{'fraction_non_alphanumeric': 0.026657997399219768, 'fraction_numerical': 0.033810143042912875, 'mean_word_length': 4.85171102661597, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Field dependence study of in vivo brain 31P MRS up to 16.4 T

In vivo 31P MRS provides a unique tool for studying bioenergetics of living organs. Although its utility has been limited by the relatively low 31P NMR sensitivity, increasing magnetic field strength (B0) could significantly improve the quality and reliability of the 31P MR spectra for biomedical research. To quantitatively understand the field dependence of in vivo 31P MRS for brain applications, 31P NMR sensitivity of phosphocreatine (PCr) in rat brains was measured and compared at 9.4 T and 16.4 T. Additionally, the linewidths and T1 relaxation times of PCr and adenosine triphosphate (ATP) resonances obtained from human and animal brains over a wide B0 range from 4 T, 7 T, and 9.4 T to 16.4 T were examined and their field dependences were quantified. The results indicate an approximate 1.74‐fold 31P signal‐to‐noise ratio (SNR) gain for PCr at 16.4 T compared with 9.4 T. An approximate power 1.4 dependence of 31P SNR on B0 was concluded. Substantial improvements in spectral resolution and significantly shortened T1 values of brain PCr and ATP were observed at high/ultrahigh fields, contributing to an additional sensitivity gain and spectral improvement. In summary, the overall findings from this study suggest that in vivo 31P MRS should greatly benefit from high/ultrahigh fields for noninvasive assessment of altered bioenergetics and metabolic processes associated with brain function and neurological diseases. Copyright © 2014 John Wiley & Sons, Ltd.