Composite Spin Locking Pulse Sequence for MRI Inhomogeneity Correction

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Solution Overview

Problem

Current MRI techniques for generating T1ρ-weighted images are sensitive to B0 and B1 RF inhomogeneities, leading to quantification errors and artifacts such as banding, which are not adequately corrected by existing methods.

Innovation Solution

The implementation of two composite spin locking pulse sequences, where the first sequence includes spin tipping pulses bounding a spin lock pulse and the second sequence includes oppositely oriented spin tipping pulses, with data acquisition and subtraction to correct for B0 and B1 inhomogeneities, allowing for accurate T1ρ quantification and improved image quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If standard spin locking pulse sequence is used, then T1ρ-weighted images can be generated, but quantification errors and banding artifacts occur due to B0 and B1 RF inhomogeneities

Engineering Contradiction:

ImproveT1ρ quantification accuracyVSAvoidimage quality

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The pulse sequence is divided into two separate sequences: a first sequence with spin tipping pulses of a first orientation and a second sequence with spin tipping pulses of a second orientation. By segmenting the measurement into multiple sequences with different orientations, the method enables cancellation of inhomogeneity effects through subtraction, thereby improving both quantification accuracy and image quality

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The method applies preliminary corrective action by designing the pulse sequences to inherently counteract B0 and B1 RF inhomogeneities. The spin locking pulses are bounded by spin tipping pulses with specific orientations that pre-compensate for inhomogeneity effects, allowing the subtraction of the two sequences to eliminate artifacts before image reconstruction

Inventive Principle:

Principle #9Preliminary anti-action

2Reliability

If pulse sequences are designed to correct for field inhomogeneities, then image quality improves, but the sequence complexity increases

Engineering Contradiction:

Improveimage qualityVSAvoidpulse sequence complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of attempting to correct inhomogeneities through complex shimming or post-processing, the method inverts the approach by using two sequences with opposite spin tipping pulse orientations. The subtraction of these inverted sequences naturally cancels out the inhomogeneity effects, achieving correction through a relatively simple structural modification rather than complex adjustment mechanisms

Inventive Principle:

Principle #13The other way round (Inversion)

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 provides robust and accurate T1ρ quantification and improved image quality by effectively compensating for B0 and B1 RF inhomogeneities, making T1ρ imaging more feasible for clinical diagnoses.

Implementation Method 1

magnetic resonance imaging (MRI) examinations are based on the interactions among a primary magnetic field, a radiofrequency (RF) magnetic field, and time varying magnetic gradient fields with gyromagnetic material having nuclear spins

Methodology Applied

Scientific EffectNuclear magnetic resonance: Electromagnetic Induction

Implementation Method 2

The precession of spins of these nuclei can be influenced by manipulation of the fields to produce RF signals that can be detected

Methodology Applied

Scientific EffectSpin precession: Precession

Implementation Method 3

pulse sequences that correct for or cancel out such inhomogeneities are desirable... having a spin lock pulse bounded by similarly oriented spin tipping pulses... and a second preparatory composite spin locking pulse sequence having a spin lock pulse bounded by oppositely oriented spin tipping pulses

Methodology Applied

Scientific EffectField inhomogeneity correction:

Data Source

PatentUS8618797B2Composite spin locking pulse sequence and method of using the same

Publication Date: 2013.12.31 GE PRECISION HEALTHCARE LLC

AI summary

Present embodiments are directed towards a magnetic resonance imaging method. In one embodiment, the method includes (a) performing a first magnetic resonance imaging sequence including: (i) a first preparatory composite spin locking pulse sequence having a spin lock pulse bounded by similarly oriented spin tipping pulses; and (ii) an acquisition pulse sequence to acquire first magnetic resonance data. The method further includes (b) performing a second magnetic resonance imaging sequence including: (i) a second preparatory composite spin locking pulse sequence having a spin lock pulse bounded by oppositely oriented spin tipping pulses; and (ii) an acquisition pulse sequence to acquire second magnetic resonance data. The method also includes (c) storing the first and second magnetic resonance data.