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MRI in patients with implanted active devices: how to combine safety and image quality using a limited transmission
Laura Lunden1, Stephan Wolff2, Sönke Peters2
1Department of Radiology and Neuroradiology, University Hospital Schleswig-Holstein Campus Kiel, Arnold-Heller-Straße 3, Haus 41, 24105, Kiel, Germany. stu117723@mail.uni-kiel.de.
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 B1+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 B1+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 B1+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 B1+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 B1+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 B1+rms≤ 2.0 μT. • This enables high-quality MRI of different body regions for patients with AD.
Insights
High-quality magnetic resonance imaging (MRI) is achievable even with restricted radio frequency (RF) transmission fields. This study demonstrates that adapting MRI sequences to a B1+rms limit of 2.0 μT maintains diagnostic image quality for various body regions.
Area of Science:
- Medical Imaging
- Biophysics
- Radiology
Background:
- Radio frequency (RF) pulses in MRI can interact with implanted devices, posing risks.
- Newer devices allow safe MRI under specific RF transmission field (B1+rms ≤ 2.0 μT) conditions.
Purpose of the Study:
- To investigate the technical limitations of MRI under liberal RF transmission field conditions (B1+rms ≤ 2.0 μT).
- To determine if MRI diagnostic quality is compromised by these restrictions.
Main Methods:
- Adapted 62 MRI sequences across six body regions (brain, spine, knee, liver, heart) on two 1.5T scanners.
- Evaluated diagnostic quality using signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and geometric deviation (GD) in phantom studies.
- Conducted blinded radiologist assessments of original and adapted sequences in healthy volunteers.
Main Results:
- Approximately one-third of sequences initially exceeded the B1+rms limit.
- 56 out of 62 adapted sequences maintained comparable image quality.
- Minor reductions in SNR/CNR occurred in 31 sequences; only one showed significant geometric deviation.
Conclusions:
- Clinically relevant MRI sequences can be adapted to B1+rms ≤ 2.0 μT with minimal impact on image quality.
- High-quality MRI is feasible despite transmission field limitations.
- Strategies for sequence adaptation were successfully derived.
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