4912

Quantification of regional lung ventilation in COPD patients: Validation of ventilation-weighted Fourier decomposition-MRI with dynamic fluorinated gas MRI and lung function testing.

Till Frederik Kaireit^1,2, Marcel Gutberlet^1,2, Andreas Voskrebenzev^1,2, Julia Freise³, Tobias Welte³, Frank Wacker^1,2, and Jens Vogel-Claussen^1,2

¹Institute of Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany, ²Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), German Center for Lung Research (DZL), Hannover, Germany, ³Clinic of Pneumology, Hannover Medical School, Hannover, Germany

Synopsis

Quantification of regional lung ventilation is of high relevance for lung diseases like chronic obstructive lung disease (COPD) or asthma. Regional ventilation of the lungs in COPD patients was assessed using ventilation-weighted Fourier decomposition-MRI and validated with real-time dynamic fluorinated MRI and lung function test. Strong correlations were found comparing both techniques with each other and with lung function testing which is used for COPD classification.

INTRODUCTION: “Why was this study/research performed? What unsolved problem are you addressing?”

Chronic obstructive lung disease (COPD) is a common chronic lung disease with a high morbidity and mortality. Pulmonary function testing, the current clinical standard for obtaining lung ventilation, is used for grading (GOLD classification) and treatment recommendations, but provides only global information. Thus, techniques for assessment of regional lung function came into focus in order to improve monitoring and clinical management of COPD patients. Pulmonary gas MRI (³He, ¹²⁹Xe, ¹⁹F) have been shown to facilitate evaluation of regional lung ventilation. However, these techniques are time-consuming and cost intensive. In contrast to that, ventilation-weighted Fourier decomposition-MRI (FD-MRI) is cost-efficient and widely available. Thus, aim of this study was to correlate regional fractional ventilation obtained by FD-MRI with dynamic fluorinated gas MRI (¹⁹F-MRI) and lung function tests.

METHODS: “How did you study this problem?”

The study was approved by the institutional ethical review board and all subjects gave written informed consent. Nine patients with COPD (median age 60 years, median FEV1 63 [51-87,5]%) underwent 1.5T MRI. For ventilation-weighted FD-MRI four coronal slices were acquired in free breathing using a spoiled gradient echo sequence with TE 0.7 ms, TR 3 ms, flip angle 8°, matrix size 128 x 96, field of view 50 x 50 cm, slice thickness 15 mm and a temporal resolution of 288 ms. After applying a non-rigid registration, fractional ventilation maps (FV-FD) were calculated as previously described^1,2.

Dynamic ¹⁹F imaging was performed with a dedicated coil (Rapid Biomedical) tuned to 59.9 MHz consisting of a transmit Helmholtz coil and a 16 channel phased-array receive coil using a 3D spoiled gradient echo sequence (TE=5.1 ms, TR=12 ms, flip angle=50°, FOV=50x50x20 cm³, matrix size=64x64x6, bandwidth=140 Hz/pixel, GRAPPA factor=2). Each patient inhaled 30l of a mixture of 79% fluorinated gas (C₃F₈) and 21% oxygen via a closed face mask. Afterwards, while inhaling 100% oxygen, wash-out dynamics were assessed. Washout time in number of breaths (washout[#breaths]) and fractional ventilation (FV-¹⁹F) were calculated as previously described^3-5.

FD-MRI and ¹⁹F-MRI were anatomically matched using a landmark driven algorithm, and only corresponding slices with an overlap of > 90% were selected for evaluation. For comparison with the current clinical standard, all patients underwent a lung function test. The obtained parameters were correlated with each other using Spearman’s correlation coefficient.

RESULTS: “Report the data and statistical analyses”

All COPD patients completed the MRI exam without any side effects. FV-FD, FV-¹⁹F and washout[#breaths] correlated with lung function tests as shown in figure 1 and 2. Exemplary corresponding maps of ventilation-weighted FV-FD and FV-¹⁹F are shown in figure 3. Correlations of regional fractional ventilation measured by FD and dynamic fluorinated gas MRI are shown in figure 4. Both methods showed strong correlations on a global level (r=0.89 p<0.001) as well as on a regional level dividing the lung in upper/lower lobes or right and left lung. On a lobar level also correlations between ventilation-weighted FV-FD and FV-¹⁹F were observed.

DISCUSSION: “How do you interpret the the data?”

Ventilation-weighted Fourier decomposition-MRI can measure impaired regional lung ventilation due to emphysema and air trapping in patients with COPD. Ventilation-weighted FV-FD and FV-¹⁹F show positive correlation to FEV1, FEV1/VC and FEF25-75%, which are used in clinical routine to grade the severity of COPD (GOLD classification⁶). These MRI techniques can be carried out in free breathing and are radiation free. In addition, FD-MRI is less time-consuming, less expensive and needs no additional hardware, which facilitates a broad use of ventilation-weighted Fourier decomposition-MRI on 1.5T scanners today.

CONCLUSION: “What is the relevance to clinical practice or future research?”

Ventilation-weighted Fourier decomposition-MRI in free breathing allows quantification of regional lung ventilation comparable to pulmonary gas MRI at lower costs and a broader availability and thus could add value to the current clinical lung function test improving diagnosis and monitoring of COPD patients.

Acknowledgements

This work was supported by the German Centre for Lung Research (DZL), Regenerative Biology and Reconstructive Therapies (REBIRTH) and Fritz-Behrens-Stiftung, Hannover.

References

1. Bauman G, Puderbach M, Deimling M, et al. Non-contrast-enhanced perfusion and ventilation assessment of the human lung by means of fourier decomposition in proton MRI. Magnetic resonance in medicine 2009;62(3):656-664.

2. Voskrebenzev A, Gutberlet M, Becker L, et al. Reproducibility of fractional ventilation derived by Fourier decomposition after adjusting for tidal volume with and without an MRI compatible spirometer. Magn Reson Med 2015; 76(5):1542–1550.

3. Halaweish AF, Moon RE, Foster WN, et al. Perfluoropropane gas as a magnetic resonance lung imaging contrast agent in humans. Chest. 2013;144(4):1300–1310.

4. Ouriadov AV, Fox MS, Couch MJ, et. al. In vivo regional ventilation mapping using fluorinated gas MRI with an x-centric FGRE method. Magn. Reson. Med. 2015;74(2):550–557.

5. Gutberlet M, Kaireit T, Voskrebenzev A, et al. Real-time dynamic fluorinated gas MRI in free breathing for mapping of regional lung ventilation in patients with COPD and healthy volunteers using a 16 channel receive coil at 1.5T. Proc. Intl. Soc. Mag. Reson. Med. 24 (2016): 1140 .

6. Rabe KF, Hurd S, Anzueto A, et al. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: GOLD executive summary. Am J Respir Crit Care Med. 2007;176(6):532-55.

Figures

Correlation of FV-FD, FV-¹⁹F and washout[#breaths] with pulmonary function testing using Spearman’s correlation coefficient.

Correlation between FEV1 and FV-19F (left) and FV-FD and FV-19F (right).

Three matching coronal slices of FD-FV (left column) and washout[#breaths] (right column) showing lower fractional ventilation in correspondence to areas with delayed gas washout.

Correlation of FV-FD with FV-¹⁹F and washout[#breaths], respectively using Spearman’s correlation coefficient.

Proc. Intl. Soc. Mag. Reson. Med. 25 (2017)

4912