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Fetal MRI

Blood Flow

Figure of healthy human fetus heart
Four-chamber CINE frames from healthy fetus during a fetal cardiac cycle. Magnitude frames and velocity components (Vz, Vx, Vy) are shown. (temporal resolution: 30ms, spatial resolution 1x1x4 mm3)

Velocity sensitive phase contrast MRI (PCMRI) is an integral facet of cardiac examinations. Using PCMRI, blood flow is measured in the major vessels providing a quantitative assessment of the circulation and cardiac output. Our research group was the first to adapt this time-resolved blood flow measurement to the human fetus [1]. 

As with anatomical imaging, fetal PCMRI is made possible by metric optimized gating, a post processing method that retrospectively synchronizes the MRI acquisition to the fetal cardiac cycle. Using PCMRI and metric optimized gating, our group has studied the normal range of fetal blood flows in late gestation as well as circulatory changes in pathologies such as intrauterine growth restriction and congenital heart disease [2-8]. 

Recent work in our group has continued to develop fetal PCMRI by incorporating methods for accelerated imaging, motion compensation, and multi-dimensional flow imaging [9]. We have also recently explored the use of volumetric multidimensional flow imaging (termed ‘4D flow MRI’) in animal models (pregnant sheep and pigs) of human pregnancy. These studies are the first of their kind to visualize the complex 3D fetal cardiac hemodynamics [10].

Matlab reconstruction code for metric optimized gating is available at: 
https://github.com/MetricOptimizedGating

Figure of sheep fetus
Animated particle traces in a cranial view of cardiac structures in a sheep fetus, shown over two cardiac cycles. Particles are emitted from the main pulmonary artery (MPA) and ascending aorta (AAo), and color-coded based on speed of streaming blood.

[1] Schrauben EM, Saini BS, Darby JRT, Soo JY, Lock MC, Stirrat E, Stortz G, Sled JG, Morrison JL, Seed M, Macgowan CK. Fetal hemodynamics and cardiac streaming assessed by 4D flow cardiovascular magnetic resonance in fetal sheep. J Cardiovasc Magn Reson. 21:8 (2019) − doi: 10.1186/s12968-018-0512-5

[2] Goolaub DS, Roy CW, Schrauben E, Sussman D, Marini D, Seed M, Macgowan CK. Multidimensional fetal flow imaging with cardiovascular magnetic resonance:  a feasibility study. J Cardiovasc Magn Reson. 20:77 (2018) − doi: 10.1186/s12968-018-0498-z

[3] Porayette P, Madathil S, Jaeggi E, Grosse-Wortmann L, Yoo SJ, Kingdom J, Ryan G, Macgowan CK, Miller S, Seed M. MRI reveals hemodynamic changes with acute maternal hyperoxygenation in human fetuses with and without congenital heart disease. Prenat. Diagn. 36(3):274-281 (2016) – doi:10.1002/pd.4762

[4] Zhu MY, Milligan N, Keating S, Windrim R, Keunen J, Thakur V, Ohman A, Portnoy S, Sled JG, Kelly E, Yoo SJ, Gross-Wortmann L, Jaeggi E, Macgowan CK, Kingdom JC, Seed M. The hemodynamics of late onset intrauterine growth restriction by MRI. Am J Obstet Gynecol. 214(3):367.e1-367.e17 (2015) – doi:10.1016/j.ajog.2015.10.004

[5] Sun L, Macgowan CK, Sled JG, Manlhiot C, Porayette P, Grosse-Wortmann L, Jaeggi E, McCrindle BW, Kingdom J, Hickey E, Miller S, Seed M. Reduced fetal cerebral oxygen consumption Is associated with smaller brain size in fetuses With congenital heart disease. Circulation 131:1313-1323 (2015) – doi:10.1161/CIRCULATIONAHA.114.013051

[6] Prsa M, van Amerom JFP, Yoo SJ, Grosse-Wortmann L, Jaeggi E, Macgowan CK, Seed M. Normal ranges of blood flow in the major vessels of the normal human fetal circulation at term by phase contrast MRI Circ Cardiovasc Imaging. 7:663-670 (2014) – doi:10.1161/CIRCIMAGING.113.001859

[7] Porayette P, van Amerom JFP, Macgowan CK, Seed M. MRI shows limited mixing between systemic and pulmonary circulations in fetal transposition of the great arteries - a potential cause of In utero pulmonary vascular disease Cardiol. Young  25(4):737-744 (2014) – doi:10.1017/S1047951114000870

[8] Al Nafisi B, van Amerom JFP, Forsey J, Jaeggi E, Grosse-Wortmann L, Yoo SJ, Macgowan CK, Seed M. Fetal circulation in left-sided congenital heart disease measured by cardiovascular magnetic resonance: a case-control study J Cardiovasc Magn Reson. 15:65 (2013) – doi:10.1186/1532-429X-15-65

[9] Seed M, van Amerom JFP, Yoo SJ, Al Nafisi B, Grosse-Wortmann L, Jaeggi E, Jansz MS, Macgowan CK. Feasibility of quantification of the distribution of blood flow in the normal human fetal circulation using CMR: a cross-sectional study J Cardiovasc Magn Reson. 14(79) (2012) – doi:10.1186/1532-429X-14-79

[10] Jansz MS, Seed M, van Amerom JFP, Wong D, Grosse-Wortmann L, Yoo SJ, Macgowan CK. Metric optimized gating for fetal cardiac MRI Magn Reson Med. 64(5): 1304-1314 (2010) – doi: 10.1002/mrm.22542