A method for optimizing MR imaging pulse sequence parameters in a statistical framework is presented. Parameters are defined to be optimal when the resulting scalar images yield optimal image segmentations using Bayesian pixel classification. Thus, Bayes risk is used as the objective function to minimize. Approximations are made to give a tractable solution in a four-step procedure. A sample ca...

Background The quest to quantify myocardial perfusion has been largely motivated by the desire to obtain quantitative, observer-independent, and reproducible measures of myocardial perfusion. Spiral pulse sequences have multiple advantages for myocardial perfusion imaging including high acquisition efficiency, high signal to noise (SNR) and robustness to motion. We have developed a spiral pulse...

An improved pulse sequence for measuring diffusion-ordered COSY spectra is achieved by incorporating the diffusion encoding directly into the evolution and detection periods of a gradient-enhanced COSY sequence, giving improved sensitivity and a 32-fold reduction in minimum experiment time.

Stimulated echoes are formed from three or more radio frequency pulses. Pulse sequences that use stimulated echoes are extremely versatile because of the availability of three pulses for timing variations and for encoding spatial or chemical shift information. This paper concentrates on the uses of stimulated echoes and on techniques for obtaining them reliably and reproducibly. (Through this u...

Most of the Nuclear Magnetic Resonance (NMR) Imaging techniques require to send and receive long electromagnetic pulse sequences [1]. To scan regions of the body which remain static is relatively simple, but in the case of Cardiac Imaging, due to the continuous movement of the heart, the pulse sequences have to be divided and its parts sent during different heartbeats in order to capture the he...

High-resolution functional MRI is a leading application for very high field (7 Tesla) human MR imaging. Though higher field strengths promise improvements in signal-to-noise ratios (SNR) and BOLD contrast relative to fMRI at 3 Tesla, these benefits may be partially offset by accompanying increases in geometric distortion and other off-resonance effects. Such effects may be especially pronounced...

We present improved line-narrowing sequences for dipolar coupled spin systems, based on a train of magic-echoes which are compensated for the effects of finite pulse widths and utilize symmetry properties of supercycles. Sequences are introduced for spectroscopy and imaging by proper choice of a phase alternating scheme. Using a 16 pulse time-suspension magic-echo cycle, the highest level of li...

Background Adenosine stress perfusion imaging with CMR has been limited by motion-induced dark-rim artifacts, which may be mistaken for true perfusion abnormalities. We have previously demonstrated that spiral pulse sequences can produce high quality first-pass perfusion images.[1] We have further improved this spiral technique using high-resolution variable density spiral trajectories and a no...

We designed a femtosecond (fs) + picosecond (ps) double-pulse sequence by using Mach–Zehnder-like apparatus to split single 120 fs pulse into two sub-pulses, and one of them was stretched width 2 ps four-pass grating system. Through observing the ripples induced on ZnO surface, we found ionization rate appeared be higher for in which arrived first. The electron equation used calculate changes d...

The use of genetic algorithms for the optimisation of magic angle spinning NMR pulse sequences is discussed. The discussion uses as an example the optimisation of the C7(2)(1) dipolar recoupling pulse sequence, aiming to achieve improved efficiency for spin systems characterised by large chemical shielding anisotropies and/or small dipolar coupling interactions. The optimised pulse sequence is ...