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Imaging is a crucial clinical tool for diagnosis and assessment of pneumonia, but quantitative methods are
lacking. Micro-computed tomography (micro CT), designed for lab animals, provides opportunities for non-invasive
radiographic endpoints for pneumonia studies.
HYPOTHESIS: In vivo micro CT scans of mice with early bacterial pneumonia can be scored quantitatively by semiautomated
imaging methods, with good reproducibility and correlation with bacterial dose inoculated, pneumonia
survival outcome, and radiologists' scores.
METHODS: Healthy mice had intratracheal inoculation of E. coli bacteria (n=24) or saline control (n=11). In vivo
micro CT scans were performed 24 hours later with microCAT II (Siemens). Two independent radiologists scored the
extent of airspace abnormality, on a scale of 0 (normal) to 24 (completely abnormal). Using the Amira 5.2 software
(Mercury Computer Systems), a histogram distribution of voxel counts between the Hounsfield range of -510 to 0 was
created and analyzed, and a segmentation procedure was devised.
RESULTS: A t-test was performed to determine whether there was a significant difference in the mean voxel value of
each mouse in the three experimental groups: Saline Survivors, Pneumonia Survivors, and Pneumonia Non-survivors. It
was found that the voxel count method was able to statistically tell apart the Saline Survivors from the Pneumonia
Survivors, the Saline Survivors from the Pneumonia Non-survivors, but not the Pneumonia Survivors vs. Pneumonia
Non-survivors. The segmentation method, however, was successfully able to distinguish the two Pneumonia groups.
CONCLUSION: We have pilot-tested an evaluation of early pneumonia in mice using micro CT and a semi-automated
method for lung segmentation and scoring system. Statistical analysis indicates that the system is reliable and merits
further evaluation.
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