Developing an analytical approach to dose quantification based on the Cerenkov light detection in radionuclide therapy

Background: Targeted treatment with radionuclides is one of the promising methods for the treatment of metastases. In TRT, there is a need for methods to quantify the dose. Unfortunately, gamma camera devices cannot be used for beta emitter radioisotopes. More recently, Cerenkov radiation has been proposed to determine the activity of the radionuclides. But, quantification of doses using this radiation is still a challenge. In this work, a mathematical method is presented to examine the relationship between dose and Cerenkov light. In this regard, the doses and the number of emitted photons are calculated for 6 beta-emitter radionuclides, and their relationship is modeled.Methods: The beta-emitter radionuclides Y-90, P-32, Sm-153, Re-186, Sr-89, Re-188, which have an energy of [0.808-2.3] MeV, with an activity of 0.1 MBq were considered. The photons generated by the Cerenkov mechanism were calculated using the Frank-Tamm equation. The environment was considered water. To calculate the range, the experimental relationship was used. The effect of the scattering and absorption of the photons were ignored. The average particle energy was used. For photon counting, an ideal detector with a surface area of 25 cm2 was placed at a distance of 5 cm from the surface of the water. The doses for a sphere equivalent to the Y-90 range was calculated theoretically and also by MCNPX simulation. All calculations were performed using MATLAB software and Bland-Altman test was used for statistical analysis. Results: For energies higher than 1 MeV, the relationship between the doses and photons resulting from the Cerenkov phenomenon, with a confidence of more than 95%, was linearly estimated. The difference between the calculated photons, on average, were about 20% of the reported amounts in the paper. The difference between Dose values for analytical and simulation are less than 1%.Conclusion: Quantification of the dose in certain conditions and assuming the use of the average beta energy was done. It was shown that for high-energy radionuclides, with a confidence level of 95%, it is possible to estimate the dose through the photons recorded.

کلیدواژه ها:

Cerenkov light ، Targeted Radionuclide Therapy (TRT) ، Dose quantification ، Analytical method