MRI RF Pulse Phase Shifting for Noise Cancellation
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Solution Overview
Problem
Conventional magnetic resonance imaging (MRI) apparatuses face challenges in effectively inhibiting radio frequency (RF) radiation noise during the transmission of RF pulse signals, which can interfere with electromagnetic compatibility (EMC) standards and contaminate the receiving system, particularly due to significant noise from transmission cables.
Innovation Solution
The MRI apparatus incorporates a transmission channel with multiple parallel channels and phase shifters to arrange RF pulse signals with varying phases, ensuring that noise from different channels cancels out, thereby reducing RF radiation noise. This is achieved through a configuration that includes a generator, a transmitter coil, a first phase shifter to vary phases among channels, and a second phase shifter to adjust phases before inputting signals to the transmitter coil, ensuring opposite or differing phases are maintained.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If RF pulse signals are transmitted through multiple parallel channels, then the RF radiation noise from different channels can cancel out, but the device complexity increases due to the need for multiple phase shifters and parallel transmission paths
Solution Approach 1:
The transmission channel is divided into multiple parallel channels, each capable of transmitting RF pulse signals independently. This segmentation allows the noise from different channels to cancel out through phase differences, directly addressing the technical contradiction by reducing RF radiation noise while managing device complexity through structured division
Solution Approach 2:
The phase of RF pulse signals is changed as a key parameter to achieve noise cancellation. By introducing phase shifters that can adjust the phase of signals in different channels, the system exploits phase differences to cause destructive interference of noise components, thereby reducing overall RF radiation noise
2Object-generated harmful factors
If phase shifters are introduced to vary phases of RF pulse signals, then noise cancellation is achieved, but the manufacturing precision requirements increase for phase control
Solution Approach 1:
Phase shifters are introduced as intermediary devices between the signal source and transmission channels. These intermediaries provide controlled phase adjustment capabilities, enabling precise phase manipulation without requiring extreme manufacturing precision across the entire system. The phase shifters act as dedicated components that can be calibrated and controlled independently
3Object-generated harmful factors
If multiple parallel transmission channels are used, then RF radiation noise is reduced through noise cancellation, but the loss of time for signal transmission increases due to coordinated phase adjustment
Solution Approach 1:
Phase adjustments are performed in advance before signal transmission begins. The phase shifters are pre-configured with appropriate phase shifts based on the desired noise cancellation pattern. This preliminary action ensures that when signals are transmitted through multiple channels, the phase relationships are already optimized for noise cancellation, eliminating the need for real-time phase adjustment during transmission
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively inhibits RF radiation noise during signal transmission, enhancing the electromagnetic compatibility (EMC) performance of the MRI apparatus by ensuring that noise from different channels cancels out, thereby improving the overall noise reduction and compliance with EMC standards.
Implementation Method 1
a first phase shifter configured to shift at least one of phases of the RF pulse signals to be transmitted via the channels, so that the phases of the RE pulse signals are in a relationship of being different from one another
Implementation Method 2
a transmitter coil configured to apply an RF magnetic field to an imaging space in which a subject is placed, on the basis of the RF pulse signals
Implementation Method 3
a second phase shifter configured to shift, in accordance with a phase amount shifted by the first phase shifter, at least one of phases of the RF pulse signals at a stage prior to inputting the RF pulse signals to the transmitter coil
Data Source
AI summary
A magnetic resonance imaging apparatus according to an embodiment includes a transmission channel, a first phase shifter, and a second phase shifter. The transmission channel is configured to arrange, in at least a partial section between a generator and a transmitter coil, radio frequency (RF) pulse signals to be transmitted parallel to one another via a plurality of channels. The first phase shifter is configured to shift at least one of phases of the RF pulse signals to be transmitted via the channels, so that the phases of the RF pulse signals are in a relationship of being different from one another. The second phase shifter is configured to shift, in accordance with a phase amount shifted by the first phase shifter, at least one of phases of the RF pulse signals at a stage prior to inputting the RE pulse signals to the transmitter coil.