Magnetic Resonance Imaging Ventilation Defect Research Articles

Chest MRI and CT Predictors of 10-Year All-Cause Mortality in COPD

Pulmonary imaging measurements using magnetic resonance imaging (MRI) and computed tomography (CT) have the potential to deepen our understanding of chronic obstructive pulmonary disease (COPD) by measuring airway and parenchymal pathologic information that cannot be provided by spirometry. Currently, MRI and CT measurements are not included in mortality risk predictions, diagnosis, or COPD staging. We evaluated baseline pulmonary function, MRI and CT measurements alongside imaging texture-features to predict 10-year all-cause mortality in ex-smokers with (n = 93; 31 females; 70 ± 9years) and without (n = 69; 29 females, 69 ± 9years) COPD. CT airway and vessel measurements, helium-3 (3He) MRI ventilation defect percent (VDP) and apparent diffusion coefficients (ADC) were quantified. MRI and CT texture-features were extracted using PyRadiomics (version2.2.0). Associations between 10-year all-cause mortality and all clinical and imaging measurements were evaluated using multivariable regression model odds-ratios. Machine-learning predictive models for 10-year all-cause mortality were evaluated using area-under-receiver-operator-characteristic-curve (AUC), sensitivity and specificity analyses. DLCO (%pred) (HR = 0.955, 95%CI: 0.934-0.976, p < 0.001), MRI ADC (HR = 1.843, 95%CI: 1.260-2.871, p < 0.001), and CT informational-measure-of-correlation (HR = 3.546, 95% CI: 1.660-7.573, p = 0.001) were the strongest predictors of 10-year mortality. A machine-learning model trained on clinical, imaging, and imaging textures was the best predictive model (AUC = 0.82, sensitivity = 83%, specificity = 84%) and outperformed the solely clinical model (AUC = 0.76, sensitivity = 77%, specificity = 79%). In ex-smokers, regardless of COPD status, addition of CT and MR imaging texture measurements to clinical models provided unique prognostic information of mortality risk that can allow for better clinical management.Clinical Trial Registration: www.clinicaltrials.gov NCT02279329

Oscillometry and pulmonary MRI measurements of ventilation heterogeneity in obstructive lung disease: relationship to quality of life and disease control.

Ventilation heterogeneity is a hallmark finding in obstructive lung disease and may be evaluated using a variety of methods, including multiple-breath gas washout and pulmonary imaging. Such methods provide an opportunity to better understand the relationships between structural and functional abnormalities in the lungs, and their relationships with important clinical outcomes. We measured ventilation heterogeneity and respiratory impedance in 100 subjects [50 patients with asthma, 22 ex-smokers, and 28 patients with chronic obstructive pulmonary disease (COPD)] using oscillometry and hyperpolarized 3He magnetic resonance imaging (MRI) and determined their relationships with quality of life scores and disease control/exacerbations. We also coregistered MRI ventilation maps to a computational airway tree model to generate patient-specific respiratory impedance predictions for comparison with experimental measurements. In COPD and asthma patients, respectively, forced oscillation technique (FOT)-derived peripheral resistance (5-19 Hz) and MRI ventilation defect percentage (VDP) were significantly related to quality of life (FOT: COPD ρ = 0.4, P = 0.004; asthma ρ = -0.3, P = 0.04; VDP: COPD ρ = 0.6, P = 0.003; asthma ρ = -0.3, P = 0.04). Patients with poorly controlled asthma (Asthmatic Control Questionnaire >2) had significantly increased resistance (5 Hz: P = 0.01; 5-19 Hz: P = 0.006) and reactance (5 Hz: P = 0.03). FOT-derived peripheral resistance (5-19 Hz) was significantly related to VDP in patients with asthma and COPD patients (asthma: ρ = 0.5, P < 0.001; COPD: ρ = 0.5, P = 0.01), whereas total respiratory impedance was related to VDP only in patients with asthma (resistance 5 Hz: ρ = 0.3, P = 0.02; reactance 5 Hz: ρ = -0.5, P < 0.001). Model-predicted and FOT-measured reactance (5 Hz) were correlated in patients with asthma (ρ = 0.5, P = 0.001), whereas in COPD patients, model-predicted and FOT-measured resistance (5-19 Hz) were correlated (ρ = 0.5, P = 0.004). In summary, in patients with asthma and COPD patients, we observed significant, independent relationships for FOT-measured impedance and MRI ventilation heterogeneity measurements with one another and with quality of life scores. NEW & NOTEWORTHY In 100 patients, including patients with asthma and ex-smokers, 3He MRI ventilation heterogeneity and respiratory system impedance were correlated and both were independently related to quality of life scores and asthma control. These findings demonstrated the critical relationships between respiratory system impedance and ventilation heterogeneity and their role in determining quality of life and disease control. These observations underscore the dominant role that abnormalities in the lung periphery play in ventilation heterogeneity that results in patients' symptoms.

