3D <sup>31</sup>P MR spectroscopic imaging of the human brain at 3 T with a <sup>31</sup>P receive array: An assessment of <sup>1</sup>H decoupling, T<sub>1</sub> relaxation times, <sup>1</sup>H‐<sup>31</sup>P nuclear Overhauser effects and NAD<sup>+</sup>
NMR in biomedicine