Gated Lung Imaging and Analysis

Keeping the object stable during the scan is one of the crucial requirements to obtain images without movement artifacts. However, when scanning the chest area of live animals this is of course not possible. In order to compensate for movement artifacts using synchronization strategies, care must be taken to optimize the anesthesia, resulting in a continuous breathing pattern throughout the scan.
Synchronizing image acquisition with breathing movement can be done in two ways: pro-spective and retro-spective synchronization. Both types of synchronization are possible with the SkyScan in vivo scanners. When aiming for the optimal image quality, a pro-spective synchronized scan, combined with intubating the animals and ventilating them using a small animal ventilator will result in optimal stability of the chest during image acquisition. Although this will result in the best image quality, it is also an invasive and time consuming procedure.

As an alternative, retro-spective synchronization can be applied. This synchronization strategy acquires multiple projection images at every rotation step. In addition, a time stamp of both the breathing pattern and the image acquisition is logged, allowing a post-scan sorting of the images into a number of bins in which the breathing cycle is divided. The advantage of the retro-spective synchronization is that it compensates for irregular breathing patterns throughout the scan. The output is a 4-dimensional dataset: 3D at multiple phases of the breathing pattern, allowing functional analysis of lung parameters such as tidal volume, and functional residual capacity. The method note "MN005_Lung analysis in vivo after synchronized scanning" describes in detail the scanning parameters, the sorting of the data into the different phases of the breathing cycle and a step by step analysis of the datasets resulting in the quantitative result of the air volume in the lungs at different phases of the breathing cycle.

Cross-section through the mouse thorax of a mouse scanned without (left) and with (right) pro-spective synchronization using a SkyScan 1076, pixel size 35μm.