scholarly journals The Effect of Oblique Image Acquisition on the Accuracy of Quantitative Susceptibility Mapping and a Robust Tilt Correction Method

2021 ◽  
Author(s):  
Oliver C. Kiersnowski ◽  
Anita Karsa ◽  
Stephen J. Wastling ◽  
John S. Thornton ◽  
Karin Shmueli
Keyword(s):  
Mean Squared Error ◽  
Image Acquisition ◽  
Similarity Index ◽  
Background Field ◽  
Phase Unwrapping ◽  
Susceptibility Mapping ◽  
Main Magnetic Field ◽  
Quantitative Susceptibility Mapping ◽  
Tilt Correction

Purpose: Quantitative susceptibility mapping (QSM) is increasingly used for clinical research where oblique image acquisition is commonplace but its effects on QSM accuracy are not well understood. Theory and Methods: The QSM processing pipeline involves defining the unit magnetic dipole kernel, which requires knowledge of the direction of the main magnetic field B0 with respect to the acquired image volume axes. The direction of B0 is dependent upon the axis and angle of rotation in oblique acquisition. Using both a numerical brain phantom and in-vivo acquisitions, we analysed the effects of oblique acquisition on magnetic susceptibility maps. We compared three tilt correction schemes at each step in the QSM pipeline: phase unwrapping, background field removal and susceptibility calculation, using the root-mean-squared error and QSM-tuned structural similarity index (XSIM). Results: Rotation of wrapped phase images gave severe artefacts. Background field removal with projection onto dipole fields gave the most accurate susceptibilities when the field map was first rotated into alignment with B0. LBV and VSHARP background field removal methods gave accurate results without tilt correction. For susceptibility calculation, thresholded k-space division, iterative Tikhonov regularisation and weighted linear total variation regularisation all performed most accurately when local field maps were rotated into alignment with B0 before susceptibility calculation. Conclusion: For accurate QSM, oblique acquisition must be taken into account. Rotation of images into alignment with B0 should be carried out after phase unwrapping and before background field removal. We provide open-source tilt-correction code to incorporate easily into existing pipelines: https://github.com/o-snow/QSM_TiltCorrection.git.

scholarly journals Longitudinal dentate nuclei iron concentration and atrophy in Friedreich ataxia: IMAGE-FRDA

2018 ◽  
Author(s):  
Phillip G. D. Ward ◽  
Ian H Harding ◽  
Thomas G. Close ◽  
Louise A Corben ◽  
Martin B Delatycki ◽  
...  
Keyword(s):  
Iron Concentration ◽  
Friedreich Ataxia ◽  
Susceptibility Mapping ◽  
Disease Stage ◽  
Healthy Controls ◽  
Quantitative Susceptibility Mapping ◽  
Rates Of Change ◽  
Longitudinal Biomarker ◽  
Baseline Disease Severity

AbstractBackgroundFriedreich ataxia is a recessively inherited, progressive neurological disease characterised by impaired mitochondrial iron metabolism. The dentate nuclei of the cerebellum are characteristic sites of neurodegeneration in the disease, but little is known of the longitudinal progression of pathology in these structures.MethodsUsing in vivo magnetic resonance imaging, including quantitative susceptibility mapping, we investigated changes in iron concentration and volume in the dentate nuclei in individuals with Friedreich ataxia (n=20) and healthy controls (n=18) over a two-year period.ResultsThe longitudinal rate of iron concentration was significantly elevated bilaterally in participants with Friedreich ataxia relative to healthy controls. Atrophy rates did not differ significantly between groups. Change in iron concentration and atrophy both correlated with baseline disease severity or duration, indicating sensitivity of these measures to disease stage. Moreover, atrophy was maximal in individuals early in the disease course, while the rate of iron concentration increased with disease progression.ConclusionsProgressive dentate nuclei pathology is evident in vivo in Friedreich ataxia, and the rates of change of iron concentration and atrophy in these structures are sensitive to the disease stage. The findings are consistent with an increased rate of iron concentration and atrophy early in the disease, followed by iron accumulation and stable volume in later stages. This pattern suggests that iron dysregulation persists after loss of the vulnerable neurons in the dentate. The significant changes observed over a two-year period highlights the utility of quantitative susceptibility mapping as a longitudinal biomarker and staging tool.

scholarly journals Quantitative Susceptibility Mapping of the Basal Ganglia and Thalamus at 9.4 Tesla

2021 ◽  
Vol 15 ◽  
Author(s):  
Vinod Jangir Kumar ◽  
Klaus Scheffler ◽  
Gisela E. Hagberg ◽  
Wolfgang Grodd
Keyword(s):  
Basal Ganglia ◽  
Functional Anatomy ◽  
Susceptibility Mapping ◽  
Paramagnetic Susceptibility ◽  
Substantial Contribution ◽  
Hemispheric Differences ◽  
Quantitative Susceptibility Mapping ◽  
Ultra High Field

