Free-breathing dynamic (19)F gas MR imaging for mapping of regional lung ventilation in patients with COPD

Purpose: To quantify regional lung ventilation in patients with chronic obstructive pulmonary disease (COPD) by using free-breathing dynamic fluorinated (fluorine 19 [(19)F]) gas magnetic resonance (MR) imaging. Materials and Methods: In this institutional review board-approved prospective study, 27 patients with COPD were examined by using breath-hold (19)F gas wash-in MR imaging during inhalation of a normoxic fluorinated gas mixture (perfluoropropane) and by using free-breathing dynamic (19)F gas washout MR imaging after inhalation of the gas mixture was finished for a total of 25-30 L. Regional lung ventilation was quantified by using volume defect percentage (VDP), washout time, number of breaths, and fractional ventilation (FV). To compare different lung function parameters, Pearson correlation coefficient and Fisher z transformation were used, which were corrected for multiple comparisons with the Bonferroni method. Results: Statistically significant correlations were observed for all evaluated lung function test parameters compared with median and interquartile range of (19)F washout parameters. An inverse linear correlation of median number of breaths (r = -0.82; P < .0001) and median washout times (r = -0.77; P < .0001) with percentage predicted of forced expiratory volume in 1 second (FEV1) was observed; correspondingly median FV (r = 0.86; P < .0001) correlated positively with percentage predicted FEV1. Comparing initial with late phase, median VDP of all subjects decreased from 49% (25th-75th percentile, 35%-62%) to 6% (25th-75th percentile, 2%-10%; P < .0001). VDP at the beginning of the gas wash-in phase (VDPinitial) significantly correlated with percentage predicted FEV1 (r = -0.74; P = .0028) and FV (r = 0.74; P = .0002). Median FV was significantly increased in ventilated regions (11.1% [25th-75th percentile, 6.8%-14.5%]) compared with the defect regions identified by VDPinitial (5.8% [25th-75th percentile, 4.0%-7.4%]; P < .0001). Conclusion Quantification of regional lung ventilation by using dynamic (19)F gas washout MR imaging in free breathing is feasible at 1.5 T even in obstructed lung segments

Artificially-generated consolidations and balanced augmentation increase performance of U-net for lung parenchyma segmentation on MR images.

PurposeTo improve automated lung segmentation on 2D lung MR images using balanced augmentation and artificially-generated consolidations for training of a convolutional neural network (CNN).Materials and methodsFrom 233 healthy volunteers and 100 patients, 1891 coronal MR images were acquired. Of these, 1666 images without consolidations were used to build a binary semantic CNN for lung segmentation and 225 images (187 without consolidations, 38 with consolidations) were used for testing. To increase CNN performance of segmenting lung parenchyma with consolidations, balanced augmentation was performed and artificially-generated consolidations were added to all training images. The proposed CNN (CNNBal/Cons) was compared to two other CNNs: CNNUnbal/NoCons-without balanced augmentation and artificially-generated consolidations and CNNBal/NoCons-with balanced augmentation but without artificially-generated consolidations. Segmentation results were assessed using Sørensen-Dice coefficient (SDC) and Hausdorff distance coefficient.ResultsRegarding the 187 MR test images without consolidations, the mean SDC of CNNUnbal/NoCons (92.1 ± 6% (mean ± standard deviation)) was significantly lower compared to CNNBal/NoCons (94.0 ± 5.3%, P = 0.0013) and CNNBal/Cons (94.3 ± 4.1%, P = 0.0001). No significant difference was found between SDC of CNNBal/Cons and CNNBal/NoCons (P = 0.54). For the 38 MR test images with consolidations, SDC of CNNUnbal/NoCons (89.0 ± 7.1%) was not significantly different compared to CNNBal/NoCons (90.2 ± 9.4%, P = 0.53). SDC of CNNBal/Cons (94.3 ± 3.7%) was significantly higher compared to CNNBal/NoCons (P = 0.0146) and CNNUnbal/NoCons (P = 0.001).ConclusionsExpanding training datasets via balanced augmentation and artificially-generated consolidations improved the accuracy of CNNBal/Cons, especially in datasets with parenchymal consolidations. This is an important step towards a robust automated postprocessing of lung MRI datasets in clinical routine

A dual center and dual vendor comparison study of automated perfusion-weighted phase-resolved functional lung magnetic resonance imaging with dynamic contrast-enhanced magnetic resonance imaging in patients with cystic fibrosis

