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"Lung perfusion" in the context of imaging conventionally refers to the delivery of blood to the pulmonary capillary bed through the pulmonary arteries originating from the right ventricle required for oxygenation. The most important physiological mechanism in the context of imaging is the so‐called hypoxic pulmonary vasoconstriction (HPV, also known as "Euler‐Liljestrand‐Reflex"), which couples lung perfusion to lung ventilation. In obstructive airway diseases such as asthma, chronic‐obstructive pulmonary disease (COPD), cystic fibrosis (CF), and asthma, HPV downregulates pulmonary perfusion in order to redistribute blood flow to functional lung areas in order to conserve optimal oxygenation. Imaging of lung perfusion can be seen as a reflection of lung ventilation in obstructive airway diseases. Other conditions that primarily affect lung perfusion are pulmonary vascular diseases, pulmonary hypertension, or (chronic) pulmonary embolism, which also lead to inhomogeneity in pulmonary capillary blood distribution. Several magnetic resonance imaging (MRI) techniques either dependent on exogenous contrast materials, exploiting periodical lung signal variations with cardiac action, or relying on intrinsic lung voxel attributes have been demonstrated to visualize lung perfusion. Additional post‐processing may add temporal information and provide quantitative information related to blood flow. The most widely used and robust technique, dynamic‐contrast enhanced MRI, is available in clinical routine assessment of COPD, CF, and pulmonary vascular disease. Non‐contrast techniques are important research tools currently requiring clinical validation and cross‐correlation in the absence of a viable standard of reference. First data on many of these techniques in the context of observational studies assessing therapy effects have just become available. Level of Evidence: 5 Technical Efficacy: Stage 5 [ABSTRACT FROM AUTHOR]

Introduction: The aim of this study was to apply quantitative computed tomography (QCT) for GOLD-grade specific disease characterization and phenotyping of air-trapping, emphysema, and airway abnormalities in patients with chronic obstructive pulmonary disease (COPD) from a nationwide cohort study. Methods: As part of the COSYCONET multicenter study, standardized CT in ex- and inspiration, lung function assessment (FEV1/FVC), and clinical scores (BODE index) were prospectively acquired in 525 patients (192 women, 327 men, aged 65.7 ± 8.5 years) at risk for COPD and at GOLD1–4. QCT parameters such as total lung volume (TLV), emphysema index (EI), parametric response mapping (PRM) for emphysema (PRMEmph) and functional small airway disease (PRMfSAD), total airway volume (TAV), wall percentage (WP), and total diameter (TD) were computed using automated software. Results: TLV, EI, PRMfSAD, and PRMEmph increased incrementally with each GOLD grade (p < 0.001). Aggregated WP5–10 of subsegmental airways was higher from GOLD1 to GOLD3 and lower again at GOLD4 (p < 0.001), whereas TD5–10 was significantly dilated only in GOLD4 (p < 0.001). Fifty-eight patients were phenotyped as “non-airway non-emphysema type,” 202 as “airway type,” 96 as “emphysema type,” and 169 as “mixed type.” FEV1/FVC was best in “non-airway non-emphysema type” compared to other phenotypes, while “mixed type” had worst FEV1/FVC (p < 0.001). BODE index was 0.56 ± 0.72 in the “non-airway non-emphysema type” and highest with 2.55 ± 1.77 in “mixed type” (p < 0.001). Conclusion: QCT demonstrates increasing hyperinflation and emphysema depending on the GOLD grade, while airway wall thickening increases until GOLD3 and airway dilatation occur in GOLD4. QCT identifies four disease phenotypes with implications for lung function and prognosis. [ABSTRACT FROM AUTHOR]

