Gradient Echo MTC Brain Stem Imaging with SAR Control
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Solution Overview
Problem
Conventional MRI imaging techniques face challenges in accurately imaging the brain stem due to its size and location, and the high specific absorption rate (SAR) safety limit, which introduces variability in noise characteristics and degrades image quality, especially when imaging small neuromelanin-containing structures like the substantia nigra and locus coeruleus.
Innovation Solution
The method employs a gradient echo sequence with moderate-powered magnetization transfer contrast (MTC) pulses, keeping the SAR below safety limits, and acquires multiple measurements to correct for motion artifacts through post-processing coregistration, allowing consistent imaging across subjects regardless of body type and reducing the impact of motion on image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high-powered MTC pulses are used to enhance neuromelanin contrast, then image contrast improves, but SAR limit is exceeded causing image quality degradation
Solution Approach 1:
The patent applies moderate-powered MTC pulses that provide sufficient neuromelanin contrast enhancement without exceeding SAR safety limits. By using partial action (moderate power rather than maximum power), the method achieves adequate contrast improvement while avoiding the harmful effects of excessive SAR that would degrade image quality.
Solution Approach 2:
The patent modifies imaging parameters including using gradient echo sequences with specific TR/TE values, moderate MTC pulse powers, and multiple measurement acquisitions. These parameter changes enable optimization of neuromelanin contrast while maintaining compliance with SAR safety limits and reducing motion artifact impact through post-processing coregistration.
2Measurement precision
If multiple measurements are acquired to correct motion artifacts, then image quality improves, but scanning time increases
Solution Approach 1:
The patent acquires multiple measurements continuously during the scan and applies post-processing coregistration to correct for motion artifacts. This continuous acquisition approach allows motion corrections to be applied retrospectively, maintaining image quality without requiring interruption of the scanning process or additional scan time beyond the initial multiple measurements.
3Stability of the object's composition
If standardized imaging protocols are implemented across diverse subjects, then imaging consistency improves, but body type variability causes SAR limit violations
Solution Approach 1:
The patent develops a universal imaging protocol using moderate-powered MTC pulses with gradient echo sequences that can be applied across diverse subject populations regardless of body type. This standardized approach ensures consistent neuromelanin contrast enhancement and SAR compliance across all subjects, eliminating the need for subject-specific protocol adjustments.
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 enables high-quality imaging of the brain stem with improved neuromelanin contrast and reduced motion artifacts, maintaining image quality while adhering to SAR safety limits, allowing for standardized imaging protocols across diverse subjects.
Implementation Method 1
The method employs a gradient echo sequence with moderate-powered magnetization transfer contrast (MTC) pulses
Implementation Method 2
Ahn S. et al., `Neuromelanin MR Imaging: Detection of Locus Coeruleus Using T1 Weighted Gradient Echo Imaging'
Data Source
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AI summary
Methods, systems and computer-readable storage mediums relate to imaging techniques of a region, for example, the brain, with magnetization transfer contrast (MTC〫) effects with less specific absorption rate (SAR). The methods, systems and computer-readable storage mediums may include acquiring MR image data from at least one magnetic resonance (MR) scan that includes a pre-pulse signal and a pulse sequence. The pre-pulse signal may be less than 500°, e.g., from about 150° to 425°, and the pulse-sequence may be a gradient echo based sequence. The methods, systems and computer-readable storage mediums may include generating information associated with an image of at least one region of a subject. The information may include quantitative or qualitative information of a region of a brain. The quantitative information may include volume information, contrast to noise ratio information, number of voxels, as well as other information.