Spatial Navigator for MRI B0 Drift Compensation
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Solution Overview
Problem
During thermal therapy guided by MRI, the main magnetic field (B0) drift can lead to inaccurate temperature measurements due to contributions from B0 shifts, necessitating the monitoring of B0 drift to calculate temperature changes accurately.
Innovation Solution
A dedicated spatial navigator is placed outside the imaging/therapy region to monitor B0 drift by receiving and processing ADC readouts from an MRI device, using techniques such as inverse Fourier transformation and phase subtraction to calculate the B0 drift, which is then used to determine temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If MRI thermometry is used to measure temperature change during thermal therapy, then temperature monitoring capability is provided, but measurement precision deteriorates due to B0 drift contributions
Solution Approach 1:
The patent segments the measurement process into two independent components: (1) a dedicated spatial navigator echo train specifically for monitoring B0 drift, and (2) the main imaging/therapy sequence for treating the target tissue. This segmentation allows B0 drift to be measured separately and compensated, thereby improving temperature measurement accuracy without interfering with the thermal therapy process.
Solution Approach 2:
The patent introduces a dedicated spatial navigator as an intermediary component that acts as a reference probe outside the thermal therapy region. This navigator serves as a mediator to capture B0 drift information independently, which is then used to correct temperature measurements in the treatment region, resolving the conflict between monitoring capability and measurement accuracy.
2Measurement precision
If a dedicated spatial navigator is placed outside the thermal therapy region to monitor B0 drift, then temperature measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges the B0 drift monitoring function with the existing MRI system infrastructure by utilizing the same RF coils and gradient system for the dedicated spatial navigator. This combining approach allows accurate B0 drift measurement without requiring separate hardware, thereby limiting the increase in device complexity while maintaining improved temperature measurement accuracy.
Solution Approach 2:
The MRI system components (RF coils, gradients, main magnet) are designed to serve multiple functions: they support both the dedicated spatial navigator for B0 drift monitoring and the main imaging/therapy sequence. This multi-functionality reduces the need for additional specialized equipment, thereby limiting device complexity increase while achieving improved measurement precision.
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 allows for accurate temperature change measurement during thermal therapy by isolating the B0 drift from the imaging/therapy region, ensuring precise temperature monitoring without impacting the therapy or imaging process.
Implementation Method 1
obtaining a main magnetic field (B0) drift of the MRI device based on the frequency of the spatial navigator at a particular time point and the frequency of the spatial navigator at the first time point
Implementation Method 2
The proton resonance frequency shift (PRFS) based Magnetic Resonance (MR) thermometry method captures this temperature change by subtracting a phase image before the thermal therapy
Implementation Method 3
processing the ADC readouts using inverse Fourier transformation; and averaging transformed ADC readouts to obtain the frequency of the navigator
Data Source
AI summary
A method, system and article of manufacture is disclosed. The method includes providing a spatial navigator outside of a thermal therapy region; receiving a plurality of analog-to-digital conversion (ADC) readouts from an MRI device at a plurality of time points, wherein the ADC readouts comprise a first ADC readout acquired at a first time point, and one or more additional ADC readouts acquired at subsequent time points; processing the ADC readouts to obtain a frequency of the spatial navigator at each of the time points; obtaining a main magnetic field (B0) drift of the MRI device based on the frequency of the spatial navigator at a particular time point and the frequency of the spatial navigator at the first time point; and obtaining the temperature change at the particular time point based on the B0 drift.