PubMed · 3201007
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
K Katoh. 1988. [Practical doses for radiation control].. https://doi.org/10.3769/radioisotopes.37.10_580
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
CT radiation output (mGy mAs-1) measured free-in-air on axis is required for compliance testing protocols. It can also be used as an input parameter for computer programs for patient dose assessment for a range of CT examinations. Output correction factors have been investigated as a function of collimation width for two chambers; an in-beam, 6 cc general diagnostic chamber, and a 3 cc pencil CT chamber. For irradiation by a fan beam perpendicular to the chamber axis, a correction factor given by the ratio, chamber active length to beam collimation width, is applicable to within +/- 5% of a measured ratio for the pencil CT chamber. However, this is not the case for the short 6 cc thimble chamber where an exponential function was found to fit the data to within similar limits. It is recommended that a pencil chamber be used for determining radiation output in air for a CT scanner. For a given scan condition static measurements are only required, obviating a need for sequential movements of an occluded small volume chamber to sample a radiation profile.
The concentrations of uranium isotopes and their decay products 226Ra, 222Rn, 210Pb and 210po have been analyzed in the mineral spring waters of a highly radioactive region of Brazil: Aguas da Prata. This region is located in the Poços de Caldas Plateau, one of the largest weathered alkaline intrusions in the world. Dose calculations were performed to evaluate the relative importance of these radionuclides in the exposure of the local population to radiation. Based upon concentrations measured in all the springs available, effective doses per year varying from 1.4 x 10(-4) mSv year(-1) for 238U to 5.1 x 10(-2) mSv year(-1) for 222Rn were observed. The doses from the ingestion of 222Rn, 210Po and 210Pb are of the same order of magnitude, and therefore these radionuclides are the most critical as far as the consumption of these waters is concerned.
BACKGROUND: In 1995, Eastman Kodak Company (Rochester, N.Y.) marketed the Ektavision Extraoral Imaging Film and Screen System. It produced high-resolution images by keeping the light emitted by intensifying screens from "punching through" one emulsion layer on the film to another. OBJECTIVES: The objectives of the experiment were (1) to compare the sensitometric properties of the Ektavision system to its predecessor, the T-Mat/RA system and (2) to determine whether films and screens of the Ektavision and the T-Mat/RA systems could be interchanged without clinically changing the sensitometric properties. Ektavision and Lanex Regular intensifying screens were used in combination with Ektavision, T-Mat G/RA, T-Mat L/RA, and T-Mat H/RA films. RESULTS: The results showed that the Ektavision film was slightly slower than the T-Mat G/RA film no matter what type of screen was used. The type of screen used had little effect on inherent contrast or exposure latitude. The Ektavision film had approximately similar inherent contrast as the T-Mat G/RA film but less than that of the T-Mat H/RA film; its latitude was less than that of the T-Mat L/RA film. The manufacturer does not recommend combining T-Mat/RA film with Ektavision screens or Lanex Regular screens with Ektavision film because of a possible reduction in image resolution. But this mismatch did not clinically affect inherent contrast and exposure latitude; however, film speed was slightly affected. CONCLUSIONS: The Ektavision system is the result of advanced technology that produces images of high resolution. The high-resolution Ektavision film is slightly slower than the T-Mat G/RA film but is equivalent to it in its contrast and latitude. Therefore when changing from the combination of T-Mat/RA film plus Lanex Regular screens to that of Ektavision film plus Ektavision screens, a slight increase in x-radiation exposure should be made.