Abstract Archives of the RSNA, 2005


SSK05-06

Novel Quantitative CT Analysis Demonstrates Delayed Small Airway Reactivity Following Cat Antigen Exposure

Scientific Papers

Presented on November 30, 2005
Presented as part of SSK05: Chest (Airways and Interstitial Lung Disease)

Participants

Jared Whiting Allen PhD, Presenter: Nothing to Disclose
Jonathan G. Goldin MD, PhD, Abstract Co-Author: Nothing to Disclose
Michelle R. Zeidler MD, Abstract Co-Author: Nothing to Disclose
Hyun J. Kim MS, Abstract Co-Author: Nothing to Disclose
Eric C. Kleerup MD, Abstract Co-Author: Nothing to Disclose
Dao Anh Truong, Abstract Co-Author: Nothing to Disclose
James Sayre PhD, Abstract Co-Author: Nothing to Disclose
Nola Kennedy PHD, Abstract Co-Author: Nothing to Disclose
Donald P Tashkin MD, Abstract Co-Author: Nothing to Disclose
et al, Abstract Co-Author: Nothing to Disclose

PURPOSE

The presence of a delayed response to cat antigen in allergic patients has been postulated but can not be demonstrated by conventional lung function tests. The purpose of this study was to determine if indeed there is a delayed response in the small airways using a novel quantitative CT technique.

METHOD AND MATERIALS

Ten subjects with known cat-induced airway hyperreactivity were studied over 3 days. On day 1 baseline (BL) pulmonary function tests (PFT) and HRCT were performed following which patients were exposed to cat room challenge (CRC). HRCT and PFT were repeated 6 and 22 hours post-CRC. All HRCT studies were performed at residual volume (RV) under spirometric control. The BL and 22hr CT studies were acquired pre- and post-methacholine challenge test (MCT). All scans were acquired on the same scanner using a 10 mm spiral reconstruction every 1mm at 3cm above and below the carina. Automated segmentation of lung fields provided 12 regions of interest (ROI) from which lung attenuation curves (LAC), including median and 10th percentile attenuation, were derived. Changes in small airways reactivity were assessed by comparing the leftward shift (decreased attenuation) of LAC between pre- and post-MCT for BL and 22 hr post-CRC using random model effect.

RESULTS

All subjects displayed immediate decline in FEV1 (mean decrease of 30 ± 11%). Six hours post-CRC, despite only moderate decreases in PFT (mean decrease 10 ± 14%), a significant shift was observed in median attenuation (mean shift -54.09Hu ± 6.80, p<.001) and its10th percentile (mean shift -45.67Hu ± 5.12, p<.001) compared to BL. At 22 hr post-CRC, no significant FEV1 drop was demonstrated but median and 10th percentile attenuation remained significantly left-shifted (increased air trapping) with mean change of -15.88Hu ± 5.20 (p=.002) and -10.42Hu ± 4.26 (p=.014), respectively. MCT at 22 hr induced further LAC shift of the median (-16.85Hu ± 5.40, p=.002) and 10th percentile (-12.81Hu ± 4.46, p=.004) compared to BL LAC shift.

CONCLUSION

Quantitative CT analysis characterized air trapping and sensitization to methacholine up to 22 hours post cat challenge despite return to normal spirometry.

Cite This Abstract

Allen, J, Goldin, J, Zeidler, M, Kim, H, Kleerup, E, Truong, D, Sayre, J, Kennedy, N, Tashkin, D, et al, , Novel Quantitative CT Analysis Demonstrates Delayed Small Airway Reactivity Following Cat Antigen Exposure.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4411231.html