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METHOD TO ADJUST RECEIVER GAIN DURING MAGNETIC RESONANCE IMAGING

IP.com Disclosure Number: IPCOM000201009D
Publication Date: 2010-Nov-04
Document File: 6 page(s) / 515K

Publishing Venue

The IP.com Prior Art Database

Abstract

A technique for real time adjustment of receiver gain during an MRI scan is disclosed. In one embodiment of the present invention, signal from a last repetition time (TR) of discard scan is used to adjust the receiver gain. The technique described herein saves pre-scan time and in addition avoids the over-range amplitude issue.

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METHOD TO ADJUST RECEIVER GAIN DURING MAGNETIC RESONANCE IMAGING

FIELD OF INVENTION

The invention generally relates to Magnetic Resonance Imaging (MRI) systems and more particularly to a method of adjusting receiver gain in MRI systems.

BACKGROUND OF THE INVENTION

An MRI system includes a transceiver which receives NMR signals of varying amplitude during a scan. The gain of the receiver is dynamically changed during the scan to provide an optimal SNR figure without overranging the transceiver's A/D converter. The quality of MRI image is related to the signal-to-noise ratio (SNR) of the receiver. SNR may be degraded when the receiver gain is lowered to handle the largest signals. If the receiver gain is set too high there is a distortion in the MRI signal.

Generally, receiver gain is adjusted to optimize signal-to-noise ratio (SNR) and avoid over-range amplitude issues. Conventionally, receiver gain is adjusted prior to scanning. However, such adjustment increases the total scan time. Figure 1 is a flow diagram illustrating the conventional method of adjusting receiver gain in a MRI system.


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FIG. 1

In case of multiple slices acquired during a scan that produce vastly different signal levels, receiver gain needs to be adjusted based on signal from each slice. Further, for fast pulse sequences, long time is required to build steady state before signal acquisition. In order to reduce tuning time, only one slice may be acquired. But using a single scan may cause over-range amplitude issue. The signal from the single scan is taken as reference to shorten the pre-scan time. However, signal reference of a single slice causes over-range amplitude issue if signal from another slice is bigger than the signal from the referred slice. Figure 2 illustrates a scan image distorted due to over-range amplitude issue.


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FIG. 2

The image on the right side in Figure 2 is normal but the image on the left side in Figure 2 is distorted due to over-range amplitude. The two images are acquired during the same scanning procedure. In orde...