Simultaneous Doppler US-low field MRI to enable comprehensive image-guided fetal intervention of the future

Project summary: Fetal MRI is an excellent opportunity to gain unique insights into life before birth. While US is the major clinical screening tool, MRI allows to visualize the fetal organs and the placenta anatomically at higher resolution and provides a range of additional functional and dynamic contrasts. These are particularly of interest for complex pregnancy complications such as spina bifida, congenital diaphragmatic hernia or twin-to-twin-transfusion syndrome (TTTS) for which fetal surgery opportunities [Maselli2016] are emerging.

Project description: 

TTTS describes a condition where a placenta shared between both twins distributes blood unequally between both via connections (anastomosis) of major placental (chorionic) vessels and, if left untreated, leads to the death of one or both fetuses [Spruijt2020]. In-utero laser ablation surgery has emerged as a treatment option: The connected chorionic vessels are separated by laser ablation under endoscopic visual guidance. However, the circulation is often shared at a deeper level within the placenta with both arterio-arterial and veno-venous anastomosis presenting with bi-lateral blood flow which are not visible during standard endoscopic surface-visualization. Suboptimal surgery success rates with a significant proportion suffering from damage to other organs such as the brain [Spruijt2020] are potential consequences. Further challenges for the surgery include fetal motion and hence dynamic changes of the anatomy and function. 

In-depth knowledge of the spatial distribution and properties of the blood flow, function and fetal motion is therefore key. The directionality of the blood flow is typically assessed using Doppler US (DUS). Pre-operative anatomical planning using MRI has shown promise [Torrents-Barrena2019]. However, neither functional spatial assessment nor dynamic knowledge during the surgery exists to date. 

The conflation of novel  functional MR imaging techniques [Aughwane2020, Hutter2019,Torrents-Barrena2019], MR-compatible Doppler US (northh Hamburg) and newly emerging sophisticated low field MRI technology has huge potential to change the management in TTTS and in the wider field of in-utero surgery.  
 

This project is placed at the intersection of these developments and will explore the required technology to enable low-field DUS and MR-guided fetal interventions at low field MRI. 

Low-field MRI is ideally suited for interventional MRI, as recently demonstrated with adult heart ablations [Campbell-Washburn2019] and has ideal properties for fetal MRI. 

Functional MR technologies enable dynamic visualization and quantification of the maternal, placental and fetal blood flow, perfusion and fetal motion in real-time. Matched with simultaneously acquired Doppler information and visualized using 3D reconstruction techniques, it allows to give detailed and necessary insights to perform fetal surgery safely and optimally. 

The overall goal of this project is thus to point the way to a new generation of image guidance by combining and getting best of real time US and high fidelity MRI all in the same workspace. 

This project will focus on developing and testing a new simultaneous DUS-MRI acquisition on low-field MRI as a candidate for image guided TTTS procedures. Initially the developed capability will be applied to pre-operative planning as a means to verify and explore its potential. As a first proof of concept, results will be used for placental share analysis and planning of the ablation line in clinical cases to be managed conventionally. Results will be evaluated against outcome. 

Collaboration with both northh Hamburg and Siemens Healthineers will allow valuable training opportunities, insights and access to the expertise required for this project. 

Potential expansions of this stream of work include the assessment of the artefacts produced by existing minimally invasive fetal surgery tools both using MRI and DUS to thus assess the options with existing technology and need for new interventional devices.

References: 

[Aughwane2020] Aughwane,  Prenatal Diagnosis 2020;40:38–48

[Hutter2019] Hutter, MRM 2019;81(2):1191-1204.

[Torrents-Barrena2019] Torrents-Barrena, Comput Methods Programs 2019;179:104993.

[Maselli2016] Maselli, Ann Transl Med. 2016;4(20):394. 

[Spruijt2020] Spruijt, Expert Review of Hematology 2020;13:3,259-267

[Campbell-Washburn2019] Campbell-Washburn, Radiology. 2019;293(2):384-393

[Melbourne2019] Melbourne, MRM 2019;81:350–361

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