In this open prospective study, 6 well controlled asthmatic patients will undergo a high-resolution multi-slice computed tomography (CT) scan, lung function tests and a SPECT scan to obtain patient specific geometries of the central and peripheral small airways, patient specific boundary conditions and the in-vivo spatial distribution of inhaled aerosols.

Inclusion Criteria:

1. Patients with well controlled asthma as defined by the current GINA guidelines
2. Male or female patients aged ≥18 years
3. Patients with a documented positive response to the reversibility test (i.e. FEV1 increase ≥ 12% and 200mL from baseline value after 4 puffs of 100 µg of inhaled salbutamol pMDI) within the 12 months preceding the screening visit or performed at screening visit after a wash-out of 2 days for long acting β2 agonists or a documented positive response to the methacholine challenge test
4. Patients with a co-operative attitude
5. Written informed consent obtained
6. Patients maintained on stable respiratory medication for 4 weeks prior to visit 1

Exclusion Criteria:

1. Patients who are pregnant or are breast-feeding
2. Inability to carry out pulmonary function testing
3. Diagnosis of COPD as defined by the current GOLD guidelines
4. History of near fatal asthma
5. Hospitalization due to exacerbation or respiratory infection of the airways 4 weeks prior to visit 1
6. Current smokers or ex-smokers
7. Patients with an uncontrolled disease or any condition that might, in the judgement of the investigator, place the patient at undue risk or potentially compromise the results or interpretation of the study
8. Cancer or any other chronic disease with poor prognosis and/or affecting patient status
9. BMI ≥ 35 kg/m2
10. Patients treated with CPAP or BiPAP
11. Known active tuberculosis
12. A history of cystic fibrosis, central bronchiectasis or interstitial lung disease
13. A history of thoracotomy with pulmonary resection
14. Patients unlikely to comply with the protocol or unable to understand the nature, scope and possible consequences of the study
15. Patients who received any investigational new drug within the last 4 weeks prior to the screening visit