MRI Contrast via Segmented Echo Train Crusher Gradients
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Solution Overview
Problem
Current magnetic resonance angiography (MRA) techniques struggle to visualize arteries with reduced flow difference between systole and diastole phases, often resulting in blurring, enhanced background signals, and fine line artifacts, while also failing to enhance visualization of tissues with faster signal decay.
Innovation Solution
A method involving multiple MR image scans with distinct flip angles for refocusing pulses in first and second fast spin echo (FSE) scan sequences, allowing for the creation of high-contrast difference images that reduce artifacts and emphasize tissues with faster signal decay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If readout spoiler gradient amplitudes are modified in real-time between acquisitions to visualize slower flowing arteries, then arterial signal visualization is improved, but image blurring increases due to longer echo spacing
Solution Approach 1:
The patent segments the echo train into multiple groups, applying different crusher gradient amplitudes to different groups. This allows selective dephasing of flowing blood signals in specific temporal segments while maintaining consistent gradient parameters within each segment, thereby visualizing slower flowing arteries without causing overall image blurring.
Solution Approach 2:
The patent dynamically adjusts crusher gradient amplitudes based on the echo group index, creating a time-varying gradient scheme that adapts to different portions of the echo train. This dynamic adjustment enables enhanced arterial signal visualization during systole while maintaining image sharpness through controlled gradient application.
2Measurement precision
If readout spoiler gradient amplitudes are modified between systolic and diastolic acquisitions, then arterial signal contrast is improved, but background signal enhancement occurs due to different eddy currents
Solution Approach 1:
The patent applies different crusher gradient amplitudes to different echo groups within the same acquisition, creating local variations in dephasing effects. This localized approach enhances arterial signal contrast in specific temporal regions while minimizing background signal enhancement that would result from global gradient modifications.
3Measurement precision
If different readout crushers are used between the two acquisitions, then slower flowing arteries are dephased during systole, but fine line artifacts appear due to uncrushed free induction decay signal
Solution Approach 1:
The patent segments the echo train and applies crushers selectively to different segments. By crushing only specific echo groups while leaving others uncrushed, the method achieves flow differentiation without generating fine line artifacts from completely uncrushed free induction decay signals.
Solution Approach 2:
The patent applies partial crushing to specific echo groups rather than crushing all echoes or applying no crushing. This partial action approach provides sufficient dephasing to differentiate arterial flow while avoiding excessive crushing that would leave residual uncrushed signal causing fine line artifacts.
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
The approach enhances the visualization of arteries with reduced flow difference and tissues experiencing faster signal decay, while minimizing blurring and background noise, resulting in improved diagnostic imaging.
Implementation Method 1
When utilizing these signals to produce images, magnetic field gradients (Gx, Gy, and Gz) are employed
Implementation Method 2
the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency
Implementation Method 3
If the substance, or tissue, is subjected to a magnetic field (excitation field B1) which is in the x-y plane and which is near the Larmor frequency, the net aligned moment, or 'longitudinal magnetization', MZ, may be rotated, or 'tipped', into the x-y plane to produce a net transverse magnetic moment Mt
Implementation Method 4
A signal is emitted by the excited spins after the excitation signal B1 is terminated and this signal may be received and processed to form an image
Data Source
AI summary
A system and method for enhanced contrast MR imaging include a computer programmed to perform a first scan of an imaging object based on a first fast spin echo (FSE) scan sequence comprising a first series of RF pulses having a first flip angle sequence to acquire a first MR data set and perform a second scan of the imaging object based on a second FSE scan sequence comprising a second series of RF pulses having a second flip angle sequence, wherein the second flip angle sequence is different from the first flip angle sequence to acquire a second MR data set. The computer is further programmed to generate a difference image based on the first and second MR data sets.