Editorial for “Volume‐Controlled 19F MR Ventilation Imaging of Fluorinated Gas”

Over the last two decades, pulmonary magnetic resonance imaging (MRI) techniques have gained significant attractiveness to clinicians and radiologists for the regional quantification of pulmonary function with mapping of key parameters of pulmonary physiology such as ventilation, perfusion, gas exchange, or pulmonary biomechanics. The increasing clinical importance of MRI in the diagnosis of lung diseases and patient management is tied to several methodological advances and technological breakthroughs, including Ultrashort echo Time (UTE)type sequences and hyperpolarization techniques for isotopes of rare gas helium-3 and xenon-129 (Xe). Together these new techniques have positioned MRI as an imaging modality of first choice for indications such as cystic fibrosis—driven by the absence of ionizing radiations— and as shown more recently for long COVID disease with the possibility to image dissolved Xe in red blood cell in patients. Despite its high diagnostic value, demonstrated on numerous pathologies (Chronic Obstructive Pulmonary Disease (COPD), asthma, cystic fibrosis), Xe MRI remains limited to a few leading clinical research centers in the world, due to its relative technical complexity and cost (need for polarizer, broadband imaging capabilities, and dedicated RF coil). Alternative approaches to the use of Xe for lung ventilation imaging exist, however. Among them, the use of inert fluorinated gases is the most advanced in terms of clinical applications and has the potential for large-scale deployment. Despite inferior capabilities (lower Signal-to-noise ratio (SNR), no imaging of dissolved phase) to hyperpolarized gas, this approach offers a number of advantages in terms of cost (no polarizer needed) and ease of preparation and delivery of inhalable gas to the patient. As a matter of fact, fluorine-19 (F) MRI has already shown its applicability and potential for certain pulmonary pathologies such as COPD and asthma. However, validation studies are still needed to strengthen the robustness of F MRI, establish its reproducibility and extend its attractiveness for the radiologists and clinicians. The authors of the “Volume-controlled F MR ventilation imaging of fluorinated gas” paper aimed precisely at this kind of objective. In this study, they investigated the use of a fluorinated gas delivery device and assessed its impact on the acquisition, the quantification, and the repeatability of several F ventilation readouts. Additionally, they computed the correlation of F imaging parameters with predicted forced expiratory volume in 1 second (FEV1% pred) derived from pulmonary function testing. For this purpose, 30 healthy volunteers and 26 COPD patients were examined using a normoxic mixture of perfluoropropane (C3F8) and oxygen. On the same imaging session, the subjects underwent successively a lung ventilation MRI protocol with and without the use of the volume-controlled gas delivery system. This MRI protocol was repeated for each subject 1 week later. The F MRI readouts assessed in this study were both static—the ventilated volume percentage at the initial first and last F images—and dynamic—time to fill, fractional ventilation, and wash-in time. The authors observed that, as a sign of improved reproducibility, the intraclass correlation coefficients between the first and second scan 1 week later increased for all the F MRI readouts when using gas delivery system. In the same way, they also reported that the coefficients of variation between first and second scan for static and dynamic imaging readouts were lower for COPD and healthy subjects when using the gas delivery system. Additionally, strong and moderate linear correlations between F MRI readouts and FEV1% pred were strengthened when using the gas delivery system. Overall, this study demonstrates on a relatively large population the feasibility and interest of using a gas delivery system for F lung MRI. This type of device can be particularly useful to standardize F acquisitions based on multiple time-resolved breaths that generate ventilation dynamic measurements. Furthermore, this device will be especially important for patients with chronic lung diseases such as COPD or Cystic Fibrosis (CF), where reliable follow-up is essential for patient management.

O ver the last two decades, pulmonary magnetic resonance imaging (MRI) techniques have gained significant attractiveness to clinicians and radiologists for the regional quantification of pulmonary function with mapping of key parameters of pulmonary physiology such as ventilation, perfusion, gas exchange, or pulmonary biomechanics. 1 The increasing clinical importance of MRI in the diagnosis of lung diseases and patient management is tied to several methodological advances and technological breakthroughs, including Ultrashort echo Time (UTE)type sequences and hyperpolarization techniques for isotopes of rare gas helium-3 and xenon-129 ( 129 Xe). Together these new techniques have positioned MRI as an imaging modality of first choice for indications such as cystic fibrosis-driven by the absence of ionizing radiationsand as shown more recently for long COVID disease with the possibility to image dissolved 129 Xe in red blood cell in patients. 2 Despite its high diagnostic value, demonstrated on numerous pathologies (Chronic Obstructive Pulmonary Disease (COPD), asthma, cystic fibrosis), 129 Xe MRI remains limited to a few leading clinical research centers in the world, due to its relative technical complexity and cost (need for polarizer, broadband imaging capabilities, and dedicated RF coil).
Alternative approaches 3,4 to the use of 129 Xe for lung ventilation imaging exist, however. Among them, the use of inert fluorinated gases is the most advanced in terms of clinical applications and has the potential for large-scale deployment. 5 Despite inferior capabilities (lower Signal-to-noise ratio (SNR), no imaging of dissolved phase) to hyperpolarized gas, this approach offers a number of advantages in terms of cost (no polarizer needed) and ease of preparation and delivery of inhalable gas to the patient. As a matter of fact, fluorine-19 ( 19 F) MRI has already shown its applicability and potential for certain pulmonary pathologies such as COPD and asthma. 6,7 However, validation studies are still needed to strengthen the robustness of 19 F MRI, establish its reproducibility and extend its attractiveness for the radiologists and clinicians.
The authors of the "Volume-controlled 19 F MR ventilation imaging of fluorinated gas" paper 8 aimed precisely at this kind of objective. In this study, they investigated the use of a fluorinated gas delivery device and assessed its impact on the acquisition, the quantification, and the repeatability of several 19 F ventilation readouts. Additionally, they computed the correlation of 19 F imaging parameters with predicted forced expiratory volume in 1 second (FEV 1 % pred) derived from pulmonary function testing.
For this purpose, 30 healthy volunteers and 26 COPD patients were examined using a normoxic mixture of perfluoropropane (C 3 F 8 ) and oxygen. On the same imaging session, the subjects underwent successively a lung ventilation MRI protocol with and without the use of the volume-controlled gas delivery system. This MRI protocol was repeated for each subject 1 week later.
The 19 F MRI readouts assessed in this study were both static-the ventilated volume percentage at the initial first and last 19 F images-and dynamic-time to fill, fractional ventilation, and wash-in time.
The authors observed that, as a sign of improved reproducibility, the intraclass correlation coefficients between the first and second scan 1 week later increased for all the 19 F MRI readouts when using gas delivery system. In the same way, they also reported that the coefficients of variation between first and second scan for static and dynamic imaging readouts were lower for COPD and healthy subjects when using the gas delivery system. Additionally, strong and moderate linear correlations between 19 F MRI readouts and FEV 1 % pred were strengthened when using the gas delivery system.
Overall, this study demonstrates on a relatively large population the feasibility and interest of using a gas delivery system for 19 F lung MRI. This type of device can be particularly useful to standardize 19 F acquisitions based on multiple time-resolved breaths that generate ventilation dynamic measurements. Furthermore, this device will be especially important for patients with chronic lung diseases such as COPD or Cystic Fibrosis (CF), where reliable follow-up is essential for patient management.
While the publication of Obert et al represents an important step toward routine clinical practice of 19 F lung MRI, it remains to be seen whether its imaging markers will provide clinically valuable information for the diagnosis and phenotyping of lung diseases, the evaluation of drug or treatment efficacy, and the understanding of lung disease onset and progression.