Magnetization transfer contrast (MTC) experiments using off-resonance irradiation have been performed with an agar gel model by systematically varying offset frequency, amplitude of the RF irradiation and gel concentration. The experimental results are shown to be quantitatively modelled by a two-pool system consisting of a liquid pool with a Lorentzian line shape and a small semisolid pool with a Gaussian lineshape. The fitted model yields physically realistic fundamental parameters with a T2 of the semisolid pool of 13 microseconds. Further analysis shows that the off-resonance irradiation MTC experiment had significant limitations in its ability to saturate the semisolid pool without directly affecting the liquid component.

We propose a multicomponent fitting algorithm for multiecho T(2) data which allows for correction of T(2) distributions in the presence of stimulated echoes. Tracking the population of spins in many coherence pathways via the iterated method of the Extended Phase Graph algorithm allows for accurate quantification of echo magnitudes. The resulting decay curves allow for correction of errors due to nonideal refocusing pulses as a result of inhomogeneities in the B(1) transmit field. Non-Negative Least Squares fitting is used to quantify the magnitude of T(2) components at various T(2) values. This method, allowing calculation of the T(2) distribution with simultaneous extraction of the refocusing pulse flip angle, requires no change to image acquisition procedures and no extra data input. Validation by means of both simulations and in vivo data shows excellent interscan reproducibility while vastly improving the accuracy of extracted T(2) parameters in voxels where poor B(1) homogeneity leads to refocusing pulse flip angles significantly less than 180°. Most notably, myelin water fraction values in these regions are found to have increased consistency and accuracy.

A new method is introduced for water-fat imaging. With three acquisitions, a general direct phase encoding (DPE) of the chemical shift information is achieved. Pixels containing both water and fat are solved directly. Pixels with only a single component are resolved with local and global orientation filters, which use phase information from neighboring pixels. The fact that a single component is more likely to be water than fat in living tissues is also useful. A second pass solution yields water and fat images with superior signal-to-noise ratio. Unlike other methods, DPE does not rely on the error-prone phase unwrapping; also, it easily handles disconnected tissues. Because the magnetization vectors of water and fat are sampled not only at parallel or antiparallel, they can be not only separated but also identified respectively, which is desirable for routine clinical work. DPE has been implemented on several imagers at various field strengths and has been demonstrated in a large number of clinical cases to be useful and robust in various parts of the body.

Through the convergence of nano- and microtechnologies (quantum dots and microfluidics), we have created a diagnostic system capable of multiplexed, high-throughput analysis of infectious agents in human serum samples. We demonstrate, as a proof-of-concept, the ability to detect serum biomarkers of the most globally prevalent blood-borne infectious diseases (i.e., hepatitis B, hepatitis C, and HIV) with low sample volume (<100 microL), rapidity (<1 h), and 50 times greater sensitivity than that of currently available FDA-approved methods. We further show precision for detecting multiple biomarkers simultaneously in serum with minimal cross-reactivity. This device could be further developed into a portable handheld point-of-care diagnostic system, which would represent a major advance in detecting, monitoring, treating, and preventing infectious disease spread in the developed and developing worlds.