Multiband Pulse Sequence for MRI Signal-to-Noise Ratio

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Solution Overview

Problem

Lower magnetic field MRI systems face challenges in achieving high signal-to-noise ratio (SNR) due to lower sample magnetization, which results in lower quality magnetic resonance images, and existing methods to improve SNR either require larger voxel sizes or longer sampling times.

Innovation Solution

Implementing a multiband pulse sequence in MRI systems that includes a multiband excitation pulse and refocusing pulses, where the phases of the pulses are set according to an orthogonal encoding matrix, allowing for simultaneous excitation and refocusing of multiple slices, thereby increasing the sampling time and improving SNR without significantly increasing voxel size.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If lower magnetic field is used in MRI systems, then cost and safety are improved, but signal-to-noise ratio deteriorates

Engineering Contradiction:

ImprovecostVSAvoidsignal-to-noise ratio

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent combines multiple slice excitations into a single multiband RF pulse, allowing simultaneous excitation of multiple slices. This merging of excitation events into one pulse delivers signal from multiple slices during the same sampling window, effectively increasing the signal-to-noise ratio without requiring higher magnetic field strength

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent extends the sampling time by acquiring signals from multiple slices simultaneously over a prolonged period. By using multiband pulses with multiple frequency bands that are sampled together, the system accumulates signal information continuously across multiple slices, increasing the effective sampling time and thus improving SNR

Inventive Principle:

Principle #20Continuity of useful action

2Measurement precision

If voxel size is increased to improve SNR, then signal-to-noise ratio is improved, but spatial resolution deteriorates

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidspatial resolution

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent merges signals from multiple slices by simultaneously exciting and sampling multiple slices with a single multiband pulse. This combination of signals from multiple spatial locations increases the total signal strength without requiring enlargement of individual voxel sizes, thereby maintaining spatial resolution while improving SNR

Inventive Principle:

Principle #5Merging (Combining)

3Measurement precision

If sampling time is increased to improve SNR, then signal-to-noise ratio is improved, but imaging time deteriorates

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidimaging time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent combines multiple slice acquisitions into a single simultaneous measurement event using multiband RF pulses. By exciting and sampling multiple slices at the same time rather than sequentially, the system increases the effective sampling time for each slice without proportionally increasing the total imaging time, thus improving SNR efficiently

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent uses periodic multiband pulse sequences that repeat excitation and sampling cycles. By optimizing the timing and frequency bands of these periodic pulses, the system achieves extended effective sampling time through multiple repetitions while maintaining efficient time utilization, improving SNR without excessive imaging time

Inventive Principle:

Principle #19Periodic action

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 effectively enhances the SNR of images acquired using lower magnetic field MRI systems by increasing the sampling time for each slice, comparable to higher magnetic field systems, without requiring larger voxel sizes, thus improving image quality.

Implementation Method 1

magnetic resonance imaging (MRI) system configured to perform a multiband pulse sequence

Methodology Applied

Scientific EffectMagnetic resonance:

Implementation Method 2

a multiband excitation pulse for simultaneously exciting multiple bands

Methodology Applied

Scientific EffectRF pulse excitation:

Implementation Method 3

a multiband refocusing pulse for simultaneously refocusing the multiple bands

Methodology Applied

Scientific EffectSpin echo:

Implementation Method 4

spin-echo or multi-spin-echo imaging

Methodology Applied

Scientific EffectMagnetic resonance:

Data Source

PatentUS11269025B2System and method for increased signal-to-noise ratio in multi spin-echo pulse imaging

Publication Date: 2022.03.08 SYNAPTIVE MEDICAL INC

AI summary

The present disclosure provides a system for and a method of obtaining a magnetic resonance image by performing magnetic resonance imaging (MRI) at multiple slices simultaneously. The method comprises generating a multiband pulse sequence for spin-echo imaging, the pulse sequence comprising a multiband excitation pulse and at least one multiband refocusing pulse, wherein the multiband excitation pulse simultaneously excites multiple bands, wherein the at least one multiband refocusing pulse simultaneously refocuses the multiple bands, and wherein the phases of the bands excited by the multiband excitation pulse and the phases of the bands refocused by the at least one multiband refocusing pulse are set according to a single row of an orthogonal encoding matrix. The multiband excitation pulse and the at least one multiband refocusing pulse collectively form a multiband pulse pair.