This is what asthma looks like: Review of new and emerging functional imaging methods and results

ABSTRACTIn asthma, diffuse and homogeneously distributed airway abnormalities have been thought responsible for symptoms and disease worsening, despite evidence over six-decades ago of ventilation heterogeneity using multiple-breath gas-washout studies. Such ventilation heterogeneity could stem from heterogeneously distributed airway abnormalities and, recently, pulmonary imaging including nuclear medicine methods, x-ray computed tomography (CT) and magnetic resonance imaging (MRI), has revealed focal ventilation defects and abnormal, heterogeneous ventilation patterns in asthmatics. In this review, we summarize pulmonary functional MRI findings that provide supportive evidence that in asthmatics, some ventilation abnormalities are temporally and spatially persistent while others come and go intermittently, but in the same, predictable spatial locations. Importantly, MRI ventilation defects also worsen in response to methacholine and exercise in the same spatial locations, despite differing underlying asthma response mechanisms, and in most patients, ventilation defects improve post-bronchodilator. In asthmatics, focal ventilation defects have been shown to be quantitatively and spatially related to airways with abnormal wall and lumen morphology, possibly stemming from remodelling, smooth muscle dysfunction and/or inflammation that may occur concurrently or independently. Finally, because MRI ventilation defects were also shown to be related to eosinophilic airway inflammation, asthma symptoms and disease control, we think MRI may be considered clinically to guide asthma therapy decisions in patients, to develop novel therapies and better understand mechanisms of asthma progression and therapy response in individual patients.

On the Potential Role of MRI Biomarkers of COPD to Guide Bronchoscopic Lung Volume Reduction

In patients with severe emphysema and poor quality of life, bronchoscopic lung volume reduction (BLVR) may be considered and guided based on lobar emphysema severity. In particular, x-ray computed tomography (CT) emphysema measurements are used to identify the most diseased and the second-most diseased lobes as BLVR targets. Inhaled gas magnetic resonance imaging (MRI) also provides chronic obstructive pulmonary disease (COPD) biomarkers of lobar emphysema and ventilation abnormalities. Our objective was to retrospectively evaluate CT and MRI biomarkers of lobar emphysema and ventilation in patients with COPD eligible for BLVR. We hypothesized that MRI would provide complementary biomarkers of emphysema and ventilation that help determine the most appropriate lung lobar targets for BLVR in patients with COPD. We retrospectively evaluated 22 BLVR-eligible patients from the Thoracic Imaging Network of Canada cohort (diffusing capacity of the lung for carbon monoxide = 37 ± 12%predicted, forced expiratory volume in 1 second = 34 ± 7%predicted, total lung capacity = 131 ± 17%predicted, and residual volume = 216 ± 36%predicted). Lobar CT emphysema, measured using a relative area of <-950 Hounsfield units (RA950) and MRI ventilation defect percent, was independently used to rank lung lobe disease severity. In 7 of 22 patients, there were different CT and MRI predictions of the most diseased lobe. In some patients, there were large ventilation defects in lobes not targeted by CT, indicative of a poorly ventilated lung. CT and MRI classification of the most diseased and the second-most diseased lobes showed a fair-to-moderate intermethod reliability (Cohen κ = 0.40-0.59). In this proof-of-concept retrospective analysis, quantitative MRI ventilation and CT emphysema measurements provided different BLVR targets in over 30% of the patients. The presence of large MRI ventilation defects in lobes next to CT-targeted lobes might also change the decision to proceed or to guide BLVR to a different lobar target.

Thoracic CT-MRI coregistration for regional pulmonary structure-function measurements of obstructive lung disease.

