MR Readout Gradient Field Distortion Cancellation for PET Attenuation
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Solution Overview
Problem
Conventional magnetic resonance (MR) systems face limitations in imaging accuracy due to field inhomogeneities and nonlinearity, restricting the usable field of view and causing distortions, which affect human attenuation correction in positron emission tomography (PET) scans, especially in peripheral regions where arms of a patient are positioned, requiring additional time and specific PET tracers.
Innovation Solution
A method for acquiring MR data using a first readout gradient field that cancels distortions caused by nonlinearity and B0 field inhomogeneities, allowing for accurate imaging outside the usual field of view without significantly increasing the overall MR/PET scan time, by optimizing the gradient field to minimize distortions in peripheral regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional magnetic resonance measurement sequences are used, then imaging within the usable field of view is possible, but imaging accuracy deteriorates in peripheral regions due to field inhomogeneities and nonlinearity
Solution Approach 1:
The patent applies local quality by optimizing the readout gradient field specifically for peripheral regions rather than using a uniform gradient field across the entire field of view. The gradient field is tailored to compensate for local field inhomogeneities and nonlinearity in the peripheral zone, thereby improving imaging accuracy in these regions without compromising the overall usable field of view.
Solution Approach 2:
The patent changes the parameters of the readout gradient field to optimize performance in peripheral regions. By adjusting the gradient strength and orientation in specific regions, the system compensates for field inhomogeneities and nonlinearity, improving measurement precision in areas where conventional uniform gradient fields fail.
2Measurement precision
If additional magnetic resonance measurements are performed to improve attenuation correction in peripheral regions, then imaging accuracy improves, but scan time increases
Solution Approach 1:
The patent merges the attenuation correction imaging function with the primary diagnostic imaging sequence. By integrating the attenuation correction capability into the existing readout gradient field optimization, the system achieves both diagnostic imaging and accurate attenuation correction in a single scan, eliminating the need for separate measurement sequences and thereby reducing total scan time.
Solution Approach 2:
The optimized readout gradient field serves multiple functions simultaneously: it provides high-quality diagnostic imaging in peripheral regions and enables accurate attenuation correction for PET scans. This multi-functionality eliminates the need for dedicated attenuation correction sequences, reducing overall scan time while maintaining precision.
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 true-to-the-original imaging in peripheral regions with minimal distortion, facilitating precise attenuation correction maps for PET scans and reducing the need for additional MR measurements, thus shortening the combined MR/PET scan duration.
Implementation Method 1
a first readout gradient field is chosen such that at a predetermined location of the field of view of the magnetic resonance system a distortion caused by a nonlinearity of the first readout gradient field and a distortion caused by a B0 field inhomogeneity substantially cancel each other out
Data Source
AI summary
A method is disclosed for performing a combined magnetic resonance/positron emission tomography scan of an examination object in an MR/PET system. An embodiment of the method entails acquiring first magnetic resonance data using a first readout gradient field. The first readout gradient field is chosen such that, at a location of the field of view of the magnetic resonance system, a distortion caused by a nonlinearity of the first readout gradient field and a distortion caused by a B0 field inhomogeneity substantially cancel each other out. First magnetic resonance images for planning the combined magnetic resonance/positron emission tomography session and determining an attenuation correction map for a positron emission tomography scan are determined on the basis of the first magnetic resonance data. Positron emission data and second magnetic resonance data are acquired using a second readout gradient field.