Abstract
BackgroundScanning techniques such as magnetic resonance imaging (MRI) and computed tomography (CT) are useful tools in veterinary and human medicine. Here we demonstrate the usefulness of these techniques in the study of the anatomy of wild marine mammals as part of a necropsy. MRI and CT scans of sperm whale teeth (n = 4) were performed. The methods were compared and further compared to current standard methods for evaluation of tooth layering. For MRI a zero echo time sequence was used, as previously done for imaging of intact human teeth. For CT two different clinical scanners were used.ResultsThe three scanners did not provide sufficient information to allow age estimation, but both MRI and CT provided anatomical information about the tooth cortex and medulla without the need for sectioning the teeth. MRI scanning was also employed for visualizing the vascularization of an intact eye from one of the stranded sperm whale.ConclusionsClearly, MRI was useful for investigation of the retinal vasculation, but optimum results would require well-preserved tissue. It was not possible to estimate age based on CT scans of tooth growth lines. Further research is needed to clarify the usability of MRI and CT as tools for marine mammal research when samples need to remain intact or when a spatial (three dimensional) arrangement of features needs to be determined.
Highlights
Scanning techniques such as magnetic resonance imaging (MRI) and computed tomography (CT) are useful tools in veterinary and human medicine
Modern scanning techniques have much to offer in this research field—at least as a supplement to dissection: first, modern scanners offer the possibility of noninvasive imaging of organs providing access to data about organ structure in situ, e.g. vasculature of soft tissue
Medical CT scanners consist of a rotating X-ray source, which is rigidly linked to an X-ray detector located on the other side of the target [10]
Summary
Scanning techniques such as magnetic resonance imaging (MRI) and computed tomography (CT) are useful tools in veterinary and human medicine. Alstrup et al Acta Vet Scand (2017) 59:38 described for terrestrial vertebrates by Lauridsen et al [5] Both magnetic resonance imaging (MRI) and computed tomography (CT) provide detailed images with millimeter spatial resolution for routine scans and cellular level resolution is attainable when imaging samples [6,7,8,9]. In MRI a constant external magnetic field sets up a magnetization in the subject or sample being imaged This magnetization may be manipulated with radiofrequency pulses to induce a signal in a detector coil. During the scan the magnetization is encoded in frequency and phase by additional time-dependent magnetic fields (called gradients) This encoding makes it possible to reconstruct an image from the signal received in the coil. The resulting CT image is linearly rescaled into CT numbers in Hounsfield units
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