Surrogate Soft Tissue Device for MRI Susceptibility Artifact Mitigation
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Solution Overview
Problem
Magnetic resonance imaging (MRI) scans with metal implants often result in significant local susceptibility artifacts, leading to signal voids that distort image quality and hinder accurate diagnosis due to the strong magnetic field interactions.
Innovation Solution
A method involving a surrogate soft tissue device is used to mitigate these artifacts by providing a visible boundary during image segmentation, which includes determining the metal implant parameters, selecting a suitable surrogate device, applying it over the implant, acquiring MR scan data, reconstructing the image with the surrogate boundary, and segmenting to correct for artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal implants are present in the patient's body for medical treatment, then therapeutic benefit is achieved, but local susceptibility artifacts and signal voids are generated that degrade image quality
Solution Approach 1:
A surrogate soft tissue device is introduced as an intermediary object placed over the metal implant. This device has MRI-compatible properties that mimic soft tissue signal characteristics, thereby mediating between the harmful metal implant and the MRI imaging process. The surrogate device blocks the susceptibility artifact from propagating into the image while maintaining the therapeutic function of the original implant.
Solution Approach 2:
The surrogate soft tissue device creates a copy or representation of what the tissue would look like if the metal implant were not present. By placing this surrogate over the implant, the system captures an image that reflects the underlying anatomy without the artifact, effectively copying the desired tissue appearance while excluding the harmful metal interference.
2Productivity
If standard MRI scanning is performed on patients with metal implants, then scan acquisition is completed, but image segmentation accuracy deteriorates due to signal voids
Solution Approach 1:
The surrogate soft tissue device is applied to the patient's body before the MRI scan is acquired. This preliminary action ensures that when the scanning process occurs, the susceptibility artifact is already blocked, allowing standard scanning protocols to proceed without modification while achieving accurate segmentation results.
Solution Approach 2:
The surrogate device is specifically positioned only over the region containing the metal implant, providing localized artifact suppression. This allows the rest of the image to maintain its normal imaging characteristics while the problematic region is selectively corrected, preserving overall image quality and segmentation accuracy.
3Object-affected harmful factors
If the surrogate soft tissue device is applied to encompass the artifact, then artifact mitigation is achieved, but device complexity and application procedure increase
Solution Approach 1:
The surrogate soft tissue device is designed to serve multiple functions: it acts as an artifact-blocking shield, provides a soft tissue signal reference for segmentation algorithms, and maintains patient comfort during scanning. This multi-functionality reduces the need for multiple separate devices or complex post-processing corrections.
Solution Approach 2:
The surrogate soft tissue device can be implemented as a disposable component that is applied once for the duration of the scan and then discarded. This approach eliminates the need for complex cleaning, sterilization, or maintenance procedures, significantly reducing the operational complexity despite the added step of application.
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 image quality and diagnostic accuracy by reducing the impact of metal-induced artifacts, allowing for more precise segmentation and attenuation correction in both MRI and PET images.
Implementation Method 1
The main magnetic field polarizes the nuclear spin system of a patient being imaged within the examination region. The main magnetic field polarizes the nuclear spin system of a patient being imaged within the examination region.
Implementation Method 2
The main magnetic field polarizes the nuclear spin system of a patient being imaged within the examination region. The main magnetic field polarizes the nuclear spin system of a patient being imaged within the examination region.
Implementation Method 3
Magnetic resonance is excited in dipoles which align with the main magnetic field by transmitting radio frequency excitation signals into the examination region. Specifically, radio frequency pulses transmitted via a radio frequency coil assembly tip the dipoles out of alignment with the main magnetic field and cause a macroscopic magnetic moment vector around an axis parallel to the main magnetic field.
Implementation Method 4
The magnetic moment, in turn, generates a corresponding radio frequency magnetic signal as it relaxes and returns to its former state of alignment with the main magnetic field.
Implementation Method 5
Spatial position is encoded with magnetic field pulses that alter resonance frequency in accordance with spatial position.
Implementation Method 6
Metallic implants generate a local susceptibility artifact, which results in a signal void in the vicinity of the artifact.
Data Source
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Figure 2A~2B
Figure 3A~3B
AI summary
When generating MR images for segmentation and/or use in correcting attenuation in subsequent images using other modalities (e.g., PET, SPECT, etc.), a surrogate soft tissue device is provided and positioned on the patient near the artifact source to provide a surrogate soft tissue boundary that can be imaged and interpreted during segmentation to mitigate the deleterious effects of a local susceptibility artifact in the MR image. More specifically, a metal implant may generate a signal void in MRI which may confound the segmentation of the lung in the MR image in such a manner that the lung and the air outside of the patient is falsely identified as one connected region. By providing the surrogate soft tissue device and positioning it in such a manner that its soft tissue boundary separates the lung and the outside air despite the signal void, the segmentation can be improved, thereby improving the attenuation correction which is based on the segmentation result.