Using hyperpolarized ¹²⁹ Xe MRI to investigate longitudinal effects of long COVID on pulmonary function

<title>Extract</title> Post-acute COVID-19 syndrome, or long COVID, is a condition where individuals continue to experience or develop symptoms >4–12 weeks following the initial SARS-CoV-2 infection, with symptoms often persisting for months. Some common symptoms include fatigue, cough, shortness of breath (dyspnoea), and brain fog [1, 2]. These symptoms vary from mild to severe, with impacts observed in multiple organs [3]. Imaging modalities such as chest radiography and computed tomography (CT) are currently used to investigate pulmonary abnormalities caused by long COVID [4], but these tools often fail to reveal abnormal structural findings [5]. In contrast, hyperpolarized ¹²⁹Xe magnetic resonance imaging (Xe-MRI) has the capacity for functional assessment of the lungs by detecting abnormalities in ventilation and regional gas exchange. Key metrics include ventilation defect percent (VDP; percentage of lungs lacking ¹²⁹Xe gas signal), membrane-to-gas (Mem/Gas; reflects alveolar membrane uptake), red blood cell (RBC)-to-membrane (RBC/Mem; marker of gas exchange efficiency), and RBC-to-gas (RBC/Gas; reflects ¹²⁹Xe transfer to capillary RBCs).