Background: In chronic obstructive pulmonary disease (COPD) abnormal lung function is related to emphysema and airway obstruction, but their relative contribution in each GOLD-stage is not fully understood. In this study, we used quantitative computed tomography (QCT) parameters for phenotyping of emphysema and airway abnormalities, and to investigate the relative contribution of QCT emphysema and airway parameters to airflow limitation specifically in each GOLD stage., Methods: Non-contrast computed tomography (CT) of 492 patients with COPD former GOLD 0 COPD and COPD stages GOLD 1-4 were evaluated using fully automated software for quantitative CT. Total lung volume (TLV), emphysema index (EI), mean lung density (MLD), and airway wall thickness (WT), total diameter (TD), lumen area (LA), and wall percentage (WP) were calculated for the entire lung, as well as for all lung lobes separately. Results from the 3rd-8th airway generation were aggregated (WT 3-8 , TD 3-8 , LA 3-8 , WP 3-8 ). All subjects underwent whole-body plethysmography (FEV1%pred, VC, RV, TLC)., Results: EI was higher with increasing GOLD stages with 1.0 ± 1.8% in GOLD 0, 4.5 ± 9.9% in GOLD 1, 19.4 ± 15.8% in GOLD 2, 32.7 ± 13.4% in GOLD 3 and 41.4 ± 10.0% in GOLD 4 subjects ( p < 0.001). WP 3-8 showed no essential differences between GOLD 0 and GOLD 1, tended to be higher in GOLD 2 with 52.4 ± 7.2%, and was lower in GOLD 4 with 50.6 ± 5.9% ( p = 0.010 - p = 0.960). In the upper lobes WP 3-8 showed no significant differences between the GOLD stages ( p = 0.824), while in the lower lobes the lowest WP 3-8 was found in GOLD 0/1 with 49.9 ± 6.5%, while higher values were detected in GOLD 2 with 51.9 ± 6.4% and in GOLD 3/4 with 51.0 ± 6.0% ( p < 0.05). In a multilinear regression analysis, the dependent variable FEV1%pred can be predicted by a combination of both the independent variables EI ( p < 0.001) and WP 3-8 ( p < 0.001)., Conclusion: QCT parameters showed a significant increase of emphysema from GOLD 0-4 COPD. Airway changes showed a different spatial pattern with higher values of relative wall thickness in the lower lobes until GOLD 2 and subsequent lower values in GOLD3/4, whereas there were no significant differences in the upper lobes. Both, EI and WP 5-8 are independently correlated with lung function decline., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Konietzke, Brunner, Konietzke, Wagner, Weinheimer, Heußel, Herth, Trudzinski, Kauczor and Wielpütz.)

Background: Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) allows the assessment of pulmonary perfusion, which may play a key role in the development of muco-obstructive lung disease. One problem with quantifying pulmonary perfusion is the high variability of metrics. Quantifying the extent of abnormalities using unsupervised clustering algorithms in residue function maps leads to intrinsic normalization and could reduce variability., Purpose: We investigated the reproducibility of perfusion defects in percent (QDP) in clinically stable patients with cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD)., Methods: 15 CF (29.3 ± 9.3y, FEV1%predicted = 66.6 ± 15.8%) and 20 COPD (66.5 ± 8.9y, FEV1%predicted = 42.0 ± 13.3%) patients underwent DCE-MRI twice 1 month apart. QDP, pulmonary blood flow (PBF), and pulmonary blood volume (PBV) were computed from residue function maps using an in-house quantification pipeline. A previously validated MRI perfusion score was visually assessed by an expert reader., Results: Overall, mean QDP, PBF, and PBV did not change within 1 month, except for QDP in COPD ( p < 0.05). We observed smaller limits of agreement (± 1.96 SD ) related to the median for QDP (CF: ± 38%, COPD: ± 37%) compared to PBF (CF: ± 89%, COPD: ± 55%) and PBV (CF: ± 55%, COPD: ± 51%). QDP correlated moderately with the MRI perfusion score in CF ( r = 0.46, p < 0.05) and COPD ( r = 0.66, p < 0.001). PBF and PBV correlated poorly with the MRI perfusion score in CF ( r =-0.29, p = 0.132 and r =-0.35, p = 0.067, respectively) and moderately in COPD ( r =-0.57 and r =-0.57, p < 0.001, respectively)., Conclusion: In patients with muco-obstructive lung diseases, QDP was more robust and showed a higher correlation with the MRI perfusion score compared to the traditionally used perfusion metrics PBF and PBV., Competing Interests: Authors MW, H-UK, and CH declared advisory board membership with Boehringer Ingelheim unrelated to the present study. Authors MK, SB, HH, and FR were employed by the Boehringer Ingelheim. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Konietzke, Triphan, Eichinger, Bossert, Heller, Wege, Eberhardt, Puderbach, Kauczor, Heußel, Heußel, Risse and Wielpütz.)