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PubMed1988

Thorotrast-induced oro- and hypopharyngeal fibrosis with recurrent bleeding.

Thorium dioxide, widely used as a contrast material, is a producer of alpha particle radiation. This is well demonstrated by autoradiography. The case described illustrates that life-threatening, thorium dioxide-induced pharyngeal haemorrhage may occur even with an occluded carotid artery. The radiation exposure caused an intense foreign body reaction with a marked cell-deficient fibrosis. The alpha particles are well demonstrated by autoradiography. In addition, we were able to show a defect in the wall of the carotid artery due to the Thorotrast injection, which was closed by cell-depleted connective tissue. As the radioactivity of the nuclides of thorium dioxide peaks 30-40 years after its first application, the morbidity will increase and the disease has to be taken into careful consideration in head and neck tumour lesions.

Aneurysm↗

PubMed1983

Measurement techniques for radium and the actinides in man at the Center for Human Radiobiology.

Various techniques are employed to determine the amounts, retention, and distribution of radioactivity in human subjects in vivo. The principal method is gamma-ray spectrometry with large NaI(Tl) scintillation crystals ("whole-body counting"). The geometries used include an arc of 1.5-m radius in which all parts of the body are roughly equidistant from the detector, a reclining chair and a flat bed with detectors placed above and below the subject. When a sufficient amount of radioactivity is present in a subject, scanning techniques assist in determining its distribution in the body. Specialized instruments such as a xenon-filled proportional counter and a dual-crystal (phoswich) detector are used to measure low-energy photon emitters, primarily plutonium and americium. americium. There are three primary methods of calibrating the detectors. The first is analytical, in which a rigorous mathematical treatment is employed; the second involves the administration of tracer amounts of radioactivity to human volunteers; the third consists of determining detector response to known amounts of radioactivity in a phantom. All three methods can be intercompared, and further evaluated by comparing the results of measurements in vivo with those of postmortem analyses. For both radium and thorium cases measured in vivo, the interpretation of the results is complicated by the fact that neither radium nor thorium emit gamma rays of any consequence. Instead, the observed gamma rays result from the decay of 214Bi (RaC) and 208Tl (ThC"), respectively. Since each of these nuclides is preceded in the decay chain by an isotope of the noble gas radon, some of which is exhaled, its activity is not equal to that of the parent radium or thorium. Therefore, breath samples are collected to determine the exhalation rate of the precursor isotope, 222Rn (radon) or 220Rn (thoron). The total body content is then the sum of the gamma activity and the exhaled radioactivity, referred to as the retained and emanating fractions, respectively.

Actinoid Series Elements↗

PubMed1983

Levels of 234U, 238U and 230Th in excreta of uranium mill crushermen.

Pacific Northwest Laboratory conducted a research program to measure uranium and thorium levels in excreta of uranium mill crushermen who are routinely exposed to airborne uranium ore dust. The purpose of this work was to determine whether 230Th was preferentially retained in the body over either 234U or 238U. Urine and fecal samples were obtained from 14 active crushermen with long histories of exposure to uranium ore dust, plus four retired crushermen and three control individuals for comparison. Radiochemical procedures were used to separate out the uranium and thorium fractions which were then electroplated on stainless steel discs and assayed by alpha spectrometry. Significantly greater activity levels of 234U and 238U were measured in both urine and fecal samples obtained from uranium mill crushermen, indicating that uranium in the inhaled ore dust was cleared from the body with a shorter biological half-time than the daughter product 230Th. The measurements also indicated that uranium and thorium separate in vivo and have distinctly different metabolic pathways and transfer rates in the body.

Alpha Particles↗

PubMed1994

Modeling to optimize operational practices to limit shallow dose and dose to the lens at the Weldon Spring Site Remedial Action Project.

