Simultaneous Multi-Slice NMR Imaging with Driven Equilibrium
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Solution Overview
Problem
Conventional NMR imaging techniques require lengthy scan times for obtaining T1-weighted and T2-weighted images, leading to patient discomfort and diagnostic inefficiencies, especially in multiple-slice scans, due to the need for prolonged patient immobility and the resulting motion artifacts.
Innovation Solution
The implementation of a simultaneous multiple-slice excitation method combined with driven equilibrium and fast-spin echo techniques, allowing for the simultaneous detection of nuclear magnetic resonance signals from multiple slices using a uniform polarizing magnetic field and orthogonal gradients, and processing these signals to provide diagnostic information with improved resolution and contrast control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional NMR imaging techniques are used to obtain T1-weighted and T2-weighted images, then diagnostic information is obtained, but scan time is excessively long
Solution Approach 1:
The imaging process is segmented into multiple independent slice acquisitions that can be performed simultaneously. Each slice is excited and imaged separately using slice-selective RF pulses, allowing parallel processing of multiple anatomical regions without compromising diagnostic quality of individual slices
Solution Approach 2:
The patent employs periodic RF pulse sequences with specific timing patterns to excite multiple slices in succession. By carefully controlling the repetition time and echo times of these periodic pulses, the system achieves fast spin echo imaging that reduces total scan time while maintaining T1 and T2 contrast information
2Measurement precision
If multiple-slice scans are performed with prolonged patient immobility, then comprehensive diagnostic coverage is obtained, but motion artifacts increase
Solution Approach 1:
The examination is divided into multiple rapid sequential slice acquisitions rather than one prolonged scan. Each slice is imaged quickly and independently, so that even if patient motion occurs between slices, each individual slice image remains free from motion artifacts, preserving diagnostic reliability
Solution Approach 2:
The imaging system maintains continuous data acquisition across multiple slices without interruption. By continuously exciting and imaging different slices in rapid succession, the system maximizes the use of the imaging window while minimizing total examination time, reducing opportunities for patient motion
3Productivity
If simultaneous multiple-slice excitation is implemented, then scan time is reduced, but signal-to-noise ratio may deteriorate
Solution Approach 1:
Each slice receives optimized RF excitation and signal detection parameters tailored to its specific anatomical location and depth. Slice-selective RF pulses are applied with appropriate amplitude and duration to achieve uniform signal intensity across different slices, ensuring that signal-to-noise ratio is maintained at diagnostic levels for each local region
Solution Approach 2:
The patent combines multiple slice signals into a single composite data set that is processed together. By merging the signal information from multiple slices and applying coherent processing techniques, the system maintains signal-to-noise ratio while achieving the speed benefits of simultaneous multi-slice imaging
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 significantly reduces scan time, enhances image quality, and allows for more reliable patient diagnosis by enabling faster, motion-artifact-free imaging, particularly beneficial for stand-up MRI scans, while maintaining or improving signal-to-noise ratios.
Implementation Method 1
when a sample composed of such nuclei is placed in the homogeneous magnetic field, a greater number of nuclear magnetic moments align with the direction of the magnetic field to produce a net macroscopic magnetization in the direction of the field
Implementation Method 2
The pulsed magnetic field gradients, together with radio frequency excitation of the nuclear spins and acquisition of signal information, are commonly referred to as a pulse sequence
Implementation Method 3
If, however, the tissue is also subjected to a magnetic field (excitation field B1) that is in the X-Y plane and that is at the Larmor frequency, the net aligned moment, M, may be rotated, or 'tipped', into the X-Y plane to produce a net transverse magnetic moment Mt
Implementation Method 4
The practical value of this phenomenon resides in the signal that is emitted by the excited spins after the excitation field B1 is removed
Data Source
AI summary
An NMR imaging process includes subjecting an imaging object to a uniform polarizing magnetic field. Orthogonal magnetic field gradients are applied to the imaging object. RF energy is applied to the imaging object. The RF energy includes a plurality of angular precession frequencies simultaneously applied to correspond to a respective plurality of selected slices of the imaging object. A corresponding plurality of nuclear magnetic resonance signals emitted by the imaging object are simultaneously detected. The nuclear magnetic resonance signals are processed to provide diagnostic information related to individual ones of the plurality of selected slices. In this way, multiple slices are excited and sampled simultaneously. The RF energy can be applied by applying RF energy to the imaging object according to a fast-spin echo technique and subsequently applying RF energy to the imaging object according to a driven equilibrium technique.