Abstract Introduction: Our goal is to evaluate the role of using extracelluar pH (pHe) as a predictor of pancreatic ductal adenocarcinoma (PDAC) development using a non-invasive, in vivo imaging technique called acidoCEST MRI, to improve early detection of pancreatic tumors. Methods: Spontaneous PDAC development was initiated by administering 14 caerulein injections over a 62 hour period to a KrasLSL.G12D/+; PdxCre mouse model. Caerulein induces pancreatitis which drives tumor development in the context of a Kras mutation. Animals were imaged with a Bruker BioSpin 7T MRI scanner with an acidoCEST MRI protocol at pre-injection, 1 hour and 48 hours post final injection of caerulein, and weekly until tumors reached a size of 200mm3. During all MR imaging, mice were anesthetized with 2.0% isofluorane, maintained at a respiration rate of 35-40 bpm, and maintained at a body temperature of 37°C. For acidoCEST MR imaging, mice were injected with 370 mg/mL iopamidol (200 μL IV bolus and 400 μL/hr IV infusion) and scanned with a 6 sec saturation time at 3.5 μT, with a 300 ms acquisition time. Pixel-wise parametric maps of pancreatic pHe values were generated via fitting the CEST spectrum with the Bloch-McConnell equations in MATLAB R2016a. Average pancreatic pHe was recorded. Results: AcidoCEST MRI was successful in acquiring in vivo pHe of normal and tumor pancreatic tissue, both with sufficient uptake of the iopamidol contrast agent. The pHe values for healthy pancreatic tissue ranged from 6.83 to 7.33 with an average of 6.96 (n=14). 1 hour after the last caerulein injection, during pancreatic inflammation, pHe ranged from 6.78 to 7.00, with an average of 6.92 (n=6). Tumors began to reach a size of 200mm3 at 5 weeks post caerulein injections. In tumor tissue, pHe was 6.59 (n=1), demonstrating tumor acidosis. Conclusions: We have demonstrated that acidoCEST MRI can be used to quantify pHe in healthy pancreatic tissue, pancreatitis, and pancreatic ductal adenocarcinoma. These pHe values will be used to determine if acidity in pancreatitis correlates with future development of PDAC and/or a more aggressive phenotype. Further pre-clinical studies using acidoCEST MRI may be performed to monitor early therapeutic response to pancreatic tumor treatment. Citation Format: Rachel A. High, Edward A. Randtke, Kyle M. Jones, Mark D. Pagel. Evaluation of pancreatic ductal adenocarcinoma with acidoCEST MRI [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3046.