Four-Dimensional Spectral Spatial PH Mapping of Mouse Tumour Using Continuous Wave-Electron Paramagnetic Resonance Imaging (CW-EPRI) and PH Sensitive Imidazoline Nitroxide

Jonathan Goodwin¹, Shunichi Koda¹, Masashi Ohfuchi¹, Anna Pawlak¹, Hironobu Yasui², Valery Khramstov³, Hiroshi Hirata¹

In this work we assess the viability of pH sensitive imidazoline nitroxide for in-vivo pH mapping of mouse tumour using continuous wave electron paramagnetic resonance imaging (CW-EPR) to perform four dimensional spectral-spatial imaging. Comparison of pH in tumour model mouse leg was found to be reduced compared control mouse leg. Co-registration with 7T MRI demonstrated anatomical distribution of acquired pH map obtained from tumour model mouse. Successful demonstration of the technique in a larger population will allow further exploration of the relationship between pHe in tumour, and how the relationship changes in response to radiotherapy with and without radio-sensitizing drugs.