pCASL RF Pulse Offsets for B0 Field Deviation Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Arterial-spin labeling (ASL) techniques, particularly pseudo-continuous ASL (pCASL), are limited by deviations in the B0 field, which skew phase calculations and reduce labeling efficiency due to the fixed main magnetic field of MR scanners, limiting the flexibility of existing correction and shimming methods.
Innovation Solution
Introduce frequency and phase offsets based on B0 field deviations and gyromagnetic ratio to adjust RF pulses in the labelling and control phases, using a pseudo-0th order shim to enhance labeling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed main magnetic field is used in MR scanners, then the system structure is simple and stable, but B0 field deviations occur that skew phase calculations and reduce labeling efficiency
Solution Approach 1:
The patent applies parameter changes by introducing frequency and phase offsets to the RF pulses based on measured B0 field deviations. Instead of physically adjusting the magnetic field, the system changes the operational parameters (frequency and phase) of the RF pulses to compensate for field inhomogeneities, thereby maintaining labeling efficiency without adding complex hardware
Solution Approach 2:
The patent replaces mechanical/shimming-based field correction with a computational approach. Instead of using physical shimming materials or adjusting magnetic field hardware, the system uses software-based phase and frequency corrections applied to the RF pulses, substituting a mechanical correction system with an electronic/software-based solution
2Adaptability or versatility
If conventional correction methods are used for B0 field deviations, then some compensation is achieved, but the flexibility is limited due to fixed main magnetic field
Solution Approach 1:
The patent implements feedback by measuring the actual B0 field deviations and using this information to dynamically adjust the frequency and phase offsets of subsequent RF pulses. This closed-loop approach allows the system to adapt to varying field conditions and maintain accurate phase calculations, significantly improving both flexibility and precision compared to fixed correction methods
3Productivity
If RF pulses without frequency and phase offsets are used, then the pulse sequence is simple, but labeling efficiency is reduced due to B0 field deviations
Solution Approach 1:
The patent applies preliminary action by measuring and characterizing the B0 field deviations before performing the actual ASL labeling. The frequency and phase offsets are pre-calculated based on these measurements, allowing the RF pulses to be properly configured in advance to compensate for known field inhomogeneities, thereby maximizing labeling efficiency
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
The proposed method improves pCASL labeling efficiency by accurately positioning the labeling plane and maintaining nuclear spin magnetization, resulting in enhanced imaging quality and perfusion mapping.
Implementation Method 1
Arterial-spin labeling (ASL) is a non-invasive magnetic resonance (MR) technique used to measure blood perfusion by magnetically labeling water nuclei in blood
Implementation Method 2
deviations in the B0 field, which skew phase calculations and reduce labeling efficiency due to the fixed main magnetic field of MR scanners
Data Source
AI summary
A system for performing arterial-spin labeling (“ASL”) includes at least one memory configured to store instructions and at least one processor configured to execute the instructions to cause the system to perform a labelling phase and a control phase. The labelling phase includes a first plurality of radio frequency (“RF”) pulses and each RF pulse of the first plurality of RF pulses has a frequency offset and a phase offset. The control phase includes a second plurality of RF pulses and each RF pulse of the second plurality of RF pulses has the frequency offset and the phase offset and alternating RF pulses of the second plurality of RF pulses has an additional phase shift.