Harmonic analysis for the characterization and correction of geometric distortion in MRI

Tadic, Tony; Jaffray, David A.; Stanescu, T.

doi:10.1118/1.4898582

Cited by 24 publications

(42 citation statements)

References 46 publications

(46 reference statements)

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“…This may be due to gross, uncorrectable off resonance effects. In other works the forward and reversed gradient readout polarity images themselves are subjected to a position estimation step, and then those positions are averaged to find an off-resonance free distortion map[28]. We chose to do the B0 correction upfront and perform a single position estimation step, but the other method could be used as well.…”

Section: Discussionmentioning

confidence: 99%

Image-based gradient non-linearity characterization to determine higher-order spherical harmonic coefficients for improved spatial position accuracy in magnetic resonance imaging

Weavers

Tao

Trzasko

et al. 2017

Magnetic Resonance Imaging

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Purpose Spatial position accuracy in magnetic resonance imaging (MRI) is an important concern for a variety of applications, including radiation therapy planning, surgical planning, and longitudinal studies of morphologic changes to study neurodegenerative diseases. Spatial accuracy is strongly influenced by gradient linearity. This work presents a method for characterizing the gradient non-linearity fields on a per-system basis, and using this information to provide improved and higher-order (9th vs 5th) spherical harmonic coefficients for better spatial accuracy in MRI. Methods A large fiducial phantom containing 5229 water-filled spheres in a grid pattern is scanned with the MR system, and the positions all the fiducials are measured and compared to the corresponding ground truth fiducial positions as reported from a computed tomography (CT) scan of the object. Systematic errors from off-resonance (i.e., B0) effects are minimized with the use of increased receiver bandwidth (±125 kHz) and two acquisitions with reversed readout gradient polarity. The spherical harmonic coefficients are estimated using an iterative process, and can be subsequently used to correct for gradient non-linearity. Test-retest stability was assessed with five repeated measurements on a single scanner, and cross-scanner variation on four different, identically-configured 3T wide-bore systems. Results A decrease in the root-mean-square error (RMSE) over a 50 cm diameter spherical volume from 1.80 mm to 0.77 mm is reported here in the case of replacing the vendor’s standard 5th order spherical harmonic coefficients with custom fitted 9th order coefficients, and from 1.5mm to 1mm by extending custom fitted 5th order correction to the 9th order. Minimum RMSE varied between scanners, but was stable with repeated measurements in the same scanner. Conclusions The results suggest that the proposed methods may be used on a per-system basis to more accurately calibrate MR gradient non-linearity coefficients when compared to vendor standard corrections.

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Section: Discussionmentioning

confidence: 99%

Image-based gradient non-linearity characterization to determine higher-order spherical harmonic coefficients for improved spatial position accuracy in magnetic resonance imaging

Weavers

Tao

Trzasko

et al. 2017

Magnetic Resonance Imaging

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“…

Δ_{res}

for common quadratic geometries and R9 show a good agreement between HA and

F_{ref}

with % > 1 mm within 0.5% and 0.2% for the axial components and δr , respectively. In particular for the sphere case, the FEM approach shows improved results when compared to our previous method based on a semianalytical formulation, specifically the max

Δ_{res}

values decreased from approximately 3–0.3%. This is due to finer computations relying on improved discretization of the space and basis functions provided by FEM.…”

Section: Resultsmentioning

confidence: 78%

“…The 3D system‐related distortion field (

scriptF

) is intrinsically related to the superposition of magnetic fields specific to an MR imaging system, that is, B 0 and imaging gradients. The resultant distortion field is in a steady‐state, which implies no dependence on the time variable, and can be described by the Laplace's equation . Therefore, a boundary value problem can be formulated and solved in a given domain

scriptD

by finding a solution u to Laplace's equation, which satisfy certain conditions imposed on the boundary of

scriptD

(i.e.,

\partial D

).…”

