Fast 3D coronary artery contrast-enhanced magnetic resonance angiography with magnetization transfer contrast, fat suppression and parallel imaging as applied on an anthropomorphic moving heart phantom

Scoping review of magnetic resonance motion imaging phantoms

To review and analyze the currently available MRI motion phantoms. Publications were collected from the Toronto Metropolitan University Library, PubMed, and IEEE Xplore. Phantoms were categorized based on the motions they generated: linear/cartesian, cardiac-dilative, lung-dilative, rotational, deformation or rolling. Metrics were extracted from each publication to assess the motion mechanisms, construction methods, as well as phantom validation. A total of 60 publications were reviewed, identifying 48 unique motion phantoms. Translational movement was the most common movement (used in 38% of phantoms), followed by cardiac-dilative (27%) movement and rotational movement (23%). The average degrees of freedom for all phantoms were determined to be 1.42. Motion phantom publications lack quantification of their impact on signal-to-noise ratio through standardized testing. At present, there is a lack of phantoms that are designed for multi-role as many currently have few degrees of freedom.

Dynamic Phantom for Flow Model in Magnetic Resonance Angiography

Purpose. To develop phantom for flow modeling in magnetic resonance angiography (MRA): relative contrast assessment, accuracy of the linear velocity and volumetric flow, what improve accuracy of diagnostic in cardiac and neurosurgical clinics (quality assessment of blood and cerebrospinal fluid motion). To compare scanners of different manufactures in points of the MRA efficiency using the developed phantom.

Materials and methods. The main part of dynamic phantom consists of a disc filled with agarose gel (for linear and volumetric velocity control) and silicone tubes for fluid flow modelling. MR study was performed at MRI units of two manufactures for comparing quantitative assessments of MRA sequences: 2DTOF, 3DTOF, and at three MRI units of one firm for estimated accuracy calibration curve calculating and linear velocity and volumetric flow determination for PC MRA. Phantom study well correlate with clinical MRA results.

Results. Obtained phantom scanning results in 2DTOF, 3DTOF sequences allow for objective comparing two MRI units of different manufactures. For 2DTOF mode was showed more effective signal enhancement affected by TOF effect for scanner of manufacture 2, then manufacture 1: 8.86 ± 0.88 и 6.07 ± 0.03 corresponding. For 3DTOF was observed rather more inflow relative contrast affected by TOF effect for scanner of manufacture 1: 6.06 ± 0.47 and 3.17 ± 0.83 corresponding. However, for manufacture 1 was showed more significant signal suppression for fat tissue, which improve vasculature visualization. Accuracy linear velocity fluid flow measurement in 2DPC is equal to ±2σ = ±0,4 by five pixels for three scanners of one manufacture. Using developed phantom was modelled MRA effects in 3DPC and Time-SLIP modes.

Conclusions. The developed dynamic phantom can be used for calibration tests in MRA. The case of MRI units of two manufactures were compared quantitative assessments of MRA sequences and analyzed methods of enhancement fluid flow signal.

Realistic analytical polyhedral MRI phantoms

PURPOSE

Analytical phantoms have closed form Fourier transform expressions and are used to simulate MRI acquisitions. Existing three-dimensional (3D) analytical phantoms are unable to accurately model shapes of biomedical interest. The goal of this study was to demonstrate that polyhedral analytical phantoms have closed form Fourier transform expressions and can accurately represent 3D biomedical shapes.

METHODS

The Fourier transform of a polyhedron was implemented and its accuracy in representing faceted and smooth surfaces was characterized. Realistic anthropomorphic polyhedral brain and torso phantoms were constructed and their use in simulated 3D and two-dimensional (2D) MRI acquisitions was described.

RESULTS

Using polyhedra, the Fourier transform of faceted shapes can be computed to within machine precision. Smooth surfaces can be approximated with increasing accuracy by increasing the number of facets in the polyhedron; the additional accumulated numerical imprecision of the Fourier transform of polyhedra with many faces remained small. Simulations of 3D and 2D brain and 2D torso cine acquisitions produced realistic reconstructions free of high frequency edge aliasing compared with equivalent voxelized/rasterized phantoms.

CONCLUSION

Analytical polyhedral phantoms are easy to construct and can accurately simulate shapes of biomedical interest. Magn Reson Med 76:663-678, 2016. © 2015 Wiley Periodicals, Inc.