The Weldon Spring Site Remedial Action Project (WSSRAP) began remediation of its chemical plant buildings in June 1992. The chemical plant was used by the Atomic Energy Commission in the 1950's and 1960's to process uranium ore and natural thorium. Many remaining equipment surfaces were highly contaminated with uranium and thorium product residues, which are relatively weak gamma emitters, but are strong beta emitters that deposit the majority of their energy within the first centimeter of tissue. An essential part of the remediation, therefore, is to control the dose to the skin, extremities, and the lens of the eye from the broad range of betas emitted by uranium and thorium decay series radionuclides. The WSSRAP planned to quantitatively record the dose to the skin, extremities, and the lens of the eye, when warranted, through selection and use of appropriate passive dosimeters. That would not, however, constitute control. A direct-reading instrument was needed that could be used by field technicians to anticipate and prevent work methods and situations that would otherwise result in the unnecessary commitment of dose. However, the interpretation of real-time instrument readings produced by a broad spectrum of beta energies is typically challenging at best, particularly when the shallow dose rate and the lens dose rate are both of interest. The purpose of this effort was, therefore, to (1) select a direct-reading instrument for use in the buildings that could be used to provide rule-of-thumb action levels for field technicians, which, if exceeded, would warrant worker protective measures; (2) determine the approximate conversions between the instrument readings and the shallow (including extremity) dose rate and lens of the eye dose rate; and (3) specify protective measures and dosimetry for the lens of the eye, if warranted. Methods described in the literature are used to estimate action levels for direct instrument readings and to demonstrate that lens dosimetry and special protective measures for the lens of the eye are not necessary at the WSSRAP.

Humans↗

PubMed1996

Overview of radiation safety in the tin by-product (amang) industry of South East Asia.

Processing of by-product heavy minerals (amang) from tin mining involves potential exposure to external and internal sources of radioactivity. The radioactivity arises through the presence of thorium and uranium series radionuclides in the various minerals. Monazite is the most radioactive mineral, containing 3% to 7% thorium by weight, while ilmenite is generally the least radioactive mineral containing typically less than 0.05% thorium. External exposure occurs when workers are in close proximity to accumulations or stockpiles of the radioactive minerals, whereas internal exposure occurs when workers are involved in dusty processes. This paper summarizes the nature of the amang industry in South East Asia and presents the results of preliminary measurements of external radiation and airborne radioactivity in twelve Malaysian and Thai plants. Although constrained by a paucity of exposure data, it is concluded that radiation doses to some amang plant workers may approach or exceed international standards and that appropriate control measures are required as a matter of priority, Radiation doses may approach or exceed 100 mSv in situations where workers are exposed to excessive levels of ambient dust and no protective measures are used. Observations and recommendations are made relating to monitoring and surveillance, instruction and training, and engineering and administrative protection measures.

Air Pollutants, Radioactive↗

PubMed1978

Transplacental transmission and fetal parasitosis of Trypanosoma cruzi in outbred white Swiss mice.

Two strains of Trypanosoma cruzi, isolated from humans and assayed for their biological capacity to kill outbred white Swiss mice (HaM/CR-CD) following reticuloendothelial system blockade with thorium dioxide, were used in these experiments: the Maria Cristina strain, which killed all blocked mice at a rate following a rectangular dose-response curve, and the José Cardoso strain, which did not kill blocked mice at comparable dosages. When inoculated into pregnant HaM/CR-CD mice, the non-pathogenic José Cardoso strain did not cross the placental barrier, in either blocked or unblocked mice, to cause fetal parasitosis. The pathogenic Maria Cristina strain did not cross the barrier in non-blocked mice, but in thorium-dioxide blocked mice it produced an incidence of fetal parasitosis of 8.9% (7 of 79 fetuses). These results indicate that the transplacental transmission of T. cruzi was dependent on two restrictions: pathogenicity of the strain of T. cruzi, and blockade of phagocytic activity by thorium dioxide, suggesting that transplacental transmission of T. cruzi is related to interference with the phagocytic activity of the placenta.

Animals↗

PubMed1998

[Dependence of the elastic characteristics and contractile activity of the rat tail artery on the transmural difference of potentials].

Change in the diffuse portion of the double electric layer at the blood-vascular wall border under the effect of thorium nitric oxide and heparin affects the tone and contractile ability of the rat tail artery: thorium diminishes the vessel rigidity and the amplitude of its contractile response, whereas heparin augments the rigidity as well as the amplitude of the response. Thorium nitric oxide also diminishes rigidity of the vessel connective tissue skeleton. The difference of potentials between the vessel lumen and its wall seems to be capable of affecting the contractile apparatus of the smooth muscle cells by means of activation of potential-sensitive ionic channels.

