Simultaneous Evaluations of pH and Enzyme Activity with a CEST MRI Contrast Agent.

The extracellular tumor microenvironment of many solid tumors has high acidosis and high protease activity. Simultaneously assessing both characteristics may improve diagnostic evaluations of aggressive tumors and the effects of anticancer treatments. Noninvasive imaging methods have previously been developed that measure extracellular pH or can detect enzyme activity using chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI).

Technical Note: A deuterated C-urea reference for clinical multiparametric MRI prostate cancer studies including hyperpolarized pyruvate.

Purpose: Metabolic magnetic resonance imaging (MRI) using hyperpolarized [1- C]-pyruvate offers unprecedented new insight into disease and response to therapy. C-enriched reference standards are required to enable fast and accurate calibration for C studies, but care must be taken to ensure that the reference is compatible with both C and H acquisitions. The goal of this study was to optimize the composition of a C-urea reference for a dual-tuned C/ H endorectal coil and minimize imaging artifacts in metabolic and multiparametric MRI studies involving hyperpolarized [1- C]-pyruvate.