Recent pulmonary imaging research has revealed that in patients with chronic obstructive pulmonary disease (COPD) and asthma, structural and functional abnormalities are spatially heterogeneous. This novel information may help optimize treatment in individual patients, monitor interventional efficacy, and develop new treatments. Moreover, by automating the measurement of regional biomarkers for the 19 different anatomical lung segments, there is an opportunity to embed imaging biomarkers into clinically acceptable clinical workflows and improve lung disease clinical care. Therefore, to exploit the regional structure-function information provided by thoracic imaging, and as a first step toward this goal, our objective was to develop a fully automated registration pipeline for thoracic x-ray computed tomography (CT) and inhaled gas functional magnetic resonance imaging (MRI) whole lung and segmental structure-function biomarkers. Thirty-five patients including 15 severe, poorly controlled asthmatics and 20 COPD patients [classified according to the global initiative for chronic obstructive lung disease (GOLD) criteria)] provided written informed consent to a study protocol approved by Health Canada and underwent pulmonary function tests, MRI, and CT during a single 2-hour visit. Using this diverse patient dataset, we developed and evaluated a joint deformable registration approach to simultaneously coregister CT with both 1 H and 3 He MRI by enforcing the similarity of the deformation fields from the two individual registrations. We derived a simpler model that was equivalent to the original challenging optimization problem through variational analysis and the simpler model gave rise to an efficient numerical solver that was parallelized on a graphics processing unit. The coregistered CT-3 He MRI and whole lung/segmental lung masks were used to generate whole lung and segmental 3 He MRI ventilation defect percent (VDP). To estimate fiducial localization reproducibility, a single observer manually identified 109 pairs of CT and 3 He MRI fiducials for 35 patient images on five separate occasions and determined the fiducial localization error (FLE). CT-3 He MRI registration accuracy was evaluated using the target registration error (TRE). Whole lung VDP generated using the algorithm was compared with VDP generated using a previously validated semiautomated approach and computational efficiency was evaluated using run time. In 35 patients including 15 with severe asthma and 20 with COPD, mean forced expiratory volume in 1s (FEV1 ) was 63±24%pred and FEV1 /forced vital capacity (FVC) was 54±17%. FLE was 0.16mm and 0.34mm for 3 He MRI and CT, respectively. TRE was 4.5±2.0mm, 4.0±1.7mm, 4.8±2.3mm for asthma, COPD GOLD II, and GOLD III groups, respectively, with a mean of 4.4±2.0mm for the entire dataset. TRE was significantly improved for joint CT-1 H/3 He MRI registration compared with CT-1 H MRI rigid registration (P<0.0001). Whole lung VDP generated using the pipeline was not significantly different (P=0.37) compared to a semiautomated method with which it was strongly correlated (r=0.93, P<0.0001). The fully automated pipeline required 11±0.4 min to generate whole lung and segmental VDP. For a diverse group of patients with COPD and asthma, whole lung and segmental VDP was measured using an automated lung image analysis pipeline which provides a way to incorporate lung functional biomarkers into clinical research and patient care.

Noncystic Fibrosis Bronchiectasis: Regional Abnormalities and Response to Airway Clearance Therapy Using Pulmonary Functional Magnetic Resonance Imaging

Evidence-based treatment and management for patients with bronchiectasis remain challenging. There is a need for regional disease measurements as focal distribution of disease is common. Our objective was to evaluate the ability of magnetic resonance imaging (MRI) to detect regional ventilation impairment and response to airway clearance therapy (ACT) in patients with noncystic fibrosis (CF) bronchiectasis, providing a new way to objectively and regionally evaluate response to therapy. Fifteen participants with non-CF bronchiectasis and 15 age-matched healthy volunteers provided written informed consent to an ethics board-approved Health Insurance Portability and Accountability Act-compliant protocol and underwent spirometry, plethysmography, computed tomography (CT), and hyperpolarized 3He MRI. Bronchiectasis patients also completed a Six-Minute Walk Test, the St. George's Respiratory questionnaire, and Patient Evaluation Questionnaire (PEQ), and returned for a follow-up visit after 3weeks of daily oscillatory positive expiratory pressure use. CT evidence of bronchiectasis was qualitatively reported by lobe, and MRI ventilation defect percent (VDP) was measured for the entire lung and individual lobes. CT evidence of bronchiectasis and abnormal VDP (14 ± 7%) was observed for all bronchiectasis patients and no healthy volunteers. There was CT evidence of bronchiectasis in all lobes for 3 patients and in 3 ± 1 lobes (range = 1-4) for 12 patients. VDP in lobes with CT evidence of bronchiectasis (19 ± 12%) was significantly higher than in lobes without CT evidence of bronchiectasis (8 ± 5%, P = .001). For patients, VDP in lung lobes with (P < .0001) and without CT evidence of bronchiectasis (P = .006) was higher than in healthy volunteers (3 ± 1%). For all patients, mean PEQ-ease-bringing-up-sputum (P = .048) and PEQ-patient-global-assessment (P = .01) were significantly improved post-oscillatory positive expiratory pressure. An improvement in regional VDP greater than the minimum clinical important difference was observed for 8 of the 14 patients evaluated. There was CT and MRI evidence of structure-function abnormalities in patients with bronchiectasis; in approximately half, there was evidence of ventilation improvements after airway clearance therapy.

