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Enhancing Nuclear Safety


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OEDIPE Personalised dosimetric evaluation tool

Simulation of anthroporadiametric measurements and the calculation of doses delivered to organs or tissues based on realistic parameters for the contaminated subject

The absorption of radionuclides into the body may result in the exposure of tissues within the human body to ionising radiation. This absorption may be accidental (via a wound, ingestion or inhalation) or deliberate as in the case of nuclear medicine where radionuclides are administered to a patient for diagnostic or therapeutic purposes.

The OEDIPE personalised dosimetric evaluation tool is used to evaluate the received dose following internal exposure, and to display the results in a simple and accurate manner. The results may be displayed in two alternative ways:

  • The characteristics of the radiation emitted by the radionuclides are displayed in the form of a simulated energy spectrum which may be used to calibrate the absorbed activity measurement system and to analyse the experimental spectra obtained by anthroporadiametry.
    This option is particularly useful for estimating accidental contamination.
  • The values of the received internal doses are indicated directly on the MRI (Magnetic Resonance Imaging) or X-ray scan of the patient by superimposing the isodose lines (Figure 1).
    OEDIPE may also assist nuclear medicine practitioners seeking the best compromise between diagnostic or therapeutic effectiveness and minimising the irradiation of healthy tissue within the patient.

A more accurate estimation of accidental contamination

In the event of accidental internal exposure, the first concern is to make a rapid and reliable estimate of the extent, nature and anatomical distribution of the contamination in order to make the best possible decisions regarding treatment. In order to achieve this, both the retained activity and received dose in each type of tissue must be determined.
One of the methods used is to measure experimentally the X and gamma radiation emitted by the contaminant radionuclides within the body. These in vivo measurements are known as anthroporadiametric measurements. Anthroporadiametric systems are traditionally calibrated using mannequins which provide only an approximate representation of the anatomy of a contaminated patient.
The OEDIPE code overcomes these measurement accuracy problems as the spectra generated by the tool may be used to perform a calibration specific to the individual system based on the actual morphology of a real patient. The anthroporadiametric measurements will then provide a more realistic characterisation of the contamination of the patient being examined.

More effective treatment for the patient

Targeted radiotherapy* combines the two concepts of the preservation of healthy tissue and the notion of effective treatment. These two factors may be evaluated by means of a posteriori dosimetric studies. In particular, these can predict the onset of side effects and radiation-induced cancers.
A priori dosimetric studies can also be used to optimise the standard treatment by personalising it. This results in improved therapeutic results while also minimising the associated risk.

*Method of cancer treatment in which the radionuclide is carried by a vector specific to the tumour.

Principle

The original feature of OEDIPE is its ability to build numerical phantoms that are personalised from radiological images (scanner or MRI) of the patient contaminated by the radionuclides. The code associates data from this numerical phantom with the characteristics of the contamination and automatically creates a data file that can be used as input to the MCNPX Monte Carlo particle transport code.
The MCNPX code calculates the energy absorbed by the tissues or emitted outside the body. Following processing of this data, OEDIPE provides the user with the distribution of the activities or doses to the resolution of an individual tissue or organ. The user-friendly graphical interface in OEDIPE presents these results in the form of a spectrum or as data superimposed on the original scanner or MRI image enabling a rapid assessment and interpretation of the results.
A diagram of the architecture is given in Figure 2.

OEDIPE is therefore capable of both simulating anthroporadiametric measurements to improve the calibration of measurement systems and of displaying the dose distribution in a patient in order to aid treatment decisions.

Technical prerequisites

OEDIPE will run on both PCs and Macs. Its simple interface means that only one or two hours of training are needed for users experienced in using the MCNPX codes. It will soon be available for download from a dedicated site.

Historical Background and publications

Historical Background

OEDIPE was developed from the ANTHROPO interface**. This interface was developed in 2000 by the Internal Dosimetry department of the IRSN (SDI) as a tool for calibrating the anthroporadiametric systems used to evaluate internal contamination cases. The first version of OEDIPE, written in PV-Wave®, was a direct extension of dosimetric calculations. A separate module, dedicated to the dosimetric calculations needed for targeted radiotherapy*, was developed in collaboration with group U601 at the INSERM, Nantes.
Unlike earlier versions, the current version of OEDIPE can calculate doses targeted on a single organ and takes account of the temporal distribution of radionuclides within the body. Another important development has been the new graphical interface, especially its ability to superimpose the results of the calculations on patient images. This feature has been made possible by the use of an alternative programming language. The tool was ported to IDL® (Interactive Data Language) by the company RSI® under the direction of the IRSN. This multi-use language has made it possible for OEDIPE to run under all operating systems (Windows, Mac OSX, Linux, etc).


Publications on this topic

CHIAVASSA S, AUBINEAU-LANIECE I, BITAR A, FERRER L, LISBONA A, BARBET J, FRANCK D, JOURDAIN JR, BARDIES M (2006). Validation of a personalised dosimetric evaluation tool (OEDIPE) for targeted radiotherapy based on the Monte Carlo MCNPX code. Phys. Med. Biol, 51 :601-616.

CHIAVASSA S, BARDIES M, GUIRAUD-VITAUX F, BRUEL D, JOURDAIN JR, FRANCK D, AUBINEAU-LANIECE I (2005). OEDIPE: A personalised dosimetric tool associating voxel-based models with MCNPX. Cancer Biotherapy and Radiopharmaceutical, 20(3):325-332.

PIERRAT N, DE CARLAN L, CAVADORE D, FRANCK D (2005). Application of Monte Carlo calculation for the virtual calibration of a low-energy in vivo counting system. IEEE TNS, 52(5):1353-1358.

**BORISSOV N, FRANCK D, DE CARLAN L, LAVAL L (2002). A new graphical user interface for fast construction of computation phantoms and MCNP calculations: Application to calibration of in vivo measurement system. Health Phys, 83(2):272-279.


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Figure-1-Superimposition-of-isodose-lines-on-MRI-images-in-the-case-of-a-wound-contamination-to-the-finger

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