Section: Theorymentioning

confidence: 99%

“…The key assumption is that there is a direct link between the local spatial distortion values recorded in the MR images via measurements and the magnetic fields involved in performing the imaging. This leads to the concept that dedicated magnetic field analysis can also be applied (with certain modifications) to the distortion fields . Specifically, we solved the Laplace equation with BCs for the case of 3D MR image distortion fields.…”

Section: Introductionmentioning

confidence: 99%

“…Specifically, we solved the Laplace equation with BCs for the case of 3D MR image distortion fields. The new method allows for the generalization of the concept presented in our previous work which dealt only with spherical volumes . Specifically, the new work includes complex geometries (i.e., cylinder, cuboid, D‐shape, ellipsoid, and Reuleaux 9‐gon) and the arbitrary and irregular shape of the entire imaging volume of an MR scanner as characterized by a large field of view (FOV) phantom.…”

Section: Introductionmentioning

confidence: 99%

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Technical Note: Harmonic analysis applied to MR image distortion fields specific to arbitrarily shaped volumes

Stanescu

Jaffray

2018

Medical Physics

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A novel harmonic analysis approach relying on finite element methods was introduced and validated for multiple volumes with surface shape functions ranging from simple to highly complex. Since a boundary value problem is solved the method requires input data from only the surface of the desired domain of interest. It is believed that the harmonic method will facilitate (a) the design of new phantoms dedicated for the quantitation of MR image distortions in large volumes and (b) an integrative approach of combining multiple imaging tests specific to radiotherapy into a single test object for routine imaging quality control.

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Optimization of a novel large field of view distortion phantom for MR‐only treatment planning

Price

Knight

Hwang

et al. 2017

J Applied Clin Med Phys

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Purpose MR-only treatment planning requires images of high geometric fidelity, particularly for large fields of view (FOV). However, the availability of large FOV distortion phantoms with analysis software is currently limited. This work sought to optimize a modular distortion phantom to accommodate multiple bore configurations and implement distortion characterization in a widely implementable solution. Method and Materials To determine candidate materials, 1.0 T MR and CT images were acquired of twelve urethane foam samples of various densities and strengths. Samples were precision-machined to accommodate 6 mm diameter paintballs used as landmarks. Final material candidates were selected by balancing strength, machinability, weight, and cost. Bore sizes and minimum aperture width resulting from couch position were tabulated from the literature (14 systems, 5 vendors). Bore geometry and couch position were simulated using MATLAB to generate machine-specific models to optimize the phantom build. Previously developed software for distortion characterization was modified for several magnet geometries (1.0 T, 1.5 T, 3.0 T), compared against previously published 1.0 T results, and integrated into the 3D Slicer application platform. Results All foam samples provided sufficient MR image contrast with paintball landmarks. Urethane foam (compressive strength ~1000 psi, density ~20 lb/ft3) was selected for its accurate machinability and weight characteristics. For smaller bores, a phantom version with the following parameters was used: 15 foam plates, 55 × 55 × 37.5 cm3 (L×W×H), 5,082 landmarks, and weight ~30 kg. To accommodate > 70 cm wide bores, an extended build used 20 plates spanning 55 × 55 × 50 cm3 with 7,497 landmarks and weight ~44 kg. Distortion characterization software was implemented as an external module into 3D Slicer’s plugin framework and results agreed with the literature. Conclusion The design and implementation of a modular, extendable distortion phantom was optimized for several bore configurations. The phantom and analysis software will be available for multi-institutional collaborations and cross-validation trials to support MR-only planning.

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Harmonic analysis for the characterization and correction of geometric distortion in MRI

Cited by 24 publications

References 46 publications

Image-based gradient non-linearity characterization to determine higher-order spherical harmonic coefficients for improved spatial position accuracy in magnetic resonance imaging

Image-based gradient non-linearity characterization to determine higher-order spherical harmonic coefficients for improved spatial position accuracy in magnetic resonance imaging

Technical Note: Harmonic analysis applied to MR image distortion fields specific to arbitrarily shaped volumes

Optimization of a novel large field of view distortion phantom for MR‐only treatment planning

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