Radiation dose to the testes after 131I therapy for ablation of postsurgical thyroid remnants in patients with differentiated thyroid cancer. (1/93)

Radioiodine-131 is used in differentiated thyroid cancer (DTC) for ablation of postsurgical thyroid remnants and destruction of metastases. The question may be raised of whether 131I treatment of DTC in male patients may give an irradiation dose to the testes that could impair fertility. Few data in the literature concern the dose absorbed by the testes after 1311 therapy for DTC. Because 131I kinetics may be altered by the hypothyroid condition commonly present at the time of treatment and by the radioiodinated iodoproteins released by the damaged thyroid tissue, the dose values reported in the International Commission on Radiological Protection (ICRP) tables for euthyroid men may not be appropriate. To clarify this problem, three male subjects undergoing 131I therapy for ablation of thyroid remnants shortly after thyroidectomy for DTC were studied. METHODS: The mean administered activity was 1256 MBq, and the duration of the study was 2 wk. The gamma dose was measured by thermoluminescent dosimeters (TLDs) applied to the lower poles of the testes. Correction factors were calculated for the distance of the TLD from the center of the testes and for attenuation by the testes of the gamma rays reaching the TLD. After correction, the gamma dose to the testes ranged from 21 to 29 mGy. The gamma dose calculated by the Medical Internal Radiation Dose (MIRD) method from blood and urine samples was similar (18-20 mGy) to that measured by TLDs. The beta dose was estimated by the MIRD method from blood activity and testicular volume and ranged between 14 and 31 mGy. RESULTS: The total (beta and gamma) doses to testes were 30, 33 and 43 microGy/MBq in the three subjects. CONCLUSION: These values are close to those derived from the ICRP tables (26-37 microGy/MBq 131I) for euthyroid subjects. The present data indicate that significant irradiation is delivered to the testes after the administration of the 131I ablative dose to thyroidectomized patients. The relevance of the radiation absorbed by testes on fertility remains to be established.  (+info)

External doses of residents near Semipalatinsk nuclear test site. (2/93)

Accumulated external radiation doses of residents near the Semipalatinsk nuclear test site of the former USSR are presented as a results of study by the thermoluminescence technique for bricks sampled at several settlements in 1995 and 1996. The external doses that we evaluated from exposed bricks were up to about 100 cGy for resident. The external doses at several points in the center of Semipalatinsk City ranged from a background level to 60 cGy, which was remarkably high compared with the previously reported values based on military data.  (+info)

Application of a newly developed photoluminescence glass dosimeter for measuring the absorbed dose in individual mice exposed to low-dose rate 137Cs gamma-rays. (3/93)

A photoluminescence glass dosimeter, GD-301, was applied to the measurement of low absorbed doses in mice exposed to low-dose rate 137Cs gamma-rays. The dosimeter system consists of small rod-shaped glass chip detectors capable of embedded in the body of a mouse and an automatic readout device equipped with a standard detector irradiated with 137Cs gamma-source. The measured absorbed doses were compared with the "exposure" estimated by an ionization chamber and with the doses measured by a BeO:Na thermoluminescence system. The results clearly demonstrate the superiority of the glass dosimetry regarding simplicity of operation, stability of long-term dose accumulation and good detector uniformity, which allow accurate tissue dosimetry.  (+info)

Glow-peak stability in 6LiF:Mg,Ti (TLD-600) exposed to a Fe-ion beam. (4/93)

The stability of glow peaks in 6LiF:Mg,Ti (TLD-600) exposed to a high-energy Fe-ion beam was examined in comparison to 137Cs gamma-ray irradiation under changing annealing conditions. The peak areas induced by the Fe ions were much smaller than those by gamma-rays. The sizes and positions of peaks 3-5 in Fe-ion irradiated samples were hardly changed after post-annealing at 100 degrees C x 30 min, regardless of the pre-annealing conditions (fast quenching or subsequent pre-annealing at 100 degrees C x 2 h). Whereas, the peaks in gamma-ray irradiated samples were notably affected by post-annealing; the peak positions and peak-area sizes changed in different ways depending on the pre-annealing conditions. The effects of post-annealing on peak 6 were identical for Fe ions and gamma-rays. These facts suggest that peaks 3-5 in TLD-600 comprised both stable and unstable luminescent centers, and that the latter part would be easily depleted in highly dense ionization.  (+info)

Conceptus radiation dose and risk from cardiac catheter ablation procedures. (5/93)

BACKGROUND: The aim of the current study was to estimate the conceptus radiation dose and risk associated with fluoroscopic imaging during a catheter ablation procedure for supraventricular tachycardia performed on the expectant mother. METHODS AND RESULTS: Exposure parameters and fluoroscopy times for each projection of the cardiac ablation procedure performed in 20 female patients of childbearing age were recorded. Radiation doses for a potential conceptus were estimated by using dose data obtained in anthropomorphic phantoms simulating pregnancy at the first, second, and third trimesters. Dose measurements were carried out using thermoluminescent dosimeters. For a typical examination, the average radiation dose to the conceptus was <1 mGy in all periods of gestation. Average excess fatal cancer was 14.5/10(6) unborn children irradiated during the first postconception weeks. Corresponding values for the second and third trimesters were 30 and 55.7/10(6), respectively. The risk for hereditary effects in future generations was 1.5/10(6) cases for conceptus irradiation during the first postconception weeks. Corresponding values for the second and third trimesters were 3.0 and 5.6/10(6), respectively. Formulas and dose data are presented for estimating the conceptus risk from any technique and x-ray system used for catheter ablation procedures. CONCLUSIONS: A typical catheter ablation procedure results in a very small increase in risk of harmful effects to the conceptus. However, estimation of conceptus dose from catheter ablation procedures is always needed to assess the risk to the individual developing in utero.  (+info)

