Quantitative magnetic resonance imaging (MRI) is of great value to both clinical diagnosis and scientific research. However, most MRI experiments remain qualitative, especially dynamic MRI, because repeated sampling with variable weighting parameter makes quantitative imaging time consuming and sensitive to motion artifacts. A single-shot quantitative T2 mapping method based on multiple overlapping-echo acquisition (dubbed MOLED-4) was proposed to obtain reliable T2 mapping in milliseconds. Different from traditional MRI acceleration methods, such as compressed sensing and parallel imaging, MOLED-4 accelerates quantitative T2 mapping via synchronized multisampling and then deep learning to map the complex nonlinear relationship that is difficult to solve by traditional optimization-based method. The results of simulation, phantom and in vivo human brain experiments show the great performance of the proposed method. The principle of MOLED-4 may be extended to other ultrafast quantitative parameter mappings, and potentially lead to new dynamic MRI with high efficiency to catch quantitative variation of tissue properties.

Purpose: To investigate the characteristics of nuclear Overhauser enhancement (NOE) imaging signals in the brain at 7T.Methods: Fresh hen eggs, as well as six healthy, and six C6 glioma‐bearing Wistar rats were scanned using chemical exchange saturation transfer‐magnetic resonance imaging (CEST‐MRI) and chemical exchange saturation transfer‐magnetic resonance spectroscopy (CEST‐MRS) sequences (saturation duration 3 s, power 1.47 µT) with and without lipid suppression. CEST data were acquired over an offset range of −6 to +6 ppm relative to the water resonance in 0.5 ppm steps.Results: The water signals were not disrupted by other protons during the CEST‐MRS sequences, and true NOE signals could be observed. Using the CEST‐MRI sequence without lipid suppression, pseudo NOE imaging signals were observed in the lipid‐containing regions (egg yolk, scalp, and even white matter). These pseudo NOE signals were almost (but incompletely) removed with the lipid suppression. Egg yolk results indicated the presence of the NOE to olefinic protons overlapping with the water signal. In vivo experiments showed that the amide proton transfer signal was larger in the tumor, whereas the NOE signal was larger in the normal white matter.Conclusions: True NOE signals can be detected using MRS sequences, and considerable pseudo NOE imaging signals may be observed using MRI sequences. Magn Reson Med 73:1615–1622, 2015. © 2014 Wiley Periodicals, Inc.

Reducing the acquisition time for two-dimensional nuclear magnetic resonance (2D NMR) spectra is important. One way to achieve this goal is reducing the acquired data. In this paper, within the framework of compressed sensing, we proposed to undersample the data in the indirect dimension for a type of self-sparse 2D NMR spectra, that is, only a few meaningful spectral peaks occupy partial locations, while the rest of locations have very small or even no peaks. The spectrum is reconstructed by enforcing its sparsity in an identity matrix domain with ℓ_p (p = 0.5) norm optimization algorithm. Both theoretical analysis and simulation results show that the proposed method can reduce the reconstruction errors compared with the wavelet-based ℓ₁ norm optimization.