air kerma


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air Kerma

The amount of Kerma in a specified mass of air; measured in Gray (Gy); for x-rays with energies less than 300 kiloelectronvolts (keV), 1 Gy = 100 rad. In air, 1 Gy of absorbed dose is delivered by 114 roentgens (R) of exposure.

air kerma

The kerma in an air mass, measured in grays.
See also: kerma
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A one-way ANOVA is used to analyze the effect of BMI and age on the measured outcomes, while for the nonnormal variables of air kerma, DAP, and fluoroscopy time, a Kruskal-Wallis H test is used.
For calculation, the maximum possible activity of 1.47 GBq per patient was used, along with the factor of air Kerma rate constant for the Tcm99 from Table 1.
Since the incident air kerma to be measured is generally only slightly higher than background levels, the standards and guidance documents in Table 1 generally recommend, for sensitivity, using a largevolume, free-air (thin-walled) ionization chamber (IC) with a high-quality electrometer with 0.1 pC resolution for the charge collection.
Units must produce at least 21 mGy air kerma (2400 mR) within a 3-second period to meet the amended final requirement.
These standards are based on the realization of air kerma produced by the sources in question using free-air chambers (FACs).
The results were compared at the same amount of air kerma (exposure) at the imaging plate when possible.
Air kerma calibration coefficients for a reference class ionization chamber from narrow x-ray spectra and cesium 137 gamma-ray beams were compared between the National Institute of Standards and Technology (NTST) and the Kenya Bureau of Standards (KEBS).
Key words: air kerma; free-air ionization chamber; mammography qualities; primary standard; reference radiation qualities; x-ray calibration; x-rays.
The Wide-Angle Free-Air Chamber (WAFAC) is specially designed to realize air kerma from a single-seed source emitting photons with energies up to about 40 keV, and is now used to measure the wide variety of seeds used in prostate-cancer therapy that has appeared in the last few years.
national primary standard for air kerma (and exposure) for gamma rays from [.sup.60]Co, [.sup.137]Cs, and [.sup.192]Ir sources.
Keywords: air kerma; free-air ionization chamber; primary standard; reference radiation qualities; medium-energy x rays; x-ray calibration.
For this presentation, those units, usually in exposure terms, i.e., mr or mr per unit time (now termed mR or mR per unit time), have been converted to air kerma rate units, i.e., nGy/h, by evaluating the period of the measurement, if necessary, and introducing a time factor.