In Vivo Computed Tomography as a Research Tool to Investigate Asthma and COPD: Where Do We Stand?

The lower respiratory airway wall in children in health and disease

Alone or in association with other lung or thorax component disorders, the airway wall (AWW) remains one of the most frequently involved elements in paediatric lung diseases. A myriad of AWW disorders will present with similar symptomatology. It is thus important for the clinician to reappraise the normal development and structure of the AWW to better understand the underlying disease patterns. We herein provide an overview of the structure of the AWW and a description of its development from the fetal period to adulthood. We also detail the most common AWW changes observed in several acute and chronic respiratory disorders as well as after cigarette smoke or chronic pollution exposure. We then describe the relationship between the AWW structure and lung function. In addition, we present the different ways of investigating the AWW structure, from biopsies and histological analyses to the most recent noninvasive airway (AW) imaging techniques. Understanding the pathophysiological processes involved in an individual patient will lead to the judicious choice of nonspecific or specific personalised treatments, in order to prevent irreversible AW damage.

Direct assessment of lung function in COPD using CT densitometric measures

To investigate whether lung function in patients with chronic obstructive pulmonary disease (COPD) can be directly predicted using CT densitometric measures and assess the underlying prediction errors as compared with the traditional spirometry-based measures. A total of 600 CT examinations were collected from a COPD study. In addition to the entire lung volume, the extent of emphysema depicted in each CT examination was quantified using density mask analysis (densitometry). The partial least square regression was used for constructing the prediction model, where a repeated random split-sample validation was employed. For each split, we randomly selected 400 CT exams for training (regression) purpose and the remaining 200 exams for assessing performance in prediction of lung function (e.g., FEV1 and FEV1/FVC) and disease severity. The absolute and percentage errors as well as their standard deviations were computed. The averaged percentage errors in prediction of FEV1, FEV1/FVC%, TLC, RV/TLC% and DLco% predicted were 33%, 17%, 9%, 18% and 23%, respectively. When classifying the exams in terms of disease severity grades using the CT measures, 37% of the subjects were correctly classified with no error and 83% of the exams were either correctly classified or classified into immediate neighboring categories. The linear weighted kappa and quadratic weighted kappa were 0.54 (moderate agreement) and 0.72 (substantial agreement), respectively. Despite the existence of certain prediction errors in quantitative assessment of lung function, the CT densitometric measures could be used to relatively reliably classify disease severity grade of COPD patients in terms of GOLD.

Longitudinal characterization of a model of chronic allergic lung inflammation in mice using imaging, functional and immunological methods

The present study investigated the role that imaging could have for assessing lung inflammation in a mouse model of HDM (house dust mite)-provoked allergic inflammation. Inflammation is usually assessed using terminal procedures such as BAL (bronchoalveolar lavage) and histopathology; however, MRI (magnetic resonance imaging) and CT (computed tomography) methods have the potential to allow longitudinal, repeated study of individual animals. Female BALB/c mice were administered daily either saline, or a solution of mixed HDM proteins sufficient to deliver a dose of 12 or 25 μg total HDM protein±budesonide (1 mg/kg of body weight, during weeks 5–7) for 7 weeks. AHR (airway hyper-responsiveness) and IgE measurements were taken on weeks 3, 5 and 7. Following imaging sessions at weeks 3, 5 and 7 lungs were prepared for histology. BAL samples were taken at week 7 and lungs prepared for histology. MRI showed a gradual weekly increase in LTI (lung tissue intensity) in animals treated with HDM compared with control. The 25 μg HDM group showed a continual significant increase in LTI between weeks 3 and 7, the 12 μg HDM-treated group showed a similar rate of increase, and plateaued by week 5. A corresponding increase in AHR, cell counts and IgE were observed. CT showed significant increases in lung tissue density from week 1 of HDM exposure and this was maintained throughout the 7 weeks. Budesonide treatment reversed the increase in tissue density. MRI and CT therefore provide non-invasive sensitive methods for longitudinally assessing lung inflammation. Lung tissue changes could be compared directly with the classical functional and inflammatory readouts, allowing more accurate assessments to be made within each animal and providing a clinically translatable approach.