Is ventilation heterogeneity related to asthma control?

In asthma patients, magnetic resonance imaging (MRI) and the lung clearance index (LCI) have revealed persistent ventilation heterogeneity, although its relationship to asthma control is not well understood. Therefore, our goal was to explore the relationship of MRI ventilation defects and the LCI with asthma control and quality of life in patients with severe, poorly controlled asthma.18 patients with severe, poorly controlled asthma (mean±sd 46±12 years, six males/12 females) provided written informed consent to an ethics board approved protocol, and underwent spirometry, LCI and (3)He MRI during a single 2-h visit. Asthma control and quality of life were evaluated using the Asthma Control Questionnaire (ACQ) and Asthma Quality of Life Questionnaire (AQLQ). Ventilation heterogeneity was quantified using the LCI and (3)He MRI ventilation defect percent (VDP).All participants reported poorly controlled disease (mean±sd ACQ score=2.3±0.9) and highly heterogeneous ventilation (mean±sd VDP=12±11% and LCI=10.5±3.0). While VDP and LCI were strongly correlated (r=0.86, p<0.0001), in a multivariate model that included forced expiratory volume in 1 s, VDP and LCI, VDP was the only independent predictor of asthma control (R(2)=0.38, p=0.01). There was also a significantly worse VDP, but not LCI in asthma patients with an ACQ score >2 (p=0.04) and AQLQ score <5 (p=0.04), and a trend towards worse VDP (p=0.053), but not LCI in asthma patients reporting ≥1 exacerbation in the past 6 months.In patients with poorly controlled, severe asthma MRI ventilation, but not LCI was significantly worse in those with worse ACQ and AQLQ.

Hyperpolarized 3He magnetic resonance imaging ventilation defects in asthma: relationship to airway mechanics.

In patients with asthma, magnetic resonance imaging (MRI) provides direct measurements of regional ventilation heterogeneity, the etiology of which is not well‐understood, nor is the relationship of ventilation abnormalities with lung mechanics. In addition, respiratory resistance and reactance are often abnormal in asthmatics and the frequency dependence of respiratory resistance is thought to reflect ventilation heterogeneity. We acquired MRI ventilation defect maps, forced expiratory volume in one‐second (FEV 1), and airways resistance (Raw) measurements, and used a computational airway model to explore the relationship of ventilation defect percent (VDP) with simulated measurements of respiratory system resistance (Rrs) and reactance (Xrs). MRI ventilation defect maps were experimentally acquired in 25 asthmatics before, during, and after methacholine challenge and these were nonrigidly coregistered to the airway tree model. Using the model coregistered to ventilation defect maps, we narrowed proximal (9th) and distal (14th) generation airways that were spatially related to the MRI ventilation defects. The relationships for VDP with Raw measured using plethysmography (r = 0.79), and model predictions of Rrs>14 (r = 0.91, P < 0.0001) and Rrs>9 (r = 0.88, P < 0.0001) were significantly stronger (P = 0.005; P = 0.03, respectively) than with FEV 1 (r = −0.68, P = 0.0001). The slopes for the relationship of VDP with simulated lung mechanics measurements were different (P < 0.0001); among these, the slope for the VDP‐Xrs0.2 relationship was largest, suggesting that VDP was dominated by peripheral airway heterogeneity in these patients. In conclusion, as a first step toward understanding potential links between lung mechanics and ventilation defects, impedance predictions were made using a computational airway tree model with simulated constriction of airways related to ventilation defects measured in mild‐moderate asthmatics.

