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Supplemental material, sj-pdf-1-jcb-10.1177_0271678X221148970 for In vivo imaging of cerebral glucose metabolism informs on subacute to chronic post-stroke tissue status – A pilot study combining PET and deuterium metabolic imaging by Anu E Meerwaldt, Milou Straathof, Wija Oosterveld, Caroline L van Heijningen, Mandy MT van Leent, Yohana C Toner, Jazz Munitz, Abraham JP Teunissen, Charlotte C Daemen, Annette van der Toorn, Gerard van Vliet, Geralda AF van Tilborg, Henk M De Feyter, Robin A de Graaf, Elly M Hol, Willem JM Mulder and Rick M Dijkhuizen in Journal of Cerebral Blood Flow & Metabolism

Supplemental material, sj-docx-1-css-10.1177_24705470221092734 for Prefrontal Glutamate Neurotransmission in PTSD: A Novel Approach to Estimate Synaptic Strength in Vivo in Humans by Lynnette A. Averill, Lihong Jiang, Prerana Purohit, Anastasia Coppoli, Christopher L. Averill, Jeremy Roscoe, Benjamin Kelmendi, Henk M. De Feyter, Robin A de Graaf, Ralitza Gueorguieva, Gerard Sanacora, John H. Krystal, Douglas L. Rothman, Graeme F. Mason and Chadi G. Abdallah in Chronic Stress

PURPOSE: The robust and reliable utilization of proton MRSI at ultra-high fields is hampered by several key technical difficulties, including contamination from extracranial lipids. To that end, this work presents novel lipid suppression sequences for proton MRSI in the human brain utilizing elliptical localization with pulsed second order fields (ECLIPSE). METHODS: Two lipid suppression methods were implemented with the ECLIPSE gradient insert. One method is a variable power, four-pulse sequence optimized to achieve outer volume suppression (OVS) and compared against a standard, eight-slice OVS method. The second ECLIPSE method is implemented as an inversion recovery (IR) sequence with elliptical inner volume selection (IVS) and compared against a global IR method. RESULTS: The ECLIPSE-OVS sequence provided a 116-fold mean lipid suppression (range 104–134), while an optimized 8-slice OVS sequence achieved 15-fold suppression (range 13–18). Furthermore, the superior ECLIPSE-OVS suppression was achieved at 30% of the RF power required by 8-slice OVS. The ECLIPSE based IR sequence suppressed skull lipids by 155-fold (range 122–257), compared to 16-fold suppression (range 14–19) achieved with IR. CONCLUSION: OVS and IVS executed with ECLIPSE provide robust and effective lipid suppression at reduced RF power with high immunity to variations in B(1) and T(1).

Purpose: 13C magnetic resonance spectroscopy (MRS) in combination with infusion of 13C-labeled substrates has led to unique insights into human brain metabolism and neurotransmitter cycling. However, the low sensitivity of direct 13C MRS and high radiofrequency power requirements has limited 13C MRS studies to predominantly data acquisition in large volumes of the occipital cortex. The purpose of this study is to develop an MRS technique for localized detection of 13C-labeling of glutamate and glutamine in the human frontal lobe. Methods: We used an indirect (1H-[13C]), proton-observed, carbon-edited MRS sequence (selPOCE) for detection of 13C-labeled metabolites in relatively small volumes located in the frontal lobe at 4 T. The SelPOCE method allows for selective and separate detection of glutamate and glutamine resonances, which significantly overlap at magnetic field strengths used for clinical MRI. Results: Phantom data illustrate how selPOCE can be tuned to selectively detect 13C labeling in different metabolites. Three-dimensional specific absorption rate simulations of radiofrequency power deposition show that the selPOCE method operates comfortably within the global and local Food and Drug Administration specific absorption rate guidelines. In vivo selPOCE data are presented, which were acquired from a 45-mL volume in the frontal lobe of healthy subjects. The in vivo data show the time-dependent 13C-labeling of glutamate and glutamine during intravenous infusion of [1-13C]-glucose. Metrics describing spectral fitting quality of the glutamate and glutamine resonances are reported. Conclusions: The SelPOCE sequence allows the detection of 13C-labeling in glutamate and glutamine from a relatively small volume in the human frontal lobe at low radiofrequency power requirements. Magn Reson Med 80:11–20, 2018.