Dosimetric Model for the Gastrointestinal Tract

Abstract

A dosimetric model is proposed for the gastrointestinal tract based upon the physiological model of EVE (1966a). A general equation describing the kinetics of linear first order phenomena is applied to obtain the burden of radionuclides or disintegrations in the contents of the various segments of the GI tract. The model gives equations for the calculation of the "dosimetric" average dose equivalent and dose equivalent rate to an entire segment as well as instantaneous values at any location within a given segment as applicable to single or continuous uptakes of parent and daughter radionuclides. Allowance is made for both the absorption of radionuclides as well as mass from the contents of all segments; although, this is not always considered significant. The model permits the determination of the quantities of a radionuclide absorbed into the blood, the ratio of daughter to parent disintegrations and the maximum to average dose equivalent rate in a particular segment of the GI tract. Numerical examples are given for various intakes. Maximum permissible daily ingestion rates of fictitious single soluble and insoluble radionuclides with an effective energy term of unity in all segments are given over a large range of half-lives and are compared to values calculated on the basis of current ICRP recommendations. It is proposed that ratios of the maximum to dosimetric average dose equivalent rate be used to define a distribution factor to take into account relatively high dose rates at particular locations within a segment of the GI tract.All equations have been derived using the more fundamental units of atoms or disintegrations and disintegration rates rather than the more popular pCi and pCi-day units. The former units are more fundamentally related to dosimetric quantities of interest.

Commissioning of the BRIKEN detector for the measurement of very exotic β-delayed neutron emitters

“…The corresponding histogram bin is not included in the fit region. The number of accidental one-neutron counts per detected β is r 1 = 0.006793 (29), much smaller than the values obtained in the May-June 2017 run (see Section 4). This reflects the different background conditions in the two experiments.…”

“…Thus to disentangle the parent and descendant contributions we must fit the histograms using the appropriate solution of the Bateman equations which describe the time evolution of all activities. We use the generic form of the solution proposed in [29] which in our case simplifies to:…”

Evaluation of Simultaneous Fitting Method for \(\beta\)-Decay Half-Lives and \(\beta\)-Delayed Multi Neutron Emission Probabilities Developed for the Briken Experiment

“…The number of decaying nuclei for each linear decay path (as in Fig. 3) can be written explicitly by using a general solution of Batemann equations [17]:…”

“…A generalized flow path involving production and destruction of a member N j in series with corresponding total removal constant λ j and branching ratio b j[17] (a) and an abstract flow diagram of a decay chain considered in the simulation, starting from an implantation of nuclei A Z X, the red arrows indicate the decay channel with delayed neutron emission (b).…”

General Activation and Decay Formulas and Their Application in Neutron Activation Analysis with k0 Standardization

“…The pioneering work of Bateman and Rubinson is fully recognized in the field. General equations have been reported also by others. − The general solution was translated into recursive formulas by Hamawi, later extended by Scherpelz 7 to deal with the problem of identical time constants in a single chain and by Miles 8 for use in complex chains with branching. Blaauw 9 tackled also the problem of backward branching.

1 Sequential activation and decay series.

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