Tumors, inflammation and circulatory disorders locally disturb the body’s acid-base balance. These changes in pH value could be used for example to verify the success of cancer treatments. Up to now, however, there has been no imaging method to render such changes visible in patients. Now a team from the Technical University of Munich (TUM) has developed a pH sensor that renders pH values visible through magnetic resonance imaging (MRI) – in a non-invasive, radiation-free manner.