Hyperpolarized ¹H NMR employing low γ nucleus for spin polarization storage

Here, we demonstrate the utility of low gamma nuclei for spin storage of hyperpolarization followed by proton detection, which theoretically can provide up to ∼(gamma[1H]/gamma[X]) ² gain in sensitivity in hyperpolarized biomedical MR. This is exemplified by hyperpolarized 1 - ¹³C sites of 2,2,3,3-tetrafluoropropyl 1-¹³C-propionate- d₃ (TFPP), ¹³C T ₁ = 67 s in D₂O, and 1-¹³C-succinate-d₂, ₁₃C T ₁ = 105 s in D₂O, pH 11, using PASADENA. In a representative example, the spin polarization was stored on ¹³C for 24 and 70 s, respectively, while the samples were transferred from a low magnetic field polarizer operating at 1.76 mT to a 4.7 T animal MR scanner. Following sample delivery, the refocused INEPT pulse sequence was used to transfer spin polarization from ¹³C to protons with an efficiency of 50% for TFPP and 41% for 1- ¹³C-succinate-d₂ increasing the overall NMR sensitivity by a factor of 7.9 and 6.5, respectively. The low gamma nuclei exemplified here by ¹³C with a T ₁ of tens of seconds acts as an efficient spin polarization storage, while J-coupled protons are better for NMR detection.