On-Coil Switched Mode MRI Amplifiers for Synchronized RF Control

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Solution Overview

Problem

Conventional MRI parallel transmission systems face challenges with scaling, synchronization, interference, and low efficiency due to the use of multiple independent external transmitters and analog signal processing, leading to poor fidelity and increased power consumption.

Innovation Solution

The implementation of on-coil switched mode amplifiers, specifically current-mode class-D (CMCD) amplifiers, which receive digital control signals and reduce interference, allowing for improved synchronization and efficiency in RF signal transmission, using VMCD pre-amplifiers and feedback control to modulate amplitude and phase.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If multiple independent external transmitters are used for parallel transmission, then transmission speed and volumetric excitation capability are improved, but system complexity, cabling requirements, and synchronization difficulty increase

Engineering Contradiction:

Improvetransmission speedVSAvoidsystem complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent combines multiple transmitter functions into a single on-coil transmitter unit that can drive multiple coil elements. This integration eliminates the need for multiple independent external transmitters while maintaining parallel transmission capability, thereby reducing system complexity and cabling requirements while preserving transmission speed improvements

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent transitions from external transmitters to on-coil transmitters by moving the amplification function into a different spatial dimension (directly at the coil). This dimensional change enables direct digital control of coil elements without requiring complex external cabling and synchronization infrastructure

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Productivity

If multiple independent external transmitters are used, then parallel transmission capability is achieved, but synchronization between transmitters becomes difficult

Engineering Contradiction:

Improveparallel transmission capabilityVSAvoidsynchronization time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The patent implements feedback control in the on-coil transmitter system to maintain precise synchronization between multiple coil elements. The feedback mechanism monitors and adjusts phase and amplitude relationships in real-time, ensuring accurate parallel transmission without the synchronization delays associated with multiple independent external transmitters

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

By moving transmitters onto the coil, the patent enables direct digital control of each coil element from a centralized location. This spatial reconfiguration allows for precise timing control and synchronization through digital means rather than requiring complex analog synchronization between external transmitters

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Adaptability or versatility

If conventional analog-in-analog-out RF transmitters are used, then existing system compatibility is maintained, but power consumption increases and efficiency decreases

Engineering Contradiction:

Improvesystem compatibilityVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The patent replaces conventional analog-in-analog-out RF transmitters with on-coil switched mode amplifiers that accept digital control signals. This substitution of digital control for analog signal processing reduces power consumption and improves efficiency while maintaining system compatibility through the unified transmitter interface

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating parameters of the transmitter system by implementing switched mode amplification with digital control. This parameter change from analog to digital operation enables more efficient power utilization while maintaining compatibility with existing MRI systems through standardized coil interfaces

Inventive Principle:

Principle #35Parameter changes

4Productivity

If multiple independent external transmitters are used, then parallel transmission is achieved, but interference and cross-talk between coils increases

Engineering Contradiction:

Improveparallel transmission capabilityVSAvoidinterference and cross-talk

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent merges multiple transmitter functions into a single on-coil unit that can precisely control multiple coil elements. This integration eliminates the interference and cross-talk problems associated with multiple independent external transmitters while maintaining parallel transmission capability through unified digital control

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS8294465B2Switched mode pre-amplification and am feedback for on-coil switched mode amplifiers in parallel transmission MRI

Publication Date: 2012.10.23 SIEMENS HEALTHINEERS AG

AI summary

Example systems, apparatus, circuits, and so on described herein concern parallel transmission in MRI with on-coil current-mode (CMCD) amplifiers. One example apparatus includes switched voltage-mode class D (VMCD) pre-amplifiers. Another example apparatus includes amplitude modulation of the output of the CMCD amplifiers using feedback control based, at least in part, on a comparison of an envelope of transmit coil current to an envelope of an input RF pulse.