Modified Monte Carlo program for SAND-II with solution weighting and error analysis

Oster, C.A.; McElroy, W.N.; Simons, RL; Lippincott, E.P.; Odette, G.R.

doi:10.2172/7246920

Cited by 6 publications

(2 citation statements)

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“…By using T k (0) measured by TLDs, T k (∞) of nine TLD positions were obtained from equation (3). The cumulated activities of nine source organs, Ã-vector, were then calculated through an inverse transformation of equation ( 4) by utilizing a slightly modified SAND-II unfolding code (Oster et al 1976) as described in our previous study (Nakamura et al 1998) based on the successive iteration method. This unfolding method starts from the initial guess values Ã(0)…”

Section: Cumulated Activities Of Source Organsmentioning

confidence: 99%

Internal absorbed dose estimation by a TLD method for -FDG and comparison with the dose estimates from whole body PET

et al. 1999

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The thermoluminescent dosimeter (TLD) method has been proposed as a useful tool for estimating internal radiation absorbed dose in nuclear medicine. An efficient approach to verify the accuracy of the TLD method has been performed in this study. Under the standard protocol for 2-[F-18]fluoro-2-deoxy-D-glucose (18F-FDG), whole body PET experiments and simultaneous body surface dose measurements by TLDs were performed on six normal volunteers. By using the body surface dose measured with TLDs, the cumulated activities of nine source organs were estimated with a mathematical unfolding technique for three different initial guesses. The accuracy of the results obtained by the TLD method was investigated by comparison with the actual cumulated activity of the same source organs measured by whole body PET. The cumulated activities of the source organs obtained by the TLD method and whole body PET show a significant correlation (correlation coefficient, r > 0.98, level of confidence, p < 0.001) with each other. The mean effective doses in this study are 3.2 x 10(-2) mSv MBq(-1) obtained from the TLD method and 2.9 x 10(-2) mSv MBq(-1) obtained from the whole body PET. Good agreement between the results of the TLD method and whole body PET was observed.

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Section: Cumulated Activities Of Source Organsmentioning

confidence: 99%

Internal absorbed dose estimation by a TLD method for -FDG and comparison with the dose estimates from whole body PET

et al. 1999

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“…The SAND-2 code cannot give the errors of unfolded values, so they were estimated using the modified Monte Carlo program for SAND-2 with error analysis (Oster et al 1976).…”

Section: Estimation Of Cumulated Activity By Unfoldingmentioning

confidence: 99%

Estimation of organ cumulated activities and absorbed doses on intakes of several labelled radiopharmaceuticals from external measurement with thermoluminescent dosimeters

et al. 1998

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We have developed a method for obtaining the cumulated activities in organs from radionuclides, which are injected into the patient in nuclear medicine procedures, by external exposure measurement with thermoluminescent dosimeters (TLDs) which are attached to the patient's body surface close to source organs to obtain information on body-surface doses. As the surface dose is connected to the cumulated activities in source organs through radiation transmission in the human body which can be estimated with the aid of a mathematical phantom, the organ cumulated activities can be obtained by the inverse transform method. The accuracy of this method was investigated by using a water phantom in which several gamma-ray volume sources of known activity were placed to simulate source organs. We then estimated by external measurements the organ cumulated activities and absorbed doses in subjects to whom the radiopharmaceuticals 11C-labelled Doxepin, 11C-labelled YM09151-2 and 11C-labelled Benzotropin were administered in clinical nuclear medicine procedures. The cumulated activities in the brain obtained with TLDs for Doxepin and YM09151-2 are 63.6 +/- 6.2 and 32.1 +/- 12.0 kBq h MBq-1 respectively, which are compared with the respective values of 33.3 +/- 9.9 and 23.9 +/- 6.2 kBq h MBq-1 with direct PET (positron emission tomography) measurements. The agreement between the two methods is within a factor of two. The effective doses of Doxepin, YM09151-2 and Benzotropin are determined as 6.92 x 10(-3), 7.08 x 10(-3) and 7.65 x 10(-3) mSv MBq-1 respectively with the TLD method. This method has great advantages, in that cumulated activities in several organs can be obtained easily with a single procedure, and the measurements of body surface doses are performed simultaneously with the nuclear medicine procedure, as TLDs are too small to interfere with other medical measurements.

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Unfolding Techniques for Activation Detector Analysis

Routti¹,

Sandberg²

1980

Computer Techniques in Radiation Transport and Dosimetry

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Activation detectors are widely used in measurements of radiation fields. In particular, the energy dependent radiation spectrum or integral quantities, such as the total flux, dose rate or reaction rates, are of interest in these measurements.Activation detectors do not directly yield the quantities of interest. Solving the radiation spectrum from measured activities requires unfolding or deconvolution. No unique solutions typically exist and prior knowledge is also applied to obtain physically meaningful solutions.Prior knowledge available depends on the application. In reactor neutron spectroscopy theoretical estimates for the shape of the spectrum are available and the unfolding problem may even be reduced to modifying a trial spectrum to match the measured activities. For accelerators or cosmic radiation spectra good trial spectra are often not available, and more general unfolding methods must be used.Dose rate and reaction rates can be calculated from unfolded spectra or, in some cases, directly from measurements. is the unknown distribution, K(E' ,E) is the known kernel or resolution function,is the measured response, and E (E') is the uncertainty.With discrete activation detectors eq. ( 1 ) reduces to A. is the saturation activity of detector 1 E.is the uncertainty of activity A. , 1 1 m is the number of detectors.i,For numerical solution the continuous energy variable is made discrete. Numerical quadrature transforms eq. ( 2 ) to a group ofor in matrix form,where n 1S the number of discrete energy points,is the cross section of reaction i at 1J J 1 J energy point E. multiplied by quadrature weight w .. J J UNFOLDING TECHNIQUES FOR ACTIVATION DETECTOR ANALYSIS 391Nonuniqueness of the Solution Even without uncertainties, E(E'), eq. ( 1 ) would have a unique solution only if the kernel K(E' ,E) had no zero eigenvalues.The experimental errors make the problem of nonuniqueness even worse.Suppose that ¢(E) were a unique solution of eq. ( 1 ) with E(E') = O.There might then exist a number of functions ~(E) for whichand each of functions ¢(E) + ~(E) satisfies eq. ( 1 ) Especially when n > m,the unfolding problem is ill-conditioned in the sense that small changes in the measured responses may cause large relative errors in the solution. Hence, special methods have been developed for unfolding activation measurements. Generally they make use of prior knowledge of the spectrum, such as a trial spectrum to which the solution is tied in some way, or smoothness and nonnegativity conditions. Different KernelsThe choice of the best unfolding method depends on the detector kernel. Problems can be classified as few channel and many channel unfolding problems according to the number of measured responses.Activation detectors typically lead to few channel problems with up to about 10-30 measured responses and 20-100 energy points. In some ... Some codes are oriented to specific apFlications while others can be flexibly used for various problems. Functional RepresentationsIn some cases analytical formulae with a few unknow...

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Modified Monte Carlo program for SAND-II with solution weighting and error analysis

Cited by 6 publications

References 0 publications

Internal absorbed dose estimation by a TLD method for -FDG and comparison with the dose estimates from whole body PET

Internal absorbed dose estimation by a TLD method for -FDG and comparison with the dose estimates from whole body PET

Estimation of organ cumulated activities and absorbed doses on intakes of several labelled radiopharmaceuticals from external measurement with thermoluminescent dosimeters

Unfolding Techniques for Activation Detector Analysis

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