Praseodymium-142 microspheres for brachytherapy of nonresectable hepatic tumors

Purpose: To perform dosimetric study of ¹⁴²Pr microspheres for the use as a possible choice of radionuclide in microsphere brachytherapy of nonresectable hepatic tumor for faster dose delivery and facilitated dosimetry for quality assurance. Methods and Materials: Dose distributions of ¹⁴²Pr and ⁹⁰Y microspheres within hepatic tumors and blood vessels were calculated using MCNPX2.6 Monte Carlo code. The biological effective doses (BEDs) for ¹⁴²Pr and ⁹⁰Y microspheres were calculated and compared using the linear-quadratic model. Results: Dose distributions due to beta particles were similar for both ¹⁴²Pr and ⁹⁰Y. Total initial activity required to achieve the same total dose of 150Gy at 2cm from the center of the tumor was 0.662 GBq and 0.191 GBq for ¹⁴²Pr and ⁹⁰Y, respectively. For α/β ratio equal to 10Gy, calculated BED values were 301.0 and 194.7 for ¹⁴²Pr and ⁹⁰Y, respectively, considering a total physical dose of 150Gy. Conclusions: Total dose delivery and dose distributions for both ¹⁴²Pr and ⁹⁰Y within tumors and blood vessels were obtained and compared. Shorter half-life of ¹⁴²Pr is an advantage, enabling a faster dose delivery. The higher BED found for ¹⁴²Pr implies potential improvement in the treatment effectiveness. ¹⁴²Pr showed to be an attractive option for applications in microsphere brachytherapy.