MRI Receiver Direct A/D Conversion Noise Filtering
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Solution Overview
Problem
Existing MRI technologies face challenges in reducing noise and errors in MR signals when using the direct sampling method, which affects the quality of generated MR images.
Innovation Solution
The MRI apparatus employs a receiver configuration that performs direct A/D conversion of analog MR signals without downconversion, separates them into in-phase and quadrature-phase signals, and applies filter processing to remove noise, while also correcting phase errors in the detection carrier clock using a method other than a direct digital synthesizer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If direct sampling method is used for detection processing of MR signals, then device complexity is reduced, but noise and errors are superimposed on MR signals
Solution Approach 1:
The patent applies preliminary filtering action by performing filter processing on the MR signals after direct A/D conversion but before image reconstruction. This preliminary noise removal action addresses the noise problem created by direct sampling while maintaining the simplicity of the direct sampling approach.
2Object-affected harmful factors
If frequency down conversion is performed before A/D conversion, then noise folding is prevented, but device complexity and processing time increase
Solution Approach 1:
The patent inverts the conventional signal processing sequence by performing A/D conversion first on the high-frequency MR signals and then applying digital filtering and down-conversion in the digital domain. This inversion eliminates the need for analog down-conversion hardware while effectively preventing noise folding through digital filter processing.
3Speed
If direct A/D conversion is applied to analog MR signals, then processing speed is improved, but phase errors in detection carrier clock occur
Solution Approach 1:
The patent applies feedback by using the known phase characteristics of the transmission carrier to correct phase errors in the detection carrier clock. The system measures or calculates the phase error and applies compensating phase correction to align the detection carrier with the transmission carrier, ensuring accurate signal detection.
Data Source
AI summary
According to one embodiment, a magnetic resonance imaging apparatus includes a static field magnet, a gradient coil, at least one radio frequency coil, a receiver and processing circuitry. The static field magnet, the gradient coil, the at least one radio frequency coil and the receiver are configured to acquire magnetic resonance signals from an object. The processing circuitry is configured to generate magnetic resonance image data based on the magnetic resonance signals. The receiver is configured to convert analog magnetic resonance signals received by the at least one radio frequency coil into digital magnetic resonance signals without a downconversion; separate the digital magnetic resonance signals into in-phase signals and quadrature-phase signals; and perform filter processing for removing noises of the in-phase signals and the quadrature-phase signals.