17 Matching Results

Search Results

Advanced search parameters have been applied.

Practical methods of dose reduction to the bladder wall. [Radionuclide administration to patients]

Description: The radiation dose to the bladder wall following the administration of radionuclides to patients can be reduced by a factor between 25 percent and 75 percent when the effective half-life for the radioactivity entering the urine is two hours or less. A significant but smaller reduction in dose to the gonads may also be achieved in situations where the major fraction of the administered activity is rapidly excreted in the urine. This reduction in dose is achieved by ensuring that the patient has between 50 and 150 ml of urine in his bladder when the radioactivity is injected, and is encouraged to void between one and two hours after the activity has been administered. The interrelationship of voiding schedule, effective half-life, initial urine volume, and demand urination has been analyzed in these studies. In addition, the significance of the rate of urine production and volume of urine in the bladder on the radiation dose to the bladder is demonstrated. (auth)
Date: January 1, 1976
Creator: Smith, E. M. & Warner, G. G.
Partner: UNT Libraries Government Documents Department

Experimental validation of Monte Carlo calculations for organ dose

Description: The problem of validating estimates of absorbed dose due to photon energy deposition is examined. The computational approaches used for the estimation of the photon energy deposition is examined. The limited data for validation of these approaches is discussed and suggestions made as to how better validation information might be obtained. (ACR)
Date: January 1, 1980
Creator: Yalcintas, M.G.; Eckerman, K.F. & Warner, G.G.
Partner: UNT Libraries Government Documents Department

Distribution of dose within the body from a photon emitter present in an organ

Description: A dosimetric system was developed which provides estimates of mean radiation dose to organs from photon sources distributed uniformly in one or more organs. Although the sources of photons are assumed to be distributed uniformly, it is not true that dose from these photons is uniformly distributed. In particular, when a source of photons is located in a particular organ, nearby tissues will be irradiated at doses which decrease markedly with distance from the source. The mean dose may give a poor approximation to the actual dose if the tissues over which dose is averaged are extensive, for example, the remainder of the body. A set of enveloping organs was devised for liver, lungs, etc., which give mean dose at distances from zero to one centimeter from the source organ, from one to two centimeters, etc. These can be used to yield estimates of the extent of inhomogeneity of the dose distribution from a source of photons located in the source organ.
Date: January 1, 1977
Creator: Snyder, W. S.; Ford, M. R. & Warner, G. G.
Partner: UNT Libraries Government Documents Department

Evaluation of the distribution of absorbed dose in child phantoms exposed to diagnostic medical x rays

Description: The purpose of this study was to determine, by theoretical calculation and experimental measurement, the absorbed dose distributions in two heterogeneous phantoms representing one-year- and five-year-old children from typical radiographic examinations for those ages. Theoretical work included the modification of an existing internal dose code which uses Monte Carlo methods to determine doses within the Snyder-Fisher mathematical phantom. A Ge(Li) detector and a pinhole collimator were used to measure x-ray spectra which served as input to the modified Monte Carlo codes which were used to calculate organ doses in children. The calculated and measured tissue-air values were compared for a number of organs. For most organs, the results of the calculated absorbed doses agreed with the measured absorbed doses within twice the coefficient of variation of the calculated value. The absorbed dose to specific organs for several selected radiological examinations are given for one-year-old, five-year-old, and adult phantoms.
Date: April 1, 1978
Creator: Chen, W. L.; Poston, J. W. & Warner, G. G.
Partner: UNT Libraries Government Documents Department

Detection of internally deposited actinides. Part IV. Preliminary considerations in the use of large, planar intrinsic Ge detectors

Description: Many inherent advantages are apparent in the use of large planar Ge detectors for the detection, identification, and quantitative assessment of internally deposited actinide nuclides ($sup 238$Pu, $sup 239$Pu, $sup 240$Pu, $sup 242$Pu, $sup 241$Am, $sup 244$Cm, $sup 246$Cm, and $sup 250$Cf). The superior energy resolution in contrast to Phoswich type scintillation detectors, permits isotopic identifications to be made and reduces ambiguities introduced by natural and human background effects. Preliminary studies indicate that a 10 cm$sup 2$ x 1.2 cm Ge detector is comparable in detection sensitivity to that of one 125 cm$sup 2$ Phoswich detector. Some preliminary considerations and evaluations, photon transport studies based on Monte Carlo modeling and measurements of absolute L-series X-ray yields in the decay of several actinide nuclides, are presented. (auth)
Date: January 1, 1975
Creator: Bemis, C.E. Jr.; Goans, R.E.; Good, W.M. & Warner, G.G.
Partner: UNT Libraries Government Documents Department

