Chest Imaging of Lung Nodule(s) Under High-frequency Non-invasive Ventilation (HF-NIV)

Imaging of chest disorders is mainly achieved by using computed tomography. This is especially the case for detection, morphologic assessment and followup of pulmonary nodules. A positron emission tomography (PET) /CT may be additionally required for lung nodule management in some conditions including a size greater than 8 mm with morphologic or growing characteristics suspicious of malignancy. Magnetic Resonance Imaging (MRI) represents however an interesting alternative diagnostic radiation-free method, in particular owing to the recent development of sequences dedicated to lung parenchyma analysis. A major limitation remains the control of respiratory artefacts.

High Frequency non-invasive ventilation, HF-NIV, has the potential to allow chest stabilization and is currently used in the department of radio-oncology at the Lausanne University Hospital. It has been recently applied to perform MRI and PET examinations at end inspiration during an "apnea " generated by the system. Continuous periods of respiratory stabilization of several minutes at end-inspiration are thus obtained, allowing prolonged MR and PET acquisitions with improvement of image quality as observed in our preliminary studies (Beigelman-Aubry et al., Prior et al.). Interestingly, the lung volume explored by using this ventilation technique is similar to that of CT studies, conversely to respiratory gated MR sequences which are currently performed at end-expiration, this potentially generating underevaluation of lung disorders especially at lung bases.

The present project aims to determine the impact of HF-NIV in the management of patients with pulmonary nodule(s). After a first step of optimization of acquisition parameters of HF-NIV-MR in healthy volunteers, the performances of MRI and PET/CT (when required) under this ventilation technique will be compared to the current method(s) of reference in cases of pulmonary nodule(s) (CT scan and PET when required) and histological data when available. All MRI and PET/CT (when required) acquisitions will be performed without the ventilation technique, as used in current practice, and with it.

The project was completed with an amendment to investigate MRI under continuous positive airway pressure (CPAP). The MR-CPAP combination will be evaluated with optimized parameters in healthy volunteers and compared to free-breathing acquisitions without any device.