Pulmonary Fourier decomposition MRI compared to multiple breath washout and spirometry: A preliminary study in Primary Ciliary Dyskinesia
Grzegorz Bauman1,2, Sylvia Nyilas2,3,4, Orso Pusterla1,2, Christoph M Heyer5, Cordula Koerner-Rettberg6, Philipp Latzin3,4, and Oliver Bieri1,2

1Division of Radiological Physics, Deparment of Radiology, University Hospital of Basel, Basel, Switzerland, 2Department of Biomedical Engineering, University of Basel, Basel, Switzerland, 3Department of Pediatric Pneumology, University Children's Hospital Basel (UKBB), Basel, Switzerland, 4Division of Respiratory Medicine, Department of Pediatrics, University Children's Hospital of Bern, Bern, Switzerland, 5Institute of Diagnostic Radiology, Interventional Radiology and Nuclear Medicine, Ruhr-University of Bochum, Bochum, Germany, 6Department of Pediatric Pneumology, University Children's Hospital of Ruhr University Bochum at St Josef-Hospital, Bochum, Germany

Synopsis

In this work, the feasibility of contrast-media-free pulmonary Fourier decomposition (FD) MRI is assessed in patients with primary ciliary dyskinesia (PCD). An automatic evaluation of regional functional defects on fractional ventilation and perfusion FD maps has been developed. Furthermore, the lung function evaluated using FD MRI is compared to the parameters obtained using multiple breath washout technique and spirometry. Statistical analysis was used to find significant correlations between FD MRI and lung function techniques.

Purpose

Primary ciliary dyskinesia (PCD) is a rare, ciliopathic, autosomal recessive genetic disorder that causes defects in the action of cilia and can be accompanied by situs inversus. The main impact of impaired ciliary function on the respiratory system is the reduced mucus clearance from the lungs, which leads to highly increased susceptibility to chronic recurrent respiratory infections and impairment of pulmonary function1. To this end, the assessment of the lung ventilation and perfusion in PCD patients and periodic monitoring of the disease progression, is of high importance. In the recent years a novel, non-invasive and contrast-agent free technique called Fourier decomposition (FD) MRI2 was proposed for evaluation of regional ventilation and perfusion. The purpose of this work was to assess the pulmonary function in PCD patients using FD MRI in combination with the multiple breath washout (MBW) technique3 and spirometry.

Methods

MR measurements

Nine PCD patients (mean age: 11.1 years , 5.9-17.2 years range) were examined. Scans were performed on a 1.5 T MR-scanner (Avanto, Siemens Healthcare, Germany) using a combination of 12-channel body and 24-channel spine matrix coils. Time-resolved sets of coronal images were acquired using ultra-fast steady-state free precession (ufSSFP) sequence4 in free-breathing to cover the whole lung volume. The imaging parameters were: TE/TR/TA=0.69/1.57/119 ms, FA=60°, field-of-view=400x400 mm2, matrix=128x128 (interpolated to 256x256), slice thickness=12 mm, bandwidth=2056 Hz/pixel, GRAPPA factor=2, imaging rate=4 images/s, 200 images.

MBW and spirometry

All subjects underwent nitrogen-multiple breath washout examination with a commercially available device (ExhalyzerD, EcoMedics, Switzerland). Main outcome parameters representing global ventilation inhomogeneity (VI) was the lung clearance index $$$LCI_{2.5\%}$$$, second moment ratio $$$M_2/M_0$$$; conductive airways VI - $$$S_{cond}$$$; acinary VI - $$$S_{acin}$$$. Subsequently, spirometry was performed using a Jaeger MasterScreen bodyplethysmograph (CareFusion, Hoechberg, Germany). Outcome parameters were $$$FEV_1$$$ (forced expiratory volume in 1 second) and $$$FEF_{25-75}$$$ (forced expiratory flow 25–75 %) as a marker for obstruction in the central airways.

Image postprocessing

Nonrigid image registration was used to correct for the respiratory motion5. Subsequently, the first image in every registered dataset was semi-automatically segmented and projected along the time axis. Fourier decomposition was applied to detect and spectrally separate periodic changes of the lung proton density caused by the respiratory and cardiac cycles. Maps of fractional ventilation $$$FV$$$6, perfusion $$$Q$$$7 and blood arrival time $$$BAT$$$8 were generated.

Automated evaluation of perfusion and ventilation defects

Distributions of voxel values on the segmented $$$FV$$$ and $$$Q$$$ images were calculated for every slice position. Voxel values lower than thresholds defined as $$$0.75{\cdot}{median}\{FV,Q\}$$$ of the voxel distribution were regarded as regions with impaired ventilation or perfusion. The ratio of the lung volume with impaired perfusion $$$R_Q$$$ and fractional ventilation $$$R_{FV}$$$ and the whole lung volume was calculated for every patient.

