Publications de Kieran O'Brien

Automated Detection and Segmentation of Multiple Sclerosis Lesions Using Ultra-High-Field MP2RAGE

Meritxell Bach Cuadra, Tobias Kober, Cristina Granziera, Kieran O'Brien, Mario Joao Fartaria de Oliveira

Objectives The aim of this study was to develop a new automated segmentation method of white matter (WM) and cortical multiple sclerosis (MS) lesions visible on magnetization-prepared 2 inversion-contrast rapid gradient echo (MP2RAGE) images acquired at 7 ...

LIPPINCOTT WILLIAMS & WILKINS2019

Cerebellar cortical laminar analysis of T1 relaxation times at 7T MRI shows widespread cerebellar cortex damage in early relapsing-remitting MS patients but no correlation with clinical deficits

Wietske Van der Zwaag, Yohan Boillat, Cristina Granziera, Kieran O'Brien

SAGE PUBLICATIONS LTD2019

Surface-based characteristics of the cerebellar cortex visualized with ultra-high field MRI

Guillaume Bonnier, Wietske Van der Zwaag, Gunnar Krüger, Yohan Boillat, Cristina Granziera, Kieran O'Brien, Mario Joao Fartaria de Oliveira

Although having a relatively homogeneous cytoarchitectonic organization, the cerebellar cortex is a heterogeneous region characterized by different amounts of myelin, iron and protein expression profiles. In this study, we used quantitative T1 and T2* mapp ...

2018

An Ultra-High Field Study of Cerebellar Pathology in Early Relapsing-Remitting Multiple Sclerosis Using MP2RAGE

Meritxell Bach Cuadra, Guillaume Bonnier, Gunnar Krüger, Tobias Kober, Cristina Granziera, Alexis Roche, Kieran O'Brien, Pavel Falkovskiy, Mario Joao Fartaria de Oliveira

Objectives: The aim of this study was to study focal cerebellar pathology in early stages of multiple sclerosis (MS) using ultra-high-field magnetization-prepared 2 inversion-contrast rapid gradient-echo (7T MP2RAGE). Materials and Methods: Twenty early-st ...

Lippincott, Williams & Wilkins2017

3D T 2-weighted imaging at 7T using dynamic kT-points on single-transmit MRI systems

Rolf Gruetter, Florent Eggenschwiler, José Pedro Rebelo Ferreira Marques, Kieran O'Brien, Daniel Gallichan

OBJECTIVES: For turbo spin echo (TSE) sequences to be useful at ultra-high field, they should ideally employ an RF pulse train compensated for the B 1 + inhomogeneity. Previously, it was shown that a single kT-point pulse designed in the small tip-angle re ...

Springer Verlag2016

Decline of Fiber Tract Integrity Over the Adult Age Range: A Diffusion Spectrum Imaging Study

Kieran O'Brien

Purpose: We applied a novel diffusion spectrum imaging (DSI) acquisition to determine associations between aging and subcortical fiber tract integrity. Materials and Methods: We studied 35 cognitively healthy subjects (17 women), spanning the adult age ran ...

Wiley-Blackwell2014

Simulation-based evaluation of susceptibility distortion correction methods in diffusion MRI for connectivity analysis

Meritxell Bach Cuadra, Alessandro Daducci, Kieran O'Brien

Connectivity analysis on diffusion MRI data of the whole- brain suffers from distortions caused by the standard echo- planar imaging acquisition strategies. These images show characteristic geometrical deformations and signal destruction that are an import ...

2014

Dielectric pads and low- B1+ adiabatic pulses: Complementary techniques to optimize structural T1w whole-brain MP2RAGE scans at 7 tesla

François Lazeyras, Gunnar Krüger, Tobias Kober, José Pedro Rebelo Ferreira Marques, Kieran O'Brien

Purpose To evaluate the combination of low-B1+ adiabatic pulses and high permittivity (εr ≈ 165) dielectric pads effectiveness to reproducibly improve the inversion efficiency for whole-brain MP2RAGE scans, at ultra-high field. Materials and Methods Two lo ...

Wiley-Blackwell2014

Improving T2 -weighted imaging at high field through the use of kT -points

Rolf Gruetter, Florent Eggenschwiler, José Pedro Rebelo Ferreira Marques, Kieran O'Brien

PURPOSE: At high magnetic field strengths (B0 >/= 3 T), the shorter radiofrequency wavelength produces an inhomogeneous distribution of the transmit magnetic field. This can lead to variable contrast across the brain which is particularly pronounced in T2 ...

Wiley-Blackwell2014

Robust T1-Weighted Structural Brain Imaging and Morphometry at 7T Using MP2RAGE

Patric Hagmann, François Lazeyras, Gunnar Krüger, Tobias Kober, José Pedro Rebelo Ferreira Marques, Alexis Roche, Kieran O'Brien

Purpose To suppress the noise, by sacrificing some of the signal homogeneity for numerical stability, in uniform T1 weighted (T1w) images obtained with the magnetization prepared 2 rapid gradient echoes sequence (MP2RAGE) and to compare the clinical utilit ...

Public Library of Science2014

A simple method to denoise ratio images in magnetic resonance imaging

Alexis Roche, Kieran O'Brien

Disclosed is a Magnetic Resonance Imaging method comprising the steps of: generating an MRI sequence designed for acquiring data from an object to be imaged, wherein the MRI sequence is configured for generating at least two different standard images, resp ...

2014

Assessing white matter microstructure of the newborn with multi-shell diffusion MRI and biophysical compartment models

Nicolas Kunz, François Lazeyras, Kieran O'Brien, Hui Zhang

Brain white matter connections have become a focus of major interest with important maturational processes occurring in newborns. To study the complex microstructural developmental changes in-vivo, it is imperative that non-invasive neuroimaging approaches ...

Elsevier2014

A simple method to denoise MP2RAGE

François Lazeyras, Rolf Gruetter, Gunnar Krüger, Alexis Roche, Kieran O'Brien

2013

3D Residual Eddy Current Field Characterisation: applied to Diffusion Weighted Magnetic Resonance Imaging

François Lazeyras, Rolf Gruetter, Gunnar Krüger, Alessandro Daducci, Kieran O'Brien

Clinical use of the Stejskal-Tanner diffusion weighted images is hampered by the geometric distortions that result from the large residual 3D eddy current field induced. In this work we aimed to predict, using linear response theory, the residual 3D eddy c ...

Institute of Electrical and Electronics Engineers2013

A multi-center study: Intra-scan and inter-scan variability of Diffusion Spectrum Imaging

Jean-Philippe Thiran, François Lazeyras, Alia Lemkaddem, Gunnar Krüger, Alessandro Daducci, Kieran O'Brien

The objective of this study was to investigate whether it is possible to pool together diffusion spectrum imaging data from four different scanners, located at three different sites. Two of the scanners had identical configuration whereas two did not. To m ...

Elsevier2012