Double Inversion Recovery MRI Sequence for T1 Weighting Reduction
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Solution Overview
Problem
Current FLAIR imaging techniques suffer from unavoidable T1 weighting, which decreases detectability of lesions and may lead to mischaracterization, especially in brain imaging, as they are less sensitive due to pronounced T1 contrast and require additional image acquisitions.
Innovation Solution
A double inversion recovery (DIR) sequence is implemented, optimizing the first and second inversion times (TI1 and TI2) to suppress certain tissues and reduce T1 contrast between others, using a pair of inversion pulses and an excitation pulse in an MRI system, allowing for the acquisition of images with pure T2 weighting and simultaneous suppression of cerebrospinal fluid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FLAIR imaging is used to suppress CSF signal, then CSF visibility is reduced and lesion detectability improves, but T1 weighting is introduced which decreases lesion detectability and may lead to mischaracterization
Solution Approach 1:
The patent applies segmentation by dividing the inversion recovery process into two separate inversion pulses with different inversion times. The first inversion pulse suppresses CSF signal, while the second inversion pulse is optimized to minimize T1 weighting effects. This segmentation allows independent optimization of CSF suppression and T1 weighting reduction, resolving the contradiction between these two requirements.
Solution Approach 2:
The patent utilizes parameter changes by optimizing the inversion times (TI1 and TI2) of the two inversion pulses. By carefully selecting specific TI values, the sequence achieves CSF suppression while minimizing T1 weighting. The excitation pulse timing and echo time are also optimized to further reduce T1 contrast, thereby eliminating the harmful T1 weighting effect while maintaining CSF suppression.
2Measurement precision
If long TR and long TE are used in FLAIR to detect MS lesions, then lesion detectability improves, but imaging time increases
Solution Approach 1:
The patent applies parameter changes by optimizing the inversion times TI1 and TI2 to achieve effective CSF suppression and T1 weighting reduction at shorter TR values. This allows the use of shorter TR and TE times while maintaining lesion detectability, thereby reducing imaging time without sacrificing diagnostic accuracy.
3Measurement precision
If double inversion recovery sequence is used to suppress two tissue types, then tissue contrast improves, but T1 contrast between remaining tissues becomes stronger
Solution Approach 1:
The patent applies parameter changes by carefully optimizing both inversion times TI1 and TI2. The first inversion time is set to suppress CSF, while the second inversion time is specifically optimized to minimize T1 weighting effects on remaining tissues. This dual optimization allows the sequence to achieve the desired tissue contrast while preventing excessive T1 contrast enhancement.
Solution Approach 2:
The patent employs feedback by using signal intensity measurements from preliminary scans to iteratively optimize the inversion times TI1 and TI2. This feedback mechanism allows real-time adjustment of the inversion parameters to achieve the desired balance between tissue contrast and T1 weighting reduction.
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 minimizes T1 effects, enhancing the detectability of lesions by reducing T1 contrast, thereby improving image quality and reducing the need for additional image acquisitions, allowing for quicker and more cost-effective FLAIR imaging.
Implementation Method 1
When a substance such as human tissue is subjected to a uniform magnetic field (polarizing field B0), the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency. If the substance, or tissue, is subjected to a magnetic field (excitation field B1) which is in the x-y plane and which is near the Larmor frequency, the net aligned moment, or 'longitudinal magnetization', MZ, may be rotated, or 'tipped', into the x-y plane to produce a net transverse magnetic moment Mt. A signal is emitted by the excited spins after the excitation signal B1 is terminated
Data Source
AI summary
A system and method for double inversion recovery for reduction of T1 contribution to fluid-attenuated inversion recovery imaging include a computer programmed to prepare a double inversion recovery (DIR) sequence comprising a pair of inversion pulses and an excitation pulse, execute the DIR sequence to acquire MR data from an imaging subject, and reconstruct an image based on the acquired MR data. The preparation of the DIR sequence comprises optimizing a first inversion time (TI1) between the pair of inversion pulses and a second inversion time (TI2) between one of the pair of inversion pulses and the excitation pulse to cause a first tissue of the imaging subject to be suppressed in the image and to reduce a T1 contrast between a second tissue and a third tissue of the imaging subject in the image.