Quantitative susceptibility mapping (QSM) of the cardiovascular system: challenges and perspectives

Abstract

Quantitative susceptibility mapping (QSM) is a powerful, non-invasive, magnetic resonance imaging (MRI) technique that relies on measurement of magnetic susceptibility. So far, QSM has been employed mostly to study neurological disorders characterized by iron accumulation, such as Parkinson’s and Alzheimer’s diseases. Nonetheless, QSM allows mapping key indicators of cardiac disease such as blood oxygenation and myocardial iron content. For this reason, the application of QSM offers an unprecedented opportunity to gain a better understanding of the pathophysiological changes associated with cardiovascular disease and to monitor their evolution and response to treatment. Recent studies on cardiovascular QSM have shown the feasibility of a non-invasive assessment of blood oxygenation, myocardial iron content and myocardial fibre orientation, as well as carotid plaque composition. Significant technical challenges remain, the most evident of which are related to cardiac and respiratory motion, blood flow, chemical shift effects and susceptibility artefacts. Significant work is ongoing to overcome these challenges and integrate the QSM technique into clinical practice in the cardiovascular field.

Characterization of quantitative susceptibility mapping in the left ventricular myocardium

“…A material’s magnetic susceptibility depends on its molecular electronic configuration, with unpaired electrons generating a strong positive susceptibility and paired electrons a weak negative susceptibility. This means that metal ions, such as iron (II/III) or gadolinium (III), with several unpaired electrons, have strong positive shifts, allowing them to be visualized with QSM at concentrations seen in disease [1] .…”

“…Myocardial quantitative susceptibility mapping (QSM) is a promising technique for the diagnosis and evaluation of several cardiac conditions involving excess iron [1] . One particular area of interest is the detection of the focal iron deposits found following a hemorrhagic myocardial infarction, which can give insight into the severity of the infarct and have a pathological role in adverse left ventricular remodeling [2] , [3] .…”

Recommended implementation of quantitative susceptibility mapping for clinical research in the brain: A consensus of the ISMRM electro‐magnetic tissue properties study group

“…[44][45][46] An important feature of QSM, when compared to, for example, R 1 or R 2 relaxometry, is that its results may be less independent of field strength and scanner manufacturer when a consistent reconstruction QSM pipeline is used. 47,48 Nevertheless, there is currently no consensus or white paper on how to perform brain QSM in the clinical setting, despite extensive reviews on QSM techniques and applications 3,6,7,[49][50][51][52][53][54][55][56][57][58][59][60][61][62] and strong QSM community interest in identifying the best algorithms. [63][64][65][66] QSM is not yet a standard product on most MRI systems, although some scanner vendors are beginning to offer works-in-progress or even product software packages for QSM.…”

“…Nevertheless, there is currently no consensus or white paper on how to perform brain QSM in the clinical setting, despite extensive reviews on QSM techniques and applications 3,6,7,49–62 and strong QSM community interest in identifying the best algorithms 63–66 . QSM is not yet a standard product on most MRI systems, although some scanner vendors are beginning to offer works‐in‐progress or even product software packages for QSM.…”

Residue-guided phase unwrapping in fringe projection measurements using second differences

“…Current methods for phase unwrapping can be categorized into three main groups: path-dependent methods [12][13][14][15][16][17], minimum norm methods [18][19][20][21], and path-independent (temporal) unwrapping approaches [22][23][24][25]. Temporal unwrapping algorithms excel at unwrapping objects with physical discontinuities, but they face challenges in noisy conditions due to their reliance on the ratio between multiple wavelengths (low and high frequencies), which amplifies noise during phase unwrapping.…”