Regional Heterogeneity of Chronic Obstructive Pulmonary Disease Phenotypes: Pulmonary 3He Magnetic Resonance Imaging and Computed Tomography

Pulmonary ventilation may be visualized and measured using hyperpolarized 3He magnetic resonance imaging (MRI) while emphysema and its distribution can be quantified using thoracic computed tomography (CT). Our objective was to phenotype ex-smokers with COPD based on the apical-to-basal distribution of ventilation abnormalities and emphysema to better understand how these phenotypes change regionally as COPD progresses. We evaluated 100 COPD ex-smokers who provided written informed consent and underwent spirometry, CT and 3He MRI. 3He MRI ventilation imaging was used to quantify the ventilation defect percent (VDP) for whole-lung and individual lung lobes. Regional VDP was used to generate the apical-lung (AL)-to-basal-lung (BL) difference (ΔVDP); a positive ΔVDP indicated AL-predominant and negative ΔVDP indicated BL-predominant ventilation defects. Emphysema was quantified using the relative-area-of-the-lung ≤−950HU (RA950) of the CT density histogram for whole-lung and individual lung lobes. The AL-to-BL RA950 difference (ΔRA950) was generated with a positive ΔRA950 indicating AL-predominant emphysema and a negative ΔRA950 indicating BL-predominant emphysema. Seventy-two ex-smokers reported BL-predominant MRI ventilation defects and 71 reported AL-predominant CT emphysema. BL-predominant ventilation defects (AL/BL: GOLD I = 18%/82%, GOLD II = 24%/76%) and AL-predominant emphysema (AL/BL: GOLD I = 84%/16%, GOLD II = 72%/28%) were the major phenotypes in mild-moderate COPD. In severe COPD there was a more uniform distribution for ventilation defects (AL/BL: GOLD III = 40%/60%, GOLD IV = 43%/57%) and emphysema (AL/BL: GOLD III = 64%/36%, GOLD IV = 43%/57%). Basal-lung ventilation defects predominated in mild-moderate GOLD grades, and a more homogeneous distribution of ventilation defects was observed in more advanced grade COPD; these differences suggest that over time, regional ventilation abnormalities become more homogenously distributed during disease progression.

Pulmonary Artery Abnormalities in Ex-smokers with and without Airflow Obstruction

Pulmonary vascular disease is a common complication of chronic obstructive pulmonary disease (COPD), and an important risk factor for COPD exacerbations and death. We explored the relationship between pulmonary artery volumes measured using thoracic computed tomography (CT) and lung structure-function measured using spirometry, CT and magnetic resonance imaging (MRI) in 124 ex-smokers with (n = 68) and without (n = 56) airflow obstruction, and a control group of 35 never-smokers. We observed significantly greater main (p = .01), right (p = .001) and total (p = .003) pulmonary artery volumes in ex-smokers with airflow obstruction as compared to ex-smokers without airflow obstruction. There were also significantly greater pulmonary artery volumes in both ex-smoker subgroups, compared to the never-smoker subgroup (p = .008). For all participants, there were significant correlations for pulmonary artery volumes with the ratio of the forced expiratory volume in 1 s to forced vital capacity (FEV1/FVC), the diffusing capacity of the lung for carbon monoxide (DLCO%pred), airway count, MRI ventilation defect percent and MRI apparent diffusion coefficients. In ex-smokers, ventilation defect percent was significantly correlated with right (r = 0.27, p = .02) and total (r = 0.25, p = .03) pulmonary artery volumes. Multivariate zero-inflated Poisson regression analysis showed that FEV1%pred (p = .004), DLCO%pred (p = .03), the six minute walk distance (p = .04) and total pulmonary artery volume (p = .03) were significant predictors of acute exacerbations of COPD, while the number of previous exacerbations was not. In conclusion, pulmonary artery enlargement measured using thoracic CT was observed even in ex-smokers without airflow obstruction and was predictive of COPD exacerbations in ex-smokers with airflow obstruction.