Animals↗

PubMed1981

[Hepatic angiosarcomas].

The authors describe three cases of hepatic angiosarcoma diagnosed at postmortem examination, two of them being associated to thorium dioxide. The low incidence of these tumors amongst the general population is commented upon, and an update is made on the factors involved in their appearance, with special mention of thorium dioxide. An analysis of the clinical picture of the disease is undertaken, emphasizing its diagnostic difficulties. A tentative diagnosis can be made on the basis of clear-cut epidemiological data and or the presence of increased radiological density over the liver, spleen and paraaortic lymph nodes in the cases associated to thorium dioxide. Two of the reported patients presented hemolytic anemia, and disseminated intravascular coagulation, respectively; these findings, although nonspecific, may suggest the diagnosis in the presence of a toxic clinical picture or one of the above mentioned factors. The diagnosis should be made by the usual techniques utilized clinically to detect space occupying lesions within the liver. The evolution of such patients is rapidly progressive, with a fatal outcome within three to six months after beginning of symptoms.

Aged↗

PubMed1980

Ionizing radiation from tinted single vision spectacle lenses.

Some ophthalmic lenses are tinted using materials which contain trace amounts of thorium or daughter products of the thorium and uranium chains. Such lenses emit small amounts of ionizing radiation. No tissue damage has been proven as a result of wearing these eyeglasses. Still, any radiation exposure is a potential hazard. Since there are many essentially nonradioactive lenses on the market, tinted lenses containing thorium contaminants would seem to represent an unnecessary risk.

Cataract↗

PubMed2000

Relationships between nasopharyngeal carcinoma and radioactive elements in soils in China.

Earlier comparisons of epidemiological and geochemical maps of China disclosed associations between high mortality rates from nasopharyngeal carcinoma (NPC) and low contents of magnesium in the soil. More recent work has shown that high rates of NPC are also associated with high levels of uranium and thorium in the soil. These latest findings are consistent with the earlier ones, since uranium and thorium occur predominantly in acid rocks poor in magnesium. Uranium and thorium are radioactive, and their progeny include radioactive elements such as radium and radon. Whether or not naturally occurring radioactive elements could be risk factors in NPC should, therefore, be further investigated. Direct carcinogenic properties of radon are well known, but in connection with NPC possibilities for reactivation of virus by natural ionizing radiation should also be considered.

China↗

PubMed1958

The fine structure of endothelium of large arteries.

Endothelium of large arteries from several species was studied in thin sections with the electron microscope. Before sacrifice, some animals received an intravenous injection of colloidal thorium dioxide which was visualized in the sections. Surface replicas were prepared by carbon evaporation on either frozen-dried endothelium or on endothelium dried by sublimation of naphthalene with which the tissue had been impregnated. Cell boundaries, stained with silver, were observed in sections and also from the surface by stripping off the inner part of the endothelium. In addition to the usual cytoplasmic organelles, the endothelial cells showed certain characteristic features, namely, large invaginated pockets communicating with the arterial lumen, numerous much smaller vesicular structures immediately under the plasma membrane and apparently also communicating with the lumen, and inclusions, into which injected thorium particles were incorporated. Intercellular boundaries appeared as regular double membranes in thin sections, and they were outlined by a double row of silver granules after silver staining. No evidence was obtained of permeation of intracellular spaces by colloidal thorium.

Animals↗

PubMed1999

[Thorotrast-induced liver cancer: results of the German thorotrast study].

