MRI Transmit Array System for ICRF Coil Tracking
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Solution Overview
Problem
Current methods for tracking interventional devices like catheters during MRI-guided interventions face challenges in real-time detection and rotational orientation, particularly due to limitations in conventional imaging systems and passive tracking methods, which lack reliability and accuracy.
Innovation Solution
A transmit array system is employed to detect and track the rotational orientation of interventional devices with ICRF coils by modifying conventional RF excitation pulses to create circulating linearly polarized B1 fields, resulting in phase-encoded anatomy and ICRF coil images that allow simultaneous acquisition of rotational orientation information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive tracking methods are used to detect interventional devices, then device visualization is achieved, but reliability is poor due to inability to provide real-time detection and rotational orientation
Solution Approach 1:
The patent replaces passive mechanical tracking methods with active electromagnetic interaction. ICRF coils on interventional devices are inductively coupled to receive RF excitation signals, enabling active tracking. This substitution of passive detection with active electromagnetic coupling provides reliable real-time detection and rotational orientation information.
Solution Approach 2:
The patent modifies RF excitation parameters by using circulating linearly polarized B1 fields instead of conventional excitation. This parameter change in the RF field polarization state creates phase-encoded images that shift in predictable ways, enabling simultaneous acquisition of anatomy and ICRF coil images with rotational orientation information.
2Measurement precision
If conventional imaging systems are used to visualize interventional devices, then device detection is achieved, but rotational orientation information is not provided
Solution Approach 1:
The patent changes the polarization state parameter of RF excitation from conventional to circulating linearly polarized. This single parameter change enables the system to encode rotational orientation information into the phase of the received signals, allowing measurement of rotational orientation without adding complex hardware.
Solution Approach 2:
The patent creates phase-encoded copies of the ICRF coil image that shift in the phase encoding direction. By analyzing the phase difference between these copies, rotational orientation information is extracted. This copying approach allows orientation measurement using existing imaging infrastructure.
3Productivity
If ICRF coils are used for tracking, then real-time detection is enabled, but separation of ICRF coil images from surrounding anatomy is difficult
Solution Approach 1:
The patent segments the image signal into distinguishable components by exploiting different phase encoding characteristics. Anatomy images and ICRF coil images shift in different directions or have different phase characteristics, allowing them to be separated through standard image processing techniques like thresholding or region-of-interest analysis.
Solution Approach 2:
The patent changes the phase encoding parameter of the ICRF coil signal by using circulating linearly polarized fields. This creates a phase shift that distinguishes ICRF coil images from anatomy images in the phase-encoded domain, enabling clear separation and simultaneous visualization of both structures.
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 method enables precise tracking and rotational orientation of interventional devices, enhancing the accuracy of MRI-guided procedures by separating the ICRF coil images from anatomy, facilitating color-coding and real-time monitoring, and is applicable in MR-guided intravascular focused ultrasound and RF ablation.
Implementation Method 1
conventional RF excitation pulses are modified such that circulating linearly polarized B1 fields are created
Implementation Method 2
the use of transmit array system was recently introduced in our previous study to obtain reverse polarization during transmission
Data Source
AI summary
In a method for detecting rotational orientation and position tracking of an inductively coupled RF (ICRF) coil using a transmit array system, a conventional body birdcage coil is used, but the quadrature hybrid is eliminated to use the two excitation-channels separately. The transmit array system provides RF excitations such that the body birdcage coil creates linearly polarized and circulating RF pulses instead of a conventional rotational forward polarized excitation. Inductively coupled RF (ICRF) coils can be constructed on catheters for detecting rotational orientation and tracking purposes. The modifications on anatomy and ICRF coil images are different due to the RF excitation scheme such that the ICRF coil can be separated from the anatomy in real-time. After separating the ICRF coil from the anatomy, a color-coded image can be reconstructed, for example.