Second-order Texture Measurements of 3He Ventilation MRI:: Proof-of-concept Evaluation of Asthma Bronchodilator Response

(3)He magnetic resonance imaging (MRI) can be used to quantify functional responses to asthma therapy and provocation. Ventilation imaging offers quantitative information beyond ventilation defects that have not yet been exploited. Therefore, our objective was to evaluate hyperpolarized (3)He MRI ventilation defect percent (VDP) and compare this and pulmonary function measurements to ventilation image texture features and their changes post-bronchodilator administration in patients with asthma. Volunteers with a diagnosis of asthma provided written informed consent to an ethics board-approved protocol and underwent pulmonary function tests and MRI before and after salbutamol inhalation. MR images were analyzed using VDP, and their texture was evaluated via gray-level run-length matrices. These texture classifiers were compared to VDP in responders to bronchodilation based on VDP (VDP responders) and forced expiratory volume in 1 s (FEV1) (FEV1 responders). In total, 47 patients with asthma (18 males 39 ± 13 years, FEV1 = 79 ± 21%) reported significantly improved FEV1, FEV1/forced vital capacity (FVC), residual volume (RV)/total lung capacity (TLC) (all P = .0001) and VDP (P = .01) post-salbutamol. Post-salbutamol, VDP responders and nonresponders to salbutamol were significantly different for coarse-texture features including long-run emphasis (LRE) and long-run, low gray-level emphasis (LRLGE, both P < .05) and for FEV1 responders to salbutamol, there was significantly different long-run, high gray-level emphasis (LRHGE, P = .04). There were significant relationships for VDP with LRE (R = .50, P = .0003), LRLGE (R = .34, P = .02), and LRHGE (R = .56, P = .0001). Receiver operating characteristic curves showed VDP with the strongest performance (AUC = .92), followed by coarse-texture classifier LRHGE (AUC = .83), FEV1 (AUC = .80), LRE (AUC = .66), FVC (AUC = .58), and LRLGE (AUC = .42). In patients with asthma, differences in ventilation patchiness post-salbutamol can be quantified using coarse-texture classifiers that are significantly different in bronchodilator responders.

Differences in hyperpolarized (3) He ventilation imaging after 4 years in adults with cystic fibrosis.

To evaluate cystic fibrosis (CF) subjects over 4 years using (3) He magnetic resonance imaging (MRI), pulmonary function tests, and track hospitalization and physician visits. Five CF adults provided written informed consent to an approved protocol and underwent MRI, spirometry, and plethysmography at baseline, 7 days, and 4 ± 1 years later. (3) He MRI ventilation defect percent (VDP) was generated for all subjects and timepoints. After 4 years, mean forced expiratory volume in 1 second / forced vital capacity (FEV1 /FVC) was lower (P = 0.01) in all subjects and there were no other pulmonary function test changes. Two CF adults showed significantly elevated (worse) (3) He VDP at baseline and after 4 years they had significantly greater (worsened) VDP (P = 0.02), without a significant FEV1 decline (P = 0.06) but with a greater number of exacerbations (P < 0.05). Baseline VDP strongly correlated with FEV1 (r(2) = 0.98, P = 0.0007) at 4-year follow-up. For two CF subjects, VDP was significantly worse at baseline and worsened over 4 years, which was in agreement with a greater number of hospitalizations and clinic visits. These results are limited by the very small sample size, but the strong VDP correlation with longitudinal changes in FEV1 generates the hypothesis that abnormal VDP may temporally precede FEV1 decline in CF subjects; this must be tested in a larger CF study.

Hyperpolarized 3He Magnetic Resonance Functional Imaging Semiautomated Segmentation

