PETRA RF Pulse Extension for Low-Complexity Aliasing Correction
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Solution Overview
Problem
Conventional MR sequences cannot effectively capture tissues with T2* times shorter than 500 microseconds due to signal decay before echo recording, and PETRA methods suffer from unwanted slice selection aliasing requiring computationally intensive corrections.
Innovation Solution
Extend the pulse duration of RF excitation pulses in PETRA methods to align pulse profiles, reducing the dependency on k-space positions and simplifying the correction of aliasing without matrix inversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PETRA methods are used with radial k-space acquisition, then short echo times are achieved and robustness against eddy currents is improved, but unwanted slice selection aliasing occurs requiring computationally intensive corrections
Solution Approach 1:
The patent applies parameter changes by modifying the RF pulse duration parameter. Specifically, it uses extended RF pulse durations for excitation pulses in the radial k-space acquisition sequence. This parameter modification changes the pulse profile characteristics, which reduces the dependency of pulse profiles on k-space positions and thereby minimizes unwanted slice selection aliasing effects, eliminating the need for complex computational corrections.
2Ease of manufacture
If conventional MR sequences are used, then standard imaging protocols are maintained, but tissues with T2* times shorter than 500 microseconds cannot be captured due to signal decay
Solution Approach 1:
The patent applies preliminary action by preparing the gradient system in advance. Specifically, it ramps up gradient fields to full strength before the RF excitation pulse is radiated. This preliminary gradient preparation enables the use of ultrashort echo times while maintaining the ability to capture tissues with very short T2* times (shorter than 500 microseconds) before signal decay occurs, without requiring changes to conventional imaging protocols.
3Loss of time
If gradients are ramped up before excitation in PETRA methods, then encoding time is saved and short echo times are achieved, but the k-space center area cannot be scanned by radial spokes
Solution Approach 1:
The patent applies segmentation by dividing the k-space coverage into two parts: radial spoke acquisition for the peripheral areas and single-point imaging for the k-space center. The radial spokes cover the k-space periphery where gradients are fully ramped up, while the k-space center is filled by additional single-point measurements. This segmentation allows both short echo times (through radial acquisition) and complete k-space coverage (through combined methods).
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 simplifies and accelerates image reconstruction by minimizing computationally intensive operations, improving image quality and reducing noise, especially in systems with strong gradients.
Implementation Method 1
the examination object is positioned in a magnetic resonance device in a comparatively strong, static, homogeneous basic magnetic field, also called a B0 field, with field strengths from 0.2 tesla to 7 tesla and more, so that its nuclear spins are oriented along the basic magnetic field
Implementation Method 2
radiofrequency excitation pulses (RF pulses) are radiated into the examination object, the nuclear spin resonances triggered are measured as what is known as k-space data
Implementation Method 3
For spatial encoding of the measurement data, rapidly switched magnetic gradient fields are superimposed on the basic magnetic field
Data Source
AI summary
In the context of a method according to the disclosure for generating measurement data from an imaging area in a measurement volume of a magnetic resonance system, using a PETRA method, a pulse duration of at least one RF excitation pulse radiated during a single-shot recording method of the PETRA method is extended compared to a pulse duration of RF excitation pulses radiated during a radial recording method of the PETRA method, whereby computing operations for correcting disruptive aliasing may be simplified.