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At least 1,495 records · Page 83Linked to original sources
PubMed2001

Radiation protection using Martian surface materials in human exploration of Mars.

To develop materials for shielding astronauts from the hazards of GCR, natural Martian surface materials are considered for their potential as radiation shielding for manned Mars missions. The modified radiation fluences behind various kinds of Martian rocks and regolith are determined by solving the Boltzmann equation using NASA Langley's HZETRN code along with the 1977 Solar Minimum galactic cosmic ray environmental model. To develop structural shielding composite materials for Martian surface habitats, theoretical predictions of the shielding properties of Martian regolith/polyimide composites has been computed to assess their shielding effectiveness. Adding high-performance polymer binders to Martian regolith to enhance structural properties also enhances the shielding properties of these composites because of the added hydrogenous constituents. Heavy ion beam testing of regolith simulant/polyimide composites is planned to validate this prediction. Characterization and proton beam tests are performed to measure structural properties and to compare the shielding effects on microelectronic devices, respectively.

Cosmic Radiation↗
PubMed2003

A radiation protection program prospectus based on the collection of 10 years of key performance indicator data.

In 1992, the University of Texas Health Science Center at Houston Radiation Safety Program began assembling data on a monthly basis that described various program activities. At the end of calendar year 2002, a decade of data had been collected, so the information was summarized into a novel program prospectus, displaying various indicator parameters in a format similar to that used in a commercial enterprise prospectus provided to potential investors. The consistent formatting of the data afforded a succinct and easily digestible snapshot of program activities and trends. Feedback from various program stakeholders, even those unschooled in radiation safety matters, was overwhelmingly positive. The prospectus aided in communicating the scope of work undertaken by the program, and has helped maintain program support, even in challenging economic times. The data summary is also proving to be useful in making future projections regarding program needs.

Academic Medical Centers↗
PubMed2002

No radiation protection reasons for restrictions on 14C urea breath tests in children.

Traditional (14)C urea breath tests are normally not used for younger children because the radiation exposure is unknown. High sensitivity accelerator mass spectrometry and an ultra-low amount (440 Bq) of (14)C urea were therefore used both to diagnose Helicobacter pylori (HP) infection in seven children, aged 3-6 years, and to make radiation dose estimates. The activity used was 125 times lower than the amount normally used for older children and 250 times lower than that used for adults. Results were compared with previously reported biokinetic and dosimetric data for adults and older children aged 7-14 years. (14)C activity concentrations in urine and exhaled air per unit administered activity for younger children (3-6 years) correspond well with those for older children (7-14 years). For a child aged 3-6 years who is HP negative, the urinary bladder wall receives the highest absorbed dose, 0.3 mGy MBq(-1). The effective dose is 0.1 mSv MBq(-1) for the 3-year-old child and 0.07 mSv MBq(-1) for the 6-year-old child. For two children, the 10 min and 20 min post-(14)C administration samples of exhaled air showed a significantly higher amount of (14)C activity than for the rest of the children, that is 6% and 19% of administered activity exhaled per hour compared with 0.3-0.9% (mean 0.5%) of administered activity exhaled per hour indicating that these two children that is were HP positive. For a 3-year-old HP positive child, absorbed dose to the urinary bladder wall was 0.3 mGy MBq(-1) and effective dose per unit of administered activity was 0.4 mSv MBq(-1). Using 55 kBq, which is a normal amount for older children when liquid scintillation counters are used for measurement, the effective dose will be approximately 6 micro Sv to a 3-year-old HP negative child and 20 microSv to a HP positive child. Thus there is no reason for restrictions on performing a normal (14)C urea breath test, even on young children.

Adolescent↗
PubMed1998

Non-coherent near infrared radiation protects normal human dermal fibroblasts from solar ultraviolet toxicity.

