Simultaneous Orthogonal Plane Imaging for MRI Motion Tracking
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Solution Overview
Problem
Existing methods for intrafractional motion compensation in radiation therapy, such as deformable registration in 4D-MRI, are prone to inaccuracies and lose the ability for real-time respiratory gating and tracking, necessitating improved techniques for accurate dose delivery during MR-guided radiation therapy.
Innovation Solution
The use of simultaneous orthogonal plane imaging (SOPI) in magnetic resonance imaging systems, where data are acquired from orthogonal slices with one slice remaining static and the other changing, allowing for real-time motion tracking and compensation by reconstructing 4D-MRI epochs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If deformable registration is used to dynamically update motion models throughout treatment fraction, then motion compensation accuracy is improved, but the method becomes dependent on registration accuracy and loses real-time gating capability
Solution Approach 1:
The patent segments the treatment monitoring into two distinct components: (1) a pre-treatment 4D-MRI that captures the full respiratory cycle and establishes baseline motion patterns, and (2) a real-time 2D cine imaging system that provides continuous monitoring during treatment. This segmentation allows each system to optimize for its specific function without compromising the other.
Solution Approach 2:
The patent performs preliminary action by acquiring the 4D-MRI before treatment to establish the motion model and respiratory phase relationships. This pre-acquired data serves as a reference that guides real-time gating decisions, eliminating the need for complex real-time deformable registration while maintaining accuracy.
2Loss of information
If continuous 3D stack-of-stars data are acquired during beam-on to reconstruct 4D-MRI epochs, then short-term respiratory variations are captured, but the ability to acquire real-time images for instantaneous respiratory phase determination is lost
Solution Approach 1:
The patent extracts only the essential real-time monitoring function by using 2D cine imaging during beam-on, while the comprehensive 4D respiratory phase information is extracted from the pre-acquired 4D-MRI. This extraction allows real-time gating without the computational burden of continuous 3D reconstruction.
Solution Approach 2:
The patent applies partial action by acquiring only the necessary 2D cine data during treatment rather than full 3D volumes, which would be excessive for real-time gating purposes. The pre-acquired 4D-MRI provides the complementary comprehensive information that would require excessive real-time acquisition.
3Measurement precision
If 2D multislice methods with interleaved navigator and imaging slice acquisition are used, then respiratory phase-resolved 3D volumes are built, but acquisition efficiency is reduced compared to simultaneous methods
Solution Approach 1:
The patent merges the navigator slice acquisition and imaging slice acquisition into a single simultaneous 2D cine imaging process. By acquiring both navigation and imaging data in the same 2D plane at the same time, the system eliminates the interleaved acquisition overhead while maintaining respiratory phase resolution through real-time motion surrogate correlation.
Data Source
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AI summary
Systems and methods for providing image guidance for motion tracking and compensation in magnetic resonance imaging ("MRI") guided therapies, such as MRI- guided radiation therapies using an MR-linac or other MRI -guided radiation therapy system, are described. Simultaneous orthogonal plane imaging ("SOPI") is used to acquire images from a first slice that remains static throughout the acquisition, and from a plurality of slices that are orthogonal to the first slice. This first slice can be referred to in some instances as a "tracking" or "navigator" slice, and the plurality of slices that are orthogonal to the first slice can be referred to as "imaging" slices. The tracking slice images can be used to estimate motion of the subject that occurred during the data acquisition, and to track the position of targets (e.g., anatomical targets) during the delivery of radiation treatment.