X-ray Computed Tomography (CT) is one of the most commonly utilized anatomical imaging modalities for both research and clinical purposes. CT combines high-resolution, three-dimensional data with relatively fast acquisition to provide a solid platform for non-invasive human or specimen imaging. The primary limitation of CT is its inability to distinguish many soft tissues based on native contrast. While bone has high contrast within a CT image due to its material density from calcium phosphate, soft tissue is less dense and many are homogenous in density. This presents a challenge in distinguishing one type of soft tissue from another. A couple exceptions include the lungs as well as fat, both of which have unique densities owing to the presence of air or bulk hydrocarbons, respectively. In order to facilitate X-ray CT imaging of other structures, a range of contrast agents have been developed to selectively identify and visualize the anatomical properties of individual tissues. Most agents incorporate atoms like iodine, gold, or barium because of their ability to absorb X-rays, and thus impart contrast to a given organ system. Here we review the strategies available to visualize lung, fat, brain, kidney, liver, spleen, vasculature, gastrointestinal tract, and liver tissues of living mice using either innate contrast, or commercial injectable or ingestible agents with selective perfusion. Further, we demonstrate how each of these approaches will facilitate the non-invasive, longitudinal, in vivo imaging of pre-clinical disease models at each anatomical site.

At present, a limited number of strategies exist for diagnostic imaging of patients with bacterial infection. While radiolabeled probes and white blood cells provide robust solutions to detect bacteria in humans, they also give false positives in cases of sterile inflammation. With the onset of bacterial drug resistance, and a clinical trend toward reducing the prescription of antibiotics, the need for highly specific infection detection protocols has been renewed. The preclinical research community has recently utilized new optical imaging strategies, alongside traditional radioimaging research, to develop novel infection probes with translational potential. Here we review the current clinical methods for imaging bacteria in humans, and discuss the efforts within the preclinical community to validate new strategies. The review of preclinical infection imaging probes is limited to those probes that could be feasibly adapted for use in humans with currently available clinical modalities.

Three-dimensional printing allows for the production of highly detailed objects through a process known as additive manufacturing. Traditional, mold-injection methods to create models or parts have several limitations, the most important of which is a difficulty in making highly complex products in a timely, cost-effective manner.1 However, gradual improvements in three-dimensional printing technology have resulted in both high-end and economy instruments that are now available for the facile production of customized models. 2 These printers have the ability to extrude high-resolution objects with enough detail to accurately represent in vivo images generated from a preclinical X-ray CT scanner. With proper data collection, surface rendering, and stereolithographic editing, it is now possible and inexpensive to rapidly produce detailed skeletal and soft tissue structures from X-ray CT data. Even in the early stages of development, the anatomical models produced by three-dimensional printing appeal to both educators and researchers who can utilize the technology to improve visualization proficiency. 3, 4 The real benefits of this method result from the tangible experience a researcher can have with data that cannot be adequately conveyed through a computer screen. The translation of pre-clinical 3D data to a physical object that is an exact copy of the test subject is a powerful tool for visualization and communication, especially for relating imaging research to students, or those in other fields. Here, we provide a detailed method for printing plastic models of bone and organ structures derived from X-ray CT scans utilizing an Albira X-ray CT system in conjunction with PMOD, ImageJ, Meshlab, Netfabb, and ReplicatorG software packages. Video LinkThe video component of this article can be found at https://www.jove.com/video/50250/ Protocol 1. Animals 1. For the results reported below, one male Lobund-Wistar rat of ten months of age was obtained from the Freimann Life Science Center, University of Notre Dame (Notre Dame, Indiana, USA). An ex vivo New Zealand White Rabbit (Male, age = 8 weeks) skull sample, preserved in 10% formalin, was obtained from the laboratory of Prof. Matthew Ravosa, University of Notre Dame. 2. For in vivo imaging, the rat was anesthetized by Isofluorane (2.5% flow rate) with maintenance via a nose-cone system. The animal was positioned prone in the standard rat bed (M2M Imaging Inc., Cleveland, Ohio) supplied with the Albira image station. Limbs were positioned lateral from the torso for a uniform CT acquisition. 3. After image acquisition was completed, the rat was removed from the nose cone and returned to the recovery cage until ambulatory. 4. For scans of the rabbit skull, the specimen was placed in the rat bed in a sealed plastic bag containing formalin. Image Acquisition and Reconstruction1. In Vivo and Ex Vivo Image acquisitions were performed using the Albira CT system (Carestream Molecular Imaging, Woodbridge, CT). The system was set to scan a bed of 180 mm length by perf...

Selective laser sintering (SLS) is a prominent 3D printing modality that typically uses a polyamide (PA) powder as the substrate. One commercially available SLS material is known as PA2200, which is comprised of nylon 12 and titanium dioxide (TiO2) and is widely used to generate 3D-printed parts. Here, we report a unique optical photoluminescence (PL) characteristic of native, white PA2200, in which it yields a persistent, phosphorescence-type emission. An analysis of luminescence imaging data with emission measurements demonstrated that the anatase phase of the titanium dioxide additive is the source of the persistent PL properties. This characteristic of PA2200 enables advanced optical imaging applications, as demonstrated by luminescence imaging of an anatomical rat skeleton and a novel Derenzo-type phantom on a commercial image station. In summary, the light emission properties of PA2200 induced by the presence of anatase titanium dioxide open the door to a vast new array of complex optical applications, including the generation of imaging phantoms for training, calibration, and quality control.

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