Abstract: Electron paramagnetic resonance imaging (EPRI), where electron spins are the subject of the investigation, is a promising tool and has the ability to provide maps of multiple tissue microenvironment parameters, such as partial oxygen pressure (pO2) and pH. However, currently, there is no instrument available that can provide multi-parametric maps due to very different requirements on the instrument hardware. Current instrumentation, such as a 25 mT pulse EPRI instrument JIVA-25Ô developed by us, only provides pO2 maps and does not provide images of other parameters as its hardware does not support the continuous wave (CW) acquisition methods needed for imaging pH. In the current project, our goal is to develop a multifunctional imager (MFI) that can perform both pulse and CW acquisition for simultaneous pO2 and pH imaging. Towards this goal, we will develop a 25 mT Halbach-type permanent magnet (Aim 1), new muli-modal transmit-receive electronics based on field programmable gate array (FPGA) (Aim 2), and finally, we will build the MFI instrument (Aim 3). Our long-term goal is to make functional imaging affordable to scientists in biomedical fields to enhance therapies and understand biology.