Combined ¹H MRI, PET and Multinuclear MRS hybrid imaging system

In this abstract we describe a novel method of combining three imaging modalities: ¹H Magnetic Resonance Imaging (MRI), Positron Emission Tomography (PET), and multinuclear Magnetic Resonance Spectroscopy (MRS) in one system dedicated for true molecular imaging.

The addition of PET to MRI was introduced to provide functional/metabolic information about diseases or natural processes in the human body. High resolution and soft tissue contrast of ¹H MRI morphological images is complemented by PET’s ability to depict metabolic processes through the use of biologically active radioactively labeled imaging agents, paving the way for molecular imaging.

The application of localized ¹H MRS is implemented by using the imaging coil tuned to proton resonances. Localized, or MRI-guided, MR spectroscopy enables quantification of chemical composition of different tissue components in small volumes of less than 0.1 ml. Particularly in the brain, ¹H MRS can for example measure accurately N-acetyl aspartate (NAA), lactate, glutamate, creatine, and choline to provide a view of the progression of neuro-degeneration.

However, the use of coil exclusively tuned to ¹H significantly limits the “window” of observation by elimination of other biologically relevant nuclei like ¹³C, ¹⁴N, ¹⁷O, or ³¹P. Therefore we propose introducing a second resonator that will be tuned to these nuclei. We anticipate that MRS of other than ¹H nuclei will provide more spectroscopic details and remove the ambiguity that exists in the ¹H spectra from overlapping lines. The additional coil tuned to specific X-nuclei can be embedded within the existing ¹H coil or can be removable, to be added whenever MRS on these nuclei is deemed necessary.