AIMS: The X-ray contrast medium Thorotrast, used worldwide between 1930 to 1950 predominantly for arteriography, consisted of a colloidal solution of thorium dioxide. The radioactive thorium-232 (half-life 1.4x10(10) years) is stored lifelong in the organs of the reticulo-endothelial system after intravascular injection, causing chronic exposure to alpha radiation. The aim of the German Thorotrast study is the assessment of radiation late effects and the calculation of risk estimates. MATERIAL AND METHODS: The German Thorotrast study started in 1968 as a cohort study and comprises 2326 Thorotrast patients and 1890 patients of a matched control group. The Thorotrast patients who were still alive at the beginning of the study were examined by X-ray plain films of the upper abdomen and of the injection site of the contrast medium as well as by whole-body counter measurements. At the beginning we offered the patients ultrasound and later on CT and MRI at regular intervals for early detection of liver cancer. RESULTS: To date 454 primary liver cancers have been registered in the group of Thorotrast patients compared to 3 cases in the control group. With the help of modern imaging methods relatively small liver cancers were detected and could be surgically removed. DISCUSSION: There is a correlation between the mean accumulated dose to the liver and the incidence of liver cancer. The cumulative risk for liver malignancies is about 600 diseases per 10(4) persons whose liver was exposed to 1 Gy. Also the incidence of liver cirrhosis is correlated with the mean accumulated dose to the liver.

Alpha Particles↗

PubMed1989

Long-term tissue distribution and steady state activity ratios of 232Th and its daughters in rats after intravascular injection of Thorotrast.

To estimate the absorbed dose in the critical organs of Thorotrast patients, it is necessary to know not only the distribution and concentration of 232Th but also its daughter nuclides in the body. The present investigation was undertaken in order to clarify the long-term 232Th tissue distribution and steady state activity ratios between subsequent daughters in the critical tissues using about 30 Wister male rats, as a basis for estimating absorbed doses. The tissue distribution of thorium was examined by means of an autoradiography of the whole body and/or the gamma-ray spectrometry at various times during 2 to 24 months following injection. The concentrations of daughter nuclides in tissues were determined by repetitive gamma examination over a period from 1 hr to 35 days after being sacrificed. The data indicate (1) that approximately 90% of injected Thorotrast is retained in the body for a prolonged period, but about 50% of radium and 10% of radon produced from thorium are eliminated from the body, (2) that the mean steady state activity ratios of 224Ra and 212Pb to 228Th for liver are 0.56 and 0.28, and 0.54 and 0.16 for spleen, 0.58 and 0.82 for lungs, respectively, and (3) that the parent 228Th is translocated to the bone.

Animals↗

PubMed2004

Tissue distribution of Thorotrast and role of internal irradiation in carcinogenesis.

Carcinogenesis in Thorotrastosis has been assumed due to direct bombardment by alpha-particle with high linear energy transfer during decay of 232Th. To revisit the mechanism of carcinogenesis by Thorotrast (THR), we examined the tissue distribution of THR granules and two-dimensional distribution of radioactivity in the organs of Thorotrastosis patients and studied their spatial relationship to histopathological changes. The high radioactivity in the patients' organ was predominantly derived from decay of Thorium series and showed unique distribution, while the far lower natural radioactivity was mainly from Uranium series decay and fairly evenly distributed. It was found that a large majority of THR granules were phagocytized by macrophages and were embedded in extensive fibrosis. Cancer was rarely in the center of THR deposition but rather at a distance from the deposits. These observations may indicate that the predominant feature of THR deposition is the tissue damage by direct hit of alpha-particles and subsequent fibrosis. The effect of THR resembles action of toxic chemical agents, as several authors have pointed out. We therefore assume that carcinogenesis in Thorotrastosis is a combination of events, such as regeneration of liver tissue after radiation damage, emission of secondary electrons, ionization of the surrounding tissue, and beta- or gamma-ray from daughter nuclei of Thorium (Th). In this context, the role of alpha-particle is important but more intriguing.

Aged↗

PubMed1976

Nonsecretory plasma cell dyscrasia followed by acute granulocytic leukemia 25 years after Thorotrast administration.

Twenty-three years after an injection of Thorotrast, profound depression of humoral and cellular immunity associated with extensive marrow plasmocytosis developed in a man aged 75 years. Twelve months of chemotherapy with L-phenylalanine mustard, resulted in hematologic remission. Radioautograph of his marrow showed signs of alpha-radiation; whole body counting revealed a significant thorium burden. One year after chemotherapy was stopped, and two years after initial presentation, aleukemic acute granulocytic leukemia led to his death. The role of thorium in the etiology of possibly two successive hematopoietic neoplasms is discussed.

Aged↗

PubMed1978

Osteosarcoma associated with Thorotrast administration: report of two cases and literature review.

