released daily into the rivers along with the other mine effluents from all Polish coal mines. Technical measures such as inducing the precipitation of radium in gobs, decreasing the amount of meteoric inflow water into underground workings, etc. have been undertaken in several coal mines, and as a result of these measures, the total amount of radium released to the surface waters has diminished by about 60% during the last 5-6 years. Mine water can have a severe impact on the natural environment, mainly due to its salinity. However, associated high levels of radium concentration in river waters, bottom sediments and vegetation have also been observed. Sometimes radium concentrations in rivers exceed 0.7 kBq/m3, which is the permitted level for waste waters under Polish law. The extensive investigations described here were carried out for all coal mines and on this basis the total radium balance in the effluents has been calculated. Measurements in the vicinity of mine settling ponds and in rivers have given us an opportunity to study radium behaviour in river waters and to assess the degree of contamination. Solid waste materials with enhanced natural radioactivity have been produced in huge amounts in the power and coal industries in Poland. As a result of the combustion of coal in power plants, low-radioactive waste materials are produced, with 226Ra concentration seldom exceeding a few hundreds of Bq/kg. A different situation is observed in coal mines, where, as a result of precipitation of radium from radium-bearing waters, highly radioactive deposits are formed. Sometimes the radioactivity of such materials is extremely high; precipitates from coal mines may have radium concentrations of 400,000 Bq/kg--equivalent to 3% uranium ore. Usually, such deposition takes place underground, but sometimes co-precipitation of radium with barium takes place on the surface, in settling ponds and in rivers. Therefore management of solid waste with technologically enhanced natural radioactivity (TENR) is a very important subject.
Based on the probability that extraterrestrial life is biochemically somewhat similar to life on Earth, a life detection experiment is being prepared to explore Mars. The experiment will be performed by an automated device which will carry a microbiological medium being developed to support a wide range of earth microorganisms. Selected ingredients of the medium will be labeled with radioactive isotopes. A sticky string, shot out from and reeled back into the device, will gather a sample of the Martian soil. It is hoped the radioactive atoms in the compounds will be metabolized by the unknown organisms in the soil and evolved in a labelled gas. The gas will be collected by a chemical "getter" and the radioactivity measured for transmission to Earth. A positive response from the test unit and a negative, or lesser, response from a poisoned control unit would constitute evidence of life. The device can also differentiate between photosynthetic and nonphotosynthetic metabolic activity. Data from field tests on Earth are presented.