MR Tracking Coils for PET Attenuation Correction
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Solution Overview
Problem
Dual modality imaging systems, such as PET/MR, face challenges due to attenuation artifacts caused by external non-therapeutic structures like patient support equipment, which are not visible to standard imaging techniques and complicate image reconstruction, especially when these structures are movable or articulable.
Innovation Solution
The use of MR tracking coils to determine the position and orientation of external non-therapeutic structures, allowing for correction of attenuation in imaging data from non-MR modalities like PET, by acquiring MR non-imaging foreign structure information and integrating it into the reconstruction process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If surface coils, patient support equipment, or positioning equipment are placed between the patient and PET detectors to enable dual modality imaging, then the benefits of combined PET/MR imaging are achieved, but significant attenuation of 511 keV photons occurs causing PET image artifacts and quantitation errors
Solution Approach 1:
The patent introduces MR tracking coils as intermediary devices that are attached to the external non-therapeutic structures. These tracking coils enable indirect detection of the structures' positions through MR signals, which then inform the PET reconstruction process to correct for attenuation without requiring the structures themselves to be visible to PET detectors.
Solution Approach 2:
The patent replaces direct mechanical/optical detection methods with magnetic resonance-based detection. Instead of relying on PET detectors to directly observe the external structures (which fails due to photon attenuation), the system uses MR tracking coils to detect positions through magnetic field interactions, substituting one detection mechanism for another that is sensitive to different physical properties.
2Measurement precision
If fiducial markers are used to identify external structures in MR images, then the position and orientation of equipment can be determined, but MR image quality deteriorates and geometric fidelity remains insufficient
Solution Approach 1:
The patent extracts the tracking function from the main imaging process. Instead of embedding fiducial markers that contaminate the MR image, the system uses dedicated MR tracking coils attached to external structures that are specifically designed for tracking purposes only. The tracking data is then separated and used independently in the PET reconstruction process, leaving the MR images clean and free of fiducial marker artifacts.
3Device complexity
If a priori knowledge of initial position and orientation is used for equipment, then reconstruction can proceed without additional tracking, but the solution fails when equipment is movable or articulable
Solution Approach 1:
The patent transitions from a static tracking approach (fixed position and orientation) to a dynamic tracking approach. MR tracking coils are attached to external structures and continuously track their positions and orientations throughout the imaging process. This dynamic tracking capability allows the system to adapt to movable and articulable equipment, updating the attenuation correction parameters in real-time as the equipment moves.
4Ease of operation
If standard PET and MR imaging techniques are used without tracking, then the imaging process remains simple, but attenuation correction cannot be performed for invisible external structures
Solution Approach 1:
The patent makes the MR imaging system multi-functional by using the same MR scanner to perform both anatomical imaging and tracking of external structures. The MR tracking coils serve dual purposes: they enable the MR scanner to detect positions of external structures for PET attenuation correction while maintaining the primary MR imaging function. This universal approach integrates tracking into the existing MR workflow without requiring separate dedicated tracking hardware.
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
This approach improves the accuracy of image reconstruction by correcting for attenuation caused by external structures, enhancing quantitation and reducing artifacts in PET imaging, while maintaining high geometric fidelity and image quality.
Implementation Method 1
a magnetic resonance (MR) acquisition module configured to acquire magnetic resonance (MR) information associated with an external non-therapeutic (ENT) structure with in the FOV that includes MR non-imaging, foreign structure (NIFS) information associated with the ENT structure. The MR NIFS information is acquired via at least one tracking coil associated with the ENT structure.
Data Source
AI summary
A magnetic resonance imaging (MRI) radio frequency (RF) receive coil assembly is disclosed. The assembly comprises a deformable pad which comprises an array of tracking coils disposed on a surface of the deformable pad, each tracking coil corresponding to a grid point of the surface and configured to provide information of a position of the grid point. One or more RF receive coils are disposed within the deformable pad.