Taurus Base enables users to perform basic internal dosimetry calculations with an easy-to-understand user interface. The software is designed to handle the analysis of intake scenarios and to assist in dose assessments for acute and/or chronic inhalation, ingestion, or injection exposures.

Function

Taurus Base enables users to perform prospective calculations to predict bioassay quantities, equivalent organ doses, and effective doses from user defined intakes, and perform retrospective calculations to estimate the intake and resulting dose from measurements of activity in the body and/or excreta.

Input

The intake scenario is defined with parameters the user selects:

  • Nuclide (all 880 nuclides in ICRP-OIR series).
  • Deposition parameters (aerosol particle size and occupational breathing classes).
  • Absorption parameters ('ICRP OIR series defaults' or 'User-defined' values to be used with ICRP respiratory and alimentary tract models).
  • Systemic, Alimentary tract and Respiratory tract (only the ICRP-OIR default transfer rates are available in Taurus Base).
  • Up to twenty intake regimes, each defined by its:
    • Route of intake (inhalation, ingestion, and injection)
    • Acute or chronic mode of intake and start/end time of intake

Bioassay quantities can be specified for up to a total of 2000 measurements with a choice of the monitoring nuclide (i.e. the parent nuclide or one of the progeny).


+ Whole body + Blood + Kidneys
+ Urine + Faeces + Liver
+ GI tract + Lungs + Thyroid
+ Skeleton

The inputs can be saved in a Taurus file that can be loaded for later analysis.

Results

The calculation results are presented in graphical and tabulated forms:

  • Plots of bioassay predictions, measurements, errors, and the maximum-likelihood fit to them.
  • Bioassay predictions in tabulated form.
  • The effective, equivalent, and total doses, with contributions from each intake regime in tabulated form.

The results can be saved in an HTML report containing the intake regime(s) parameters, graphical plots, and tables.


Further information

Multiple intake regimes

An intake regime defines both the mode of intake (inhalation of aerosols or vapours, ingestion, or injection) and the time of intake (e.g., an acute intake on a certain day, or a chronic intake between two time points). This option enables the user to deal with up to 20 separate intake regimes simultaneously. When calculating doses or predicting bioassay quantities, the software automatically includes the contribution from each intake. It is also possible to assign different model parameter values separately to each intake regime if required. This option also works during intake estimation and so up to 20 intakes can be fitted to the measurement data simultaneously.

Multiple bioassay types

Taurus enables the user to fit the intake to different bioassay types simultaneously. The base version can manage 10 different bioassay quantities (whole body, lungs, liver, skeleton, GI tract, kidneys, thyroid and blood, urinary and faecal excretion). This can be used in conjunction with the multiple intake regimes option to enable multiple intakes to be fitted to multiple bioassay data types simultaneously.

Measurement errors and fitting

The measurement uncertainty can be assigned as standard deviation for normally distributed data and as geometric standard deviation or 'scattering factor' for lognormally distributed data. Measurements below the limit of detection (LOD) can be labelled accordingly and treated as censored data by the fitting routine. Taurus estimates radionuclide intakes from bioassay measurements using the well proven maximum-likelihood fitting module previously used in IMBA, which can produce robust estimates of multiple intakes using several types of bioassay data, including censored observations.

Statistics

The user can view useful statistical information immediately after fitting intakes to measurement data. It calculates the chi-square value for each bioassay type, the total chi-square, and the associated P value (probability of obtaining a chi-square greater than or equal to the calculated value by random chance). It calculates the autocorrelation coefficient for each bioassay, the total autocorrelation coefficient, and the associated P value (the probability of obtaining an autocorrelation greater than or equal to the calculated value by random chance).


Taurus includes the following features. This functionality is now applicable to all radionuclides addressed in ICRP Occupational Intakes of Radionuclides Parts 1-5:

  • Calculate the best estimate of the intake - from a single exposure event (intake regime), based on the user-specified intake scenario
  • Analyse any of the above types of bioassay measurement - for a given indicator radionuclide
  • Specify the times of each bioassay measurement
  • Specify the collection period for each urine and faecal sample (in days)
  • Define absorption parameter values - or choose from the International Commission on Radiological Protection (ICRP) recommended values.
  • Perform calculations for both Reference Worker light activity and heavy activity
  • ICRP biokinetic models for each element
  • ICRP Publication 107 radiation decay database
  • The ability to deal with chelated intakes by marking and excluding treatment-enhanced excretion data from the intake assessment
  • Apply the maximum likelihood fitting method - to deal with:
    • Data recorded as less than the limit of detection (< LOD)
    • Explicit error on each data point
    • Normal or lognormal error distributions up to 2000 data points
  • Exclude unreliable data points from the fitting process - but not from the data record - and mark these as such in the associated graph of the data
  • Calculate the committed equivalent dose to each organ or tissue - and the effective dose - for an indicator radionuclide
  • Calculate bioassay quantities over specified time intervals - for the design of future monitoring programs
  • View bioassay data (with error bars and the fitted bioassay function) graphs using plotting software
  • View tables of bioassay data and predicted bioassay quantities
  • Copy data to-and-from spreadsheets and other Windows applications
  • Copy data to-and-from an ASCII file
  • Create a comprehensive report file containing administrative details and input options
  • Save all input options to a file which can be loaded for future use