MR Fingerprinting With Dynamic Information Density
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Solution Overview
Problem
MR fingerprinting methods are less tolerant to disturbances such as patient movements, making it difficult to obtain reliable quantitative results, as artifacts in representational MR imaging are easier to detect, whereas MR fingerprinting data is abstract and harder to identify errors in.
Innovation Solution
The method involves repeatedly outputting an MR pulse sequence succession with varying pulse sequence parameters, allowing for a short initial data acquisition at low information density, which is then incrementally increased with each repetition, enabling robust reconstruction and detection of disturbances, and allowing for early termination of measurements if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MR fingerprinting measurement time is extended to improve measurement precision and reduce susceptibility to errors, then reliability of quantitative results improves, but patient cooperation requirement increases and measurement time increases
Solution Approach 1:
The measurement process is divided into multiple segments: a first output of the MR pulse sequence succession acquires raw data at low information density (shorter duration), followed by one or more additional outputs that incrementally increase information density. This segmentation allows obtaining usable parameter maps earlier in the measurement process, reducing the minimum measurement time required while maintaining reliability for patients with limited cooperation.
2Measurement precision
If information density is increased to improve measurement precision and diagnostic relevance, then quality of parameter maps improves, but measurement time increases
Solution Approach 1:
The information density is made dynamic rather than static. The system starts with low information density acquisition and incrementally increases it in subsequent outputs of the pulse sequence succession. This dynamic approach allows the measurement to adapt to patient cooperation levels, providing diagnostically relevant parameter maps in minimal time while offering the option to enhance precision if the patient can tolerate longer measurement durations.
3Ease of operation
If MR fingerprinting is performed with short measurement time to improve patient cooperation tolerance, then ease of operation improves, but susceptibility to errors increases
Solution Approach 1:
The system performs preliminary action by first acquiring raw data at low information density, which requires minimal measurement time and thus ensures patient cooperation. This preliminary low-density acquisition establishes a baseline that can be used to generate parameter maps even if the measurement must be terminated early, thereby maintaining reliability while improving ease of operation.
Solution Approach 2:
The system incorporates feedback mechanisms to monitor the measurement process and detect disturbances. Based on this feedback, the system can determine whether to continue with additional high-density outputs or terminate early using the low-density data already acquired. This feedback-driven approach maintains reliability by adapting to actual measurement conditions while preserving ease of operation.
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 reduces the susceptibility to errors, allows for a shorter minimum measurement duration, and provides flexible measurement time configurations, enabling the production of usable parameter maps even with brief patient cooperation, while maintaining diagnostic relevance.
Implementation Method 1
After the main field is applied, nuclei in the object under examination align themselves along the field by a non-zero nuclear magnetic dipole moment, also frequently known as spin. This collective behavior of the spin system is described by the macroscopic 'magnetization'.
Implementation Method 2
In addition to the main field, a gradient system is used to apply a magnetic field gradient, which defines the magnetic resonance frequency (Larmor frequency) at the particular location.
Implementation Method 3
Radiofrequency excitation signals (RF pulses) are then emitted via a radiofrequency transmit system by means of suitable antenna devices, with the aim of causing the nuclear spins of certain nuclei, which this radiofrequency field has excited to resonance (i.e. at the Larmor frequency that exists at the particular location), to be tipped by a defined flip angle with respect to the magnetic field lines of the main magnetic field.
Implementation Method 4
Radiofrequency signals, known as magnetic resonance signals, are emitted resonantly when the excited nuclear spins relax, which signals are received by suitable receive antennas (also known as magnetic resonance coils or receive coils) then demodulated and digitized
Data Source
AI summary
MR fingerprinting method in which an MR pulse sequence succession is output multiple times. The MR pulse sequence succession has MR pulse sequences of a same type output successively in time and differing in terms of a pulse sequence parameter that is varied according to a predefined scheme. During the first output, raw data from a region of interest (ROI) of an object is acquired in a short time interval by the raw data being acquired at a low information density. The total information density of the acquisition is increased with each repetition of the output. After the acquisition, image data from the ROI is reconstructed based on the acquired raw data. MR-parameter value datasets associated with reference image data and having MR parameter values, are determined by comparing the reconstructed image data with the reference image data. MR parameter maps are determined based on the determined MR parameter values.