Deuterium metabolic imaging (DMI) for MRI-based 3D mapping of metabolism in vivo

Abstract

DMI shows metabolism of acetate and glucose in the brain and liver and reveals the Warburg effect in patients with brain tumors.

On the magnetic field dependence of deuterium metabolic imaging

“…However, for equal noise levels, the CRLBs at 4 and 7 T are nearly identical due to the lack of significant spectral overlap, even at 4 T. The strong spectral overlap between Glu and Gln is not significantly reduced at 7 T, such that only the sum of Glx can be reliably quantified. The spectral linewidths continue to be nearly independent of the magnetic field even beyond 7 T, as has been shown for animal brain at 11.7 and 16.4 T . The independence of T 2 * relaxation on the magnetic field strength is mirrored for T 1 and T 2 relaxation times, which were shown to be essentially constant between 4.0 and 11.7 T and even up to 16.4 T .…”

“…The spectral linewidths continue to be nearly independent of the magnetic field even beyond 7 T, as has been shown for animal brain at 11.7 and 16.4 T . The independence of T 2 * relaxation on the magnetic field strength is mirrored for T 1 and T 2 relaxation times, which were shown to be essentially constant between 4.0 and 11.7 T and even up to 16.4 T . The near‐constant relaxation times continue to benefit DMI at all magnetic fields by allowing rapid signal averaging due to short T 1 s, while maintaining reasonable spectral resolution.…”

“…The similar 2 H and 13 C T 2 * times of 35 and 50 ms, respectively, give a slight enhancement for 13 C MR. For 2 H and 13 C, the number of equivalent nuclei are 2 and 1 using [6,6‐ 2 H 2 ]‐glucose and [1‐ 13 C]‐glucose as substrate, respectively. The number of equivalent 2 H nuclei for downstream metabolic products is reduced to ~ 1.5 as some 2 H label is lost to water . Experimentally, 13 C MR of protonated 13 C nuclei is always performed with signal enhancement via polarization transfer or nuclear Overhauser effects, thereby improving the 13 C sensitivity by ~ 2‐fold .…”

“…The initial studies of DMI were performed on a clinical research 4 T MR scanner and results were acquired at a nominal resolution of 8 mL. 1 This spatial resolution was primarily determined by the low transmit homogeneity of the four-channel RF coil that was employed, forcing reduced nutation angles in the center of the brain in order to maintain signal in all positions within the active coil volume. As a result, DMI sensitivity in more superficial locations was up to 3-fold higher than in the center of the brain.…”

“…The sensitivity and thereby the utility of MRI and MRS improves at higher magnetic fields, as has previously been demonstrated for 1 H, 7,8 17 O, 9 23 Na 10 and 31 P 11 nuclei. The low 2 H Larmor frequency, together with the field-independent T 1 and T 2 relaxation constants, 1,12 predicts a near-quadratic magnetic field dependence of the SNR in a coil noise-dominant regime. In this study, the magnetic field dependence of DMI is experimentally investigated for a range of magnetic fields and RF coils in order to understand the possibilities of DMI in clinical 3 T magnetic fields and to predict the potential gains achievable at 7 T for humans or at ultrahigh magnetic fields for animals.…”