MRgFUS Alignment Calibration via Phased Array Tracking
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Solution Overview
Problem
Magnetic-resonance-guided focused ultrasound systems face inaccuracies due to mechanical production errors, causing deviations in the alignment between ultrasound transducers and MR trackers, which affect the precision of ultrasound focusing in medical treatments.
Innovation Solution
A calibration method involving the use of a phased array of ultrasound transducers with associated MR trackers, where different sonication geometries are applied to estimate and compensate for misalignment parameters by measuring targeting errors on an acoustic phantom, allowing for precise adjustments to achieve accurate ultrasound focusing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If nominal relative positions are used between transducers and MR trackers, then device complexity is reduced, but manufacturing precision deteriorates due to production errors
Solution Approach 1:
The patent transforms fixed nominal position parameters into variable parameters that can be adjusted through calibration. By introducing calibration matrices and transformation parameters, the system adapts to actual production variations while maintaining operational simplicity. The calibration process modifies position and orientation parameters to compensate for manufacturing errors.
2Manufacturing precision
If calibration procedures are implemented to compensate for production errors, then manufacturing precision is improved, but device complexity increases due to additional calibration steps
Solution Approach 1:
The patent performs calibration actions before actual ultrasound procedures. By pre-determining calibration parameters and transformation matrices during an initial setup phase, the system eliminates the need for complex real-time adjustments during treatment. The preliminary calibration stores correction data that automatically compensates for production errors during subsequent operations.
3Measurement precision
If multiple sonication geometries are used for calibration, then measurement precision is improved, but loss of time increases due to multiple measurements
Solution Approach 1:
The patent uses a sufficient number of sonication geometries to achieve accurate calibration without performing exhaustive measurements. By selecting a representative subset of sonication configurations that provide adequate spatial coverage, the system achieves reliable calibration results with minimal measurement time. The calibration process uses enough data points to ensure accuracy but stops before becoming unnecessarily time-consuming.
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
The method improves the accuracy of magnetic-resonance-guided focused ultrasound systems by ensuring the ultrasound focus coincides with the intended target location within a tolerance of 1 mm, enhancing the precision of medical treatments.
Implementation Method 1
An ultrasound focusing system generally utilizes an acoustic transducer surface, or an array of transducer surfaces, to generate an ultrasound beam
Implementation Method 2
In transducer arrays, the individual surfaces are typically individually controllable, i.e., their vibration phases and/or amplitudes can be set independently of one another, allowing the beam to be steered in a desired direction and focused at a desired distance
Implementation Method 3
MRI involves placing a subject, such as the patient, into a static magnetic field, thus aligning the spins of hydrogen nuclei in the tissue, and then applying radio-frequency electromagnetic pulses to temporarily destroy the alignment, inducing a response signal
Implementation Method 4
MR trackers—e.g., fiducials visible in MR images—that are rigidly attached to the transducer system
Data Source
AI summary
A magnetic-resonance-guided focused ultrasound system may be calibrated by generating ultrasound foci using ultrasound transducers, establishing coordinates of the foci and of magnetic-resonance trackers associated with the transducers, and determining a geometric relationship between the trackers and the transducers.