More than 10,000-fold enhanced magnetic resonance signals with >20-min signal lifetimes on universal biomolecular markers.

A novel deep learning architecture (XmasNet) based on convolutional neural networks was developed for the classification of prostate cancer lesions, using the 3D multiparametric MRI data provided by the PROSTATEx challenge. End-to-end training was performed for XmasNet, with data augmentation done through 3D rotation and slicing, in order to incorporate the 3D information of the lesion. XmasNet outperformed traditional machine learning models based on engineered features, for both train and test data. For the test data, XmasNet outperformed 69 methods from 33 participating groups and achieved the second highest AUC (0.84) in the PROSTATEx challenge. This study shows the great potential of deep learning for cancer imaging.

Long-lived nuclear spin states could greatly enhance the applicability of hyperpolarized nuclear magnetic resonance. Using singlet states between inequivalent spin pairs has been shown to extend the signal lifetime by more than an order of magnitude compared to the spin lattice relaxation time (T1), but they have to be prevented from evolving into other states. In the most interesting case the singlet is between chemically equivalent spins, as it can then be inherently an eigenstate. However this presents major challenges in the conversion from bulk magnetization to singlet. In the only case demonstrated so far, a reversible chemical reaction to break symmetry was required. Here we present a pulse sequence technique that interconverts between singlet spin order and bulk magnetization without breaking the symmetry of the spin system. This technique is independent of field strength and is applicable to a broad range of molecules.

‡ These authors contributed equally.Long-lived (symmetry protected) hyperpolarized spin states offer important new opportunities (for example, in clinical MR imaging), but existing methods for producing these states are limited by either excess energy dissipation or high sensitivity to inhomogeneities. We extend recent work on continuouswave irradiation of nearly-equivalent spins (spin-lock induced crossing) by designing composite pulse and adiabatic shaped-pulse excitations which overcome the limitations. These composite and adiabatic pulses differ drastically from the traditional solutions in two-level systems. We also show this works in chemically equivalent spin pairs, which has the advantage of allowing for polarization transfer from and to remote spins. The approach is broadly applicable to systems where varying excitation strength induces an avoided crossing to a dark state, and thus to many other spectroscopic regimes.Hyperpolarization methods produce nuclear magnetization many orders of magnitude larger than what is available at thermal equilibrium, and are particularly promising in clinical and preclinical applications of magnetic resonance imaging [1][2][3]. However, a fundamental challenge is the nuclear spin-lattice relaxation time T 1 , which typically is too short in solution or tissue (tens of seconds for carbon-13) to monitor many meaningful biological processes. For this reason, symmetry-protected nuclear spin states (such as the singlet, which is a "dark state" with no dipole allowed transitions) have drawn considerable attention [4][5][6][7][8][9][10][11][12][13][14][15][16][17].The first demonstrations [6,7] used inequivalent spins to convert population from the normally accessible triplet stateinto the singlet, then strong spin locking or translation to a low field to preserve the singlet state. More recent work has shown that chemically equivalent [4,[18][19][20] [8,10,19,20]. Specifically, the so-called "M2S" sequence, consisting of precisely spaced π pulses, can interconvert magnetization and singlet-state polarization. It has become clear that multiple families of biologically compatible molecules exist that can bear protected singlet states with lifetimes of many minutes to hours, giving this approach transformative potential.However, serious obstacles remain to using such reagents in MRI. The most important challenge is that in clinical applications, allowable energy deposition is limited. Recently, DeVience et. al. [21,22] introduced a new approach for pumping singlet states in nearly-equivalent spins, called spin-lock induced crossing (SLIC), which drastically decreases power dissipation but is not robust to the inevitable rf or static field inhomogeneities in MRI. Here we extend their approach to the equivalent-spin case, and create an energy-efficient and robust method for population transfer using novel composite and shaped pulses. Composite pulses have been used for decades to improve robustness in magnetic resonance [23,24] and laser [25,26] applications, as have shaped pulses;...

Hyperpolarized magnetic resonance imaging is a powerful technique enabling real time monitoring of metabolites at concentration levels not accessible by standard MRI techniques. A considerable challenge this technique faces is the T1 decay of the hyperpolarization upon injection into the system under study. Here we show that AnA’nXX’ spin systems such as 13C2-1,2-diphenylacetylene (13C2-DPA) sustain long-lived polarization for both 13C and 1H spins with decay constants of almost 4.5 min at high magnetic fields of up to 16.44 T without spin-locking; the T1 of proton polarization is only 3.8 s. Therefore, storage of the proton polarization in a 13C2-singlet state causes a 69 fold extension of the spin lifetime. Notably, this extension is demonstrated with proton-only pulse sequences, which can be readily implemented on standard clinical scanners.