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Loop Transmit Coil for Ultra-High Field MRI

IP.com Disclosure Number: IPCOM000247133D
Publication Date: 2016-Aug-09
Document File: 1 page(s) / 47K

Publishing Venue

The IP.com Prior Art Database

Abstract

Loop coils are known and widely used in MRI at various field strengths (at 1.5T, 3T, 7T and above). At 1.5T and 3T, the transmit |B1+| field from a transmit loop coil behaves relatively uniform in the area near the loop coil conductor plane and |B1+| decreases away from the conductor plane. At ultra-high fields such as 7T, the|B1+| field from the transmit loop coil behaves differently due to the increase dielectric effect of a loading subject. In the transverse plane, there is a weak |B1+| spot near the loop coil conductor plane. This causes a negative effect on the MR imaging/spectroscopy quality in the loop coil coverage area when a loop coil is used for transmit. A loop coil used for receive also has the same weak receive sensitivity problem near loop conductor surface. This abstract describes placing an extra conducting strip across a conventional loop coil. The resulting loop coil structure is similar to a ladder coil structure. The extra conducting strip is placed off-center of the loop coil and along the direction of main magnet B0 field. The strip off-center distance to the center of loop coil conductor is adjusted for best |B1+| uniform distribution in the imaging region. The RF feed could be placed in the opposite side of the added conducting strip to drive the modified loop coil. The added strip provides a non-symmetric loop structure along the transverse axis (x-axis) which can reduce the weak|B1+| spot in the transverse slice near the coil conductor plane, increase loop coil transmit efficiency, and reduce SAR. Adding an extra conducting strip on a loop transmit coil improve transmit |B1+|field is also applicable to improve receive |B1-|field of a loop receive coil. E.g.,the modified loop receive coil could be a standalone receive coil that is intended to be used together with a transmit coil or the proposed loop transmit coil can be further modified to include functions of a loop receive coil. A new loop transmit/receive (T/R) coil can be achieved.

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Title: Loop Transmit Coil for Ultra-High Field MRI

BACKGROUND

Loop coils are known and widely used in MRI at various field strengths (at 1.5T, 3T, 7T and above). At
1.5T and 3T, the transmit |B1+| field from a transmit loop coil behaves relatively uniform in the area near the loop coil conductor plane and |B1+| decreases away from the conductor plane. At ultra- high fields such as 7T, the|B1+| field from the transmit loop coil behaves differently due to the increase dielectric effect of a loading subject. In the transverse plane, there is a weak |B1+| spot near the loop coil conductor plane. This causes a negative effect on the MR imaging/spectroscopy quality in the loop coil coverage area when a loop coil is used for transmit. A loop coil used for receive also has the same weak receive sensitivity problem near loop conductor surface.

SUMMARY

This disclosure describes placing an extra conducting strip across a conventional loop coil, as illustrated above. The resulting loop coil structure is similar to a ladder coil structure. The extra conducting strip is placed off-center of the loop coil and along the direction of main magnet B0 field. The strip off-center distance to the center of loop coil conductor is adjusted for best |B1+| uniform distribution in the imaging region. The RF feed could be placed in the opposite side of the added conducting strip to drive the modified loop coil. The added strip provides a non-symmetric loop structure along the transverse ax...