Water luminescence imaging for visualization of therapeutic effects of proton therapy and radiosensitizers

Chemoradiotherapy, which combines chemotherapy and radiotherapy, has recently gained popularity. However, some chemoradiotherapy drugs have yet to be used in clinical practice because biocompatibility and the mechanism of their therapeutic effects are not clearly understood. Therefore, we focused on the luminescence imaging proposed by Yamamoto et al. (2015); Yamamoto (2021). It is a method for observing luminescence that occurs even under radiation with energy below the Cherenkov threshold. Moreover, the emission profiles were consistent with the dose distribution (Yamamoto, 2021; Yabe et al., 2018). We examined the luminescence mechanism of water irradiated with proton beams to determine whether it can be used to monitor the therapeutic effect of drugs that are going to be used for chemoradiotherapy. We succeeded in obtaining images and spectra of luminescence, and the results suggested that water luminescence may have complex structures. These findings may provide not only a new step toward understanding physical and chemical phenomena, but also the sensitization effect depends on drugs that occurs when water is irradiated with proton beams.