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Abstract:
of fishes is currently a field of intense, multidisciplinary research. Of special
interest are certain species of fish like tuna and several types of sharks
(thunniform swimmers), that have developped an especially effective way of
swimming and can reach velocities up to 70 km/h with only little movement
of the body. To understand the swimming mechanics of these fishes, a threedimensional
model of the muscle structure is required. While histologic
techniques are extremely time-consuming for the examination of these large
structures, MRI could reveal the inner muscle structures fast and without
damaging the sample.
Subjects and Methods: To investigate on the possibilities of examining the
muscle structure of sharks with MRI, a formalin-fixated zebra shark with a
length of 50 cm, and excised muscle tissue from a thresher shark were examined
in a human 3T scanner. The fish was positioned prone on the spine
coil. Since the goal was to differentiate between muscle and connective tissue,
which has a thickness in the order of 0.1 mm, highly resolved 3D-images
with a resolution of (0.4 mm)3 and a high SNR were acquired. Best contrast
and sufficient SNR was achieved with a 3D FLASH sequence with a TR of 15
ms and an echo time of 5.59 ms. 22 averages were taken with a matrix size of
1024×256×256 within 6 hours.
Results: The following figure shows a coronal slice through the entire shark.
Throughout the whole body, the connective tissue can clearly be identified as
dark lines in the brighter muscle tissue.
