Ruth Angela Hartley MBBCh, MRCS, Presenter: Nothing to Disclose

Sherif Gonem, Abstract Co-Author: Nothing to Disclose

Jennifer Boes, Abstract Co-Author: Nothing to Disclose

Maria Bule, Abstract Co-Author: Nothing to Disclose

Sumit Gupta MRCP, PhD, Abstract Co-Author: Nothing to Disclose

Christopher Brightling MRCP, PhD, Abstract Co-Author: Nothing to Disclose

Brian Dale Ross PhD, Abstract Co-Author: Co-founder, ImBio, LLC Shareholder, ImBio, LLC Advisor, ImBio, LLC

Craig J. Galban PhD, Abstract Co-Author: Inventor, ImBio, LLC

Salman Siddiqui MRCP, Abstract Co-Author: Nothing to Disclose

Asthma is a chronic inflammatory airway disease that is characterised by variable airflow obstruction. The parametric response map (PRM) image analysis technique has recently been utilised to differentiate functional small airway disease (fSAD) from emphysema (using image registration techniques) in patients with chronic obstructive pulmonary disease (COPD) [Galban et al, Nature Med 2012]. It is not known whether fSAD or emphysema are features of asthma, or whether they correlate with the degree of airflow obstruction.

Fifty-two patients with asthma were recruited and underwent inspiratory and expiratory computed tomography (CT). Images were analysed using the PRM algorithm, and the relative lung volumes exhibiting fSAD and emphysema were determined, as well as the centre of mass of the voxel distribution. Lung function was measured using spirometry, and multiple breath inert gas washout (MBW), a technique for measuring ventilation heterogeneity (VH) in the conductive (Scond) and intra acinar (Sacin) small airways. Data is presented as the mean [standard deviation]

The relative volume of fSAD in patients with asthma was 14.3 [10.7], whereas significant emphysema was not observed in patients with asthma (2.9 [3.0]). The ratio of forced expiratory volume in one second to forced vital capacity correlated negatively with fSAD (R = -0.295, p <0.05), and positively with the median of the voxel distribution along the expiration HU axis (R = 0.409, p <0.01) The relative volume of emphysema correlated significantly with Scond (R=0.28, p <0.05) with Sacin showing a similar trend. In contrast fSAD did not correlate with any marker of VH.

Functional small airway disease, but not emphysema, occurs commonly in patients with asthma, and correlates significantly with spirometric airflow obstruction. Further studies are required to determine if fSAD as measured by PRM on CT may be used to predict prognosis or response to treatment in patients with asthma.

PRM provides an objective quantitative assessment and visualisation of lung disease extent and discriminates between emphysema and functionally impoprtant small airways disease.

Hartley, R, Gonem, S, Boes, J, Bule, M, Gupta, S, Brightling, C, Ross, B, Galban, C, Siddiqui, S, CT- PRM: A Novel Imaging Biomarker of Small Airways Disease in Asthma.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13019678.html