Two cases of osteosarcoma are described arising in patients who had undergone angiography with Thorotrast during childhood. In both patients, there was radiographic and pathologic evidence of radioactive thorium dioxide deposition in bone as well as throughout the reticuloendothelial system. Thorotrast deposits were demonstrated in the immediate vicinity of the primary tumors by both histology and autoradiography. Previous cases of osteosarcoma associated with Thorotrast administration from the literature are cited, and possible causal relationships are discussed between thorium retention in bone and neoplastic transformation by chronic radiation.

Adolescent↗

PubMed1991

[Synchronous development of benign cholangiomas and a cholangiocarcinoma in the liver of a patient 43 years after thorotrast administration].

This is a report on a 59-year-old patient in whom the synchronous occurrence of benign cholangiomas and a cholangiocarcinoma was observed in the liver 43 years after single intraarterial application of thorotrast. Despite a half-life of over 130 years (alpha radiation), X-ray contrast media containing thorium (colloidal thorium dioxide) were used up to the 1950's in X-ray diagnosis, particularly for angiographies. Thorotrast is mainly stored in the liver, in the spleen and in epigastric lymph nodes and can therefore be easily detected radiologically in a survey radiograph of the abdomen. International studies have shown that thorotrast patients have an up to 100 times greater risk of contracting hepatic malignancies compared to control collectives. Among the causes of death of thorotrast carriers in the (old) Federal Republic of Germany, 15% are attributed to primary hepatic tumours (cholangiocarcinomas, malignant haemangioendotheliomas, hepatic cell carcinomas). In the patient presented here, a cystic mass approximately 2 cm in diameter was detected in the right lobe of the liver during computed tomography of the epigastric region conducted as part of the German Thorotrast Study at the German Cancer Research Centre in Heidelberg, as well as in sonography. Intraoperatively, this finding corresponded to a cystic cholangioma. By chance, a cholangiocarcinoma approximately 1 cm in size and several benign cholangiofibromas were also found in the left lobe of the liver. All of the tumours were excised in toto by atypical segment resection. As shown by this case report, thorotrast-induced hepatic tumours are still to be expected, even 40 years after thorotrast was removed from the market.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma, Bile Duct↗

PubMed2001

Immunohistochemical and charge-specific localization of anionic constituents in pseudoexfoliation deposits on the central anterior lens capsule from individuals with pseudoexfoliation syndrome.

BACKGROUND: Pseudoexfoliation (PSX) syndrome is a degenerative systemic disorder that is characterized primarily by deposits of distinct fibrillar material on the surface lining the anterior and posterior chambers of the eye and is often associated with cataract and glaucoma. Although some components of the PSX material have been identified, the precise composition is obscure. METHODS: High-resolution scanning electron microscopy in conjunction with colloidal cationic gold labeling was used to localize anionic constituents at the surface of PSX aggregates. Transmission electron microscopy was applied for the immunocytochemical detection of glycosaminoglycans, and to monitor the charge-specific distribution of colloidal thorium dioxide and ferritin in PSX material. The specific binding of antibodies was confirmed by immunohistological staining of paraffin-embedded specimens. RESULTS: Paraffin-embedded tissue sections revealed immunoreactivity for keratan sulfate and dermatan sulfate proteoglycan within PSX material deposited on the surface of the anterior lens capsule. Post-embedding immunogold labeling of keratan sulfate demonstrated an intense label of PSX aggregates primarily associated with mature PSX fibrils, whereas dermatan sulfate proteoglycon appeared to be present in low quantities. Additionally, keratan sulfate was found at the humoral periphery of the lens capsules. To further investigate the distribution of anionic sites in PSX material, we used cationic colloidal tracers of different size, such as gold, thorium dioxide and ferritin. PSX aggregates exhibited a strong negative charge, resulting very likely from glycosaminoglycan chains of proteoglycans. The density of anionic sites was higher at the interfibrillar matrix. Lens capsules associated with PSX material revealed a diminished accumulation of cationic ferritin at the humoral surfaces. CONCLUSIONS: Increased amounts of different glycosaminoglycans identified in PSX material suggest an important role of proteoglycans for the pathogenic pathway in PSX.

Aged↗