Virtual Frequency Selective Inversion MRI Fat Suppression
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Solution Overview
Problem
Current MRI fat suppression methods, such as STIR and SPAIR, face limitations in clinical imaging due to long data acquisition times, sensitivity to magnetic field inhomogeneity, and the need for dark blood preparation, which restricts the application and quality of fat suppression.
Innovation Solution
The virtual frequency selective inversion (VFSI) method employs interleaved acquisitions with different echo times and phase-sensitive reconstruction to invert MR signals without applying inversion RF pulses, reducing the number of RF pulses needed and enhancing signal-to-noise ratio while minimizing power deposition and sensitivity to magnetic field inhomogeneity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency selective saturation pulses (CHESS) are used for fat suppression, then fat signal suppression is achieved, but data acquisition time becomes excessively long (100-300 ms) causing fat magnetization recovery and poor suppression capability
Solution Approach 1:
The patent applies preliminary inversion recovery to null fat signal before the main imaging sequence begins. The non-frequency selective IR pulse is timed to null fat magnetization at the start of the TSE readout, preparing the system in advance so that subsequent imaging does not require prolonged suppression periods.
Solution Approach 2:
The patent segments the fat suppression function into two parts: (1) a non-frequency selective IR pulse that inverts all magnetization including fat, and (2) the main imaging sequence that acquires data before fat magnetization can recover. This segmentation allows fat suppression without requiring long frequency-selective saturation periods.
2Adaptability or versatility
If non-frequency selective IR pulse is used with gradient echo or steady state free precession readouts, then T1-contrast can be imparted, but timing restrictions limit the maximum number of lines that can be acquired and require dark blood preparation
Solution Approach 1:
The patent makes the inversion time dynamic and adaptable to different readout sequences. By allowing flexible timing between the IR pulse and dataset acquisition, the system can be optimized for TSE, gradient echo, or steady state free precession readouts without requiring fixed timing constraints or additional dark blood preparation.
3Adaptability or versatility
If multiple RF pulses are applied to achieve both fat suppression and T1-contrast, then both functions can be performed, but image luminance contrast is adversely altered and fat signal suppression is prevented
Solution Approach 1:
The patent makes a single non-frequency selective IR pulse perform multiple functions: it provides both fat suppression by nulling fat magnetization and T1-contrast by inverting all magnetization. This universal approach eliminates the need for separate frequency-selective saturation pulses, preserving image luminance contrast while achieving dual functionality.
4Measurement precision
If STIR sequence is used with TSE readout and dark blood preparation, then fat suppression is achieved, but the method is restricted to use without contrast agent due to timing limitations
Solution Approach 1:
The patent changes the timing parameters of the inversion recovery sequence to be compatible with contrast agent administration. By optimizing the inversion time and acquisition timing, the system maintains effective fat suppression while allowing contrast agents to be administered and imaged, removing the restriction that limited STIR to non-contrast studies.
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
VFSI achieves effective fat suppression with reduced data acquisition time and improved image quality, insensitive to magnetic field inhomogeneity, and allows for the use of contrast agents, providing enhanced luminance contrast and tissue differentiation.
Implementation Method 1
separates components representing anatomical material having different ranges of resonance frequencies associated with different ranges of phases between an anatomical MR image representative dataset and an associated reference image dataset
Implementation Method 2
different ranges of resonance frequencies associated with different ranges of phases
Data Source
AI summary
Magnetic resonance imaging (MRI) acquisition and reconstruction techniques that invert MR signals of selected frequencies without the application of inversion RF pulses are disclosed. An example method comprises acquisition of at least one MR image representative dataset and an associated phase reference dataset, and classifies anatomical material into a first component representing anatomical material having a first range of resonance frequencies associated with a first range of phase differences between the MR image representative dataset and the reference image dataset and a second component representing anatomical material having a second range of resonance frequencies associated with a second range of phase differences between the MR image representative dataset and the reference image dataset. The method assigns different visual attributes to first and second components derived using phase differences between the MR image representative dataset and the reference image dataset and displays an image.