NeuroMix-A single-scan brain exam.

Purpose: Implement a fast, motion-robust pulse sequence that acquires T -weighted, T -weighted, T -weighted, T fluid-attenuated inversion recovery, and DWI data in one run with only one prescription and one prescan.

Methods: A software framework was developed that configures and runs several sequences in one main sequence. Based on that framework, the NeuroMix sequence was implemented, containing motion robust single-shot sequences using EPI and fast spin echo (FSE) readouts (without EPI distortions).

Control of a wireless sensor using the pulse sequence for prospective motion correction in brain MRI.

Purpose: To synchronize and pass information between a wireless motion-tracking device and a pulse sequence and show how this can be used to implement customizable navigator interleaving schemes that are part of the pulse sequence design.

Methods: The device tracks motion by sampling the voltages induced in 3 orthogonal pickup coils by the changing gradient fields. These coils were modified to also detect RF-transmit events using a 3D RF-detection circuit.

Motion-insensitive susceptibility weighted imaging.

Purpose: To enable SWI that is robust to severe head movement.

Methods: Prospective motion correction using a markerless optical tracker was applied to all pulse sequences. Three-dimensional gradient-echo and 3D EPI were used as reference sequences, but were expected to be sensitive to motion-induced B changes, as the long TE required for SWI allows phase discrepancies to accumulate between shots.

Chemical shift encoding using asymmetric readout waveforms.

Purpose: To describe a new method for encoding chemical shift using asymmetric readout waveforms that enables more SNR-efficient fat/water imaging.

Methods: Chemical shift was encoded using asymmetric readout waveforms, rather than conventional shifted trapezoid readouts. Two asymmetric waveforms are described: a triangle and a spline.

Prospective motion correction for diffusion weighted EPI of the brain using an optical markerless tracker.

Purpose: To enable motion-robust diffusion weighted imaging of the brain using well-established imaging techniques.

Methods: An optical markerless tracking system was used to estimate and correct for rigid body motion of the head in real time during scanning. The imaging coordinate system was updated before each excitation pulse in a single-shot EPI sequence accelerated by GRAPPA with motion-robust calibration.

T -FLAIR imaging during continuous head motion: Combining PROPELLER with an intelligent marker.

Purpose: The purpose of this work is to describe a T -weighted fluid-attenuated inversion recovery (FLAIR) sequence that is able to produce sharp magnetic resonance images even if the subject is moving their head throughout the acquisition.

Methods: The robustness to motion artifacts and retrospective motion correction capabilities of the PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) trajectory were combined with prospective motion correction. The prospective correction was done using an intelligent marker attached to the subject.

RARE two-point Dixon with dual bandwidths.

Purpose: To investigate the impact of dual readout bandwidths (dBW) in a dual echo fat/water acquisition and describe a dBW-rapid acquisition relaxation enhanced, or turbo spin echo sequence where the concept is used to improve SNR by removing dead times between refocusing pulses and avoiding redundant Chemical-shift encoded.

Methods: Cramér-Rao bounds and Monte Carlo simulations were used to investigate a two-point fat/water model where the difference in bandwidths is incorporated. In vivo images were acquired at 1.

Projection-based 3D/2D registration for prospective motion correction.

Purpose: To develop a registration method that is capable of estimating the full range of rigid body motion from three orthogonal collapsed images of the head. These images can be obtained using the collapsed FatNav, a previously introduced navigator for prospective motion correction. It combines a short duration with wide compatibility with different main sequences due to its robustness against spin history effects.

Optimizing 3D EPI for rapid T -weighted imaging.

Purpose: To investigate the use of 3D EPI for rapid T -weighted brain imaging, focusing on the RF pulse's influence on the contrast between gray and white matter.

Methods: An interleaved 3D EPI sequence use partial Fourier and CAIPIRINHA sampling was used to acquire T -weighted brain volumes with isotropic resolution, low echo times, and low geometric distortions. Five different RF pulses were evaluated in terms of fat suppression performance and gray-white matter contrast.

Fat/water separation in k-space with real-valued estimates and its combination with POCS.

Purpose: To develop reconstruction methods for improved image quality of chemical shift displacement-corrected fat/water imaging combined with partial Fourier acquisition.

Theory: Fat/water separation in k-space enables correction of chemical shift displacement. Modeling fat and water as real-valued rather than complex improves the conditionality of the inverse problem.

Brown adipose tissue in young adults who were born preterm or small for gestational age.

Background: Brown adipose tissue (BAT) is present and functions to dissipate energy as heat in young adults and can be assessed using magnetic resonance imaging (MRI) to estimate the voxel fat fraction, i.e. proton density fat fraction (PDFF).

T1 weighted fat/water separated PROPELLER acquired with dual bandwidths.

Purpose: To describe a fat/water separated dual receiver bandwidth (rBW) spin echo PROPELLER sequence that eliminates the dead time associated with single rBW sequences. A nonuniform noise whitening by regularization of the fat/water inverse problem is proposed, to enable dual rBW reconstructions.

Methods: Bipolar, flyback, and dual spin echo sequences were developed.

Simultaneous multi-slice combined with PROPELLER.

Purpose: Simultaneous multi-slice (SMS) imaging is an advantageous method for accelerating MRI scans, allowing reduced scan time, increased slice coverage, or high temporal resolution with limited image quality penalties. In this work we combine the advantages of SMS acceleration with the motion correction and artifact reduction capabilities of the PROPELLER technique.

Methods: A PROPELLER sequence was developed with support for CAIPIRINHA and phase optimized multiband radio frequency pulses.

A 1-minute full brain MR exam using a multicontrast EPI sequence.

Purpose: A new multicontrast echo-planar imaging (EPI)-based sequence is proposed for brain MRI, which can directly generate six MR contrasts (T -FLAIR, T -w, diffusion-weighted (DWI), apparent diffusion coefficient (ADC), T2*-w, T -FLAIR) in 1 min with full brain coverage. This could enable clinical MR clinical screening in similar time as a conventional CT exam but with more soft-tissue information.

Methods: Eleven sequence modules were created as dynamic building blocks for the sequence.

The effect of radiotherapy on fat content and fatty acids in myxoid liposarcomas quantified by MRI.

Background: Myxoid liposarcomas are highly radiosensitive. Consequently radiotherapy is often used pre-operatively to reduce tumor volume and lessen the post-operative deficit. In soft-tissue sarcomas therapy response is mainly evaluated using magnetic resonance imaging (MRI) and the fundamental criterion for a positive response is decreased tumor size.

Quantification of severe liver iron overload using MRI offset echoes.

Magnetic resonance imaging (MRI) has become the clinical standard to estimate liver iron overload. The most commonly used method is to measure the transversal relaxation time, T2*, from a multi gradient recalled echo sequence (MGRE). While this technique is reliable in low to moderate liver iron concentrations (LIC), it will be inaccurate when it is severe.

Value of MRI and MRS fat measurements to complement conventional screening methods for childhood obesity.

Purpose: To evaluate a protocol combining abdominal fat-water magnetic resonance imaging (MRI) and liver single voxel magnetic resonance spectroscopy (MRS) for studies of childhood obesity.

Materials And Methods: Six obese male children and five age-matched normal-weight controls underwent abdominal fat-water Dixon MRI based on a gradient echo sequence with multiple echo times and single voxel liver MRS at a field strength of 3T. The MRI/MRS data were compared with data previously acquired from an obese adult cohort and with anthropometric and blood parameters that are typically acquired for screening in childhood obesity.