The thalamus (Th) and basal ganglia (BG) are central subcortical connectivity hubs of the human brain, whose functional anatomy is still under intense investigation. Nevertheless, both substructures contain a robust and reproducible functional anatomy. The quantitative susceptibility mapping (QSM) at ultra-high field may facilitate an improved characterization of the underlying functional anatomy in vivo. We acquired high-resolution QSM data at 9.4 Tesla in 21 subjects, and analyzed the thalamic and BG by using a prior defined functional parcellation. We found a more substantial contribution of paramagnetic susceptibility sources such as iron in the pallidum in contrast to the caudate, putamen, and Th in descending order. The diamagnetic susceptibility sources such as myelin and calcium revealed significant contributions in the Th parcels compared with the BG. This study presents a detailed nuclei-specific delineation of QSM-provided diamagnetic and paramagnetic susceptibility sources pronounced in the BG and the Th. We also found a reasonable interindividual variability as well as slight hemispheric differences. The results presented here contribute to the microstructural knowledge of the Th and the BG. In specific, the study illustrates QSM values (myelin, calcium, and iron) in functionally similar subregions of the Th and the BG.

scholarly journals Abdominal single-step quantitative susceptibility mapping with spherical mean value filter and structure prior-based regularization

2020 ◽  
Author(s):  
Anton Abyzov ◽  
Bernard E. Van Beers ◽  
Philippe Garteiser
Keyword(s):  
Subcutaneous Fat ◽  
Background Field ◽  
Mean Value ◽  
Single Step ◽  
Susceptibility Mapping ◽  
Small Animals ◽  
Quantitative Susceptibility Mapping ◽  
Split Bregman ◽  
Spherical Mean ◽  
Susceptibility Maps

Abdominal quantitative susceptibility mapping (QSM), especially in small animals, is challenging because of respiratory motion and blood flow that, in addition to noise, deteriorate the quality of the input data. Efficient artefact suppression in QSM reconstruction is crucial in these conditions. Single-step QSM algorithms combine background field removal and magnetic field-to-susceptibility inverse problem regularization in a single optimization equation. Here, we propose a single-step QSM algorithm that uses spherical mean value kernels of different radii for background field removal and structure prior (consistency with magnitude image) with L1 norm for regularization. The optimization problem is solved using the split-Bregman method on the graphic processor unit. The method was compared with previously reported singlestep methods: a method using discrete Laplacian instead of spherical mean value kernels, a method using total variational penalty instead of structure prior, and a method using L2 norm for structure prior. With the proposed method relative to the previous ones, a numerical susceptibility phantom was reconstructed more precisely. In living mice, susceptibility maps with more homogeneous liver, higher contrast between liver and blood vessels, and well-preserved structural details were obtained. In patients, susceptibility maps with more homogeneous subcutaneous fat and higher contrast between subcutaneous fat and liver were obtained. These results show the potential of the proposed single-step method for abdominal QSM in small animals and humans.

Patents on Quantitative Susceptibility Mapping (QSM) of Tissue Magnetism

2019 ◽  
Vol 13 (2) ◽  
pp. 90-113
Author(s):  
Feng Lin ◽  
Martin R. Prince ◽  
Pascal Spincemaille ◽  
Yi Wang
Keyword(s):  
Neurological Diseases ◽  
Background Field ◽  
Bayesian Framework ◽  
Susceptibility Mapping ◽  
Quantitative Susceptibility Mapping ◽  
Liver Iron ◽  
Seamless Integration ◽  
Tissue Ischemia ◽  
Susceptibility Maps ◽  
Wide Range

<P>Background: Quantitative susceptibility mapping (QSM) depicts biodistributions of tissue magnetic susceptibility sources, including endogenous iron and calcifications, as well as exogenous paramagnetic contrast agents and probes. When comparing QSM with simple susceptibility weighted MRI, QSM eliminates blooming artifacts and shows reproducible tissue susceptibility maps independent of field strength and scanner manufacturer over a broad range of image acquisition parameters. For patient care, QSM promises to inform diagnosis, guide surgery, gauge medication, and monitor drug delivery. The Bayesian framework using MRI phase data and structural prior knowledge has made QSM sufficiently robust and accurate for routine clinical practice.Objective:To address the lack of a summary of US patents that is valuable for QSM product development and dissemination into the MRI community.Method:We searched the USPTO Full-Text and Image Database for patents relevant to QSM technology innovation. We analyzed the claims of each patent to characterize the main invented method and we investigated data on clinical utility. </P><P> Results: We identified 17 QSM patents; 13 were implemented clinically, covering various aspects of QSM technology, including the Bayesian framework, background field removal, numerical optimization solver, zero filling, and zero-TE phase.Conclusion:Our patent search identified patents that enable QSM technology for imaging the brain and other tissues. QSM can be applied to study a wide range of diseases including neurological diseases, liver iron disorders, tissue ischemia, and osteoporosis. MRI manufacturers can develop QSM products for more seamless integration into existing MRI scanners to improve medical care.</P>

Sign in / Sign up

Export Citation Format

Share Document