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    Original Research

    Opportunities in Interventional and Diagnostic Imaging by Using High-Performance Low-Field-Strength MRI

    Published Online:Oct 1 2019https://doi.org/10.1148/radiol.2019190452
    See related article

    Abstract

    Low-field MRI combined with contemporary high-performance MRI hardware and advanced image acquisition and reconstruction strategies has advantages for some technically demanding applications including MRI-guided interventions, imaging anatomy near air-tissue interfaces, and efficient image acquisition methods.

    Background

    Commercial low-field-strength MRI systems are generally not equipped with state-of-the-art MRI hardware, and are not suitable for demanding imaging techniques. An MRI system was developed that combines low field strength (0.55 T) with high-performance imaging technology.

    Purpose

    To evaluate applications of a high-performance low-field-strength MRI system, specifically MRI-guided cardiovascular catheterizations with metallic devices, diagnostic imaging in high-susceptibility regions, and efficient image acquisition strategies.

    Materials and Methods

    A commercial 1.5-T MRI system was modified to operate at 0.55 T while maintaining high-performance hardware, shielded gradients (45 mT/m; 200 T/m/sec), and advanced imaging methods. MRI was performed between January 2018 and April 2019. T1, T2, and T2* were measured at 0.55 T; relaxivity of exogenous contrast agents was measured; and clinical applications advantageous at low field were evaluated.

    Results

    There were 83 0.55-T MRI examinations performed in study participants (45 women; mean age, 34 years ± 13). On average, T1 was 32% shorter, T2 was 26% longer, and T2* was 40% longer at 0.55 T compared with 1.5 T. Nine metallic interventional devices were found to be intrinsically safe at 0.55 T (<1°C heating) and MRI-guided right heart catheterization was performed in seven study participants with commercial metallic guidewires. Compared with 1.5 T, reduced image distortion was shown in lungs, upper airway, cranial sinuses, and intestines because of improved field homogeneity. Oxygen inhalation generated lung signal enhancement of 19% ± 11 (standard deviation) at 0.55 T compared with 7.6% ± 6.3 at 1.5 T (P = .02; five participants) because of the increased T1 relaxivity of oxygen (4.7e−4 mmHg−1sec−1). Efficient spiral image acquisitions were amenable to low field strength and generated increased signal-to-noise ratio compared with Cartesian acquisitions (P < .02). Representative imaging of the brain, spine, abdomen, and heart generated good image quality with this system.

    Conclusion

    This initial study suggests that high-performance low-field-strength MRI offers advantages for MRI-guided catheterizations with metal devices, MRI in high-susceptibility regions, and efficient imaging.

    © RSNA, 2019

    Online supplemental material is available for this article.

    See also the editorial by Grist in this issue.

    Download as PowerPoint

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    Article History

    Received: Feb 26 2019
    Revision requested: Apr 15 2019
    Revision received: Aug 6 2019
    Accepted: Aug 15 2019
    Published online: Oct 01 2019
    Published in print: Nov 2019