Multi-Contrast Cardiac MRI Segmented IR-SSFP Pulse Sequence
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Solution Overview
Problem
Current delayed enhancement cardiac MRI methods face challenges in accurately distinguishing between healthy myocardium, infarcted myocardium, and blood, leading to difficulties in visualizing wall motion and determining the border between blood and infarcted tissue, especially due to long scan times and lower spatial resolution in real-time methods.
Innovation Solution
A cardiac-gated, segmented inversion recovery steady-state free precession (IR-SSFP) pulse sequence is employed, which uses a succession of SSFP pulse segments throughout the cardiac cycle to produce image frames with varying tissue contrast, allowing for the visualization of wall motion and segmentation of healthy and infarcted myocardium, and blood, enabling the calculation of ejection fractions in a single breath hold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional delayed enhancement cardiac MRI methods are used, then tissue contrast is achieved, but scan time is prolonged and spatial resolution is reduced
Solution Approach 1:
The cardiac cycle is divided into multiple segments (first segment, second segment, third segment) with different inversion times. Each segment acquires data for specific tissue types at optimized contrast points, allowing simultaneous visualization of healthy myocardium, infarcted myocardium, and blood without requiring separate scans. This segmentation enables comprehensive tissue characterization within a single breath-hold scan.
Solution Approach 2:
The pulse sequence employs periodic inversion pulses at different inversion times (TI1, TI2, TI3) throughout the cardiac cycle. Each inversion pulse resets the magnetization and creates different tissue contrast characteristics in subsequent images. This periodic action with varying inversion times allows the system to capture multiple tissue types with optimal contrast in a time-efficient manner.
2Productivity
If real-time MRI methods are used to reduce scan time, then temporal resolution is maintained, but spatial resolution and image quality deteriorate
Solution Approach 1:
The pulse sequence continuously acquires data throughout the entire cardiac cycle without interruption, maintaining steady-state free precession conditions. The continuous acquisition ensures that no useful signal is lost while capturing wall motion and tissue contrast information. This continuous action allows real-time imaging with maintained spatial resolution by efficiently utilizing all available time within the cardiac cycle.
3Loss of time
If single contrast imaging is used, then scan time is reduced, but ability to distinguish between healthy myocardium, infarcted myocardium, and blood is compromised
Solution Approach 1:
Each image segment is optimized for specific tissue types with different inversion times. The first segment (TI1) optimizes for healthy myocardium nulling, the second segment (TI2) for infarcted myocardium enhancement, and the third segment (TI3) for blood pool visualization. This local quality optimization ensures that each tissue type is imaged at its optimal contrast point while maintaining comprehensive tissue differentiation within a single scan.
Solution Approach 2:
The multi-contrast pulse sequence serves multiple functions simultaneously: it visualizes healthy myocardium, infarcted myocardium, and blood pool in a single scan. The sequence is universal in that it can detect various pathologies including transmural and non-transmural infarcts, wall motion abnormalities, and ejection fraction changes without requiring separate imaging protocols.
4Measurement precision
If multiple separate scans are performed to achieve different tissue contrasts, then comprehensive tissue characterization is achieved, but total scan time and patient burden increase
Solution Approach 1:
The invention merges multiple imaging functions into a single pulse sequence. Instead of performing separate scans for healthy myocardium, infarcted myocardium, and blood pool imaging, the multi-contrast sequence combines all these functions in one acquisition. The pulse sequence integrates multiple inversion times and contrast mechanisms into a unified protocol that can be executed within a single breath-hold, simplifying the imaging workflow while maintaining comprehensive tissue characterization.
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 method enables the acquisition of detailed myocardium viability images and wall motion information simultaneously, improving the visualization of infarcted tissue and reducing scan time, while maintaining adequate spatial and temporal resolution, allowing for better detection of small subendocardial infarcts and assessment of infarct transmurality.
Implementation Method 1
A cardiac-gated, segmented inversion recovery steady-state free precession (IR-SSFP) pulse sequence is employed
Implementation Method 2
a succession of SSFP pulse segments throughout the cardiac cycle to produce image frames with varying tissue contrast
Implementation Method 3
magnetic field gradients (Gx, Gy and Gz) are employed
Data Source
AI summary
A series of MR image frames are acquired that depict a subject's heart at successive cardiac phases. Delayed enhancement of infarcted myocardium is depicted in some of the image frames by administering a contrast agent prior to data acquisition. Data acquisition is performed in a single breath hold by producing an RF inversion pulse followed by segments of SSFP pulse sequences during a succession of cardiac gated heart beats. The acquired MR image frames depict contrast between blood, viable myocardium and nonviable myocardium, and they depict left ventricle wall thickness and wall thickening throughout the cardiac cycle.