fMRI Control Using Extended Echo Time for Low Field Contrast
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Solution Overview
Problem
Current functional magnetic resonance imaging (fMRI) systems require high magnetic field strengths of 1.5 tesla and above, making them costly and limiting their application due to equipment effort and image noise, which prevents meaningful acquisitions at lower field strengths.
Innovation Solution
A method and device for controlling a magnetic resonance imaging system that uses a main magnetic field of up to 1.4 tesla with a longer echo time in the measurement sequence, allowing the BOLD effect to be measured at lower field strengths by increasing the spin dephasing relevant to T2* contrast, thereby enhancing sensitivity and reducing image artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high magnetic field strength (1.5 T and above) is used for fMRI, then BOLD contrast and T2* contrast increase, but equipment cost and complexity increase significantly
Solution Approach 1:
The patent changes the echo time parameter from conventional short echo times (e.g., 30-50 ms) to long echo times (e.g., 100-200 ms or longer). This parameter change compensates for the reduced T2* contrast at low field strengths by allowing more time for spin dephasing, thereby maintaining BOLD sensitivity without requiring high magnetic field strengths and reducing equipment complexity
Solution Approach 2:
Instead of increasing magnetic field strength to improve BOLD contrast (conventional approach), the patent inverts the approach by using lower field strengths and compensating through extended echo times. This reversal achieves similar contrast enhancement while avoiding the complexity and cost of high-field equipment
2Measurement precision
If high magnetic field strength (1.5 T and above) is used for fMRI, then T2* contrast increases, but equipment cost increases
Solution Approach 1:
The patent modifies the echo time parameter to be substantially longer than conventional values, which enhances T2* contrast through increased spin dephasing over time. This parameter modification allows achievement of adequate T2* contrast using lower magnetic field strengths, thereby reducing equipment cost while maintaining measurement precision
3Productivity
If conventional echo time is used at low field strength, then measurement time is short, but BOLD sensitivity is insufficient
Solution Approach 1:
The patent extends the echo time parameter to long durations (100-200 ms or more), which increases BOLD sensitivity by allowing greater spin dephasing relevant to T2* contrast. Although this extends measurement time, it achieves the necessary sensitivity that cannot be obtained with conventional short echo times at low field strengths
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 fMRI measurements at lower magnetic field strengths, such as 0.55 T, with improved BOLD sensitivity and signal-to-noise ratio, reducing equipment costs and expanding the range of usable brain regions, while maintaining image quality and allowing for lower-cost, lower-field MRI systems.
Implementation Method 1
a measurement sequence is applied that has a longer echo time TE, wherein the readout is performed such that spin dephasing relevant to T2* contrast is increased
Implementation Method 2
The basis for fMRI in MRI imaging using the typical high field strengths is the BOLD effect. This exploits a local susceptibility difference between paramagnetic deoxyhemoglobin in erythrocytes and diamagnetic oxyhemoglobin
Data Source
AI summary
In a method for controlling a magnetic resonance imaging system as part of functional magnetic resonance imaging, a main magnetic field B0 is provided having a field strength of at most 1.4 tesla at a main field magnet system (4) of the magnetic resonance imaging system (1); and a measurement is performed as part of functional magnetic resonance imaging, wherein a measurement sequence (MS) is applied that has a longer echo time TE (e.g. longer than 100 ms).