Time-series hyperpolarized xenon-129 MRI of lobar lung ventilation of COPD in comparison to V/Q-SPECT/CT and CT

Purpose To derive lobar ventilation in patients with chronic obstructive pulmonary disease (COPD) using a rapid time-series hyperpolarized xenon-129 (HPX) magnetic resonance imaging (MRI) technique and compare this to ventilation/perfusion singlephoton emission computed tomography (V/Q-SPECT), correlating the results with high-resolution computed tomography (CT) and pulmonary function tests (PFTs).Materials and methods Twelve COPD subjects (GOLD stages I–IV) participated in this study and underwent HPX-MRI, V/QSPECT/CT, high-resolution CT, and PFTs. HPX-MRI was performed using a novel time-series spiral k-space sampling approach. Relative percentage ventilations were calculated for individual lobe for comparison to the relative SPECT lobar ventilation and perfusion. The absolute HPX-MRI percentage ventilation in each lobe was compared to the absolute CT percentage emphysema score calculated using a signal threshold method. Pearson’s correlation and linear regression tests were performed to compare each imaging modality.Results Strong correlations were found between the relative lobar percentage ventilation with HPX-MRI and percentage ventilation SPECT (r = 0.644; p Conclusion Lobar ventilation with HPX-MRI showed a strong correlation with lobar ventilation and perfusion measurements derived from SPECT/CT, and is better than the emphysema score obtained with high-resolution CT.</div

Time-series hyperpolarized xenon-129 MRI of lobar lung ventilation of COPD in comparison to V/Q-SPECT/CT and CT

PurposeTo derive lobar ventilation in patients with chronic obstructive pulmonary disease (COPD) using a rapid time-series hyperpolarized xenon-129 (HPX) magnetic resonance imaging (MRI) technique and compare this to ventilation/perfusion single-photon emission computed tomography (V/Q-SPECT), correlating the results with high-resolution computed tomography (CT) and pulmonary function tests (PFTs).Materials and methodsTwelve COPD subjects (GOLD stages I–IV) participated in this study and underwent HPX-MRI, V/Q-SPECT/CT, high-resolution CT, and PFTs. HPX-MRI was performed using a novel time-series spiral k-space sampling approach. Relative percentage ventilations were calculated for individual lobe for comparison to the relative SPECT lobar ventilation and perfusion. The absolute HPX-MRI percentage ventilation in each lobe was compared to the absolute CT percentage emphysema score calculated using a signal threshold method. Pearson’s correlation and linear regression tests were performed to compare each imaging modality.ResultsStrong correlations were found between the relative lobar percentage ventilation with HPX-MRI and percentage ventilation SPECT (r = 0.644; p < 0.001) and percentage perfusion SPECT (r = 0.767; p < 0.001). The absolute CT percentage emphysema and HPX percentage ventilation correlation was also statistically significant (r = 0.695, p < 0.001). The whole lung HPX percentage ventilation correlated with the PFT measurements (FEV1 with r = − 0.886, p < 0.001*, and FEV1/FVC with r = − 0.861, p < 0.001*) better than the whole lung CT percentage emphysema score (FEV1 with r = − 0.635, p = 0.027; and FEV1/FVC with r = − 0.652, p = 0.021).ConclusionLobar ventilation with HPX-MRI showed a strong correlation with lobar ventilation and perfusion measurements derived from SPECT/CT, and is better than the emphysema score obtained with high-resolution CT

Functional lung assessment using hyperpolarised xenon gas magnetic resonance imaging