Mutation frequency of Dictyostelium discoideum spores exposed to the space environment. (6/93)

Two strains of cellular slime mold Dictyostelium discoideum, a radiosensitive mutant and the parental wild-type strain, were used to investigate the effects of cosmic radiation on viability and mutation frequency at the spore stage for about 9 days in Space Shuttle of NASA. We measured little effect of space environment on viability and cell growth in the both strains as compared to ground controls. The mutation frequency of the flown spores were similar to that of ground control. These results suggest that there could be no effect of cosmic radiation, containing high linear energy transfer radiation at about 0.9 mSv/day as detected by real-time radiation monitoring device on the induction of mutation at the spore stage.  (+info)

Measurements of LET distribution and dose equivalent onboard the Space Shuttle IML-2 (STS-65) and S/MM#4 (STS-79). (7/93)

Space radiation dosimetry measurements have been made onboard the Space Shuttle STS-65 in the Second International Microgravity Laboratory (IML-2: 28.5 degrees x 300 km: 14.68 days) and the STS-79 in the 4th Shuttle MIR mission (S/MM#4: 51.6 degrees x 300-400km: 10.2 days). In these measurements, three kinds of detectors were used; one is a newly developed active detector telescope called "Real-time Radiation Monitoring Device (RRMD-I for IML-2 and RRMD-II with improved triggering system for S/MM#4)" utilizing silicon semi-conductor detectors and the other detectors are conventional passive detectors of thermoluminescence dosimeters (TLDs) and CR-39 plastic track detectors. The main contribution to dose equivalent for particles with LET > 5.0 keV/micrometer (IML-2) and LET > 3.5 keV/micrometer (S/MM#4) is seen to be due to galactic cosmic rays (GCRs) and the contribution of the South Atlantic Anomaly (SAA) is less than 5% (IML-2: 28.5 degrees x 300 km) and 15% (S/MM#4: 51.6 degrees x 400 km) in the above RRMD LET detection conditions. For the whole LET range (> 0.2 kev/micrometer) obtained by TLDs and CR-39 in these two typical orbits (a small inclination x low altitude and a large inclination x high altitude), absorbed dose rates range from 94 to 114 microGy/day, dose equivalent rates from 186 to 207 microSv/day and average quality factors from 1.82 to 2.00 depending on the locations and directions of detectors inside the Spacelab at the highly protected IML-2 orbit (28.5 degrees x 300 km), and also, absorbed dose rates range from 290 to 367 microGy/day, dose equivalent rates from 582 to 651 microSv/day and average quality factors from 1.78 to 2.01 depending on the dosimeter packages around the RRMD-II "Detector Unit" at the S/MM#4 orbit (5l.6 degrees x 400km). In general, it is seen that absorbed doses depend on the orbit altitude (SAA trapped particles contribution dominant) and dose equivalents on the orbit inclination (GCR contribution dominant). The LET distributions obtained by two different types of active and passive detectors, RRMDs and CR-39, are in good agreement for LET of 15 - 200 kev/micrometer and difference of these distributions in the regions of LET < 15 kev/micrometer and LET > 200 kev/micrometer can be explained by considering characteristics of CR-39 etched track formation especially for the low LET tracks and chemical etching conditions.  (+info)

Comparative study of effects of artificial electron donors on the AT-band of photosystem II thermoluminescence. (8/93)

Extraction of the Mn-cluster from photosystem II (PS II) inhibits the main bands of thermoluminescence and induces a new AT-band at -20 degrees C. This band is attributed to the charge recombination between acceptor QA- and a redox-active histidine residue on the donor side of PS II. The effect of Mn(II) and Fe(II) cations as well as the artificial donors diphenylcarbazide and hydroxylamine on the AT-band of thermoluminescence was studied to elucidate the role of the redox-active His residue in binding to the Mn(II) and Fe(II). At the Mn/PS II reaction center (RC) ratio of 90 : 1 and Fe/PS II RC ratio of 120 : 1, treatment with Mn(II) and Fe(II) causes only 60% inhibition of the AT-band. Preliminary exposure of Mn-depleted PS II preparations to light in the presence of Mn(II) and Fe(II) causes binding of the cations to the high-affinity Mn-binding site, thereby inhibiting oxidation of the His residue involved in the AT-band formation. The efficiency of the AT-band quenching induced by diphenylcarbazide and hydroxylamine is almost an order of magnitude higher than the quenching efficiency of Mn(II) and Fe(II). Our results suggest that the redox-active His is not a ligand of the high-affinity site and does not participate in the electron transport from Mn(II) and Fe(II) to YZ. The concentration dependences of the AT-band inhibition by Mn(II) and Fe(II) coincide with each other, thereby implying specific interaction of Fe(II) with the donor side of PS II.  (+info)