The Kinetics of Chlorine Atoms in Aqueous Solution

In this study the techniques of pulse radiolysis and laser flash photolysis have been used to investigate the reactions of the chlorine atom with organic and inorganic solutes in aqueous solution. The aim was to assess for the the first time its contribution to the chemistry within cloud droplets

Minimizing echo and repetition times in magnetic resonance imaging using a double half‐echo k‐space acquisition and low‐rank reconstruction

Sampling k-space asymmetrically (ie, partial Fourier sampling) in the readout direction is a common way to reduce the echo time (TE) during magnetic resonance image acquisitions. This technique requires overlap around the center of k-space to provide a calibration region for reconstruction, which limits the minimum fractional echo to ~60% before artifacts are observed. The present study describes a method for reconstructing images from exact half echoes using two separate acquisitions with reversed readout polarity, effectively providing a full line of k-space without additional data around central k-space. This approach can benefit sequences or applications that prioritize short TE, short inter-echo spacing or short repetition time. An example of the latter is demonstrated to reduce banding artifacts in balanced steady-state free precession

Trimmed autocalibrating k-space estimation based on structured matrix completion

International audiencePURPOSE: Parallel imaging allows the reconstruction of undersampled data from multiple coils. This provides a means to reject and regenerate corrupt data (e.g. from motion artefact). The purpose of this work is to approach this problem using the SAKE parallel imaging method. THEORY AND METHODS: Parallel imaging methods typically require calibration by fully sampling the center of k-space. This is a challenge in the presence of corrupted data, since the calibration data may be corrupted which leads to an errors-in-variables problem that cannot be solved by least squares or even iteratively reweighted least squares. The SAKE method, based on matrix completion and structured low rank approximation, was modified to detect and trim these errors from the data. RESULTS: Simulated and actual corrupted datasets were reconstructed with SAKE, the proposed approach and a more standard reconstruction method (based on solving a linear equation) with a data rejection criterion. The proposed approach was found to reduce artefacts considerably in comparison to the other two methods. CONCLUSION: SAKE with data trimming improves on previous methods for reconstructing images from grossly corrupted data

The use of SPIRIT to reject and replace motion-corrupted data

International audienceThe SPIRIT parallel imaging algorithm was evaluated for use in a data rejection and replacement scheme to reduce motion artefacts

The use of SPIRIT to reject and replace motion-corrupted data

International audienceThe SPIRIT parallel imaging algorithm was evaluated for use in a data rejection and replacement scheme to reduce motion artefacts

Validation and Initial Results from Dynamic 23Na fMRI

International audienceIn this abstract we develop and validate an MRI acquisition/reconstruction method to derive the temporal dynamics of 23Na within a 20 min scan

Validation and Initial Results from Dynamic 23Na fMRI

International audienceIn this abstract we develop and validate an MRI acquisition/reconstruction method to derive the temporal dynamics of 23Na within a 20 min scan

Ultra-High Contrast MRI: Using Divided Subtracted Inversion Recovery (dSIR) and Divided Echo Subtraction (dES) Sequences to Study the Brain and Musculoskeletal System

Divided and subtracted MRI is a novel imaging processing technique, where the difference of two images is divided by their sum. When the sequence parameters are chosen properly, this results in images with a high T1 or T2 weighting over a small range of tissues with specific T1 and T2 values. In the T1 domain, we describe the implementation of the divided Subtracted Inversion Recovery Sequence (dSIR), which is used to image very small changes in T1 from normal in white matter. dSIR has shown widespread changes in otherwise normal-appearing white matter in patients suffering from mild traumatic brain injury (mTBI), substance abuse, and ischemic leukoencephalopathy. It can also be targeted to measure small changes in T1 from normal in other tissues. In the T2 domain, we describe the divided echo subtraction (dES) sequence that is used to image musculoskeletal tissues with a very short T2*. These tissues include fascia, tendons, and aponeuroses. In this manuscript, we explain how this contrast is generated, review how these techniques are used in our research, and discuss the current challenges and limitations of this technique