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PubMed1987

Chromosome aberration frequency and radiation dose to lymphocytes by alpha-particles from internal deposit of Thorotrast.

Frequencies of chromosome aberrations in peripheral blood lymphocytes from 63 Thorotrast patients were analysed basing on the age distribution of lymphocytes. The frequency and distribution of chromosome aberrations among lymphocytes are best explained if we assume that the lymphocytes are renewed as an exponential function of time and spend most of their lifetime in the distributive pool where, while exchange of lymphocytes is taking place, the lymphocytes are hit by alpha-particles from Thorotrast aggregates resulting in the formation of chromosome aberrations and killing at specific rates per hit. The model predicts that the aberration frequency is rather insensitive to the fluence rate because of modulation by cell killing by hit. Fitting the observed data to the model showed that approximately 0.8 dicentrics and rings were produced by a single path of alpha-particle and average fluence rate to lymphocytes in a group of patients with the highest aberration frequency was estimated to be about 1.5 hits or 87 rad/lymphocyte/year.

Aged↗
PubMed1975

Cholagiocarcinoma in a patient previously given thorotrast.

The long-term effects of thorotrast administration include local granulomas, blood cell abnormalities, and cancer. To date, more than 100 cases of liver cancer have been reported in patients previously given this radioactive contrast material, with a latency period of approximately 22 years. We report such a case; the patient not only had a thorotrast-induced cholangiocarcinoma, but also showed striking morphologic changes in the red blood cells secondary to splenic dysfunction.

Adenoma, Bile Duct↗
PubMed1981

Biophysical investigations of the dose-effect relationship in chromosome aberrations of human lymphocytes caused by thorotrast deposits. I. Physical aspects.

Thorotrast is a X-ray contrast medium which has been used in the years 1930-1950. It is hardly ever eliminated from the body and is stored in the organs of the reticulohistiocytic system (RHS). Since Thorotrast contains all radionuclides of the thorium decay chain, the effect of internal irradiation by these radionuclides can be investigated in the so called "Thorotrast patients". It is the purpose of this study to determine the radiation dose absorbed by the lymphocytes of the peripheral blood of these persons, and to correlate it with their chromosome aberration rate. Part I of the paper describes the physical aspects of dose evaluation. The chromosome aberration rates of Thorotrast patients were subjected to a repeated statistical test. They show a logarithmic normal distribution at a mean value of about seven dicentric chromosomes per 100 cells. The corresponding dose has to be determined. The method for evaluating size and distribution of Thorotrast conglomerates in the examined tissue is demonstrated, and the function and resolution power of the applied "texture analysing system" (TAS) is described. Size-distributions of Thorotrast conglomerates of lymph nodes from the neck, the lung and from the lower aorta (bifurcatio) are given. In the lymphatic system more than 90% of the absorbed dose in tissue is due to alpha-particles. The computation method of calculating the self-absorption of alpha-particles in the conglomerates and of calculating the annual doses in the lymph nodes is described. The values lie between 135 and 1200 rad/year. The contribution to irradiation from outside the lymphatic system can be neglected. The method of dose determination is discussed and compared with microdosimetric methods. With these methods, the dose of a lymphocyte caused by one hit of an alpha-particle lies between 80 and 920 rad. An energy dissipation does not take place and the total energy emitted acts on the lymphocytes thus inducing chromosome aberrations.

Animals↗
PubMed1981

Biophysical investigations of the dose-effect relationship in chromosome aberrations of human lymphocytes caused by thorotrast deposits. II. Biological and medical aspects.

The biological effect of alpha-radiation, which has been examined in this investigation, is the occurrence of chromosome aberrations in lymphocytes from the peripheral blood of Thorotrast patients. To set up a dose-effect relationship, it is necessary to estimate the absorbed dose of a single lymphocyte found in a blood sample. Then it would be possible to use chromosome aberrations of lymphocytes from peripheral blood as an indicator for estimating the effective radiation dose. The physical aspects of this investigation have been described in part I of this paper. In part II, biomedical considerations are described and discussed. The irradiation of the lymphocytes takes place in the whole lymphatic system, but the lymph node could have been used as a model for the lymphatic system. Based on the evaluation of size and distribution of Thorotrast conglomerates, the average annual dose in different structures of the lymph node has been determined. The Thorotrast content in lymph nodes depends on the region of the body from where the lymph nodes originate. It has been tried to compile the distribution of the lymph nodes in the different regions of the body. Annual doses have been calculated in these different regions in order to find a representative value for the whole body. The values describing the kinetics of the lymphocytes in the body have been used to convert the annual dose in lymph nodes into the dose of a lymphocyte found in a sample of peripheral blood. It is pointed out that the calculated dose of the lymphocytes, being 250 rad, is an estimation of an upper value. The lymphocytes are "in vivo" irradiated by the Thorotrast, but most of the calibrations used for biological dosimetry are referred to as "in vitro" experiments. The discrepancy between "in vivo" and "in vitro" results are discussed in the findings of this study and in other results.

Alpha Particles↗
PubMed1993

Spurious dual-energy X-ray absorptiometry images in a patient exposed to the contrast agent Thorotrast.

A 69-year-old woman presented with a 20-year history of back pain and a 10 cm height loss. She had received an injection of the contrast agent, Thorotrast, at age 23. There was no history of fluoride exposure. Multiple vertebral compression fractures were seen on radiographs. Dual-energy X-ray absorptiometry (DXA) scans revealed high normal bone mineral content on the spine and, on whole body scan, visualization of the liver and spleen regions. Given the attenuation coefficient of thorium and the thorium concentrations reported for liver, spleen and vertebral bodies, it is likely that thorium was visualized in the liver and spleen and that it caused spurious elevation in her DXA bone mineral content values.

Absorptiometry, Photon↗