MRI Motion Correction Using Projection Moments
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current MRI systems using radial acquisition and projection reconstruction methods struggle to effectively correct for in-plane rotational motion, which is common in clinical applications, leading to motion artifacts in images.
Innovation Solution
The method modifies the view order of radial projection acquisition to 45 degrees between successive projections, allowing for the calculation of translational and rotational corrections using 0th, 1st, and 2nd order moments of the acquired projections, eliminating the need for additional navigator signals and enabling real-time correction with incomplete data sets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If radial acquisition with projection reconstruction is used, then motion artifacts are reduced compared to Cartesian methods, but correction for in-plane rotational motion is insufficient
Solution Approach 1:
The patent applies preliminary action by calculating and storing the moments of the projections during the data acquisition phase. The 0th, 1st, and 2nd moments are computed for each projection as it is acquired, preparing the necessary information in advance for rotational motion correction before image reconstruction occurs. This allows the correction to be applied efficiently during reconstruction without requiring additional acquisition time.
Solution Approach 2:
The patent introduces moments as an intermediary mathematical representation that bridges the raw projection data and the final corrected image. By computing moments (particularly the 2nd moment) of the projections, the system creates an intermediate quantity that encodes rotational motion information, which then serves as the basis for calculating correction factors that are applied during image reconstruction.
2Measurement precision
If additional navigator signals are used for motion correction, then motion correction accuracy improves, but scan time and system complexity increase
Solution Approach 1:
The patent applies universality by making the projection data serve multiple functions simultaneously. The same projections used for image reconstruction are also used to calculate the moments for motion correction. This eliminates the need for separate navigator signals, as the primary imaging data performs the dual role of both diagnostic imaging and motion monitoring, thereby avoiding additional scan time requirements.
Solution Approach 2:
The system applies self-service by using its own projection data to perform motion correction without requiring external navigator signals. The moments are calculated directly from the acquired projections themselves, allowing the imaging system to self-correct for motion using information already contained in the primary data acquisition, thus eliminating the need for separate correction mechanisms.
3Measurement precision
If complete data sets are required for motion correction, then correction accuracy improves, but real-time correction during scanning is prevented
Solution Approach 1:
The patent applies partial action by demonstrating that complete projection data sets are not necessary for effective motion correction. The moments can be calculated and motion corrections can be applied using partial or incomplete sets of projections as they are acquired. This allows the correction process to begin before all data is collected, enabling real-time or near-real-time correction capabilities while maintaining sufficient accuracy.
Data Source
AI summary
Magnetic resonance images reconstructed from a radial/projection acquisition are corrected for motion corruption caused by in-plane translational and in-plane rotational motion of an imaged subject using only the projection data itself. The method is based on the consistency properties of the 0th, 1st, and 2nd order moments of the spatial domain projections. In-plane translational motion is corrected by shifting/aligning the spatial projections according to the center of mass of each projection, which is calculated using the 0th and 1st moments. In-plane rotational motion is accounted for by determining the rotational motion time record using the 2nd moment information. The determination of the rotational motion time record using the 2nd moments is made possible by acquiring the successive MR projections at a view angle spacing that is substantially 45° and thus achieves sufficient linear independence. The translation-corrected spatial projections are reconstructed using the actual projection view angles, which are sum of the intended projection view angles plus the detected in-plane rotational motion time record. The calculation may also be performed in real-time during data acquisition in order to reacquire projections found to be too inconsistent due to through plane motion or other changes that are not in-plane rigid body motions or to acquire projections determined to be missing from the data set due to rotational motion.