MRI Phase Calibration Using Pre-Scan Reference Echoes

Solution Overview

Problem

High field strength MRI systems face phase jumping errors due to RF penetration, leading to unclear images and artifacts because conventional methods often skip constant phase calibration, which is necessary to correct these errors.

Innovation Solution

A method and apparatus for phase-calibrating MRI pulse sequences by performing a pre-scan without phase encoding gradients, calculating both linear and constant phases, and using the reference echo to correct the constant phase, ensuring accurate phase calibration and image reconstruction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional phase calibration methods are used that skip constant phase calibration, then the calibration process is simpler and faster, but phase jumping errors occur leading to unclear images and artifacts

Engineering Contradiction:

Improvecalibration speedVSAvoidimage quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent performs a pre-scan before the actual imaging scan to obtain reference data for phase calibration. This preliminary action allows the system to calculate both linear and constant phases in advance, so that when the actual scan is performed, the phase calibration can be applied correctly without adding significant time to the main imaging process. The pre-scan data is used to determine the constant phase that compensates for RF penetration effects.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the conventional approach of skipping constant phase calibration with a computational method that uses Fourier transformation and correlation calculations on pre-scan data. Instead of relying on simplified assumptions, the system uses mathematical processing to accurately determine both linear and constant phases, substituting complex calculation with a more robust algorithmic approach.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If constant phase calibration is performed to correct phase jumping errors, then image quality improves, but the calibration process becomes more complex and time-consuming

Engineering Contradiction:

Improvephase calibration accuracyVSAvoidcalibration process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent performs a pre-scan before the actual imaging scan to obtain reference data for phase calibration. This preliminary action allows the system to calculate both linear and constant phases in advance, so that when the actual scan is performed, the phase calibration can be applied correctly without adding significant time to the main imaging process. The pre-scan data is used to determine the constant phase that compensates for RF penetration effects.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses the pre-scan data as a reference copy to determine the constant phase for the actual scan. By copying the approach of using reference echoes from a pre-scan, the system can accurately determine phase parameters without directly measuring them during the main scan, thereby simplifying the overall process while maintaining accuracy.

Inventive Principle:

Principle #26Copying

3Measurement precision

If a pre-scan is performed to calculate constant phase, then phase calibration accuracy improves, but the total scan time increases

Engineering Contradiction:

Improveconstant phase accuracyVSAvoidscan time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent performs a pre-scan before the actual imaging scan to obtain reference data for phase calibration. This preliminary action allows the system to calculate both linear and constant phases in advance, so that when the actual scan is performed, the phase calibration can be applied correctly without adding significant time to the main imaging process. The pre-scan data is used to determine the constant phase that compensates for RF penetration effects.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent performs a pre-scan that acquires the same number of k-space lines as the actual scan, which may seem excessive. However, this partial redundancy ensures that sufficient reference data is obtained for accurate phase calibration, particularly for determining the constant phase. The pre-scan uses the same matrix size and field of view as the actual scan, ensuring compatibility and accuracy.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS7492155B2Method and apparatus for phase calibration of an MRI pulse

Publication Date: 2009.02.17 SIEMENS HEALTHINEERS AG

AI summary

The present invention concerns a method and an apparatus for phase-calibrating an MRI pulse sequence which is used to calculate a linear phase and a constant phase to perform phase calibration on the scanned data, wherein a corresponding pre-scan without a phase encoding gradient is performed before a diagnostic scan. A reference echo is selected from the echoes obtained in the pre-scan. On the basis of the reference echo the constant phase is calculated to be used in performing the phase calibration in the scan. The constant phase that is obtained is correct and not affected by phase jumping. A further image reconstruction performed on the phase-calibrated data produces clear and artifact-free images.