MRI Geometric Distortion Correction via Harmonic Analysis
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic Resonance Imaging (MRI) is limited in radiation therapy due to geometric image distortions, which affect treatment accuracy and patient outcomes, as MR images lack tissue electron density information and are prone to system and patient-induced distortions.
Innovation Solution
A method for measuring and characterizing geometric distortions using harmonic analysis, involving phantom scans, control points, and harmonic expansion summation to derive 3D distortion vectors, allowing for image correction and shimming of the MR imaging field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If MRI is used for radiation therapy guidance, then soft-tissue image contrast is improved, but geometric image distortion increases
Solution Approach 1:
A distortion correction map is introduced as an intermediary between the distorted MR image and the treatment planning system. This map, generated from phantom scans and harmonic analysis, transforms the distorted coordinates to corrected coordinates, enabling accurate spatial registration without compromising the superior soft-tissue contrast of MRI
Solution Approach 2:
The patent changes the parameter representation by transforming spatial coordinates using harmonic analysis. The distortion correction process modifies the coordinate system parameters, converting distorted MR image coordinates into accurate spatial coordinates that match the treatment planning system's reference frame
2Measurement precision
If distortion correction is applied to improve spatial accuracy, then treatment accuracy is improved, but measurement and characterization complexity increases
Solution Approach 1:
Distortion correction parameters are determined in advance through phantom scans and harmonic analysis before actual patient imaging. The correction map is pre-computed and stored, allowing rapid application during treatment planning without adding real-time complexity to the imaging process
Solution Approach 2:
The patent uses a phantom copy of the patient's anatomical region to measure and characterize distortions. By scanning a phantom with known geometry and applying the same imaging parameters as used for patients, the distortion characteristics are captured and corrected without exposing patients to additional complexity or risk
Data Source
AI summary
Various embodiments are described herein for an apparatus and a method for measuring and characterizing geometric distortions for a region of interest in images obtained using magnetic resonance. The method comprises deriving a computed set of 3D distortion vectors for a set of points within a region of interest covered by a phantom by using harmonic analysis to solve an associated boundary value problem based on boundary conditions derived from a measured set of 3D distortion vectors. The characterized image distortions may be used for various purposes such as for image correction or for shimming, for example.