Metal-Resistant MR Imaging via Adaptive Echo Sequences
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Solution Overview
Problem
Current MR imaging techniques are compromised by susceptibility effects from metal implants, leading to signal voids and geometric distortions, particularly in SENSE reference scans, which are sensitive to these effects and result in insufficient image quality, necessitating longer, more robust scans even when metal implants are not present.
Innovation Solution
Automatically selecting between a gradient echo sequence and a stimulated echo sequence for the SENSE reference scan based on the presence of metal implants, with the stimulated echo sequence being more robust against susceptibility effects and only employed when necessary, allowing for efficient and fast imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a gradient echo sequence is used for the SENSE reference scan, then the scan time is short and imaging is efficient, but susceptibility effects from metal implants cause signal voids and geometric distortions degrading image quality
Solution Approach 1:
The system dynamically adapts the reference scan sequence type based on the presence of metal implants. When metal is detected, the system switches from gradient echo sequence to stimulated echo sequence, making the imaging protocol flexible and condition-dependent rather than static
Solution Approach 2:
The invention changes the sequence parameters (type of echo sequence) based on the detected presence of metal implants. The stimulated echo sequence uses different timing parameters (TE, TR) and gradient configurations compared to gradient echo, reducing susceptibility artifacts while maintaining adequate scan efficiency
2Reliability
If a stimulated echo sequence is used for the SENSE reference scan, then susceptibility effects are reduced and image quality is improved, but the scan time increases making imaging less efficient
Solution Approach 1:
The system applies different sequence characteristics to different imaging scenarios. The stimulated echo sequence is applied locally (only when metal implants are present) rather than universally, optimizing image quality where needed while maintaining efficiency where possible
Solution Approach 2:
The imaging protocol dynamically switches between sequence types based on patient-specific conditions (presence of metal implants), making the system adaptive rather than static. This allows the system to optimize for either speed or quality depending on the clinical situation
3Ease of operation
If the phase-encoding direction for the parallel imaging scan is not matched to the calibration scan, then setup is simpler, but image reconstruction accuracy deteriorates
Solution Approach 1:
The system performs preliminary matching of the phase-encoding direction between the reference scan and the parallel imaging scan during the setup phase. This preliminary configuration ensures that the sensitivity profiles derived from the reference scan are compatible with the subsequent parallel imaging reconstruction, improving accuracy without adding complexity to the main imaging sequence
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 enables robust and efficient MR imaging by automatically selecting a stimulated echo sequence for metal implants, reducing susceptibility effects and minimizing unnecessary longer scans, thus improving image quality and reducing scan time.
Implementation Method 1
Image-forming MR methods which utilize the interaction between magnetic fields and nuclear spins in order to form two-dimensional or three-dimensional images
Implementation Method 2
This produces an echo signal (spin echo) in the receiving coils
Implementation Method 3
subjecting the portion of the body to a first imaging sequence of RF pulses and switched magnetic field gradients, wherein first MR signals are acquired
Data Source
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AI summary
The invention relates to a method of parallel MR imaging which comprises the steps of: • - subjecting a portion of a body (10) to a first imaging sequence (21,22) of RF pulses and switched magnetic field gradients, wherein first MR signals (11,12) are acquired via at least two RF coils having different spatial sensitivity profiles within the examination volume, • - deriving the spatial sensitivity profiles of the at least two RF coils from the acquired first MR signals, • - subjecting the portion of the body to a second imaging sequence of RF pulses and switched magnetic field gradients, wherein second MR signals are acquired by parallel acquisition via the at least two RF coils with sub-sampling of k-space, and • - reconstructing a MR image from the acquired second MR signals and from the spatial sensitivity profiles of the at least two RF coils. According to the invention, the type and/or parameters of the first imaging sequence are selected automatically depending on the presence of a metal implant in the body. The selection of the type of the first imaging sequence is made between a gradient echo sequence, if no metal implants are present, and a spin echo sequence or a stimulated echo sequence, if a metal implant is present.