41 Magnetic Resonance insights 2015:8(s1) Application of the Steady-State Variable Nutation Angle Method for Faster Determinations of Long T 1 s—An Approach Useful for the Design of Hyperpolarized MR Molecular Probes Supplementary Issue: New Concepts in Magnetic Resonance as Applied to Cellular and In Vivo Applications Marc Jupin 1, *, ayelet gamliel 1, *, Yonatan hovav 2 , Jacob sosna 1 , J. Moshe gomori 1 and Rachel Katz-Brull 1 1 Department of Radiology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel. 2 Weizmann Institute of Science, Rehovot, Israel. *These authors contributed equally to this article. ABSTRACT: In the dissolution-dynamic nuclear polarization technique, molecular probes with long T 1 s are preferred. 13 C nuclei of small molecules with no directly bonded protons or sp 3 13 C nuclei with proton positions substituted by deuterons may ful fll this requirement. Te T 1 determination of such new molecular probes is crucial for the success of the hyperpolarized observation. Although the inversion-recovery approach remained by and large the standard for T 1 measurements, we show here that the steady-state variable nutation angle approach is faster and may be better suited for the determination of relatively long T 1 s in thermal equilibrium. Specifcally, the T 1 of a new molecular probe, [uniformly labeled (UL)- 13 C 6 , UL- 2 H 8 ]2-deoxy-d-glucose, is determined here and compared to that of [UL- 13 C 6 , UL- 2 H 7 ]d-glucose. KEYWORDS: T 1 measurement, steady state, variable nutation angle, DNP probes SUPPLEMENT: new concepts in Magnetic Resonance as applied to cellular and in Vivo applications CITATION: Jupin et al. application of the steady-state Variable nutation angle Method for Faster Determinations of Long T 1 s—an approach Useful for the Design of hyperpolarized MR Molecular Probes. Magnetic Resonance Insights 2015:8(s1) 41–47 doi:10.4137/MRi.s29358. TYPE: original Research RECEIVED: May 6, 2015. RESUBMITTED: July 16, 2015. ACCEPTED FOR PUBLICATION: July 26, 2015. ACADEMIC EDITOR: sendhil Velan, editor in chief PEER REVIEW: Five peer reviewers contributed to the peer review report. Reviewers’ reports totaled 1,232 words, excluding any confdential comments to the academic editor. FUNDING: this study was supported by an isF grant (no. 284/10) and an eRc grant (No. 338040) to RK-B. The authors confrm that the funder had no infuence over the study design, content of the article, or selection of this journal. COMPETING INTERESTS: Authors disclose no potential conficts of interest. COPYRIGHT: © the authors, publisher and licensee Libertas academica Limited. this is an open-access article distributed under the terms of the creative commons cc-BY-nc 3.0 License. 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Introduction Te dissolution-dynamic nuclear polarization (DNP) tech- nique has revolutionized the solution state and in vivo nuclear magnetic resonance (NMR) spectroscopy feld, by ofering an increase of 10,000-fold in signal. 1 However, this approach is limited by the need to obtain a substrate molecule that has a reporting nucleus with long T 1 . Tis is because it takes a minimum of 20 seconds for the processes of dissolution and transfer of the hyperpolarized liquid samples to an NMR scanner. During this time and further on, the induced mas- sive spin polarization decays at a rate that is governed by the spin–lattice relaxation with a time constant T 1 . Terefore, use- ful molecular probes for this technique need to have nuclei with slow relaxation rates, ie, 5 T 1   20 seconds. 13 C of small molecules that have no direct protons attached, eg, carbonyl, carboxyl, certain quaternary carbons, or perdeuterated carbons, 2 may ful fll this requirement. Other requirements for successful dissolution-DNP molecular probes relate to their biological activity. 3,4 Molecular probes for this technique should be transported and metabolized within very few minutes to enable the evaluation of their activity, while the hyperpolarized signal is still at a sufcient level. 5 Te selection of a metabolite candidate for development into a dissolution-DNP molecular probe depends heavily on the T 1 of the reporting nuclei in this probe and on the deter- mination of this T 1 . T 1 can in principle be determined based on the decay curve of the hyperpolarized signal. 6 Tis is an extremely fast and reliable way of measuring T 1 , 4,6 provided that the efects of radio-frequency (RF) pulses and the temperature are well controlled during the measurement. However, this technique critically depends on the availability of a dissolution-DNP polarizer, which is much less abundant than NMR spectrom- eters or magnetic resonance imaging (MRI) scanners. Also, it is preferred that a 13 C (or 13 C and D)-labeled compound is available. Non- 13 C-labeled compounds have a 100-fold lower signal, which could be a limiting factor, as hyperpolarized spectra cannot beneft from the advantages of signal averaging as thermal equilibrium measurements can. Because the mea- surement of T 1 is done as part of the design of a new molecular