This work applies a clustering method developed for image analysis of hyperpolarised gas lung ventilation MRI to a cohort of patients referred from a severe asthma clinic for investigation of breathlessness. Patients underwent spirometry tests and imaging at baseline and after inhalation of Salbutamol to assess reversibility. In a subset of patients, images pre and post bronchodilator were registered and a novel treatment response mapping method was applied. Results show significant correlations at baseline between imaging markers and FEV1% and between their percentage changes and the reversibility testing. The treatment response mapping method offers additional robust additional insights.