A portable phase-only parallel transmission (ppTx) interface for modifying transmit fields in human brain phosphorus magnetic spectroscopy imaging (31P MRSI) at 7T

About This Grant

Project Summary There is an unmet need for the development of whole-brain level non-invasive metabolic neuroimaging tools for quantitatively and reliably detecting abnormal energy metabolism and impaired mitochondrial function in the early stage of the Alzheimer’s disease (AD) and brain tumors. Phosphorus-31 (31P) magnetic resonance spectroscopy imaging (MRSI) at ultra-high field strength (7 Tesla) is a non-invasive metabolic imaging method for investigating essential aspects of energy metabolism involving the adenosine triphosphate (ATP) synthesis and utilization in the human brain. The 8-channel 31P transceiver array coil offers better imaging sensitivity and SNR compared to conventional volume coils, but is limited by the inhomogeneous B1+ field of the RF array coil. We will develop a phase-only parallel transmission (ppTx) interface that allows continuously adjusting the RF phase for each transmit channel and B1+ phase shimming of the RF array, to significantly improve the B1+ distribution (∝ flip angle [FA]) of the array RF coil to enhance the FA uniformity and signal-to-noise ratio (SNR) of 31P MRSI across the whole brain. Using the proposed technique, we will quantify, for the first time, the molar concentrations of inorganic phosphate (Pi), phosphocreatine (PCr), ATP, and nicotinamide adenine dinucleotide (NAD), as well as determine the intracellular pH value throughout the brain, all of which are tightly involved in ATP metabolism within brain cells. The ppTx interface is digital-controlled, RF broadband, and portable on the MRI scanner's patient table, and thus can be applied to 1.5T, 3T, and 7T MRI scanners that do not have the parallel transmission (pTx) option.