In general, the effectiveness of
radiation treatment is evaluated through the observation of morphological changes with computed tomography (CT) or magnetic resonance imaging (MRI) images
after treatment. However, the evaluation of the treatment effects can be very time consuming, and thus can delay the verification of patient cases where treatment has not been fully effective. It is known that the treatment efficacy depends on redox modulation in
tumor tissues, which is an indirect effect of oxidizing redox molecules such as
hydroxyl radicals and of
reactive oxygen species generated by
radiation treatment. In vivo dynamic nuclear polarization-MRI (DNP-MRI) using carbamoyl-PROXYL (
CmP) as a redox sensitive DNP probe enables the accurate monitoring of the anatomical distribution of
free radicals based on interactions of electrons and nuclear spin, known as Overhauser effect. However, spatiotemporal response of the redox status in
tumor tissues post-irradiation remains unknown. In this study, we demonstrate the usefulness of spatiotemporal redox status as an early imaging
biomarker of
tumor response after irradiation using in vivo DNP-MRI. Our results highlight that in vivo DNP-MRI/
CmP allowed us to visualize the
tumor redox status responses significantly faster and earlier compared to the verification of morphological changes observed with 1.5 T MRI and
cancer metabolism (Warburg effect) obtained by hyperpolarized 13C
pyruvate MRS. Our findings suggest that the early assessment of redox status alterations with in vivo DNP-MRI/
CmP probe may provide very efficient information regarding the effectiveness of the subsequent
radiation treatment.