Noise suppression for MRI signals directly sampled and digitized in imaging room

Patent metadata

Field	Value
Publication number	US-9910112-B2
Application number	US-201414326790-A
Country	US
Kind code	B2
Filing date	Jul 9, 2014
Priority date	Jul 12, 2013
Publication date	Mar 6, 2018
Grant date	Mar 6, 2018

Abstract

According to one embodiment, an MRI apparatus includes a data acquisition unit and an image generation unit. The data acquisition unit acquires an analog MR signal from an object and converts the analog MR signal into a digital MR signal. The image generation unit generates MR image data based on the digital MR signal. The data acquisition unit includes an AD converter, a signal processing part and a noise suppression part. The AD converter converts the analog MR signal, before a down conversion, into the digital MR signal, inside an imaging room. The signal processing part performs signal processing of the digital MR signal, inside the imaging room or outside the imaging room. The noise suppression part suppresses a noise arising caused by a conversion from the analog MR signal, before the down conversion, into the digital MR signal.

First claim

What is claimed is:

1. A magnetic resonance imaging (MRI) apparatus comprising:
MRI system components including static and gradient magnetic field generators, at least one radio frequency (RF) coil and analog-to-digital (AD) converter circuitry co-located inside an imaging room and at least one control processor connected to control said components, said control processor being configured to
acquire analog magnetic resonance (MR) signals from an object and directly sample the analog MR signals in order to convert them into digital (MR) signals inside said imaging room before down conversion in frequency; and
process the digital MR signals and generate magnetic resonance image data therefrom either inside the imaging room or outside the imaging room; and

noise suppression circuitry that is connected to condition said digital MR signals in said operating room before frequency down-conversion and configured to suppress RF noise, within a band of received MR signal frequencies, caused by the directly-sampled AD conversion, wherein said noise suppression circuitry comprises
encode circuitry configured to encode the digital MR signal with randomizer circuitry that is configured to randomize regularity of bits and/or bit inversion circuitry configured to invert every other bit of the digital MR signals, and
decode circuitry that is configured to decode the encoded digital MR signals which are then output as digital MR signals and processed to generate said magnetic image data.

2. The magnetic resonance imaging apparatus of claim 1 , wherein
said noise suppression circuitry is configured to suppress the noise by reducing at least one of (i) a periodicity and (ii) an intensity variation of the digital MR signals.

3. The magnetic resonance imaging apparatus of claim 1 , wherein
said noise suppression circuitry is tuned to suppress noise in a resonance frequency band including at least one of the digital MR signals and the analog MR signals.

4. The magnetic resonance imaging apparatus of claim 1 , wherein
said noise suppression circuitry includes a low voltage differential signaling system configured to perform a differential conversion of the digital MR signals into two voltage signals, inside the imaging room, and to transmit the two voltage signals to a receiving circuit located either inside or outside the imaging room that has been configured to perform a single ended conversion of the two voltage signals back into the digital MR signals by comparing the two voltage signals.

5. The magnetic resonance imaging apparatus of claim 1 , wherein
said noise suppression circuitry includes a ground plane covering a transmission line, of the digital MR signals, between said AD converter circuitry and a signal receiving and processing circuit.

6. The magnetic resonance imaging apparatus of claim 1 , wherein
said noise suppression circuitry includes a shield electromagnetically shielding at least one of said AD converter circuitry, digital MR signal receiving and processing circuitry and a transmission line, of digital MR signals, that passes between said AD converter circuitry and said digital MR signal receiving and processing circuitry.

7. The magnetic resonance imaging apparatus of claim 1 , wherein
said noise suppression circuitry includes an electromagnetically shielded connector comprising a transmission line passing the digital MR signals, between said AD converter circuitry and signal digital MR signal receiving and processing circuitry.

8. The magnetic resonance imaging apparatus of claim 1 , wherein
said noise suppression circuitry includes a connector protected by a ground plane, that forms at least part of a transmission line connection which passes the digital MR signals between said AD converter circuitry and digital MR signal receiving and processing circuitry.

9. A magnetic resonance imaging (MRI) method comprising:
acquiring and directly sampling analog MR signals from an object in an imaging room co-located with MRI system components including static and gradient magnetic field generators and at least one radio frequency (RF) coil, in order to convert MR signals into digital MR signals before frequency down-conversion; and
generating MR image data based on the converted digital MR signals by processing performed inside or outside the imaging room; and
suppressing RF noise in the resulting digital MR signals within the imaging room that are within a band of received MR signal frequencies caused by the directly sampled conversion of the analog MR signals in the imaging room, before down conversion to a lower frequency,
wherein said suppressing RF noise comprises:
(a) encoding the digital MR signals by (i) randomizing regularity of bits and/or (ii) inverting every other bit of the digital MR signals and
(b) decoding the encoded digital MR signals and outputting the decoded MR signals as digital MR signals that are then processed in order to generate said MR image data.

10. A Magnetic resonance imaging (MRI) apparatus comprising:
an analog-to-digital (AD) converter disposed in an imaging room and configured to directly sample and convert analog magnetic resonance (MR) signals, acquired by static and gradient magnetic field generators and an RF (radio frequency) coil co-located within said imaging room, into digital MR signals before down conversion to a lower frequency; and
processing circuitry, including noise suppression encode circuitry which suppresses RF noise before down conversion to a lower frequency and decode circuitry, that are connected in order to process said digital MR signals, with at least the encode circuitry being located within said imaging room,
the encode circuitry also being configured to encode the digital MR signals by using (i) a randomizer configured to randomize regularity of bits and/or (ii) bit inversion circuitry configured to invert every other bit of the digital MR signals, and
the decode circuitry being configured to decode the previously encoded digital MR signals which are then output as digital MR signals and further processed by the processing circuitry in order to generate magnetic image data.

Assignees

• Toshiba Medical Sys Corp

Inventors

• Soejima Kazuyuki

Classifications

• G01R33/3692

  involving signal transmission without using electrically conductive connections, e.g. wireless communication or optical communication of the MR signal or an auxiliary signal other than the MR signal · CPC title

• G01R33/3621 Primary

  NMR receivers or demodulators, e.g. preamplifiers, means for frequency modulation of the MR signal using a digital down converter, means for analog to digital conversion [ADC] or for filtering or processing of the MR signal such as bandpass filtering, resampling, decimation or interpolation · CPC title