Purpose Chronic obstructive pulmonary disease (COPD) is a leading cause of mortality worldwide. The standard method for assessing lung function in COPD is spirometry, which provides global lung function information but is a poor predictor of disability and quality of life. The overall aim of this thesis is to develop utility of hyperpolarised xenon gas magnetic resonance imaging (HP 129Xe-MRI) as a technique to evaluate regional lung function. Methods Studies were approved by the National Research Ethics Service (NRES). Eleven volunteers and 25 patients with COPD underwent HP 129Xe-MRI, pulmonary function tests (PFTs) and quantitative computerised tomography (QCT). Gravitational-dependent gradients of HP 129Xe-MRI were compared between prone and supine postures in healthy volunteers. Lobar quantification of HP 129Xe-MRI was completed in COPD patients, who also underwent time-resolved HP 129Xe-MRI and HP 129Xe-MRI pre- and post-salbutamol to determine feasibility of detecting regional delayed ventilation and post-intervention change. The relationship between study measures was assessed using Pearson’s correlation coefficient. Results HP 129Xe-MR ventilation gradients were more marked in the supine than prone posture in healthy volunteers, whereas diffusion-weighted gradients were more uniform. HP 129Xe-MRI was successfully quantified according to pulmonary lobes and correlated with lobar lung anatomy (QCT) and global functional transfer capability (TLCO) (r=-0.61, p&amp;LT;0.005). Delayed ventilation was observed with time-resolved breath-hold HP 129Xe-MRI. Differential regional ventilation change was detected with HP 129Xe-MRI post-salbutamol. Conclusion These data demonstrate technical optimisation of HP 129Xe-MRI in healthy volunteers and COPD patients. Successful generation of lobar HP 129Xe-MRI parameters offers an automated analysis method that can be adopted into the clinical workflow. Finally proof-of-principle data have identified roles for HP 129Xe-MRI in evaluating regional treatments and assessing therapeutic response. Future work will evaluate the role of HP 129Xe-MRI in patient selection for lung volume reduction therapy and as a surrogate end-point in drug development studies. </p

Functional lung assessment using hyperpolarised xenon gas magnetic resonance imaging

Purpose Chronic obstructive pulmonary disease (COPD) is a leading cause of mortality worldwide. The standard method for assessing lung function in COPD is spirometry, which provides global lung function information but is a poor predictor of disability and quality of life. The overall aim of this thesis is to develop utility of hyperpolarised xenon gas magnetic resonance imaging (HP 129Xe-MRI) as a technique to evaluate regional lung function. Methods Studies were approved by the National Research Ethics Service (NRES). Eleven volunteers and 25 patients with COPD underwent HP 129Xe-MRI, pulmonary function tests (PFTs) and quantitative computerised tomography (QCT). Gravitational-dependent gradients of HP 129Xe-MRI were compared between prone and supine postures in healthy volunteers. Lobar quantification of HP 129Xe-MRI was completed in COPD patients, who also underwent time-resolved HP 129Xe-MRI and HP 129Xe-MRI pre- and post-salbutamol to determine feasibility of detecting regional delayed ventilation and post-intervention change. The relationship between study measures was assessed using Pearsonâs correlation coefficient. Results HP 129Xe-MR ventilation gradients were more marked in the supine than prone posture in healthy volunteers, whereas diffusion-weighted gradients were more uniform. HP 129Xe-MRI was successfully quantified according to pulmonary lobes and correlated with lobar lung anatomy (QCT) and global functional transfer capability (TLCO) (r=-0.61, p&LT;0.005). Delayed ventilation was observed with time-resolved breath-hold HP 129Xe-MRI. Differential regional ventilation change was detected with HP 129Xe-MRI post-salbutamol. Conclusion These data demonstrate technical optimisation of HP 129Xe-MRI in healthy volunteers and COPD patients. Successful generation of lobar HP 129Xe-MRI parameters offers an automated analysis method that can be adopted into the clinical workflow. Finally proof-of-principle data have identified roles for HP 129Xe-MRI in evaluating regional treatments and assessing therapeutic response. Future work will evaluate the role of HP 129Xe-MRI in patient selection for lung volume reduction therapy and as a surrogate end-point in drug development studies. </p

