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01.05.2020 | Magnetic Resonance

MRI in patients with implanted active devices: how to combine safety and image quality using a limited transmission field?

verfasst von: Laura Lunden, Stephan Wolff, Sönke Peters, Catharina Drews, Christine Gierloff, Ulf Jensen-Kondering, Patrick Langguth, Jawid Madjidyar, Tim-Christian Piesch, Olav Jansen

Erschienen in: European Radiology | Ausgabe 5/2020

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Abstract

Objectives

Radio frequency (RF) pulses in magnetic resonance imaging (MRI) can interact with implanted devices and cause tissue damage. However, there are new devices that can safely perform measurements with liberal MRI conditions such as an RF transmission field B_1+rms ≤ 2.0 μT. We investigated whether MRI in this case is limited for these technical reasons.

Methods

We selected typical MRI protocols of six body regions (brain, cervical spine, lumbar spine, knee, liver, heart) using two typical 1.5T MRI scanners. Overall, we adapted 62 sequences to B_1+rms conditions and evaluated their diagnostic quality. For this, we measured signal-to-noise-ratio (SNR), contrast-to-noise-ratio (CNR), and geometric deviation (GD) as quality parameters, using phantom studies. For questionnaire studies, we selected pairs of original and adapted sequences in healthy volunteers. Blinded radiologists rated the images as single sequence rating and in direct comparison.

Results

Roughly one-third of the checked sequences were below the B_1+rms limit. Here, 56 of the 62 adapted sequences showed at least the same image quality in single ratings. A reduction in SNR and/or CNR was found with 31 sequences and only one sequence with considerably increased GD. Especially, sequences with original high B_1+rms values, PD sequences, and sequences of the Siemens knee and heart protocol were difficult to adapt, whereas most TSE and IR sequences had no clinical limitations.

Conclusion

By limiting the transmission field to B_1+rms ≤ 2.0 μT, clinically relevant MR sequences can be adapted with nearly no reduction in image quality. Despite limiting the transmission field, high-quality MR imaging is possible. We could derive strategies for adaptation.

Key Points

• Despite limiting the transmission field, high-quality MRI is possible.

• We could derive strategies for adapting the sequences to B _1+rms ≤ 2.0 μT.

• This enables high-quality MRI of different body regions for patients with AD.

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Titel: MRI in patients with implanted active devices: how to combine safety and image quality using a limited transmission field?
verfasst von: Laura Lunden
Stephan Wolff
Sönke Peters
Catharina Drews
Christine Gierloff
Ulf Jensen-Kondering
Patrick Langguth
Jawid Madjidyar
Tim-Christian Piesch
Olav Jansen
Publikationsdatum: 01.05.2020
Verlag: Springer Berlin Heidelberg
Erschienen in: European Radiology / Ausgabe 5/2020
Print ISSN: 0938-7994
Elektronische ISSN: 1432-1084
DOI: https://doi.org/10.1007/s00330-019-06599-6

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MRI in patients with implanted active devices: how to combine safety and image quality using a limited transmission field?