Methods for dynamic synchrotron X-ray respiratory imaging in live animals.

Small-animal physiology studies are typically complicated, but the level of complexity is greatly increased when performing live-animal X-ray imaging studies at synchrotron and compact light sources. This group has extensive experience in these types of studies at the SPring-8 and Australian synchrotrons, as well as the Munich Compact Light Source. These experimental settings produce unique challenges. Experiments are always performed in an isolated radiation enclosure not specifically designed for live-animal imaging. This requires equipment adapted to physiological monitoring and test-substance delivery, as well as shuttering to reduce the radiation dose. Experiment designs must also take into account the fixed location, size and orientation of the X-ray beam. This article describes the techniques developed to overcome the challenges involved in respiratory X-ray imaging of live animals at synchrotrons, now enabling increasingly sophisticated imaging protocols.

Visualizing treatment delivery and deposition in mouse lungs using in vivo x-ray imaging.

The complexity of lung diseases makes pre-clinical in vivo respiratory research in mouse lungs of great importance for a better understanding of physiology and therapeutic effects. Synchrotron-based imaging has been successfully applied to lung research studies, however longitudinal studies can be difficult to perform due to limited facility access. Laboratory-based x-ray sources, such as inverse Compton x-ray sources, remove this access limitation and opens up new possibilities for pre-clinical small-animal lung research at high spatial and temporal resolution. The in vivo visualization of drug deposition in mouse lungs is of interest, particularly in longitudinal research, because the therapeutic outcome is not only dependent on the delivered dose of the drug, but also on the spatial distribution of the drug. An additional advantage of this approach, when compared to other imaging techniques, is that anatomic and dynamic information is collected simultaneously. Here we report the use of dynamic x-ray phase-contrast imaging to observe pulmonary drug delivery via liquid instillation, and by inhalation of micro-droplets. Different liquid volumes (4 µl, 20 µl, 50 µl) were tested and a range of localized and global distributions were observed with a temporal resolution of up to 1.5 fps. The in vivo imaging results were confirmed by ex vivo x-ray and fluorescence imaging. This ability to visualize pulmonary substance deposition in live small animals has provided a better understanding of the two key methods of delivery; instillation and nebulization.

In vivo Dynamic Phase-Contrast X-ray Imaging using a Compact Light Source.

We describe the first dynamic and the first in vivo X-ray imaging studies successfully performed at a laser-undulator-based compact synchrotron light source. The X-ray properties of this source enable time-sequence propagation-based X-ray phase-contrast imaging. We focus here on non-invasive imaging for respiratory treatment development and physiological understanding. In small animals, we capture the regional delivery of respiratory treatment, and two measures of respiratory health that can reveal the effectiveness of a treatment; lung motion and mucociliary clearance. The results demonstrate the ability of this set-up to perform laboratory-based dynamic imaging, specifically in small animal models, and with the possibility of longitudinal studies.

Propagation-based Phase-Contrast X-ray Imaging at a Compact Light Source.

We demonstrate the applicability of propagation-based X-ray phase-contrast imaging at a laser-assisted compact light source with known phantoms and the lungs and airways of a mouse. The Munich Compact Light Source provides a quasi-monochromatic beam with partial spatial coherence, and high flux relative to other non-synchrotron sources (up to 1010 ph/s). In our study we observe significant edge-enhancement and quantitative phase-retrieval is successfully performed on the known phantom. Furthermore the images of a small animal show the potential for live bio-imaging research studies that capture biological function using short exposures.