Metabolic imaging and other applications of hyperpolarized 13C1.

Magnetic resonance imaging (MRI) is the only imaging modality that can deliver information about the molecular structure of an injected compound. Unfortunately, MRI has a relatively low sensitivity compared to other imaging modalities (ultrasound, SPECT, PET), and there is a need to improve the fundamental imaging parameters signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR). Proton MRI reveals soft tissue morphology in detail, and contrast media containing either Gd-chelates or Fe-oxides have been developed to increase the CNR and, in addition, improve the diagnostic yield by providing functional information in the form of flow and perfusion measurements. In order to obtain chemical structure information one has to use magnetic resonance spectroscopy (MRS) and its usefulness as a tool in in vivo biological diagnosis has been established. In vivo MRS of nuclei other than 1H (e.g., 31P and 13C) has extended our knowledge of metabolism (1) and the study of intermediary metabolism of biomolecules has given valuable insight into the fundamental of disease processes (2). The MRS technique used in those studies does not, however, allow acquiring images in a medically relevant time frame of seconds. In a MRI scanner operating at 1 T or higher, where the dominating sources of noise is the patient, the SNR may be expressed according to