MRI Motion Gating With Through-Plane Distortion Correction
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Solution Overview
Problem
Existing radiotherapy techniques face challenges in accurately monitoring and gating treatment beams due to geometrical distortions in real-time MR images caused by non-linear magnetic fields, leading to discrepancies between pre-treatment and real-time image mappings, which can result in inaccurate targeting of tumor regions and increased exposure to healthy tissues.
Innovation Solution
A method and system that corrects for through-plane distortion in MR image slices by obtaining and comparing MR image slices with corresponding pre-treatment slices, using a controller to manage an MR imaging apparatus and radiation source, and applying a slice offset method to align and correct for geometrical distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If real-time MR images are used for monitoring subject position during radiotherapy, then motion monitoring capability is improved, but geometrical distortion in the images causes inaccurate targeting
Solution Approach 1:
A distortion correction map is introduced as an intermediary between the real-time MR images and the pre-treatment images. This map, generated from a distortion phantom scan, compensates for geometrical distortions caused by non-linear magnetic fields, enabling accurate alignment and positioning without sacrificing real-time monitoring capability
Solution Approach 2:
The system changes the parameter of image geometric accuracy by applying distortion correction transformations. By modifying the coordinate mapping parameters through the correction map, the system transforms distorted real-time images into accurately aligned images that match the pre-treatment planning data
2Productivity
If through-plane distortion in MR images is not corrected, then image acquisition speed is maintained, but alignment with pre-treatment images becomes inaccurate
Solution Approach 1:
The distortion correction map is generated in advance through a phantom scan before actual patient treatment. This preliminary action captures the distortion characteristics of the MRI system, allowing real-time images to be quickly corrected using pre-computed transformation data without slowing down the treatment workflow
Solution Approach 2:
The system creates a corrected copy of the real-time MR images by applying the distortion correction map. This copying process preserves the original fast acquisition while producing an accurate version for alignment and gating decisions, separating the speed of acquisition from the accuracy of application
3Speed
If real-time image comparison is performed without distortion correction, then treatment delivery speed is maintained, but radiation targeting accuracy decreases
Solution Approach 1:
The distortion correction map serves as an intermediary layer in the image comparison process. It transforms real-time images into a coordinate system that matches pre-treatment images, enabling accurate gating decisions and radiation targeting while maintaining real-time treatment delivery speed through efficient transformation algorithms
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
Enables precise alignment and gating of radiotherapy beams based on real-time subject positioning, reducing exposure to healthy tissues and ensuring accurate delivery of radiation to tumor regions.
Implementation Method 1
the subject is imaged in real-time (i.e. during or immediately before radiotherapy treatment), for example using an MRI scanner
Data Source
AI summary
There are provided systems, methods and radiotherapy devices for monitoring the position of a subject during radiotherapy, which comprise obtaining an MR image slice of a subject that exhibits through-plane distortion, obtaining a pre-treatment image slice of the subject that corresponds to the MR image slice and exhibits through-plane distortion that corresponds to the through-plane distortion of the MR image slice, and comparing the MR image slice with the corresponding pre-treatment image slice.