Parametric response mapping on chest computed tomography associates with clinical and functional parameters in chronic obstructive pulmonary disease

Abstract

Background In the search for specific phenotypes of chronic obstructive pulmonary disease (COPD) computed tomography (CT) derived Parametric Response Mapping (PRM) has been introduced. This study evaluates the association between PRM and currently available biomarkers of disease severity in COPD. Methods Smokers with and without COPD were characterized based on questionnaires, pulmonary function tests, body plethysmography, and low-dose chest CT scanning. PRM was used to calculate the amount of emphysema (PRMEmph) and non-emphysematous air trapping (i.e. functional small airway disease, PRMfSAD). PRM was first compared with other biomarkers for emphysema (Perc15) and air trapping (E/I-ratioMLD). Consequently, linear regression models were utilized to study associations of PRM measurements with clinical parameters. Results 166 participants were included with a mean ± SD age of 50.5 ± 17.7 years. Both PRMEmph and PRMfSAD were more strongly correlated with lung function parameters as compared to Perc15 and E/I-ratioMLD. PRMEmph and PRMfSAD were higher in COPD participants than non-COPD participants (14.0% vs. 1.1%, and 31.6% vs. 8.2%, respectively, both p < 0.001) and increased with increasing GOLD stage (all p < 0.001). Multivariate analysis showed that PRMfSAD was mainly associated with total lung capacity (TLC) (β = −7.90, p < 0.001), alveolar volume (VA) (β = 7.79, p < 0.001), and residual volume (β = 6.78, p < 0.001), whilst PRMEmph was primarily associated with Kco (β = 8.95, p < 0.001), VA (β = −6.21, p < 0.001), and TLC (β = 6.20, p < 0.001). Conclusions PRM strongly associates with the presence and severity of COPD. PRM therefore appears to be a valuable tool in differentiating COPD phenotypes.

COPD beyond proximal bronchial obstruction: phenotyping and related tools at the bedside

“…As a result, functional small airways disease appears to be the major contributor of FEV1 decline in COPD patients. Another recent study found a strong correlation between PRM and COPD disease and severity [34]. Consistently, the functional small airway disease component correlated specifically with increased residual volume and the emphysema component with lowered carbon monoxide diffusion.…”

Emphysema quantification using chest CT: influence of radiation dose reduction and reconstruction technique

“…Chest computed tomography (CT) offers the possibility of quantifying the amount of emphysema. The number of chest CT acquisitions is expected to increase due to the favourable results of the National Lung Screening Trial [ 1 ] and the interest in subtyping chronic obstructive pulmonary disease (COPD) patients [ 2 ]. Additional quantification of emphysema on screening CT acquisitions will therefore likely gain importance.…”

Signs of Gas Trapping in Normal Lung Density Regions in Smokers

“…Multiple metrics have been proposed to measure small airway disease while minimizing the impact of emphysema (3). Parametric response mapping (PRM) uses image matching to estimate nonemphysematous gas trapping and provides an estimate of functional small airway disease (fSAD) that is associated with lung function and respiratory morbidity parameters, but it is based on determination of emphysema and gas-trapping regions using fixed lung density thresholds (4)(5)(6). Although PRM is a useful tool, the dependence on density thresholds may result in missing detection of mild density abnormalities.…”