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Deep Vascular Imaging in the Eye with Flow-Enhanced Ultrasound
Published on: October 4, 2021
Dark blood late enhancement imaging
Peter Kellman1, Hui Xue2, Laura J Olivieri3
1National Heart, Lung, and Blood Institute, National Institutes of Health, DHHS, 10 Center Drive MSC-1061, Bethesda, MD, 20892, USA. kellman@nih.gov.
Insights
This study introduces a novel dark blood phase sensitive inversion recovery (PSIR) late gadolinium enhancement (LGE) technique for improved myocardial infarction (MI) visualization. This method enhances the detection of sub-endocardial MIs, improving diagnostic accuracy in cardiovascular imaging.
Area of Science:
- Cardiovascular Magnetic Resonance Imaging
- Medical Imaging Techniques
- Cardiac Pathology
Background:
- Late gadolinium enhancement (LGE) imaging excels at differentiating infarcted from normal myocardium.
- Suboptimal contrast between myocardial infarction (MI) and the blood pool often hinders detection of sub-endocardial MIs.
- Sub-endocardial MIs, common in coronary artery disease, are frequently difficult to delineate due to poor contrast with the blood pool.
Purpose of the Study:
- To develop and evaluate a free-breathing, dark blood phase sensitive inversion recovery (PSIR) LGE technique.
- To improve the visualization and delineation of sub-endocardial myocardial infarctions (MIs).
- To overcome the limitations of bright blood LGE in cases with poor contrast between MI and the blood pool.
Main Methods:
- Combined inversion recovery (IR) T2 preparation with single-shot steady-state free precession imaging and respiratory motion-corrected averaging.
- Implemented phase-sensitive inversion recovery (PSIR) reconstruction to achieve dark blood imaging.
- Utilized a T1-map scout with a Modified Look-Locker Inversion recovery (MOLLI) protocol for automatic parameter calculation, simplifying the user interface.
- Conducted free-breathing imaging to enhance patient comfort and clinical workflow.
Main Results:
- Dark blood (DB) PSIR LGE significantly improved the conspicuity and delineation of sub-endocardial fibrosis and MI.
- The contrast between MI and the blood pool was positive in all DB cases, unlike 63% of bright blood cases where it was negative.
- While the contrast-to-noise ratio (CNR) between MI and remote myocardium showed a 13% loss compared to bright blood, the improved MI-to-blood pool contrast was clinically advantageous.
- Enhanced visualization of thin-walled structures like atrial walls, valves, and papillary muscles was also observed.
Conclusions:
- Free-breathing dark blood PSIR LGE imaging effectively enhances the visualization of sub-endocardial MI and fibrosis, particularly in cases with low contrast to the adjacent blood pool.
- The technique offers improved delineation of myocardial scar and thin-walled cardiac structures.
- This method represents a valuable advancement in cardiac MRI for diagnosing and characterizing myocardial pathologies.
Background:
Bright blood late gadolinium enhancement (LGE) imaging typically achieves excellent contrast between infarcted and normal myocardium. However, the contrast between the myocardial infarction (MI) and the blood pool is frequently suboptimal. A large fraction of infarctions caused by coronary artery disease are sub-endocardial and thus adjacent to the blood pool. It is not infrequent that sub-endocardial MIs are difficult to detect or clearly delineate.
Methods:
In this present work, an inversion recovery (IR) T2 preparation was combined with single shot steady state free precession imaging and respiratory motion corrected averaging to achieve dark blood LGE images with good signal to noise ratio while maintaining the desired spatial and temporal resolution. In this manner, imaging was conducted free-breathing, which has benefits for image quality, patient comfort, and clinical workflow in both adults and children. Furthermore, by using a phase sensitive inversion recovery reconstruction the blood signal may be made darker than the myocardium (i.e., negative signal values) thereby providing contrast between the blood and both the MI and remote myocardium. In the proposed approach, a single T1-map scout was used to measure the myocardial and blood T1 using a MOdified Look-Locker Inversion recovery (MOLLI) protocol and all protocol parameters were automatically calculated from these values within the sequence thereby simplifying the user interface.
Results:
The contrast to noise ratio (CNR) between MI and remote myocardium was measured in n = 30 subjects with subendocardial MI using both bright blood and dark blood protocols. The CNR for the dark blood protocol had a 13 % loss compared to the bright blood protocol. The CNR between the MI and blood pool was positive for all dark blood cases, and was negative in 63 % of the bright blood cases. The conspicuity of subendocardial fibrosis and MI was greatly improved by dark blood (DB) PSIR as well as the delineation of the subendocardial border.
Conclusions:
Free-breathing, dark blood PSIR LGE imaging was demonstrated to improve the visualization of subendocardial MI and fibrosis in cases with low contrast with adjacent blood pool. The proposed method also improves visualization of thin walled fibrous structures such as atrial walls and valves, as well as papillary muscles.
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