An approach is presented for high-field MRI studies of the cardiovascular system (CVS) of a marine crustacean, the edible crab Cancer pagurus, submerged in highly conductive seawater.
Materials and methods
Structure and function of the CVS were investigated at 9.4 T. Cardiac motion was studied using self-gated CINE MRI. Imaging protocols and radio-frequency coil arrangements were tested for anatomical imaging. Haemolymph flow was quantified using phase-contrast angiography. Signal-to-noise-ratios and flow velocities in afferent and efferent branchial veins were compared with Student’s t test (n = 5).
Seawater induced signal losses were dependent on imaging protocols and RF coil setup. Internal cardiac structures could be visualized with high spatial resolution within 8 min using a gradient-echo technique. Variations in haemolymph flow in different vessels could be determined over time. Maximum flow was similar within individual vessels and corresponded to literature values from Doppler measurements. Heart contractions were more pronounced in lateral and dorso-ventral directions than in the anterior–posterior direction.
Choosing adequate imaging protocols in combination with a specific RF coil arrangement allows to monitor various parts of the crustacean CVS with exceptionally high spatial resolution despite the adverse effects of seawater at 9.4 T.
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(Flow-compensated) fast low-angle shot
Maximum intensity projection
Magnetic resonance imaging
Nuclear magnetic resonance
Rapid acquisition with relaxation enhancement
Region of interest
Sternal artery, arteria sternalis
(receive-only) surface RF coil
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The authors thank Fredy Veliz Moraleda for assistance in animal care, Rolf Wittig, Felizitas Wermter and Sebastian Gutsfeld for assistance during in vivo experiments and data evaluation. Further, thanks to the AWI workshop, in particular Erich Dunker, as well as Sven Junge and Martin Tabbert from the Bruker BioSpin coil development group (Ettlingen, Germany).
The study is a contribution to the PACES II research program (WP 1.6) of the Alfred-Wegener-Institute, funded by the Helmholtz Association.
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national and institutional guidelines for the care and use of animals were followed. All procedures performed in studies involving animals were in accordance with the ethical standards of the institution at which the studies were conducted.
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Spin-echo MRI of the heart region of C. pagurus. Image was recorded with a RARE (rapid acquisition with relaxation enhancement) technique, using the resonator in transmit-receive mode. TE = 85 ms; TR = 4500 ms; 4 averages, RARE factor = 8; bandwidth = 50000 Hz, 512×384 pixels; FOV = 100×75 mm²; slice thickness = 1.0 mm. Compared to the gradient-echo scans, signal losses in the center of the image reduce the visibility of the inner structures. Scale bar = 2 cm (PDF 533 kb)
3D MIP reconstruction of the cardiovascular system of Cancer pagurus based on coronal multi-slice TOF angiography scans. The scans and their parameters are identical to those in fig. 4a-c. Total volume = 100×100×49 mm³ (l×w×h) (MP4 29288 kb)
3D MIP reconstruction of the cardiovascular system of Cancer pagurus based on axial multi-slice TOF angiography scans. The scans and their parameters are identical to those in fig. 4d-f. Total volume = 100×99×50 mm³ (l×w×h) (MP4 29783 kb)
3D MIP reconstruction of the cardiovascular system of Cancer pagurus based on sagittal multi-slice TOF angiography scans. The scans and their parameters are identical to those in fig. 4g-h. Total volume = 80×103.2×60 mm³ (l×w×h) (MP4 571 kb)
IntraGate© movie for the contraction of the heart in coronal orientation. For scan parameters, see tab. 1. One cardiac cycle was split into 10 frames, each lasting 100 ms in the movie. The real duration of the reconstructed cardiac cycle is 666 ms at a heart rate of 90 bpm. End-systolic and end-diastolic frames can be seen in fig. 7a-b (MP4 526 kb)
IntraGate© movie for the contraction of the heart in axial orientation. For scan parameters, see tab. 1. One cardiac cycle was split into 10 frames, each lasting 100 ms in the movie. The real duration of the reconstructed cardiac cycle is 666 ms at a heart rate of 90 bpm. End-systolic and end-diastolic frames can be seen in fig. 7c-d (MP4 617 kb)
IntraGate© movie for the contraction of the heart in sagittal orientation. For scan parameters, see tab. 1. One cardiac cycle was split into 10 frames, each lasting 100 ms in the movie. The real duration of the reconstructed cardiac cycle is 750 ms at a heart rate of 80 bpm. End-systolic and end-diastolic frames can be seen in fig. 7e-f (MP4 29808 kb)
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Maus, B., Pörtner, HO. & Bock, C. Studying the cardiovascular system of a marine crustacean with magnetic resonance imaging at 9.4 T. Magn Reson Mater Phy 32, 567–579 (2019). https://doi.org/10.1007/s10334-019-00752-4