Small Animal Lung Imaging

Micro-CT is becoming a very important tool for small animal imaging including imaging of mice. Different techniques have been proposed to image small 

Optimized In Situ and In Vivo Mouse Lung Protocol 

We have developed methodology for scanning the murine lung in situ and in vivo, including optimizing micro-CT acquisition and reconstruction parameters, using 

More work is stiU necessary to identify optimal trade-offs between improved image quality and scanning times. Furthermore, an iterative approach to scan protocol development will have to take into consideration methods which can accommodate image reconstruction noise and increased or decreased spatial resolution. 

Micro-CT appears a useful tool for scanning ex vivo, fixed mouse lungs with sufficient spatial resolution and tolerable levels of noise because there are no temporal constraints on image acquisition. There are no motion artifacts or fluid shifts which can occur with in situ lung scans. Thus, for instance, it is possible to use the 9 p,m pixel resolution protocol of the Skyscan 1076 scanner. Optimized protocols for fixed mouse lung with different spatial resolutions are also being developed. The basic characteristics of the 9 fim protocol are scanning time 120 min, no filter, 50 kV and 200 p.A. 

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Hedlund L, Johnson G. Mechanical ventilation for imaging the small animal lung. ILAR2002 43 159-174. 

Schuster DP, Kovacs A, Garhow J, Piwnica-Worms D. Recent advances in imaging the lungs of intact small animals. Am J Respir Cell Mol Biol 2004 30 129-138. Piwnica-Worms D, Schuster DP, Garhow JR. Molecular imaging of host-pathogen interactions in intact small animals. Cell Microbiol 2004 6 319-331. 

Until recently, limitations in spatial resolution made PET studies in small animals impossible. Eor instance, most PET scanners in clinical use have an image spatial resolution of 10-15 mm (although more recent instruments can achieve resolution approaching 1-2 mm) the mouse lung, in contrast, is 10mm wide. Other issues such as scanner sensitivity (i.e., the fraction of radioactive events actually detected by the device) and the amount of radioactivity... 

As techniques for imaging in small animals are developed, more tools will be available for assessing in vivo lung function in mice and rats. This will be particularly useful because expression of various disease states can be studied by using genetically modified animals. Additionally, more studies can be performed in... 

In large experimental animals, with only small numbers available, the kinetics of this clearance pathway can be analyzed using insoluble particles with an appropriate radiolabel and imaging gamma-spectroscopy (gamma-camera). A series of lung scans will provide activity accumulation at the sites of the TBLN as an indicator of particle transport to the TBLN, but this must finally be proved by lymph node tissue analyses at the time of sacrifice. Although carefiil radiation dose estimates would be required, this approach may also be applicable to human subjects. 

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