Experimental study of medical isotopes <sup>62,64</sup>Cu and <sup>68</sup>Ga production using intense picosecond laser pulse
Zongwei Cao, Wei Qi, Haoyang Lan, Bo Cui, Xiaohui Zhang, Zhigang Deng, Zhimeng Zhang, Guanlin Wang, Liang-Qi Zhang, Xiankai Li, Yun Yuan, Xinxiang Li, Zongqing Zhao, Wen Luo, Weimin Zhou
Abstract
Abstract Radioisotopes are indispensable agents in medical diagnosis and treatment, among which copper-62, 64 ( 62,64 Cu) and gallium-68 ( 68 Ga) are medical isotopes widely used in positron emission tomography (PET) imaging. Experiments that generate these radioisotopes via laser-induced photonuclear reactions were performed on the XingGuangIII laser facility of the Laser Fusion Research Center in Mianyang. High-charge ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>Q</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> ∼ 40 nC) MeV electron ( e − ) beams were generated with 100 terawatts, picosecond laser pulses. The e − beams were then impinged on a metal stack composed of Ta foil and activation plates (natural Cu and Ga 2 O 3 ), producing high-energy bremsstrahlung x-rays and medical isotopes 62,64 Cu and 68 Ga, respectively. The characteristic emissions of the produced 62,64 Cu and 68 Ga were detected off-line , and the production yields of 62,64 Cu and 68 Ga were obtained to be of the order of 10 6 per laser shot. For electrons with energy higher than 8 MeV, the dependence of isotope production efficiency (per e − ) on electron temperature ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>T</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> ) is investigated through Geant4 simulations. It is found that the production efficiency increases with the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>T</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> . At <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>T</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> ∼ 10 MeV, the values are 10 −4 for 62 Cu and 2 × 10 − 5 for 68 Ga, respectively. The prospect of producing the medical isotopes 62,64 Cu and 68 Ga are further evaluated using a table-top femtosecond laser system of high repetition. With a repetition rate of 100 Hz, their activity is expected to reach 0.2 GBq for 62 Cu, 0.1 GBq for 64 Cu and 0.05 GBq for 68 Ga, respectively. Such activity would meet the required dose for clinical PET imaging, indicating the great potential to produce medical isotopes with an all-optical, high-repetition laser system.