MR Thermometry Phase Shift Correction via Reference Region Segmentation
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Solution Overview
Problem
Current MR thermometry techniques face challenges in accurately measuring absolute temperatures and correcting for phase shifts due to magnetic field drifts and patient movement, especially during long-term procedures, which affects the precision of temperature monitoring in MR-guided thermal treatments.
Innovation Solution
Establishing a known temperature distribution in an MR imaging area as a baseline, detecting and extrapolating phase shifts from stable regions to correct temperature measurements, and using image registration to account for movement and deformation, allowing for accurate absolute temperature calculation and phase shift compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase-sensitive imaging is used to detect temperature changes, then temperature measurement sensitivity is improved, but measurement precision deteriorates due to non-temperature-related phase shifts from magnetic field drifts and patient movement
Solution Approach 1:
The imaging area is segmented into multiple regions, with at least one region serving as a reference region having known or constant temperature. This allows separation of temperature-related phase shifts from non-temperature-related phase shifts by comparing the region of interest against the stable reference region.
Solution Approach 2:
A reference region with known or constant temperature acts as an intermediary to detect and characterize non-temperature-related phase shifts. By measuring phase changes in this reference region, the system can identify and correct for magnetic field drifts and other confounding factors before applying corrections to the region of interest.
2Duration of action of moving object
If long-term temperature monitoring is performed, then treatment duration is extended, but measurement precision deteriorates due to accumulated magnetic field drifts and patient movement
Solution Approach 1:
A baseline phase image is acquired before the thermal treatment begins, establishing a reference state. This preliminary action allows the system to account for initial magnetic field conditions and patient positioning, providing a stable baseline against which subsequent phase changes can be measured throughout the extended treatment period.
Solution Approach 2:
The system continuously monitors phase changes in the reference region during long-term treatment and uses this feedback to dynamically correct phase shifts in the region of interest. This ongoing feedback mechanism compensates for accumulating magnetic field drifts and patient movement, maintaining measurement precision throughout the extended monitoring period.
3Speed
If absolute temperature measurement is attempted without baseline phase image, then measurement speed is improved, but measurement precision deteriorates due to unknown initial temperature and magnetic field conditions
Solution Approach 1:
A baseline phase image is acquired before thermal treatment to establish the initial temperature distribution and magnetic field conditions. This preliminary action provides the necessary reference information for calculating absolute temperatures during treatment, ensuring both speed and precision of temperature measurement.
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 enhances the accuracy of temperature measurements by isolating non-temperature-related phase shifts and applying corrections, enabling more precise monitoring and potentially reducing treatment time by allowing for earlier initiation of subsequent energy deliveries in MR-guided procedures.
Implementation Method 1
The PRF shift method is based on the phenomenon that the MR resonance frequency of protons in water molecules changes linearly with temperature
Data Source
AI summary
Techniques for temperature measurement and correction in long-term MR thermometry utilize a known temperature distribution in an MR imaging area as a baseline for absolute temperature measurement. Phase shifts that arise from magnetic field drifts are detected in one or more portions of the MR imaging area, facilitating correction of temperature measurements in an area of interest.