Inside Out: Modern Imaging Techniques to Reveal Animal Anatomy Henrik Lauridsen1,2, Kasper Hansen1,2, Tobias Wang2, Peter Agger3, Jonas L. Andersen2, Peter S. Knudsen2, Anne S. Rasmussen1, Lars Uhrenholt4, Michael Pedersen1,3* 1 MR Research Center, Aarhus University Hospital Skejby, Aarhus, Denmark, 2 Zoophysiology, Department of Biological Sciences, Aarhus University, Aarhus, Denmark, 3 Institute of Clinical Medicine, Aarhus University Hospital Skejby, Aarhus, Denmark, 4 Section for Forensic Pathology, Department of Forensic Medicine, Aarhus University, Aarhus, Denmark Abstract Animal anatomy has traditionally relied on detailed dissections to produce anatomical illustrations, but modern imaging modalities, such as MRI and CT, now represent an enormous resource that allows for fast non-invasive visualizations of animal anatomy in living animals. These modalities also allow for creation of three-dimensional representations that can be of considerable value in the dissemination of anatomical studies. In this methodological review, we present our experiences using MRI, CT and mCT to create advanced representation of animal anatomy, including bones, inner organs and blood vessels in a variety of animals, including fish, amphibians, reptiles, mammals, and spiders. The images have a similar quality to most traditional anatomical drawings and are presented together with interactive movies of the anatomical structures, where the object can be viewed from different angles. Given that clinical scanners found in the majority of larger hospitals are fully suitable for these purposes, we encourage biologists to take advantage of these imaging techniques in creation of three-dimensional graphical representations of internal structures. Citation: Lauridsen H, Hansen K, Wang T, Agger P, Andersen JL, et al. (2011) Inside Out: Modern Imaging Techniques to Reveal Animal Anatomy. PLoS ONE 6(3): e17879. doi:10.1371/journal.pone.0017879 Editor: C. Boswell, Genentech, United States of America Received January 17, 2011; Accepted February 12, 2011; Published March 22, 2011 Copyright: 2011 Lauridsen et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The study was supported by The Danish Agency for Science, Technology and Innovation. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: michael@mr.au.dk Introduction The internal structures of the animal body can be difficult to visualise, and classic dissections require the unique combination of a researcher who is skilful, patient and endowed with appropriate artistic skills. Today, however, three-dimensional computer modelling can provide morphological and anatomical information in a minimal-invasive and much faster fashion [1]. Magnetic resonance imaging (MRI) and computed tomography (CT) are two modalities routinely used to scan cross-sectionally for various diseases in humans, and smaller versions are now manufactured for dedicated animal research. These techniques can image the entire body with little distortion [2,3]. In addition to static images or movies, computer graphics allow for creation of naturalistic interactive three-dimensional models of the anatomy, where dynamic processes can be simulated and visualised, enabling the researcher to extract skeleton, organs, vascular structures, etc. While both MR and CT have been used extensively to describe human anatomy [4,5] and the anatomy of classic experimental animal models in experimental medicine (e.g. mouse, rat, rabbit, pig), these techniques have been employed much less in the realm of comparative anatomy [6–17]. Amphibian and reptilian anatomy, for example, is today mostly presented in the form of illustrative drawings and pictures [18–20]. High-field MRI and micro-CT (mCT) have, nevertheless, been used to characterise the internal morphology of polychaetes [21] and echinoderms [22– 24]. Paleontologists have used mCT to study fossil invertebrates preserved in amber [25], and high-resolution CT images have been used to compliment molecular data in the construction of phylogenetic relationships amongst squamate reptiles [26]. The web-based library www.digimorph.org hosts a comprehensive collection of three-dimensional representation of animal morphol- ogy based on high-resolution CT imaging with particular focus on cranial morphology [27]. In addition, the Digital Fish Library www.digitalfishlibrary.org describes the morphological diversity of fishes using MRI [28]. In the present study, we selected animals from various Classes to illustrate the broad applicability of MR and CT to produce three- dimensional representations of animal anatomy. We demonstrate that MRI and CT are useful techniques to create exact three- dimensional representations (static models, movies and interactive presentations) of various soft and hard tissues and vascular anatomy in various animals. Methods Animals Animal procedures were conducted in accordance with the guidelines of the European Communities, Directive 86/609/EEC regulating animal research and approved by the national ethical committee (approval: #2006/561-1192). The animals used were obtained from commercial dealers or imported directly to the Department of Biological Sciences (Aarhus University), where they were maintained for physiological studies. The animals used PLoS ONE | www.plosone.org 1 March 2011 | Volume 6 | Issue 3 | e17879