For sensitive diagnosis and monitoring of pulmonary disease, ionizing radiation-free imaging methods are of great importance. A noncontrast and free-breathing proton magnetic resonance imaging (MRI) technique for assessment of pulmonary perfusion is phase-resolved functional lung (PREFUL) MRI. Since there is no validation of PREFUL MRI across different centers and scanners, the purpose of this study was to compare perfusion-weighted PREFUL MRI with the well-established dynamic contrast-enhanced (DCE) MRI across two centers on scanners from two different vendors. Sixteen patients with cystic fibrosis (CF) (Center 1: 10 patients; Center 2: 6 patients) underwent PREFUL and DCE MRI at 1.5T in the same imaging session. Normalized perfusion-weighted values and perfusion defect percentage (QDP) values were calculated for the whole lung and three central slices (dorsal, central, ventral of the carina). Obtained parameters were compared using Pearson correlation, Spearman correlation, Bland–Altman analysis, Wilcoxon signed-rank test, and Wilcoxon rank-sum test. Moderate-to-strong correlations between normalized perfusion-weighted PREFUL and DCE values were found (posterior slice: r = 0.69, p 0.07). The feasibility of PREFUL MRI across two different centers and two different vendors was shown in patients with CF and obtained results were in agreement with DCE MRI

Functional lung MRI for regional monitoring of patients with cystic fibrosis

<div><p>Purpose</p><p>To test quantitative functional lung MRI techniques in young adults with cystic fibrosis (CF) compared to healthy volunteers and to monitor immediate treatment effects of a single inhalation of hypertonic saline in comparison to clinical routine pulmonary function tests.</p><p>Materials and methods</p><p>Sixteen clinically stable CF patients and 12 healthy volunteers prospectively underwent two functional lung MRI scans and pulmonary function tests before and 2h after a single treatment of inhaled hypertonic saline or without any treatment. MRI-derived oxygen enhanced T₁ relaxation measurements, fractional ventilation, first-pass perfusion parameters and a morpho-functional CF-MRI score were acquired.</p><p>Results</p><p>Compared to healthy controls functional lung MRI detected and quantified significantly increased ventilation heterogeneity in CF patients. Regional functional lung MRI measures of ventilation and perfusion as well as the CF-MRI score and pulmonary function tests could not detect a significant treatment effect two hours after a single treatment with hypertonic saline in young adults with CF (p>0.05).</p><p>Conclusion</p><p>This study shows the feasibility of functional lung MRI as a non-invasive, radiation-free tool for monitoring patients with CF.</p></div

Comparison of CF patients to healthy volunteers.

<p>Comparison of CF patients to healthy volunteers.</p

Study protocol.

<p>Pulmonary function testing (spirometry and multiple breath nitrogen washout (MBW)) were performed 60 to 90 minutes prior to the pre treatment scan / 1^st scan. MRI was performed as follows: first, morphological images were assessed followed by phase contrast angiography (PCA) in the ascending aorta. Afterwards T1 mapping breathing room air and again after six minutes of 100% oxygen wash-in time was acquired. Regional Fractional Lung Ventilation MRI (FV) was then acquired under normoxic conditions. Then for assessment of pulmonary parenchymal perfusion, dynamic contrast enhanced (DCE) MRI was carried out followed by a morphological sequence post i.v. contrast. Afterwards inhalation treatment with hypertonic saline (HTS, treatment group) or no treatment (control group) was performed and the PFT (30 minutes after treatment) and MRI (2 h after treatment) were repeated. Healthy volunteers underwent one scan using the same functional lung MRI protocol, except for DCE-MRI and phase-contrast MRI.</p

Receiver operator characteristic analysis (ROC).

<p>Receiver operator characteristic (ROC) analysis with clinical diagnosis as the criterion showed the ability of functional MRI to discriminate young adults with CF from healthy volunteers. A: Room air T1 (cut point: 1200 ms; area under the curve (AUC) 0.89); B: Quartile coefficient of dispersion of fractional ventilation (cut point 0.351; AUC 0.89).</p

Patient cohort (CONSORT flow chart).

<p>Please note: For the control group a second visit of 4 patients of the treatment group were included resulting in 20 visits of 16 patients.</p

Subject demographics.

<p>Subject demographics.</p