Introduction and purpose

Interstitial lung diseases (ILDs) are a set of heterogeneous respiratory diseases with limited therapeutic option. Frequent high-resolution computed tomography (HRCT) has been used to long-term follow-ups in evaluation of disease progression or treatment response, leading to a large amount of cumulative radiation exposure to the patients. Pulmonary MRI provides qualitative structural and quantitative functional images of the lungs without ionizing radiation¹. Three-dimensional isotropic high-resolution using a free-breathing zero-echo time (ZTE) technique has gained increasing interest in lung imaging recently and with good image quality such as visibility of pulmonary arteries (up to the 7th generation) and the bronchi (up to the 5th generation) ^2,3. The aim of this study was to compare ZTE with HRCT in terms of the demonstration of the pulmonary interstitial abnormalities and inter-methods agreement of diagnosis in ILD.

Materials and Methods

The study was approved by the ethics committee of our hospital. 47 patients (20 males, 27 females; age from 29 to 70 years; mean: 54 years) consisted of 23 connective tissue disease-associated interstitial lung disease (CTD-ILD), 9 idiopathic pulmonary fibrosis (IPF), 7 interstitial pneumonia with autoimmune features (IPAF) , 7 idiopathic nonspecific interstitial pneumonia (iNSIP), 1 (hypersensitive pneumonia, HP) , were included in the study and given written informed consent. All patients underwent both HRCT and ZTE scan on a 3.0T MRI scanner (Discovery MR750W, GE Healthcare, Waukesha, WI) within an interval of a week. The imaging features including the ground-glass opacity, reticular opacity, honeycombing, traction bronchiectasis and consolidation for each pulmonary segments were evaluated independently by two radiologists on both HRCT and ZTE (Fig1-3). The radiology patterns of usual interstitial pneumonia (UIP), nonspecific interstitial pneumonia (NSIP), organizing pneumonia (OP), mixed NSIP and OP, unclassified were determined for each case on both HRCT and ZTE independently by two radiologists. The receiver operating characteristic analyses was performed to evaluate ability of ZTE in the demonstration of aforementioned imaging features, using HRCT as the reference standard. The inter-method agreement of the ILD radiology patterns was determined by means of kappa statistics. Statistical analyses were performed using SPSS 25.0. P value < 0.05 was regarded as statistically significant.

Results

Representative images of a patient respectively with anti-synthetase syndrome and IPF were shown in Figure 1- 3. Using HRCT as the reference standard, areas under the curve (AUC) for ground-glass opacity, reticular opacity, honeycombing, traction bronchiectasis and consolidation ranged from 0.71 to 0.80 (p < 0.001) (Table 1). The performance of ZTE in the depiction of consolidation was highest (AUC=0.80), which may due to increased protons in air space. Inter-method agreements of radiology patterns between pulmonary ZTE and HRCT was moderate (κ = 0.76) (Table 2).

Discussion and conclusion

The pulmonary interstitial abnormalities including ground-glass opacity, reticular opacity, honeycombing, traction bronchiectasis and consolidation can be well demonstrated on ZTE-MRI. The diagnosis performance of ILD radiology patterns of ZTE is comparable with HRCT. In conclusion, free-breathing 3D isotropic high-resolution pulmonary zero echo time imaging might assist long-term follow-ups in ILDs evaluation without radiation exposure.

Acknowledgements

No acknowledgement found.

References

1. HATABU H, OHNO Y, GEFTER WB, et al. Expanding Applications of Pulmonary MRI in the Clinical Evaluation of Lung Disorders: Fleischner Society Position Paper . Radiology, 2020, 297(2): 286-301.
2. Yu Deng, Qiuxi Lin, Xinchun Li, et al. Feasibility of free-breathing 3D isotropic whole-lung zero echo time imaging. ISMRM & SMRT Annual Meeting 2021
3. GIBIINO F, SACOLICK L, MENINI A, et al. Free-breathing, zero-TE MR lung imaging . Magma (New York, NY), 2015, 28(3): 207-215.