Direct NMR Signal Digitization in MRI Systems
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Solution Overview
Problem
Current MRI systems are rigid and inflexible, requiring specific hardware redesigns to accommodate changing commodity components, limiting the use of higher bandwidth and dynamic range components for improved image quality, and preventing end users from easily upgrading receiver systems without significant reconfiguration.
Innovation Solution
A system and method for direct digitization of NMR signals using commodity A/D converters and software-processing algorithms, allowing for the integration of mass-produced components and eliminating the need for intermediate analog processing steps, enabling adaptability and improved image quality without hardware-level redesigns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional hardware-based receiver systems with down-conversion are used, then signal processing is performed with dedicated hardware, but the system becomes rigid and requires hardware redesign to accommodate component changes
Solution Approach 1:
The patent replaces the mechanical hardware-based down-conversion system with a software-based direct digitization system. Instead of using physical mixers and analog processing components, the invention directly digitizes the NMR signal using high-speed A/D converters and performs all processing operations through software algorithms, eliminating the need for hardware redesign when components change
Solution Approach 2:
The patent introduces dynamic flexibility by enabling software-based signal processing that can be reconfigured without hardware changes. The system can adapt to different component configurations and upgrade A/D converters without requiring physical redesign of the receiver architecture
2Ease of manufacture
If commodity A/D converters are used for direct digitization, then manufacturing costs are reduced and bandwidth is increased, but the system requires new processing methods
Solution Approach 1:
The patent substitutes complex analog hardware processing with software-based digital signal processing. By using commodity A/D converters and moving all processing to the digital domain through software algorithms, the system reduces manufacturing costs while managing complexity through programmable solutions rather than fixed hardware designs
Solution Approach 2:
The patent changes the operating parameters by directly digitizing signals at the Larmor frequency without down-conversion, utilizing the full bandwidth capability of commodity A/D converters. This parameter change enables the use of lower-cost components while maintaining signal integrity through software processing
3Measurement precision
If hardware-based down-conversion is used, then signal processing is performed at intermediate frequency, but image quality is limited by analog processing constraints
Solution Approach 1:
The patent replaces analog intermediate frequency processing with direct digital signal processing. By eliminating analog down-conversion stages and performing all processing in the digital domain, the system achieves higher signal detection precision and improved image quality without the limitations of analog processing constraints
Solution Approach 2:
The patent performs preliminary digitization of the NMR signal at the Larmor frequency before any processing occurs. This preliminary action of direct digitization preserves the full signal bandwidth and enables subsequent software-based processing to achieve superior image quality compared to traditional analog down-conversion methods
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
Enables the use of low-cost, high-bandwidth components in MRI systems for direct detection and digitization of NMR signals, enhancing image quality and allowing for easier upgrades, while reducing manufacturing costs and complexity.
Implementation Method 1
the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency
Implementation Method 2
When a substance such as human tissue is subjected to a uniform magnetic field (polarizing field B0), the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field
Implementation Method 3
If the substance, or tissue, is subjected to a magnetic field (excitation field B1) that is in the x-y plane and which is near the Larmor frequency, the net aligned moment, Mz, may be rotated, or 'tipped', into the x-y plane to produce a net transverse magnetic moment, Mt
Implementation Method 4
A signal is emitted by the excited spins at or around the Larmor frequency after the excitation signal B1 is terminated that is then received and processed to form an image
Data Source
AI summary
A magnetic resonance imaging (MRI) system includes a transmitter that produces an RF excitation pulse that is applied to a subject positioned in the MRI system to induce emission of at least one of an NMR signal and an ESR signal therefrom, and that produces a reference signal indicative of the phase of the RF excitation pulse. A first analog-to-digital converter has an input for receiving the reference signal that is synchronous with the RF excitation pulse. One or more additional analog-to-digital converters/processors have inputs for receiving the at least one of NMR signals and ESR signals produced by a subject placed in the MRI system and produce one or more complex digital signals therefrom. A normalizer is connected to receive and normalize the digital reference signal and a mixer is connected to receive the normalized digital reference signal and the digital signal. Accordingly, the mixer is operable to multiply the normalized complex digital reference signal with the complex digital signal.