# Highly Enriched Uranium-Free Medical Radioisotope Production Methods: An Integrative Review
## 4 Conclusions and Future Directions
Hence, laser technology development, as well as further studies on LWFA optimization for radioisotope production--by using, for example, artificial intelligence algorithms [114,115]--may enable the development of greener, non-centralized radioisotope production processes. Another possible laser-based radioisotope production method is the target normal sheath acceleration (TNSA) [112,116,117], in which an ultra-intense-ultra-short laser pulse interacts with a solid target. A fraction of the laser's electromagnetic field is transferred to the target, creating plasma and heating electrons to relativistic temperatures. The electrons expand and exit the target, forming a charge separation localized next to its surface. This process generates a strong electrostatic field, perpendicular to the target surface, capable of accelerating ions from the target to several MeVs [118,119]. This ion irradiation can be used to produce radioisotopes via (p,x) and (d,x) reaction routes. The first experimental TNSA production of \({}^{99\text{m}}\)Tc through the \({}^{100}\)Mo(p,2n)\({}^{99\text{m}}\)Tc reaction route occurred in 2013 [120]. In the experiment, a 1 mm thick aluminum target was illuminated by a 50 J, 1 ps, \(5\times 10^{20}\) W/cm\({}^{2}\) laser pulse. For a single shot, a production of 8.25 kBq of \({}^{99\text{m}}\)Tc was estimated. Moreover, simulation results with the 3D PIC simulation code Mandor [121] show that a 10 J, 100 fs laser might produce 1.93 kBq of \({}^{99\text{m}}\)Tc in a single shot through the same reaction route, \({}^{100}\)Mo(p,2n)\({}^{99\text{m}}\)Tc. Hence, in principle, it should be possible to produce 300 GBq of \({}^{99\text{m}}\)Tc after 6 h of continuous 10 kHz laser irradiation on a highly enriched \({}^{100}\)Mo target [122]. Despite the encouraging progress in both experimental and theoretical research studies on laser-based radioisotope production, there are still many improvements to be made before laser-driven radioisotope production facilities become viable for medical applications. Conceptualization, R.P.N., A.B. and M.S.A.-S.; methodology, B.S.N., E.R.F.R. and J.A.F. ; writing--original draft preparation, B.S.N. ; writing--reviewing and editing, B.S.N., A.B., M.S.A.-S. and R.P.N. ; supervision, R.P.N., A.B. and M.S.A.-S.; project administration, M.S.A.-S. All authors have read and agreed with the published version of the manuscript. This study was financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior--Brasil (CAPES) (grant 88887.620985/201-00), and by the Fundacao de Amparo a Pesquisa do Estado do Rio Grande do Sul (FAPERGS) (grant 21/2551-0002027-0). Not applicable. The authors thank [PERSON] and [PERSON] from the Federal University of Health Sciences of Porto Alegre (UFCSPA) for inspiring us to write this review. The authors declare no conflict of interest. The following abbreviations are used in this manuscript: \begin{tabular}{l l} SPECT & single photon emission tomography \\ PET & positron emission tomography \\ HEU & highly enriched uranium \\ VHL & virtual health library \\ AEOB & activity at the end of the bombardment \\ TTY & thick target yield \\ SY & saturation yield \\ LINACS & linear particle accelerators \\ NPs & nanoparticles \\ LWFA & laser wakefield accelerator \\ TNSA & target normal sheath acceleration \\ \end{tabular}