Lu, Ming; Gore, John C.; Yan, Xinqiang. (2026).听.听Magnetic Resonance in Medicine. Advance online publication.听
Magnetic resonance imaging (MRI)聽often uses聽inductively coupled coils鈥攕mall receiver coils placed near the area being imaged鈥攖o improve image quality. However, when these coils are positioned close to the scanner’s primary coil, they can interfere with each other, causing effects that have traditionally been viewed as reducing image quality. This study investigated why inductively coupled coils can still perform well despite this strong interaction and examined the role of modern MRI聽preamplifiers聽(electronic components that amplify weak signals from the coils). The researchers tested different coil configurations and preamplifier settings in laboratory experiments and validated their findings with MRI scans at 7 tesla, a high-field MRI system. They found that modern low-input-impedance preamplifiers largely prevented the signal losses typically associated with strong coil coupling, allowing the secondary coils to function effectively even when placed very close to the primary coil. Although the interaction between the coils altered the electrical properties of the primary coil, it had little effect on the overall聽signal-to-noise ratio (SNR), a key measure of image quality. In contrast, reducing the effectiveness of the preamplifiers led to a 21%鈥�23% decrease in SNR. These findings suggest that modern preamplifiers play a critical role in maintaining MRI performance and could simplify the design of inductively coupled coils for future imaging systems.
FIGURE 1
(A) Setup and results of measuring the impedance of a 10-cm-diameter circular 7鈥塗 RF coil on a bottle phantom. (B) Setup and results of the same coil (primary coil) when a smaller 5-cm-diameter inductively coupled coil was placed underneath the primary coil but above the phantom. The primary coil was not retuned or rematched after introducing the inductively coupled coil. (C) Simplified equivalent circuit model of the coupled inductively coupled and primary coils illustrating resonance splitting due to strong mutual coupling.