EXAMINATION OF CORROSION SPECIMENS FROM SLURRY BLANKET MOCKUP RUNS SM-6 THROUGH SM-9

Description: Low attack rates (0.1 to 0.5 mpy) were displayed by coupon specimens of type 347 stainless steel, titanium RC-55, and Zircaloy-2 which were exposed for 2877.5 hr in an oxygenated slurry of Th--8% U oxide, 116.5 hr in water, 6.9 hr in 5% HNO/sub 3/, and 4.3 hr in 3% triscdium phosphate during mns SM-6 through SM-9 in the slurry blanket mockup. The leading coupon of type 347 stainless steel showed a slightly higher rate than the other stainless steel ccupons due to entrance effects. Specimens of SA-212-B carbon steel displayed average attack rates of 2.9 mpy. (auth)
Date: May 26, 1960
Creator: Gallaher, R B; Reed, S A & Warner, G G
Partner: UNT Libraries Government Documents Department

Pediatric phantoms for use in dosimetric calculations

Description: Estimating absorbed doses to children from external and internal radiation sources has become important to the nuclear industry and pediatric nuclear medicine. The Medical Physics and Internal Dosimetry Section at ORNL has recently completed the design of mathematical representations of children of ages newborn, 1 year, and 5 years old. These mathematical representations will be referred to as pediatric phantoms. Using these phantoms, relevant energy deposition data have been developed which establish a meaningful model for use in estimating radiation dose to children. (auth)
Date: January 1, 1976
Creator: Shoup, R.L.; Hwang, J.L.; Poston, J.W. & Warner, G.G.
Partner: UNT Libraries Government Documents Department

Mathematical descriptions of a one- and five-year old child for use in dosimetry calculations

Description: Mathematical representations for estimating the absorbed radiation dose from external and internal radiation sources of a one-year old and a five-year old human have been designed. The phantoms used consist of head, trunk and leg regions with a skeletal system and twenty-two internal organs, each. The mathematical descriptions of these phantoms have been coded into Fortran computer language for use with a Monte-Carlo photon transport code. This computer code was used to calculate absorbed fractions of energy deposited in different targets organs from a radionuclide deposited uniformly in a source organ. Absorbed dose calculations were performed for two /sup 99m/Tc-labeled pharmaceuticals. Photon absorbed fraction estimates for the pediatric phantoms from Monte-Carlo calculations were combined with biological data to estimate dose distributions in one-year old and five-year old children. (CH)
Date: March 1, 1976
Creator: Hwang, J. M. L.; Shoup, R. L.; Warner, G. G. & Poston, J. W.
Partner: UNT Libraries Government Documents Department

Development and use of a fifteen year-old equivalent mathematical phantom for internal dose calculations. [Radiation dose distributions from /sup 99m/Tc-labeled compounds]

Description: The existence of a phantom based on anatomical data for the average fifteen-year-old provides for a proficient means of obtaining estimates of absorbed dose for children of that age. Dimensions representative of an average fifteen-year-old human, obtained from various biological and medical research, were transformed into a mathematical construct of idealized shapes of the exterior, skeletal system, and internal organs of a human. The idealization for an average adult presently in use by the International Commission on Radiological Protection was used as a basis for design. The mathematical equations describing the phantom were developed to be readily adaptable to present-day methods of dose estimation. Typical exposure situations in nuclear medicine have previously been modeled for existing phantoms. With no further development of the exposure model necessary, adaptation to the fifteen-year-old phantom demonstrated the utility of the design. Estimates of absorbed dose were obtained for the administration of two radiopharmaceuticals, /sup 99m/Tc-sulfur colloid and /sup 99m/Tc-DMSA. (auth)
Date: June 1, 1976
Creator: Jones, R. M.; Poston, J. W.; Hwang, J. L.; Jones, T. D. & Warner, G. G.
Partner: UNT Libraries Government Documents Department

Tabulation of dose equivalent per microcurie-day for source and target organs of an adult for various radionuclides

Description: Data are tabulated on the radiation dose equivalent per microcurie-day for source and target organs of a human adult for 100 radionuclides. These are listed at the end of the volume. Included are several radionuclides where the parent has a daughter radionuclide of physical half-life less than five minutes. In such cases separate S tables are given for the parent and for the daughter as well as a composite table which contains S values for the parent plus S values for the daughter weighted according to the percent decay via the daughter. (CH)
Date: November 1, 1975
Creator: Snyder, W.S.; Ford, M.R.; Warner, G.G. & Watson, S.B.
Partner: UNT Libraries Government Documents Department