Welcome to the online home of Diffusible Iodine-based Contrast-enhanced Computed Tomography.
Our mission is to provide digital resources for the diceCT community and to connect interested researchers with contrast-enhanced imaging veterans. Watch this space and @diceCT for updates on new publications, tips & tricks, and diceCT-related events.
DiceCT allows visualization of organismal soft-tissue cheaply and non-destructively, thus giving comparative biologists a new toolkit for assessing morphological variation. Comparative morphologists primarily use museum collections to visualize features across a wide range of species, but the consequences of preparation and storage are not well understood. We report soft-tissue shrinkage in the brains and eyes of five bat species from museum collections and compare this to shrinkage found in specimens of six freshly-collected species. Although the magnitude of shrinkage in the museum specimens did not increase over four weeks of stain time in iodine, the brains and eyes of museum specimens shrank considerably prior to placement in iodine in comparison with field-collected specimens. While the cause of shrinkage in these specimens remains unknown, we caution against study designs that combine fresh and museum specimens.
“Our current understanding of development and evolution of head and neck musculature in vertebrates is often based on studies in a few model organisms that might or might not be at relevant positions on a phylogenetic tree to highlight key changes from a primitive to a derived character. Lungfishes, like the Australian Lungfish, are at one such relevant position as their anatomy and ontogeny can help us to understand the changes that occurred during thewater to land transition. Methods, like diceCT, that allow us to analyze in detail the anatomy of species without destructive dissections are of increasing value as they not only to reduce the amount of specimens needed to investigate but also allow the 3D visualization of complex structures, which in turn enables us to make more precise predictions about functional changes due to differences of muscles attachments at different stages of development. Comparisons of developmental changes with differences observed during the evolution of vertebrate species will then allow us to identify highly conserved or less restricted mechanisms that play a role during the evolution of diverse species from fish to humans.”
“Bats demonstrate one of the most impressive stories of independent loss of the vomeronasal organ, a specialized nasal pheromone-sensing system in mammals. We were surprised to learn of a loss-of-function mutation in a vomeronasal-specific gene within a clade of Caribbean nectar-feeding bats, as many of their mainland relatives maintain function of the gene and organ—but the morphology was not known for this clade. DiceCT permitted us to peek inside the heads of these bats and characterize the nasal soft tissues, including the first 3D reconstruction of a vomeronasal organ, a structure only thought visible through histology. We discovered that Caribbean nectarivorous bats indeed have lost or reduced the vomeronasal organ and possess more elaborate olfactory turbinals. Complete loss of morphology likely occurred prior to complete genetic loss of function revealing a deeper understanding of the process of vestigalization.”
“The ability to visualize structures in three-dimensional space will revolutionize how we can evaluate biomechanics in a wholly non-destructive approach. In addition, the possibility of algorithmic approaches (like those published recently by Dickinson and colleagues) will improve repeatability, and likely will help us save data collection time.”
“Exploring the detailed muscular anatomy of very small mammals is difficult to do using dissection alone since often the details are damaged before they can be observed properly. Here, we used diceCT to learn more about the musculature associated with the bat calcar — a skeletal novelty found in bat feet. DiceCT combined with standard histology revealed anatomical variation among the calcar musculature of different bat species that quite possibly has functional implications. This could mean that the calcar has functionally diversified among bats. DiceCT is an extremely useful tool for revealing previously-unknown anatomical diversity, especially in small animals.”
“Lepidophagous fishes, which subsist by picking scales off other fishes, have evolved independently over 30 times. Given the seemingly specialized nature of this dietary niche, we asked the question: are all scale-feeding fishes built in a similar fashion? We used microCT to measure the feeding anatomy in a host of museum specimens, coupled with diceCT to visualize jaw musculature without marring priceless specimens with dissections. Despite living in similar habitats and feeding on presumably similar prey, lepidophagous taxa do not converge on a singular morphotype; rather, there are many ways to be a scale-feeding fish.”
“Studying muscle functional morphology is often easier said than done because definitively determining muscle function requires measuring many morphological and physiological parameters simultaneously. To advance our studies of the primate hyolingual apparatus, which is composed of dozens of muscles, we developed a pipeline to integrate diceCT and EMG with X-ray Reconstruction of Moving Morphology (XROMM, Brainerd et al. 2010). XROMM obtains the high spatiotemporal resolution kinematics necessary to analyze the three dimensional complexity of hyolingual movement, and incorporating diceCT provides a new method for confirming EMG electrode location and improves the accuracy of muscle and fiber length and orientation measurements. Together, these methods will help scientists to determine how organisms navigate the many ways of tuning organismal performance through musculoskeletal design.”
“Bats exhibit an outstanding diversity of cranial morphologies and diets. However, comparative studies of jaw muscle architecture have been difficult due the small size of most bats. This study used diceCT to provide, for the first time, a detailed characterization of the gross and internal anatomy of the jaw muscles across an ecologically diverse sample of bats. DiceCT allowed me to evaluate interspecific differences in muscle attachments, compartments, and scaling in the context of dietary specialization, and to provide novel anatomical descriptions within the feeding apparatus of bats. By doing so, this study revealed unexplored anatomical diversity that can inform future work in functional and evolutionary morphology.”
“Manual dissection is both inherently destructive to specimens, and reliant upon the use of sampling sites to assess muscle fascicle properties and their distribution. We present the results of a digital technique using diceCT to identify and map whole-muscle fascicle distributions within the jaw-adductor musculature of a primate specimen. Comparing these data to dissection results of the contralateral muscles, we demonstrate an ability to determine architectural variables non-invasively through the use of diceCT. Though muscle complexity may impact the convergence between traditional and digital methods, we conclude that this technique offers great potential for future work of whole-muscle mapping, whilst circumventing specimen loss.”
This is one of the most frequently asked questions by the diceCT community, and the Witmer Lab at Ohio University has answered: “Absolutely!”
SpiceCT (selectively perfusable iodine-based contrast-enhanced CT) is particularly good at staining large specimens very rapidly. Iodine is perfused through the arterial system and across capillary beds, staining soft tissues nearly instantaneously and allowing for targeting regions of interest based on blood supply.
The Witmer lab recently presented their new protocol at the Society for Integrative and Comparative Biology meeting in San Francisco on 4 January 2018 and are now sharing that poster widely on FigShare. Download the poster, and add a new tool to your arsenal!
Thank you to authors Witmer, Porter, Cerio, Nassif, Caggiano, Griffin, and Ridgely. Find more of their work on the Witmer Lab homepage and on Twitter.