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Inhalation OCTOBER2016 17 Functional respiratory imaging (FRI): An alternative to pulmonary function tests (PFTs) In the field of respiratory medicine, the majority of lung diseases are chronic and, for the time being, incurable. Patients with asthma and chronic obstructive pulmonary disease (COPD) often need to rely on medication to keep their diseases under control and maintain an acceptable quality of life. The situation may be more dire for patients diagnosed with interstitial lung disease, such as idiopathic pulmonary fibrosis (IPF), where therapeutic options and life expectancy for patients can be very limited. Many of the discussions at pulmonary conferences revolve around the regional expression of these diseases, specifi- cally the role of the small airway disease manifestations and their links with patient-reported outcome parameters and exacerbations. Limitations of conventional pulmonary function tests At present, virtually all disease phenotyping and develop- ment of disease management guidelines have been based on conventional lung function tests, such as the forced expiratory volume in one second (FEV 1 ) or forced vital capacity (FVC). However, such tests do not yield regional information, for instance, indicating where in the lung a disease is most prevalent or revealing from where mea- sured exhaled air is coming. Consequently, they fail to express the heterogeneity of disease in individual patients. For example, two patients with the same FEV 1 can have very different expressions of the same disease (e.g., emphy- sema vs. bronchitis) or can even have very different lung diseases (e.g., asthma vs. COPD) as shown in Figure 1. It has been observed that the correlation between conven- tional lung function measures and the patient's perception of wellbeing or even mortality is weak at best. 1, 2 In a recent letter Fluidda received from the United States Food and Drug Administration (US FDA) 2 in support of our bio- marker development for IPF, the agency stated that "Forced Vital Capacity (FVC) was used as the primary endpoint for two recent drug approvals; however FVC has not been validated as a surrogate for likelihood of death or other clinically meaningful efficacy variables in IPF. Sen- sitive biomarkers measuring disease stage and biological response to treatment would facilitate clinical develop- ment decisions and accelerate drug development." "Lung health" and FRI In our view, development of the sensitive biomarkers that the FDA alluded to requires a paradigm shift from merely assessing "lung function" towards assessing "lung health," which we define as the current state of a patient's regional lung structure and function relative to a matched healthy subject. Over the last ten years, Fluidda has developed a novel technology called "functional respiratory imaging (FRI)." This method is a combination of high-resolu- tion, low-dose computerized tomography (CT) scans and computational fluid dynamics (CFD), which yields regional information related to lung structure and func- tion. FRI can provide insights about ways lung diseases affect crucial parts of the respiratory system, such as lung and lobe volumes, airway volumes and resistance, and blood vessel density. FRI has been applied in many lung diseases including asthma, COPD, IPF, cystic fibrosis, bronchiolitis obliterans syndrome and pulmonary hypertension. We believe that FRI, once fully validated, could be an appropriate tool to assess overall lung health. FRI, lung health and patients with asthma and COPD It has long been believed that a key difference between patients with asthma and those with COPD was a history of smoking. It was assumed that noxious particles from cigarette smoke were the main contributor to decline in lung function for patients with COPD and that may still The author suggests that FRI could be a useful tool in assessing the parameter defined as "lung health." Jan De Backer, MSc, PhD, MBA Fluidda nv