HOTSPA MRI Flow Encoding for Temporal Resolution
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Solution Overview
Problem
Current phase contrast magnetic resonance imaging (MRI) techniques face challenges with temporal resolution and temporal footprint, particularly in 4D flow acquisitions, which can lead to underestimation of maximum peak velocity and pressure gradients, affecting diagnostic accuracy for clinical diseases like carotid artery stenosis.
Innovation Solution
The HOTSPA technique employs a hybrid one- and two-sided flow encoding strategy, alternating flow velocity encoding polarity between cardiac phases, allowing for 3D velocity calculation using 2 samples instead of 4, reducing temporal sampling period and footprint by 50% compared to conventional 4D flow techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional 4D flow techniques with four-sided flow encoding are used, then complete velocity field measurement is achieved, but temporal resolution deteriorates and temporal footprint increases
Solution Approach 1:
The patent extracts and removes the flow compensation (FC) gradient lobes from the conventional four-sided flow encoding sequence. By eliminating these redundant FC gradients, the sequence reduces temporal footprint while maintaining velocity measurement capability through the modified three-sided encoding approach with alternating polarities
Solution Approach 2:
The patent inverts the conventional approach by using alternating flow encoding polarities (positive and negative) across different cardiac phases instead of using flow compensation gradients. This inversion allows velocity field separation through spectral methods while reducing the number of required encoding directions from four to three
2Measurement precision
If conventional phase contrast MRI with flow compensation is used, then accurate velocity measurement is achieved, but temporal resolution deteriorates
Solution Approach 1:
The patent extracts and removes the flow compensation gradient components from the pulse sequence. By eliminating these time-consuming FC gradients, the sequence achieves higher temporal resolution while maintaining velocity measurement accuracy through the alternating polarity encoding scheme
Solution Approach 2:
The patent changes the encoding parameters by implementing alternating flow encoding polarities across cardiac phases. This parameter modification allows the use of fewer gradient lobes while maintaining the ability to accurately measure peak velocities through spectral separation of the velocity fields
3Speed
If three-sided flow encoding with alternating polarities is used, then temporal resolution is improved, but measurement reliability may deteriorate
Solution Approach 1:
The patent implements a feedback mechanism through spectral separation methods that process the data from the three-sided encoding. By using Fourier transformation and spectral analysis to separate the velocity fields from the alternating polarity encodings, the system maintains measurement reliability despite the reduced number of encoding directions
Solution Approach 2:
The patent combines multiple encoding approaches into a composite sequence that integrates three-sided flow encoding with alternating polarities. This composite approach, combined with spectral separation processing, maintains measurement reliability by leveraging the complementary information from the alternating encodings
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
HOTSPA enhances temporal resolution and reduces temporal footprint, improving the accuracy of peak velocity measurements and total volumetric flow assessments, maintaining measurement accuracy while shortening acquisition time, thus providing clinically reliable information.
Implementation Method 1
magnetic field gradients (Gx, Gy, and Gz) are employed
Implementation Method 2
phase contrast (PC) MRA techniques utilize the change in the phase shifts of the flowing protons
Implementation Method 3
nuclear magnetic resonance (NMR) phenomenon
Data Source
AI summary
A system and method is provided for acquiring flow encoded data from a subject using a magnetic resonance imaging (MRI) system. The method includes acquiring flow encoded (FE) data with alternating encoding polarities and along two of three orthogonal directions through the subject over at least two cycles of the flow within the subject; and separating the FE data into directional FE datasets using a temporal filter that separates the FE data based on temporal modulation of the FE directions caused by the alternating encoding polarities extending over the at least two cycles of the flow within the subject that shift the Fourier spectrum of velocity waveforms corresponding to the FE data. The method also includes using the directional FE datasets to generate an image of the subject showing flow within the subject caused by the at least two cycles of flow within the subject.