Take a look
Conference Abstract: OE-MRI in Cystic Fibrosis
Oxygen-Enhanced MRI in Cystic Fibrosis (Conference Abstract)
Marta Tibiletti, Josephine H Naish, Katharina Martini, Thomas Frauenfelder, Geoff JM Parker
British Chapter of ISMRM Meeting 2019
Oxygen Enhanced MRI (OE-MRI) exploits the paramagnetic properties of molecular oxygen to modify local T1 values to explore local lung function. During a dynamic OE-MRI experiment, the subject breaths varying concentrations of O2. Various parameters can be extracted, such as the ventilated volume fraction (VVF), defined as is the fraction of lung tissue showing O2 enhancement, and the oxygen wash-in time (Tup) . In this work, we calculated τup, VVF, VVF-masked Tup and compared them with pulmonary function tests in a population of healthy volunteers (HV) and cystic fibrosis (CF) subjects.
Analysis was applied retrospectively to OE-MRI data acquired from a previously published study . 20 patients with CF (20 - 40 years, 13 male) and 4 HV (27-37 y, 2 male) underwent dynamic OE-MRI on a 1.5 T Philips Achieva MRI scanner. A free-breathing protocol based on an inversion-prepared centric ordered single shot 3D-turbo field echo sequence was used. The dynamic acquisition lasted 15 min (90 volumes), during which gas was delivered at 15 l/min via a disposable non-rebreathing mask and switched at minute 2 from medical air to 100% O2, and back to air at minute 10. All images were registered to correct for breathing motion using a non-linear registration algorithm . Maps of Tup were derived from the signal intensity curves for each pixel by fitting to a mono-exponential recovery function. VVF was considered positive where the Akaike information criterion favours an exponential fit over a constant function. VVF fraction, median Tu and median Tup calculated only within VVF positive pixels (masked Tup) were extracted and compared to the results from conventional spirometry (FEV1, FVC and FEV1/FVC corrected for age, height and gender). Relationships between variables were evaluated with Pearson correlation with p < 0.05 considered to indicate the presence of a statistically significant correlations.
The table present the R2 and p-values of correlation between calculated parameters and corrected spirometry results.
FVC pred [%] FEV1 pred [%] FEV1/FVC pred [%]
VVF 0.54 (p<0.001) 0.70 (p<0.001) 0.24 (p=0.02)
Tup [s] 0.00 (p=0.89) 0.01 (p=0.59) 0.12 (p=0.12)
Masked Tup [s] 0.03 (p=0.38) 0.11 (p=0.11) 0.27 (p=0.01)
VVF highly correlates with measurements of lung function derived from spirometry, particularly with FEV1. Oxygen wash-in time correlated significantly with FEV1/FVC pred [%] only when non-enhancing voxels are excluded.
Parameters calculated from dynamic OE-MRI are highly correlated with measurement of lung function derived from spirometry.
Reference:  Martini K, et al. European Radiology:1-11 (2018)