Radiology corner. Answer to last month's radiology case (# 25) and image: cystic fibrosis chest X-ray findings: a teaching analog.

The abnormal chest radiograph is often perplexing, but abnormal findings can be interpreted easily with a systematic and methodical approach. The companion cases presented this month highlights two basic, but often forgotten or confused findings that have very different meanings: tram-tracks and air-bronchograms. The authors present these two cases along with the assistance of analog imaging phantoms constructed out of household materials (straw, sponge, tape and apple), and application of some contrast media. The authors believe the presented representative cases of bronchial wall thickening (in the CF case highlighted here) and the finding of tram tracks, compared to consolidation with typical airbronchograms, should make these findings conceptually clear. An organized differential accompanies each radiographic finding to complement these two specific known diagnoses.