Free-Breathing Low-Field MRI of the Lungs Detects Functional Alterations Associated With Persistent Symptoms After COVID-19 Infection

Abstract

Objectives: With the COVID-19 pandemic, repetitive lung examinations have become necessary to follow-up symptoms and associated alterations. Low-field MRI, benefiting from reduced susceptibility effects, is a promising alternative for lung imaging to limit radiations absorbed by patients during CT examinations, which also have limited capability to assess functional alterations. The aim of this investigative study was to explore the functional abnormalities that free-breathing 0.55 T MRI in combination with the phase-resolved functional lung (PREFUL) analysis could identify in patients with persistent symptoms after COVID-19 infection. Materials and Methods: Seventy-four COVID-19 patients and 8 healthy volunteers were prospectively scanned in free-breathing with a balanced steady-state free-precession sequence optimized at 0.55 T, 5 months postinfection on average. Normalized perfusion (Q), fractional ventilation (FV), and flow-volume loop correlation (FVLc) maps were extracted with the PREFUL technique. Q, FV, and FVLc defects as well as defect overlaps between these metrics were quantified. Morphological turbo-spin-echo images were also acquired, and the extent of abnormalities was scored by a board-certified radiologist. To investigate the functional correlates of persistent symptoms, a recursive feature elimination algorithm was applied to find the most informative variables to detect the presence of persistent symptoms with a logistic regression model and a cross-validation strategy. All MRI metrics, sex, age, body mass index, and the presence of preexisting lung conditions were included. Results: The most informative variables to detect persistent symptoms were the percentage of concurrent Q and FVLc defects and of areas free of those defects. A detection accuracy of 71.4% was obtained with these 2 variables when fitting the model on the entire dataset. Although none of the single variables differed between patients with and without persistent symptoms ( P > 0.05), the combined score of these 2 variables did ( P < 0.02). This score also showed a consistent increase from healthy volunteers (7.7) to patients without persistent symptoms (8.2) and with persistent symptoms (8.6). The morphological abnormality score showed poor correlation with the functional parameters.Conclusions: Functional pulmonary examinations using free-breathing 0.55 T MRI with PREFUL analysis revealed potential quantitative markers of impaired lung function in patients with persistent symptoms after COVID-19 infection, potentially complementing morphologic imaging. Future work is needed to explore the translational relevance and clinical implication of these findings.

Inter‐ and intravisit repeatability of free‐breathing MRI in pediatric cystic fibrosis lung disease

“…As previously mentioned, a limitation of this study was that only a single coronal slice was investigated for PRE-FUL analysis. The use of an isotropic 3D 27 or multi-slice 2D PREFUL MRI [21][22][23][24][25] acquisition should help to improve repeatability by providing whole lung investigation of ventilation defects. Furthermore, the repeatability of PREFUL MRI may be limited by the seeded-region growing segmentation method that required some manual corrections.…”

“…Postprocessing techniques such as Fourier decomposition, matrix pencil, self-gated non-contrast-enhanced functional lung, and phase-resolved functional lung (PREFUL) can generate ventilation-and perfusion-weighted maps of the lung based on free-breathing MRI data and have been used to assess lung function in a variety of pulmonary diseases. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] Whereas other postprocessing methods can require extensive pulse sequence modifications, PREFUL MRI can be performed using a conventional spoiled gradient echo sequence, showing promise at both 1.5 and 3 T. PREFUL MRI also sorts images acquired during free breathing into complete respiratory cycles in the time domain, so both static and dynamic ventilation parameters, including regional ventilation (RVent) and flow-volume loops (FVL), can be obtained. Ventilation parameters derived from PREFUL MRI have been shown to correlate to PFTs and Xe-MRI in chronic obstructive pulmonary disease (COPD), CF, and health, 21 and can characterize the severity of coronavirus 2019 infection.…”

HERZ THORAX – Regionale Lungenfunktion bei Lymphangioleiomyomatose mit der MRT diagnostizieren

“…Neben der Sauerstoffinhalation stehen in der Niederfeld-MRT noch die hyperpolarisierte Edelgas-Inhalation (Xenon 123 und Helium 3) und die Fourier-Dekompositions-MRT zur Verfügung. Letztere kommt sogar ohne intravenöses oder inhalatives Kontrastmittel aus 4 . Sollte es der Niederfeld-MRT gelingen die großen Hoffnungen in eine verbesserte Verfügbarkeit und kosteneffizientere Durchführung zu realisieren, bestehen gute Chancen die LAM und andere Lungenerkrankungen in Zukunft weiter multiparametrisch zu evaluieren und etablierte Erkenntnisse in den klinischen Alltag zu überführen.…”

Evaluation of image registration algorithms for 3D phase‐resolved functional lung ventilation magnetic resonance imaging in healthy volunteers and chronic obstructive pulmonary disease patients

“…PREFUL MRI 4 has been demonstrated to be sensitive for the early detection of abnormal ventilation dynamics in patients after lung transplantation 5 and in COVID-19 survivors. 6,7 In a recent study, dynamic ventilation parameters derived by PREFUL MRI were shown to depict the treatment response to indacaterol-glycopyrronium therapy in chronic obstructive pulmonary disease (COPD) patients. 8 These recent results emphasize the applicability of functional lung MR imaging for diagnosis and patient monitoring.…”

“…Proton magnetic resonance 3D phase‐resolved functional lung (PREFUL) 1 and other 3D lung MRI techniques 2,3 provide contrast‐free ventilation‐weighted whole lung imaging using dynamic data acquisition during free breathing. PREFUL MRI 4 has been demonstrated to be sensitive for the early detection of abnormal ventilation dynamics in patients after lung transplantation 5 and in COVID‐19 survivors 6,7 . In a recent study, dynamic ventilation parameters derived by PREFUL MRI were shown to depict the treatment response to indacaterol‐glycopyrronium therapy in chronic obstructive pulmonary disease (COPD) patients 8 .…”