MRI RF Transmit Field Control for Conductive Implant Safety
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Solution Overview
Problem
Magnetic resonance imaging (MRI) systems face challenges in imaging near electrically conductive objects due to radio-frequency heating, as existing methods for suppressing electric fields can lead to uncontrolled electric fields dependent on the object's properties and shape, posing a risk of overheating.
Innovation Solution
A magnetic resonance imaging system with a multi-channel configuration that controls input drive scales to keep the magnetic field component of the radio-frequency transmit field below a predetermined value, using calculated radio-frequency sensitivities and electromagnetic models to minimize heating by optimizing the radio-frequency transmit field around conductive objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If electric field suppression methods are used in MRI, then electric field distribution is improved, but uncontrolled electric fields may still occur depending on object properties and shape causing heating
Solution Approach 1:
The patent changes the control parameter from electric field suppression to magnetic field component control. By controlling the magnetic field component of the radio-frequency transmit field to remain below a predetermined value, the system prevents radio-frequency heating of conductive objects while maintaining reliable and predictable control, avoiding the uncontrolled electric field issues associated with electric field suppression methods
Solution Approach 2:
The patent substitutes the approach of controlling electric field parameters with controlling magnetic field parameters. Instead of attempting to suppress electric fields directly (which leads to uncontrolled behavior), the system controls the magnetic field component, which provides more stable and predictable control while achieving the same goal of preventing radio-frequency heating
2Measurement precision
If radio-frequency electromagnetic field is used for MRI, then imaging of soft tissues is improved, but heating of conductive materials and surrounding tissues occurs
Solution Approach 1:
The patent applies local quality control by maintaining the magnetic field component below a predetermined value specifically within a predetermined volume that contains the conductive object, while allowing the rest of the imaging system to operate with full radio-frequency power. This localized control prevents heating of the conductive object and surrounding tissues while preserving overall imaging quality
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 reduces radio-frequency heating of conductive objects and surrounding tissues, ensuring safer imaging by limiting magnetic field strength within a predetermined volume, thereby minimizing the risk of burns during MRI procedures.
Implementation Method 1
a radio-frequency transmitter for generating a radio-frequency transmit field for acquiring the magnetic resonance data
Implementation Method 2
a large magnetic field is used to align the nuclear spins of atoms as part of the procedure for producing images within the body of a subject
Implementation Method 3
the radio-frequency electromagnetic field generated during magnetic resonance imaging may cause heating these materials or electronics and the surrounding tissues
Implementation Method 4
controlling the input drive scales for a multi-channel magnetic resonance imaging system such that the magnetic field component of the radio-frequency transmit field is kept below a predetermined value. This may have the advantage of reducing the radio-frequency heating of the object
Data Source
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AI summary
Embodiments of the invention relate to a magnetic resonance imaging system (300) for acquiring magnetic resonance data (358) from a subject (318) that may comprise an electrically conductive object (e.g. an implant or a medical device). The magnetic resonance imaging system comprises a radio-frequency transmitter (314) for generating a radio-frequency transmit field for acquiring the magnetic resonance data using a radio-frequency antenna (310). The radio-frequency transmitter has multiple transmit channels. The radio-frequency antenna comprises multiple antenna elements (312) each adapted to connect to an antenna element. According to an embodiment of the invention, the amplitude and phase values of the RF transmit field of each of the transmit channels are selected such that the magnetic field generated by the RF antenna is minimized at the location of the electrically conductive object, thereby reducing RF heating of the object.