We describe a standardized method to evaluate magnetic resonance imaging artifacts caused by implants to estimate the suitability of the implants for magnetic resonance imaging and/or the vulnerability of different pulse sequences to metallic artifacts simultaneously.
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Method Article
Protocol for the Evaluation of MRI Artifacts Caused by Metal Implants to Assess the Suitability of Implants and the Vulnerability of Pulse Sequences
In This Article
Summary
Abstract
As the number of magnetic resonance imaging (MRI) scanners and patients with medical implants is constantly growing, radiologists increasingly encounter metallic implant-related artifacts in MRI, resulting in reduced image quality. Therefore, the MRI suitability of implants in terms of artifact volume, as well as the development of pulse sequences to reduce image artifacts, are becoming more and more important. Here, we present a comprehensive protocol which allows for a standardized evaluation of the artifact volume of implants on MRI. Furthermore, this protocol can be used to analyze the vulnerability of different pulse sequences to artifacts. The proposed protocol can be applied to T1- and T2-weighted images with or without fat-suppression and all passive implants. Furthermore, the procedure enables the separate and three-dimensional identification of signal loss and pile-up artifacts. As previous investigations differed greatly in evaluation methods, the comparability of their results was limited. Thus, standardized measurements of MRI artifact volumes are necessary to provide better comparability. This may improve the development of the MRI suitability of implants and better pulse sequences to finally improve patient care.
Introduction
MRI has become an indispensable diagnostic tool. As a result, the number of MRI systems used in routine diagnostics is further increasing1. At the same time, the number of patients with implants is increasing as well2,3. In 2012, for instance, more than 1 million knee and joint replacements have been performed in the USA alone4. The prevalence of such implants was about 7 million in 2010, which corresponds to more than 10% of females in the age group 80-89 years5. As a result, the image quality and the diagnostic significance of MRI examin....
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Protocol
1. Phantom Preparation
- Determine the implant volume (e.g., by using the water displacement method).
NOTE: The volume of the CCT-T sample and the Z-T sample measured 0.65 mL and 0.73 mL, respectively. - Fix the implant position in the middle of a non-ferromagnetic, plastic, waterproof box by using a thin thread. Use a box that is larger than the expected MRI artifacts.
NOTE: If no rough estimates of the artifact volumes of the implant and/or pulse sequence of interest are available, perform a test scan by placing the phantom in a box, approximately 10x larger than the phantom, filled with water. The artifact volumes in this st....
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Results
With the above-mentioned protocol, we evaluated the artifact volume of 2 different dental implants made of Titanium (T; see the Table of Materials) supporting different crowns [porcelain-fused-to-metal non-precious alloy (CCT-T) and monolithic zirconia (Z-T); Figure 1b and 1c]. The CCT-T sample represents a highly paramagnetic material composition predicting large artifacts (Cobalt 61%, Chrome 21%, and Tungsten 11%; CCT). The.......
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Discussion
The number of patients with metallic implants and the number of MRI examinations is currently increasing1,2,3. In the past, MRI examinations were avoided after joint replacements. Today, however, MRI is not only requested for imaging such patients but should also allow for the evaluation of complications directly adjacent to joint arthroplasty. Thus, the MRI safety and MRI suitability of implants, as well as the robust pulse seq.......
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Disclosures
Tim Hilgenfeld, Franz S. Schwindling, and Alexander Juerchott received funding from a postdoctoral fellowship of the Medical Faculty of the University of Heidelberg. The study was supported in part by the Dietmar-Hopp-Stiftung (project no. 23011228). The authors have stated explicitly that there are no conflicts of interest in connection with this article.
Acknowledgements
The authors like to thank Stefanie Sauer, pharmacist at the Department of Pharmacy Heidelberg University Hospital, for her contributions to the MRI phantom. In addition, we would like to thank NORAS MRI products GmbH (Höchberg, Germany) and especially Daniel Gareis for providing a prototype of the 16-channel multipurpose coil. Furthermore, we are grateful for the kind cooperation with SIEMENS Healthcare GmbH (Erlangen, Germany) and especially Mathias Nittka for their assistance in the sequence setup.
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Materials
| Name | Company | Catalog Number | Comments |
|---|---|---|---|
| Aqua B. Braun Ecotainer | B. Braun Melsungen AG, Melsungen, Germany | ||
| Semisynthetic fat: Witepsol W25 | Caelo Caesar & Loretz GmbH, Hilder, Germany | 4051 | |
| Macrogol-8-stearate | Caelo Caesar & Loretz GmbH, Hilder, Germany | 3023 | |
| Plastic box: not specified | |||
| Implants: Nobel Replace | Nobel Biocare, Zürich, Switzerland | ||
| Water bath Haake S5P | Thermo Scientific, Waltham, MA, USA | ||
| Measuring cylinder Blaubrand Eterna, Class A, Boro 3.3 | BRAND GmbH + Co Kg, Wertheim, Germany | 32708 | |
| Coil: Variety | Noras MRI products GmbH, Höchberg, Germany | ||
| MRI: Magnetom Trio | Siemens Healthcare GmbH, Erlangen, Germany | ||
| Postprocesing software: Amira 6.4 | Thermo Scientific, Waltham, MA, USA |
References
- Matsumoto, M., Koike, S., Kashima, S., Awai, K. Geographic distribution of CT, MRI and PET devices in Japan: a longitudinal analysis based on national census data. PLoS ONE. 10 (5), (2015).
- Cram, P., et al. Total....
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