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4-D Flow

    
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Functional Cardiovascular 4D MRI in Congenital Heart Disease

Congenital heart disease (CHD) represents the most common birth defect and affects approximately 1.2% of all live births and is the leading cause of birth defect-related deaths. CHD patients require frequent diagnostic testing in order to plan surgical repair, assess preoperative risk, and/or survey for important long-term complications. Standard diagnostic tools, however, often involve invasive catheter-based procedures, ionizing radiation, and/or lengthy 60-90 minute Magnetic Resonance Imaging (MRI) exams, necessitating sedation or general anesthesia in pediatric patients. Our goal is to develop a new comprehensive cardiovascular 4D flow MR exam that can replace the long standard MR imaging protocol and reduce or eliminate exposure to general anesthesia. Patient-specific post-hoc analysis will allow retrospective quantification of cardiac function and flow without limitation to predefined 2D scan planes.

Investigators: Michael Markl (PhD), Cynthia K Rigsby (MD), Kelly Jarvis (MS), Alex Barker (PhD), Susanne Schnell (PhD), Joshua Robinson (MD), Michael Rose

Funding: National Heart, Lung, And Blood Institute of the NIH

Publication:
Thoracic Aorta 3d Hemodynamics in Pediatric and Young Adult Patients with Bicuspid Aortic Valve

4-D Flow Magnetic Resonance Imaging: Blood Flow Quantification Compared to 2-D Phase-Contrast Magnetic Resonance Imaging and Doppler Echocardiography

4d Flow Imaging: Current Status to Future Clinical Applications


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Dual VENC Phase Contrast MRI

4D flow MR imaging combines ECG-synchronized 3D phase-contrast (PC) MRI with advanced post-processing strategies for the in vivo assessment of 3D blood flow with full volumetric coverage of the vascular region of interest. Several applications of 4D flow MRI demand the measurement of flow velocities with a high dynamic range (e.g. slow venous and fast arterial flow), e.g. intracranial aneurysms (IA) or cerebral arteriovenous malformations (AVM). However, 4D flow MRI uses fixed velocity sensitivity (venc), which is set above the expected maximum velocity to avoid velocity aliasing. As the velocity noise (dv) is directly related to the velocity sensitivity (dv ~ venc/SNRmag), a high venc can substantially limit the assessment of vascular regions with low flow velocities (v << venc). Previous applications of 4D flow MRI were limited by its inability to fully capture the wide range of velocities inside aneurysms (high flow jet entering the aneurysm and low unstable flow, vortex and helix type flow). Therefore, we are developing a dual-venc sequence with shared reference scan and k-t acceleration for improved scan efficiency allowing the acquisition of both low- and high-venc data within a single scan. The resulting high-venc data can be used for complete anti-aliasing of the low-venc data while maintaining the favourable velocity to noise ratio (VNR) of the low-venc data. Validation and evaluation of the sequence showed that e.g. with a low- and high venc setting of 100cm/s and 200cm/s we observe an expected 200% VNR improvement. The sequence was to systematically tested with a dedicated rotation phantom experiment. In addition, we we were able to apply the k-t accelerated dual-venc 4D flow MRI intracranially in healthy volunteers to measure 3D blood flow velocities and could show an improved 3D flow assessment in small intracranial vessels and veins.

Investigators: Susanne Schnell (PhD)

Funding: Coming soon.

Publications:
Susanne Schnell, Can Wu, Julio Garcia, Ian Murphy, Michael Markl, Intracranial k-t Accelerated Dual-Venc 4D flow MRI, Conference Proceedings: ISMRM Workshop on Non-Contrast Cardiovascualar MRI, At Long Beach, CA, USA, 2015 (abstract)

Susanne Schnell, Julio Garcia, Can Wu, and Michael Markl, Dual-Velocity Encoding Phase-Contrast MRI: extending the dynamic range and lowering the velocity to noise ratio, Conference Proceedings: 23rd Annual Meeting of the ISMRM, abstract 5558, 2015 (abstract)