Double Pencil Beam RF Pulse for MRI Tissue Tracking
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Solution Overview
Problem
Current tissue tracking methods in focused ultrasound procedures face challenges due to physiological motion and data latency issues, requiring a system that can directly measure and track target points without a learning phase and minimize latency for improved accuracy and timeliness.
Innovation Solution
A double pencil beam RF pulse system is used to continuously track a target point in tissue by applying symmetrical Gaussian-shaped 2D RF pencil beams that saturate areas around the target point, allowing for precise localization and tracking without affecting NMR signals, and employing a refresher pulse to maintain tracking accuracy over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If preliminary imaging procedures (learning phase) are used for tissue point tracking, then tracking accuracy can be improved, but procedure time is increased
Solution Approach 1:
The patent applies preliminary action by establishing a mathematical model of tissue deformation during a learning phase, then using this pre-established model to enable rapid tracking without repeating the learning phase. The model is prepared in advance and can be reused for multiple tracking operations.
Solution Approach 2:
The patent changes parameters by transitioning from direct imaging-based tracking to model-based tracking using mathematical parameters. The system uses a deformation model with adjustable parameters to represent tissue behavior, allowing fast computation and tracking without time-consuming imaging procedures.
2Speed
If data latency is reduced for real-time tracking, then timeliness of location data is improved, but measurement precision may be affected
Solution Approach 1:
The patent uses parameter changes by transforming the tracking problem into a mathematical optimization problem with adjustable parameters. The system solves for model parameters that best fit the imaging data, enabling real-time tracking with minimal latency while maintaining precision through the mathematical framework.
Solution Approach 2:
The patent replaces the mechanical/imaging-based tracking system with a computational/mathematical system. Instead of relying on continuous imaging and mechanical tracking, the system uses mathematical models and parameter optimization to compute tissue point locations, significantly reducing data latency while maintaining or improving precision.
3Extent of automation
If RF pulses are applied to track target point, then tracking capability is improved, but NMR signal from target point may be affected
Solution Approach 1:
The patent applies local quality by making the RF pulse spatially selective, concentrating it only at the tagging locations surrounding the target point rather than applying it uniformly. This localized application provides tracking information while minimizing interference with the NMR signal from the target point itself.
Solution Approach 2:
The patent uses an intermediary approach by placing tagging locations around the target point rather than directly on it. The RF pulses tag these intermediary locations, and the movement of these tags is used to infer the position of the target point, indirectly tracking the target without directly interfering with its NMR signal.
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 real-time, accurate tracking of tissue points during focused ultrasound procedures, reducing the risk of unwanted heating and ensuring precise delivery of ultrasound energy by minimizing data latency and eliminating the need for a learning phase.
Implementation Method 1
an RF pulse is applied to imaged tissue. The RF pulse comprises two symmetrical, Gaussian-shaped, 2D RF pencil beams that are directed to tagging locations spaced equidistant and opposite from one another about a target point in the tissue such that the RF pulse saturates a small area at a distance from both sides of the target point
Implementation Method 2
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. If the substance, or tissue, is subjected to a magnetic field (excitation field B 1) which is in the x-y plane and which is near the Larmor frequency, the net aligned moment, or 'longitudinal magnetization', M z, may be rotated, or 'tipped', into the x-y plane to produce a net transverse magnetic moment M t. A signal is emitted by the excited spins after the excitation signal B l is terminated
Data Source
Figure 1
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AI summary
A system and method for MR based tracking of a tissue point includes a RF coil assembly (56) configured to emit RF pulse sequences and a system control (32) coupled to the RF coil assembly (56). The system control (32) is programmed to cause the RF coil assembly (56) to emit a first RF pulse comprising a first pair of two-dimensional (2D) spatially selective beams (70, 72), each of the beams being directed to a respective tagging location (74, 76) in the subject of interest (45) and wherein the tagging locations (74, 76) are equidistant from a pre-determined point-of-interest (78). The system control (32) is further programmed to acquire a first series of MR images from a subject of interest (45), identify the first pair of 2D spatially selective beams (70, 72) in each MR image in the first series of MR images, and track a position of the point-of-interest (78) based on the identified 2D spatially selective beams (70, 72) in the first series of MR images.