José Marques

The interaction of electro-magnetic fields with tissues is mediated by Maxwell Equations and inherently related to the existing dielectric and magnetic tissue properties.

In this presentation we will cover some of the aspects known regarding: the physical mechanisms behind of magnetic susceptibility; the conductivity and electric permittivity at the frequencies of interest in MRI (MHz in the case of the resonating radio-frequency waves, and KHz in the case of  the switching of encoding gradients).

The way these interactions influence not only the images acquired in MRI but also the comfort of subjects will be addressed.

Markus Barth

The principles of obtaining the physical quantity of magnetic susceptibility using MRI are being presented. Quantitative Susceptibility Mapping (QSM) reflects tissue susceptibility using the MR phase information acquired using a gradient echo sequence. To obtain susceptibility maps several steps are required in the reconstruction, including (i) phase measurement, (ii) field map estimation, (iii) background field removal, and (iv) susceptibility map calculation by solving the inverse problem. Examples and challenges of QSM are presented and discussed.

Cornelis van den Berg, Stefano Mandija

This study gives an overview of the principles of Electrical Properties Tomography. The aim is to introduce researchers new to EPT in the basic EPT reconstruction principles, EPT artifacts and new directions.

It reviews Helmholtz based reconstruction, B1+ phase and transceive phase, boundary errors of EPT, forward vs inversion based EPT reconstruction and the synergy of EPT at high fields.

Kristen Yeom

Clinical application of QSM in pediatric brain will be discussed including its clinical role for evaluating normal and abnormal cerebral neurovasculature, vascular malformations, and hemorrhagic conditions through various clinical scenarios. In addition, plural contrast imaging feasible with 3D GRE multi-echo imaging will be addressed and its potential role in assessing various types of pediatric brain pathology. Use of Ferumoyxtol as a nan-oparticle vascular agent to augment neurovascular diagnostic evaluation will be addressed through clinical examples.  Finally, pitfalls and artifacts associated with QSM and T2* imaging will be discussed. 

Minming Zhang

Iron measured by MRI in vivo would contribute to searching for iron-related biomarkers in neurodegenerative diseases, like Parkinson's disease. 

Here, we would like to briefly introduce the technological development of MRI in assessing brain iron, discuss the nigral iron as a potential marker for PD in both clinical and prodromal stages, further put insight into other influences of regional iron on PD symptoms.

Pascal Spincemaille

The brain has long been a major focus for QSM, while applications of QSM outside the brain have occurred more recently. This course deals with both the technical aspects specific to QSM of the body and some of its clinical applications.

Ileana Hancu, Seung-Kyun Lee

The contrast in electrical properties (EP’s) between regions of interest (ROI’s) is typically limited to less than 30%; within-subject and between-subject variability is also on the order of 30%. The SNR of reconstructed EP’s depends on the reconstruction method used; for Laplacian-based EP reconstruction, SNR depends on field strength, absolute value of EP’s and (ROI_size)3.5.  At 3T and 7T, some applications for which relatively large ROI EP’s are sought have promising results using standard EP reconstruction. In order for EP mapping to become a reality at spatial resolutions useful for clinical diagnosis, more advanced reconstruction methodologies are likely needed.

Jürgen Reichenbach

Quantitative susceptibility mapping aims to solve the magnetic dipolar inverse problem to reconstruct tissue magnetic susceptibility distributions from single- or multi-echo GRE phase data. Being an ill-conditioned inverse problem, computation of magnetic susceptibility is challenging and requires conditioning. Several approaches to solve this problem exist, including threshold-based masking or kernel modification, utilizing data redundancy achieved by multiple MRI measurements with different orientations of the object, or applying regularization techniques that incorporate prior information about the spatial distribution of susceptibility. Several of these approaches will be reviewed in this lecture.

Jeff Duyn

High field studies have brought to light not only that the composition of tissues affects MRI susceptibility contrast, but also that a tissue’s sub-voxel structure at scales all the way down to the molecular level plays an important role as well. In this overview, various ways will be discussed by which sub-voxel structure can affect magnetic susceptibility contrast, and the extraction of quantitative magnetic susceptibility values.  In addition, opportunities study the microstructural aspects of brain tissue with susceptibility weighted MRI will be reviewed, with an emphasis for inferring the orientation of fiber bundles in white matter and the relative size of the myelin water compartment.  

Berkin Bilgic

This demo focuses on the processing pipeline of the 2016 QSM Reconstruction Challenge. The aims of the Challenge were (i) to test the ability of QSM algorithms to recover the underlying susceptibility from phase data, and (ii) to provide a dataset that would help benchmark existing and future techniques. The demo begins with raw phase data and applies unwrapping, background removal, transmit phase mitigation, and finishes with fast dipole inversion techniques: TKD and Closed-Form L2-regularization. This replicates the pipeline through which the benchmark susceptibility maps were computed for the Challenge, and can serve as a starting point in future studies. 

Zhe Liu, Pascal Spincemaille, Alexey Dimov, Ludovic de Rochefort, Yi Wang

We have developed robust QSM software for both clinicians and researchers. For clinicians interested in using QSM in their daily practices, we present an automated QSM workflow that can be implemented across major MRI manufacturers at both 1.5 and 3T. QSM is automatically reconstructed and available for viewing at the end of each patient MRI session. For researchers interested in further developing QSM algorithms, we present MATLAB tools and source codes for the core Bayesian QSM algorithm, along with implementation for nonlinear field estimation, field unwrapping and background field removal. A GUI tool is provided and demonstrated.

Hongjiang Wei

Quantitative susceptibility mapping (QSM) and susceptibility tensor imaging (STI) are two recently developed imaging methods for quantifying tissue’s magnetic property. Magnetic susceptibility offers a new contrast for high-resolution anatomical imaging; it further provides important information on tissue’s chemical composition, especially myelin and iron, and white matter microstructures of the brain. However, processing QSM and STI still requires advanced technical expertise. The growing application and wider acceptance of this new technique has generated a need for a comprehensive software package that can easily perform all these analysis. Here, we have developed such a tool named “STI Suite”. This software is based on our previous works. In this Matlab-based software package, we have implemented the essential algorithms for phase processing, QSM, STI, and related analysis tools. To facilitate the dissemination and evaluation of these methods, we make STI Suite freely available at http://people.duke.edu/~cl160/ for non-commercial academic use. STI Suite contains both Matlab command-line functions and graphical user interfaces (GUIs) for phase processing, QSM, STI, and related visualization and ROI analysis tools.