Optimal Number of Signal Averages in Stimulated Echo Acquisition Mode for Proton MR Spectroscopy of Brain at 7T

We have developed a practical method to determine the optimal number of signal averages (NSAs) for acquiring a spectrum in the human brain and determined the optimal number of NSA at 7-Tesla. We performed 50 sequential data acquisitions with an NSA of 2 in healthy volunteers and then generated spectra with NSAs ranging from 2 to 100. After identifying the metabolites with Cramér-Rao lower bounds (CRLB) ≤ 15% in the NSA 100 spectrum, we examined the CRLB values, creatine+phosphocreatine (Cr + PCr) ratios and agreement of Cr + PCr ratios. Eight metabolites and 5 metabolite pairs spectrum showed CRLB values ≤ 15% when the NSA was 40 or higher. Additionally, the Cr + PCr ratios at NSA 40 closely matched those at NSA 100. By analyzing the CRLB values of metabolites in varying NSAs spectra generated from sequential data, we determined the optimal NSA needed to accurately measure the spectrum within a reasonable acquisition time.