MRI B0 Map Scout Sequence for Scan Time Reduction
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Solution Overview
Problem
Current magnetic resonance imaging (MRI) techniques require lengthy calculations for B0 maps, which are essential for adjusting the main magnetic field homogeneity, especially when imaging body regions like the shoulder, due to the large volumes scanned unnecessarily, leading to significant time losses.
Innovation Solution
A scout sequence is used to determine the object's extension and position, allowing for dynamic adjustment of the B0 field map recording sequence parameters, such as slice selection, phase encoding, and readout directions, to restrict the recording region to the minimum necessary volume, thereby reducing scan time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the complete homogeneity volume is scanned to calculate the B0 map, then sufficient information is provided for any adjustment volume, but the scan time increases significantly
Solution Approach 1:
The patent performs a preliminary localization scan before the B0 map acquisition to determine the actual position and extension of the patient. Based on this preliminary information, the recording region for the B0 map is dynamically adjusted to match only the necessary volume, avoiding unnecessary scanning of the complete homogeneity volume while still providing sufficient information for the required adjustment volume.
2Loss of time
If the recording region is reduced to only the necessary volume, then scan time is reduced, but the B0 map may not provide sufficient information for arbitrary adjustment volumes
Solution Approach 1:
The localization scan is performed in advance to determine patient position and anatomy extent. This preliminary information is used to calculate an optimized recording region that precisely covers the necessary volume for the specific patient and examination, ensuring sufficient B0 map information is obtained without scanning unnecessary areas.
Solution Approach 2:
The recording region for the B0 map is dynamically adjusted based on the actual patient position and anatomy detected in the localization scan. The system adapts the recording parameters (such as field of view, matrix size, and slice coverage) to match the specific requirements of each examination, rather than using a fixed complete homogeneity volume.
3Stability of the object's composition
If the B0 map is calculated for the entire homogeneity volume, then homogeneity can be optimized across the maximum volume, but the adjustment time increases
Solution Approach 1:
The patent applies local quality optimization by determining the specific region where homogeneity adjustment is actually needed based on patient position and anatomy. The B0 map is calculated only for this localized region rather than the entire homogeneity volume, maintaining sufficient homogeneity for the required imaging volume while reducing the calculation and adjustment time.
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 the overall scan time for B0 maps by 30% to 50%, optimizing the imaging process and improving patient comfort by minimizing the time spent in the MRI device.
Implementation Method 1
Magnetic resonance imaging (MRI) is based on spins of atomic nuclei aligned in a main magnetic field (B0 field)
Implementation Method 2
Human tissue has a relative magnetic permeability that differs from one. For example, discontinuities between air and tissue produce significant distortion of the main magnetic field
Implementation Method 3
inhomogeneity is determined three-dimensionally in the imaging volume or in the homogeneity volume (e.g., by calculating the local Larmor frequency)
Data Source
AI summary
A method for recording a B0 map of a main magnetic field of a magnetic resonance device in an imaging volume of which an object to be recorded is arranged includes scanning a recording region to be covered by the B0 map by the magnetic resonance device. The recording region is scanned by a map recording sequence slice-by-slice in successive slices in a slice selection direction extending in a phase encoding direction and a readout direction, or three-dimensionally using two phase encoding directions and one readout direction in order to ascertain the B0 map. In a preliminary scan, the magnetic resonance device ascertains extension information describing the extension of the object using a scout sequence, which is used to define the recording region in sequence parameters of the map recording sequence and/or to adjust at least one sequence parameter of the map recording sequence.