The sun is the most important and universal source of non-ionizing radiation shed on human populations. Life evolved on Earth bathed by this radiation. Solar UV damages cells, leading to deleterious conditions such as photoaging and carcinogenesis in human skin. During the process of evolution, the cells selected dark- and light-dependent repair mechanisms as a defence against these hazardous effects. This study describes the induction by non-coherent infrared radiation (700-2000 nm), in the absence of rising temperature, of a strong cellular defense against solar UV cytotoxicity as well as induction of cell mitosis. Blocking mitoses with arabinoside-cytosine or protein synthesis with cycloheximide did not abolish the protection, leading to the conclusion that this protection is independent of cell division and of protein neosynthesis. The protection provided by infrared radiation against solar UV radiation is shown to be a long-lasting (at least 24 h) and cumulatif phenomenon. Infrared radiation does not protect the lipids in cellular membranes against UVA induced peroxidation. The protection is not mediated by heat shock proteins. Living organisms on the Earth's surface are bathed by infrared radiation every day, before being submitted to solar UV. Thus, we propose that this as yet undescribed natural process of cell protection against solar UV, acquired and preserved through evolutional selection, plays an important role in life maintenance. Understanding and controlling this mechanism could provide important keys to the prevention of solar UV damage of human skin.

Cells, Cultured↗
PubMed1994

In vivo radiation protection by nitric oxide modulation.

Drugs that affect blood flow have been shown to be whole body radiation protectors. Using NG-nitro-L-arginine, a specific inhibitor of nitric oxide synthase, and the NO-releasing agent (C2H5)2N[N(O)NO-]Na+ (DEA/NO), we have studied the ability of NO to modulate whole body radiation toxicity in C3H mice. NG-Nitro-L-arginine given to mice between 15 and 60 min prior to radiation afforded significant protection from whole body irradiation, e.g., the estimated whole body irradiation dose required to kill 50% of mice by 30 days after radiation (LD50/30) in mice treated with NG-nitro-L-arginine 60 min before irradiation was 1051 cGy compared with a whole body radiation LD50/30 of 822 cGy in control mice (P < 0.00001). Treatment of mice with DEA/NO prior to whole body irradiation also significantly reduced toxicity; the estimated whole body radiation LD50/30 was 1063 and 945 cGy in mice treated with DEA/NO 10 or 30 min before irradiation, respectively (P < 0.00001 for radiation LD50/30 of either DEA/NO-treated group compared with control). Measurement of [14C]etanidazole binding to bone marrow demonstrated that DEA/NO and NG-nitro-L-arginine exacerbated bone marrow hypoxia. Perturbations of NO levels have profound effects on in vivo radiosensitivity of normal tissues. We hypothesize that alterations in regional blood flow may underlie the changes in radiosensitivity that we have observed.

Amino Acid Oxidoreductases↗
PubMed1993

The application of EPR dosimetry for radiotherapy and radiation protection.

This paper reports the first clinical trial of the application of the continuous wave electron paramagnetic resonance (CW-EPR) spectrum of alanine to determine the radiation dose received by a patient. The results of these measurements are compared with those obtained using thermoluminescent dosimetry (TLD) simultaneously. The 9 GHz EPR measurements were made at 13 degrees C. The time stability of the radiation induced radicals in alanine was confirmed. The fractionated radiation doses received in the clinical trial were determined from a calibration curve (linear regression coefficient r = 0.9995) obtained by irradiating L-alanine samples with 60-800 cGy doses using cobalt 60 gamma rays obtained from an Eldorado 8 Cobalt 60 unit at a rate of approximately 60 cGy/min. It is shown that the absorbed dose in tissue-equivalent material can be determined using EPR spectroscopy with an accuracy of approximately 3% at low dose levels (60 cGy) whereas the error using TLD is approximately 5% and that this method of dose determination is preferable to the present TLD method because it is simpler and more accurate.

Alanine↗
PubMed1980

Measurements on the radiation protection of patients irradiated with an 18-MeV electron linear accelerator.

In order to quantify the influence of some physical and geometrical treatment parameters on the stray radiation dose absorbed by patients undergoing radiotherapy on an 18-MeV linear accelerator, dose distributions were measured in a polystyrene phantom by means of LiF-dosimeters. For 10-MV X-rays, 6-MeV and 18-MeV electron radiation dose profiles, depth dose and isodose curves were obtained at various field sizes and treatment couch positions. By covering the phantom with 1 or 2 mm thick lead sheets a remarkable dose reduction was found. A two-exponential expression was derived to estimate stray radiation dosage in routine radiotherapy. The validity of the calculation method was demonstrated by comparing the gonadal load measured in an Alderson phantom with the calculated data.

Lead↗