MRI-Compatible Radiation Force Balance Calibrator
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Solution Overview
Problem
Current calibration methods for high-intensity focused ultrasound systems, particularly MRI-guided HIFU therapy devices, face challenges in accurately measuring ultrasonic power output within the strong magnetic fields of MRI systems, as traditional radiation force balance methods are not compatible with these environments and are susceptible to vibrational noise.
Innovation Solution
A radiation force balance calibrator using MR-compatible force sensors and a robust oil-filled target phantom, which measures and processes the radiation force to provide direct, traceable power calibration, capable of functioning within the MRI environment and accounting for vibrational noise through data modeling and fitting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional radiation force balance methods are used for calibration, then measurement precision is improved, but compatibility with MRI magnetic field environment deteriorates
Solution Approach 1:
The patent replaces traditional mechanical balance systems with magnetic field-compatible force sensors. Specifically, it uses capacitive force sensors or piezoelectric sensors that can operate within MRI magnetic fields, substituting the mechanical feedback balancing method with electrical measurement methods that are tolerant to magnetic field interference.
Solution Approach 2:
The patent changes the measurement parameters by using force sensors that measure radiation force directly in newton units, then converting to acoustic power through calibrated relationships. This parameter transformation allows measurement in the MRI environment where traditional balance methods fail.
2Measurement precision
If radiation force balance method is used in factory calibration, then calibration accuracy is improved, but ease of operation deteriorates due to complex reconfiguration requirements
Solution Approach 1:
The patent enables the therapy device to perform its own calibration in-situ within the MRI room using the integrated radiation force balance calibrator. The system self-calibrates by measuring radiation force directly at the treatment position, eliminating the need for external laboratory calibration services and complex reconfiguration procedures.
Solution Approach 2:
The patent creates a universal calibration system that functions both as a measurement device and as an integrated part of the therapy system. The radiation force balance calibrator serves multiple functions: it calibrates the ultrasound output, validates the treatment position, and ensures measurement traceability, all within the same device configuration used for therapy.
3Measurement precision
If laboratory balance is used for ultrasound power measurement, then measurement precision is improved, but adaptability to MRI environment deteriorates
Solution Approach 1:
The patent substitutes mechanical balance systems with electrical force sensing mechanisms that are inherently more resistant to magnetic field interference. Capacitive sensors measure force through electrical field changes, and piezoelectric sensors convert mechanical stress directly to electrical signals, both of which can be differentially measured to reject magnetic field noise.
Solution Approach 2:
The patent introduces magnetic field shielding and filtering as intermediary elements between the force sensors and the MRI magnetic field. These intermediaries protect the sensitive measurement system from harmful magnetic field effects while allowing the radiation force measurement to proceed accurately.
4Ease of operation
If field-deployable calibration system is implemented, then ease of operation is improved, but measurement precision may deteriorate due to environmental vibrations
Solution Approach 1:
The patent implements feedback mechanisms where the force sensor measurements are continuously monitored and compared against expected values. The system uses feedback control to compensate for environmental disturbances, adjusting measurements in real-time to maintain accuracy despite vibrations and other environmental factors present in the clinical setting.
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
Enables accurate in-situ calibration of high-intensity focused ultrasound transducers within MRI systems, maintaining the integrity of the therapy setup and effectively compensating for noise interference, ensuring precise power output measurements.
Implementation Method 1
a force is exerted on the target equal to the change in momentum flux associated with the wave
Implementation Method 2
The radiation force is measured with a resistive force sensor bridge, amplified, digitized and processed
Data Source
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AI summary
A radiation force balance calibrator (100) for calibrating a high intensity focused ultrasound transducer (106), the radiation force balance calibrator comprising: a balance frame (130); a force sensor (138) for measuring force, wherein the force sensor is attached to the balance frame; a balance (124) with first (132) and second ends (134), wherein the first end is attached to a pivot (128) for enabling the balance to pivot relative to the balance frame, wherein the second end is adapted for exerting force onto the force sensor; an oil target phantom (116) connected to the balance for absorbing ultrasound radiation (112, 114) from the high intensity focused ultrasound transducer, wherein the absorption of ultrasonic radiation causes a reduction in the force exerted by the balance on the force sensor; and wherein the radiation force balance calibrator is constructed of non-magnetic materials.