3D 31P MR spectroscopic imaging of the human brain at 3 T with a 31P receive array: An assessment of 1H decoupling, T1 relaxation times, 1H‐31P nuclear Overhauser effects and NAD+. (13th September 2019)

• Record Type: Journal Article
• Authors: Peeters, Tom H.; van Uden, Mark J.; Rijpma, Anne; Scheenen, Tom W.J.; Heerschap, Arend
• Other Names: Choi In‐Young guestEditor.; Kreis Roland guestEditor.
• Is Part Of: NMR in biomedicine. Volume 34:Number 5(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-09-13
• Subjects: brain -- 1H decoupling -- nuclear Overhauser effect -- 31P MR spectroscopic imaging -- T1 -- 3 T; Nuclear magnetic resonance -- Periodicals; Magnetic Resonance Spectroscopy -- Periodicals; 574
• DOI: 10.1002/nbm.4169
• Languages: English
• ISSNs: 0952-3480

Abstract

Abstract : 31 P MR spectroscopic imaging (MRSI) is a versatile technique to study phospholipid precursors and energy metabolism in the healthy and diseased human brain. However, mainly due to its low sensitivity, 31 P MRSI is currently limited to research purposes. To obtain 3D 31 P MRSI spectra with improved signal‐to‐noise ratio on clinical 3 T MR systems, we used a coil combination consisting of a dual‐tuned birdcage transmit coil and a 31 P eight‐channel phased‐array receive insert. To further increase resolution and sensitivity we applied WALTZ4 1 H decoupling and continuous wave nuclear Overhauser effect (NOE) enhancement and acquired high‐quality MRSI spectra with nominal voxel volumes of ~ 17.6 cm 3 (effective voxel volume ~ 51 cm 3 ) in a clinically relevant measurement time of ~ 13 minutes, without exceeding SAR limits. Steady‐state NOE enhancements ranged from 15 ± 9% (γ‐ATP) and 33 ± 3% (phosphocreatine) to 48 ± 11% (phosphoethanolamine). Because of these improvements, we resolved and detected all 31 P signals of metabolites that have also been reported for ultrahigh field strengths, including resonances for NAD +, NADH and extracellular inorganic phosphate. T1 times of extracellular inorganic phosphate were longer than for intracellular inorganic phosphate (3.8 ± 1.4s vs 1.8 ± 0.65 seconds). A comparison of measured T1 relaxation times and NOE enhancements at 3 T with published values between 1.5 and 9.4 T indicates that T1 relaxation of 31 P metabolite spins in the human brain is dominated by dipolar relaxation for this field strength range. Even although intrinsic sensitivity is higher at ultrahigh fields, we demonstrate that at a clinical field strength of 3 T, similar 31 P MRSI information content can be obtained using a sophisticated coil design combined with 1 H decoupling and NOE enhancement. Abstract : We performed 3D 31 P MRSI of the human brain at 3 T employing a 1 H/ 31 P dual‐tuned birdcage transmit coil and a 31 P 8‐channel phased‐array receive insert to acquire high‐quality 31 P MR spectra with and without 1 H‐decoupling and/or 1 H‐ 31 P NOE. The well‐resolved spectra allowed to analyze two peaks for inorganic phosphate and the NAD + /NADH redox ratio. Localized T1 relaxation times and NOE enhancements of 31 P spins were measured and compared with those acquired at other field strengths, indicating little effect of chemical shift anisotropy relaxation.