3D UTE Imaging via Variable-TE Stack-of-Spirals
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Solution Overview
Problem
Conventional MRI techniques face challenges in imaging biological tissues with short relaxation times, such as bone, cartilage, and lungs, due to rapid signal decay, making it difficult to acquire high-quality 3D volumetric data efficiently.
Innovation Solution
The implementation of a 3D stack-of-spirals acquisition with a nonselective excitation pulse and a 3D spoiled gradient-echo sequence, which allows for variable echo times and minimizes the duration of each through-plane phase encoding gradient waveform, enabling rapid generation of ultrashort-echo-time (UTE) images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional MRI sequences are used, then the imaging process is simple and robust, but the echo time is too long causing complete signal decay for tissues with short relaxation times
Solution Approach 1:
The patent applies preliminary action by performing the slice selection gradient and phase encoding gradients before the readout gradient, and by using a nonselective RF pulse to excite all slices simultaneously. This reordering of operations allows the echo time to be reduced to the minimum possible value (50-100 microseconds) because sampling begins immediately after excitation without waiting for sequential slice selection. The preliminary completion of gradient operations enables ultrashort echo time imaging of rapidly decaying signals from bone, cartilage, and other short-T2 tissues.
2Loss of time
If 3D radial acquisition schemes are used, then the echo time can be reduced, but the acquisition time becomes very long requiring several minutes to collect full 3D volume data
Solution Approach 1:
The patent applies segmentation by dividing the 3D k-space into multiple 2D slices that are excited simultaneously by a nonselective RF pulse. Each slice is independently phase-encoded and read out in parallel during the same TR period. This segmentation approach allows the acquisition of complete 3D volumetric data in a fraction of the time required by sequential 3D radial methods, achieving whole-head images in 67 seconds and knee images in 97 seconds while maintaining ultrashort echo times.
3Loss of time
If specialized RF pulses and acquisition schemes are used for 2D UTE imaging, then the echo time can be reduced, but the method becomes inherently challenging and has limited robustness
Solution Approach 1:
The patent applies universality by using a single nonselective RF pulse to excite all slices simultaneously and a unified 3D stack-of-spirals acquisition scheme to collect data from all slices. This multi-functional approach eliminates the need for slice-specific RF pulses and separate acquisition parameters for each slice, simplifying the overall sequence design while achieving robust ultrashort echo time imaging. The method maintains consistency across different anatomical regions and tissue types, improving reproducibility and ease of implementation.
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 reduces the minimum echo time to as low as 50 μs, allowing for efficient visualization of musculoskeletal tissues and organs, including detection of injuries or abnormalities, and achieves rapid acquisition of 3D UTE images, such as whole-head and knee images in 67 seconds and 97 seconds, respectively.
Implementation Method 1
In magnetic resonance imaging (MRI), many biological tissues exhibit such short relaxation times that their signals decay completely by the time conventional sequences begin sampling
Implementation Method 2
The 3D stack-of-spirals acquisition can achieve short echo times by beginning each spiral readout immediately after the through-plane phase-encoding gradient waveform has completed
Data Source
AI summary
Some aspects of the present disclosure relate to ultrashort-echo-time (UTE) imaging. In one embodiment, a method includes acquiring UTE imaging data associated with an area of interest of a subject. The acquiring comprises applying an imaging pulse sequence with a three-dimensional (3D) spiral acquisition and a nonselective excitation pulse. The method also includes reconstructing at least one image of the area of interest from the acquired UTE imaging data.