Statistical analysis

Parameters measured using MBW and spirometry were correlated with percentage of impaired perfusion and fractional ventilation obtained using FD MRI in all patients using Pearson's correlation coefficient. P-values<0.05 were considered statistically significant.

Results

Figure 1 shows examplar native coronal ufSSFP, fractional ventilation, perfusion and blood arrival time images obtained in a 11 year old male PCD patient using FD MRI. Regions with reduced fractional ventilation, perfusion and increased blood arrival time located in the basal parts of both lungs are marked with white arrows. Fractional ventilation and perfusion images in 8 year old male PCD patient are presented in figure 2. Regions with reduced fractional ventilation and perfusion (top row) located in the sixth segment of the left lung and basal segments of both lungs were automatically detected and masked on the morphological chest images (bottom row).

The median $$$R_{FV}$$$ in the patient group was 0.17 (max=0.23, min=0.08), the median $$$R_{Q}$$$ was 0.15 (max=0.25, min=0.07). Statistically significant correlations between $$$R_{FV}$$$ and MBW, spirometry parameters were found for $$$S_{cond}$$$ (0.80,P=0.009) and $$$FEF_{25-75}$$$ (0.71,P=0.032). No significant correlations were found between MBW, spirometry and $$$R_{Q}$$$.

Discussion and Conclusion

In this work we show the feasibility of automatic evaluation of regional lung function using the contrast-media-free FD MRI in patients with PCD. Altough the patient sample in this preliminary study was small, it was possible to find significant correlations between FD MRI and the parameters obtained using multiple breath washout technique and spirometry. Nevertheless, further evaluation in a larger patient group is needed to achieve adequate statistical power.

FD MRI can be used for detection of early and subtle functional impairment. Thank to low compliance requirements of FD MRI, the examinations were successfully performed even in the youngest patients. Hence, the technique can be recommended for non-invasive monitoring of therapy response and longitudinal follow-ups.

Acknowledgements

No acknowledgement found.

References

1. Green K, Buchvald FF, Marthin JK et al.Ventilation inhomogeneity in children with primary ciliary dyskinesia. Thorax.2012 Jan;67(1):49-53.

2. Bauman G, Puderbach M, Deimling M et al. Non-contrast-enhanced perfusion and ventilationassessment of the human lung by means of fourier decomposition in proton MRI.Magn Reson Med. 2009 Sep;62(3):656-64.3.

3. Nyilas S, Schlegtendal A, Yammine S et al. Further evidence for an association between LCI and FEV1 in patients with PCD. Thorax. 2015 Sep;70(9):896.

4. Bieri O. Ultra-fast steady state free precession and its application to in vivo (1) H morphological and functional lung imaging at 1.5Tesla. Magn Reson Med. 2013 Sep;70(3):657-63.5.

5. Chefd’hotel C, Hermosillo G, Faugeras O. Flows of diffeomorphismsfor multimodal image registration. In: Proceedings of the IEEE International Symposium on Biomedical Imaging (ISBI’2002), Washington, DC, USA, July 2002. pp. 753–756.6.

6. Zapke M, Topf HG, Zenker M et al. Magnetic resonance lung function--abreakthrough for lung imaging and functional assessment? A phantom study andclinical trial. Respir Res. 2006 Aug 6;7:106.7.

7. Kjørstad Å, Corteville DM, Fischer A et al. Quantitative lung perfusion evaluation using Fourier decompositionperfusion MRI. Magn Reson Med. 2014 Aug;72(2):558-62.8.

8. Bauman G, Eichinger M, Uecker M. High temporal resolution radial bSSFP sequence with nonlinear inverse reconstruction for the measurement of the pulmonary blood inflow time using Fourier decomposition MRI. Proceedings of the 20th annual meeting of the ISMRM, Melbourne, Australia, 2012:1955.

Figures

Figure 1. Native ufSSFP image (a), fractional ventilation (b), perfusion (c) and blood arrival time (d) maps obtained in 11 year old male patient with primary ciliary dyskinesia accompanied with situs inversus (reversed internal organs). Regions with impaired ventilation and perfusion as well as delayed blood arrival time located in the basal lung segments are marked with white arrows.

Figure 2. Automatic assessment of perfusion and ventilation defects in 8 year old male PCD patient. Top row presents segmented quantitative fractional ventilation and perfusion maps with areas of impaired function in the sixth segment in the left lung and basal segments in both lungs. Automatically generated masks of the ventilation and perfusion defects are shown in bottom row. Ratios of the impaired volume to the segmented volume are shown in the left right corner of the images.



Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)
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