Overview of quantitative susceptibility mapping

Abstract

Magnetic susceptibility describes the magnetizability of a material to an applied magnetic field and represents an important parameter in the field of MRI. With the recently introduced method of quantitative susceptibility mapping (QSM) and its conceptual extension to susceptibility tensor imaging (STI), the non-invasive assessment of this important physical quantity has become possible with MRI. Both methods solve the ill-posed inverse problem to determine the magnetic susceptibility from local magnetic fields. Whilst QSM allows the extraction of the spatial distribution of the bulk magnetic susceptibility from a single measurement, STI enables the quantification of magnetic susceptibility anisotropy, but requires multiple measurements with different orientations of the object relative to the main static magnetic field. In this review, we briefly recapitulate the fundamental theoretical foundation of QSM and STI, as well as computational strategies for the characterization of magnetic susceptibility with MRI phase data. In the second part, we provide an overview of current methodological and clinical applications of QSM with a focus on brain imaging. Copyright © 2016 John Wiley & Sons, Ltd.

MEDI+0: Morphology enabled dipole inversion with automatic uniform cerebrospinal fluid zero reference for quantitative susceptibility mapping

“…The optimization problem for QSM in literature has become converged to a MEDI type Bayesian formation : with the susceptibility map, the convolution operation, the noise weighting, the measured local field, the gradient operator and the binary edge mask derived from the magnitude image . is the dipole kernel that can be defined in both Fourier and spatial domains: where is the magnitude of position vector from the dipole source to the field observer, is the magnitude of the corresponding Fourier vector in k‐space.…”

Quantitative susceptibility mapping (QSM) as a means to monitor cerebral hematoma treatment

“…However, hypointensity in T 2 *‐weighted GRE magnitude images is known to overestimate hematoma volume, as these images suffer from susceptibility artifacts that are highly dependent on imaging parameters, such as field strength, voxel size, and echo time. In contrast, QSM based on GRE phase data can provide an accurate measurement of the hemorrhage volumes by removing blooming artifacts inherent in traditional T 2 *‐weighted imaging . QSM offers excellent image contrast by computing the spatial distribution of the underlying source of the phase contrast, ie, magnetic susceptibility .…”

Quantitative susceptibility mapping across two clinical field strengths: Contrast‐to‐noise ratio enhancement at 1.5T

“…Quantitative susceptibility mapping (QSM) is an emerging magnetic resonance imaging (MRI) postprocessing technique, which allows quantification of the spatial distribution of tissue magnetic susceptibility in vivo . Major sources of magnetic susceptibility in vivo include iron, blood products, calcium, myelin, and lipid content .…”

“…Currently, there is an increasing number of research and clinical applications for QSM, including the assessment of cerebral microbleeds, other hemorrhages, cavernous malformations, and iron content in the deep gray matter structures . In particular, iron accumulation in the brain has been associated with neurological diseases such as Parkinson's disease and multiple sclerosis, as well as with aging .…”