Patch-based lung ventilation estimation using multi-layer supervoxels

Patch-based approaches have received substantial attention over the recent years in medical imaging. One of their potential applications may be to provide more anatomically consistent ventilation maps estimated on dynamic lung CT. An assessment of regional lung function may act as a guide for radiotherapy, ensuring a more accurate treatment plan. This in turn, could spare well-functioning parts of the lungs. We present a novel method for lung ventilation estimation from dynamic lung CT imaging, combining a supervoxel-based image representation with deformations estimated during deformable image registration, performed between peak breathing phases. For this we propose a method that tracks changes of the intensity of previously extracted supervoxels. For the evaluation of the method we calculate correlation of the estimated ventilation maps with static ventilation images acquired from hyperpolarized Xenon129 MRI. We also investigate the influence of different image registration methods used to estimate deformations between the peak breathing phases in the dynamic CT imaging. We show that our method performs favorably to other ventilation estimation methods commonly used in the field, independently of the image registration method applied to dynamic CT. Due to the patch-based approach of our method, it may be physiologically more consistent with lung anatomy than previous methods relying on voxel-wise relationships. In our method the ventilation is estimated for supervoxels, which tend to group spatially close voxels with similar intensity values. The proposed method was evaluated on a dataset consisting of three lung cancer patients undergoing radiotherapy treatment, and this resulted in a correlation of 0.485 with XeMRI ventilation images, compared with 0.393 for the intensity-based approach, 0.231 for the Jacobian-based method and 0.386 for the Hounsfield units averaging method, on average. Within the limitation of the small number of cases analyzed, results suggest that the presented technique may be advantageous for CT-based ventilation estimation. The results showing higher values of correlation of the proposed method demonstrate the potential of our method to more accurately mimic the lung physiology

CT-based airway flow model to assess ventilation in chronic obstructive pulmonary disease: a pilot study

Background The lack of functional information in thoracic CT remains a limitation of its use in the clinical management of chronic obstructive pulmonary disease (COPD). Purpose To compare the distribution of pulmonary ventilation assessed by a CT-based full-scale airway network (FAN) flow model with hyperpolarized xenon 129 (129Xe) MRI (hereafter, 129Xe MRI) and technetium 99m-diethylenetriaminepentaacetic acid aerosol SPECT ventilation imaging (hereafter, V-SPECT) in participants with COPD. Materials and Methods In this prospective study performed between May and August 2017, pulmonary ventilation in participants with COPD was computed by using the FAN flow model. The modeled pulmonary ventilation was compared with functional imaging data from breath-hold time-series 129Xe MRI and V-SPECT. FAN-derived ventilation images on the coronal plane and volumes of interest were compared with functional lung images. Percentage lobar ventilation estimated by the FAN model was compared with that measured at 129Xe MRI and V-SPECT. The statistical significance of ventilation distribution between FAN and functional images was demonstrated with the Spearman correlation coefficient and χ2 distance. Results For this study, nine participants (seven men [mean age, 65 years ± 5 {standard deviation}] and two women [mean age, 63 years ± 7]) with COPD that was Global Initiative for Chronic Obstructive Lung Disease stage II-IV were enrolled. FAN-modeled ventilation profile showed strong positive correlation with images from 129Xe MRI (ρ = 0.67; P < .001) and V-SPECT (ρ = 0.65; P < .001). The χ2 distances of the ventilation histograms in the volumes of interest between the FAN and 129Xe MRI and FAN and V-SPECT were 0.16 ± 0.08 and 0.28 ± 0.14, respectively. The ratios of lobar ventilations in the models were linearly correlated to images from 129Xe MRI (ρ = 0.67; P < .001) and V-SPECT (ρ = 0.59; P < .001). Conclusion A CT-based full-scale airway network flow model provided regional pulmonary ventilation information for chronic obstructive pulmonary disease and correlates with hyperpolarized xenon 129 MRI and technetium 99m-diethylenetriaminepentaacetic acid aerosol SPECT ventilation imaging