An alternative method for tracking a radioactive particle inside a fluid

• A practical but general method was developed to reconstruct successive positions of a radioactive particle using the EM algorithm.
• This method permits to find the optimum voxel containing the particle after few iterations of the algorithm.
• The proposed method can track the movement of the particle with a maximum relative error equal to 7.8%.
• We can track the particle with accuracy suitable for each application varying detectors' number in the experimental setup.

The proposed tracking method describes the trajectory of a radioactive particle moving in a fluid as a sequence of small cubic cells occupied by successive particle positions. In addition, the EM reconstruction algorithm was applied to get the image of the unique cell which had the greatest probability to contain the particle at a given time of a test. Next, this information was useful to calculate the coordinates and velocities of the particle at that time. The method was tested in laboratory using a gamma radiation detection system, the radioisotope 198Au and a mixer. According to the results, the maximum deviation found between theoretical and experimental values of the average rotating period was less than 8% and the particle’s reconstructed trajectories are representative of its real movement. Thus, a paradigm shift permitted us to begin the development of an alternative method to solve the complex problem of tracking the movement of a radioactive particle inside an opaque unit.