To improve intra- and interobserver variability and enable the use of functional magnetic resonance imaging (MRI) for multicenter, multiobserver studies, we generated a semiautomated segmentation method for hyperpolarized helium-3 ((3)He) MRI. Therefore the objective of this study was to compare the reproducibility and spatial agreement of manual and semiautomated segmentation of (3)He MRI ventilation defect volume (VDV) and ventilation volume (VV) in subjects with asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF). The multistep semiautomated segmentation method we developed employed hierarchical K-means clustering to classify (3)He MRI pixel intensity values into five user-determined clusters ranging from signal void to hyperintense. A seeded region-growing algorithm was also used to segment the (1)H MRI thoracic cavity for coregistration to the (3)He cluster-map, generating VDV and VV. We compared manual segmentation performed by an expert observer and semiautomated measurements of (3)He MRI VDV and observed strong significant correlations between the volumes generated using each method (asthma, n = 5, r = 0.89, P < .0001; COPD, n = 5, r = 0.84, P < .0001; CF, n = 5, r = 0.89, P < .0001). Semiautomated VDV had high interobserver reproducibility (coefficient of variation [CV] = 7%, intraclass correlation coefficient [ICC] = 0.96); intraobserver reproducibility was significantly higher for semiautomated (CV = 5%, ICC = 1.00) compared to manual VDV (CV = 12%, ICC = 0.98). Spatial agreement for VV determined using the Dice coefficient (D) was also high for all disease states (asthma, D = 0.95; COPD, D = 0.88; CF, D = 0.90). Semiautomated segmentation (3)He MRI provides excellent inter- and intraobserver precision with high spatial and quantitative agreement with manual measurements enabling its use in longitudinal studies.

Sci-Thurs AM: YIS-06: Longitudinal Hyperpolarized 3He Magnetic Resonance Imaging of Chronic Obstructive Pulmonary Disease

RATIONALE: To date, no studies have quantitatively evaluated chronic obstructive pulmonary disease (COPD) longitudinally using hyperpolarized helium-3 () magnetic resonance imaging (MRI). OBJECTIVES: To evaluate COPD longitudinally using hyperpolarized MRI and to determine correlations between the changes in MRI ventilation defect volume (VDV), apparent diffusion coefficients (ADC) and changes in pulmonary function. METHODS: Hyperpolarized MRI, spirometry and plethysmography were performed in 15 COPD ex-smokers ( stage II and stage III/IV COPD) at baseline and 26±2 months later. MRI ADC values were calculated from MRI diffusion-weighted images and VDV were generated after manual segmentation of MRI spin-density images. MEASUREMENTS AND MAIN RESULTS: At follow-up, COPD subjects showed significant increases in MRI CS VDV (), WL VDV (), as well as ADC () and no significant change in (). There was a significant correlation between changes in and changes in CS VDV (, ), however no significant correlations between smoking history (years non-smoker at baseline) and changes in MRI measurements or was found. CONCLUSIONS: For COPD ex-smokers, MRI VDV and ADC measurements worsened significantly but there was no significant change in FEV1, suggesting higher sensitivity of hyperpolarized MRI to COPD changes over short periods of time.

Hyperpolarized 3He Magnetic Resonance Imaging of Ventilation Defects in Healthy Elderly Volunteers : Initial Findings at 3.0 Tesla

Hyperpolarized (3)He magnetic resonance imaging ventilation defects have been observed in subjects with respiratory disorders. We quantified (3)He ventilation defects in elderly and middle-aged subjects who had no history of smoking, respiratory, or cardiovascular disorders. Hyperpolarized (3)He magnetic resonance imaging ventilation defect volume (VDV) and ventilation defect score (VDS) were assessed in eight elderly healthy volunteers (mean 67+/-6 years) scanned twice within 7+/-2 minutes and again 7+/-2 days later. A younger cohort of 24 subjects (mean 44+/-10 years) was also scanned for direct comparison. Four observers blinded to scan timepoint and subject identity scored VDS and manually segmented VDV in all center coronal slices. Center coronal slice ventilation defects were observed in six of eight elderly subjects (ages 63-74 years, 5 males) in all scans acquired and in no middle-aged subjects. At the scan timepoint, mean VDS was 2.7 (mean VDV 52+/-34 cm(3)), whereas for same-day rescan, mean VDS was 2.5 (mean VDV 53+/-35 cm(3)) and at 7-day rescan, mean VDS was 3.6 (mean VDV 48+/-39 cm(3)). Interscan coefficients of variation (COV) for mean VDV was 1.8% (same-day rescan) and 5.3% (7-day rescan) and interobserver COV ranged from 10-12%. Elderly subjects have ventilation defects that are reproducible in same-day scanning and 7-day scanning visits. The observation of reproducible pulmonary ventilation defects in otherwise healthy elderly volunteers suggests caution must be used in interpreting results from (3)He studies of elderly subjects.

Mechanical factors in distribution of pulmonary ventilation.

Mechanical factors in distribution of pulmonary ventilation.