Quantitative magnetization transfer imaging (qMTI) increases specificity to macromolecular content in tissue by modeling the exchange process between the liquid and the macromolecular pool. However, its use has been mostly restricted to researchers that have developed these methods, in part due to the need to write complicated in-house software for modeling and data analysis. We have developed a software package (*qMTLab*) with a simple and easy to use graphical user interface that unifies three of the most widely used qMTI methods: MT spoiled gradient echo (MT-SPGR), MT balanced steady-state free precession (MT-bSSFP), and selective inversion recovery with fast spin echo (SIR-FSE). *qMTLab* is free open-source software that allows anyone interested in using these methods to easily simulate qMTI data, compare the performance of the methods under various experimental conditions, define new acquisition protocols, fit acquired data, and visualize the fitted parameters maps. By providing free software that gives end users a simple and easy to use graphical interface, we hope to make qMTI accessible to a greater number of investigators and facilitate the development, evaluation, and optimization of acquisition protocols and models. © 2016 Wiley Periodicals, Inc. Concepts Magn Reson Part A, 2016.

The goal of this work is to characterize and optimize gridding reconstruction of 3D radial hyperpolarized (HP) ^{129}Xe MRI. In support of this objective, we developed a flexible, open source reconstruction software package in MATLAB to optimally reconstruct radially acquired, undersampled HP ^{129}Xe MRI. Using this framework, we demonstrate the effects of 5 key reconstruction parameters: overgridding, gridding kernel function, kernel sharpness, kernel extent, and the density compensation algorithm. We further demonstrate how each parameter can be tuned to optimize a high-resolution 3D radially acquired HP ^{129}Xe image of a ventilated mouse. Specifically, wrap-around artifact, caused by non-selective RF excitation of signal in the trachea, was eliminated by overgridding onto a finely spaced *k*-space grid; high-frequency aliasing was reduced using iterative density compensation; image SNR and sharpness were optimized by tuning kernel sharpness; and computational burden was minimized by defining an appropriate kernel extent. Compared to our previous reconstruction methods, this optimized method extended visualization from the 5th to 6th generation of mouse airway, while maintaining comparable SNR. Although optimized here for preclinical mouse MRI, this work suggests that 3D radial acquisition offers many broader advantages to undersampled HP gas MRI. Using the methods presented here, we maintained image quality across datasets acquired with various degrees of undersampling and differing SNR by adjusting only a single parameter. These methods are now available to optimize radially acquired hyperpolarized gas images in both the clinical and preclinical arena. © 2015 Wiley Periodicals, Inc. Concepts Magn Reson Part A 44A: 190–202, 2015.

The influence of Gaussian diffusion on the magnetic resonance signal is determined by the apparent diffusion coefficient (ADC) and tensor (ADT) of the diffusing fluid as well as the gradient waveform applied to sensitize the signal to diffusion. Estimations of ADC and ADT from diffusion-weighted acquisitions necessitate computations of, respectively, the *b*-value and b-matrix associated with the employed pulse sequence. We establish the relationship between these quantities and the gradient waveform by expressing the problem as a path integral and explicitly evaluating it. Further, we show that these important quantities can be conveniently computed for any gradient waveform using a simple algorithm that requires a few lines of code. With this representation, our technique complements the multiple correlation function method commonly used to compute the effects of restricted diffusion, and provides a consistent and convenient framework for studies that aim to infer the microstructural features of the specimen. © 2015 Wiley Periodicals, Inc. Concepts Magn Reson Part A 44A: 203–213, 2015.

Complex proton dynamics in solids containing methyl groups are studied over a wide temperature range. Temperature dependences of the proton *T*_{1} relaxation time and the second moment of NMR lines are analyzed. General rules describing the temperature dependencies have been formulated from an analysis of the data. The second moments, *M*_{2}, are correlated with those based on *T*_{1} measurements. The *C*_{3} jumps over the barrier cause a minimum in *T*_{1} below the liquid nitrogen temperature in the presence of tunnelling splitting, or a little above 77 K when tunnelling splitting equals zero. The slope of the high- temperature side of this minimum permits evaluation of the activation energy, which can be used to characterize the tunnelling correlation time. The *T*_{1} is temperature independent in the lowest temperature range, indicating that the tunnelling correlation time assumes a constant value. The tunnelling splitting was estimated as the best fit parameter from the *T*_{1} temperature dependence. The high tunnelling splitting is responsible for *T*_{1} values which are high and independent from the Larmor frequency. The tunnelling jumps reduce the rigid lattice second moment at zero Kelvin. The second reduction is caused by over the barrier *C*_{3} jumps of methyl protons. The tunnelling jumps cease above a temperature *T*^{tun}. The occurrence of the minimum *T*_{1} above liquid nitrogen temperature, as well as the reduction of the second moment *M*_{2} are due to slowest motion of protons, which can be the isotropic motion of molecule. This minimum is well described by the Woessner method of calculating the correlation function of complex motion. © 2015 Wiley Periodicals, Inc. Concepts Magn Reson Part A 44A: 214–225, 2015.