Model-based Bayesian inference of the ventilation distribution in patients with cystic fibrosis from multiple breath washout, with comparison to ventilation MRI.

Background: Indices of ventilation heterogeneity (VH) from multiple breath washout (MBW) have been shown to correlate well with VH indices derived from hyperpolarised gas ventilation MRI. Here we report the prediction of ventilation distributions from MBW data using a mathematical model, and the comparison of these predictions with imaging data.

Methods: We developed computer simulations of the ventilation distribution in the lungs to model MBW measurement with 3 parameters: σ determining the extent of VH; V, the lung volume; and V, the dead-space volume.

Peripheral and proximal lung ventilation in asthma: Short-term variation and response to bronchodilator inhalation.

Background: The relative involvement of the large and small airways in asthma is not clear. Hyperpolarized gas magnetic resonance imaging (MRI) provides high-resolution 3-dimensional images of ventilation distribution that can be quantified by the ventilated volume percentage (VV%) of the lungs.

Objective: Our aims were to (1) quantify the baseline reproducibility of VV%, (2) assess the ventilation distribution between the proximal and peripheral lungs, and (3) investigate regional ventilation response to bronchodilator inhalation in a cohort of patients with asthma.

Single breath-held acquisition of coregistered 3D Xe lung ventilation and anatomical proton images of the human lung with compressed sensing.

Purpose: To develop and assess a method for acquiring coregistered proton anatomical and hyperpolarized Xe ventilation MR images of the lungs with compressed sensing (CS) in a single breath hold.

Methods: Retrospective CS simulations were performed on fully sampled ventilation images acquired from one healthy smoker to optimize reconstruction parameters. Prospective same-breath anatomical and ventilation images were also acquired in five ex-smokers with an acceleration factor of 3 for hyperpolarized Xe images, and were compared to fully sampled images acquired during the same session.

Comparison of quantitative multiple-breath specific ventilation imaging using colocalized 2D oxygen-enhanced MRI and hyperpolarized He MRI.

Two magnetic resonance specific ventilation imaging (SVI) techniques, namely, oxygen-enhanced proton (OE-H) and hyperpolarized He (HP-He), were compared in eight healthy supine subjects [age 32 (6) yr]. An in-house radio frequency coil array for H configured with the He transmit-receive coil in situ enabled acquisition of SVI data from two nuclei from the same slice without repositioning the subjects. After 3 × 3 voxel downsampling to account for spatial registration errors between the two SV images, the voxel-by-voxel correlation coefficient of two SV maps ranged from 0.

Comparison of He and Xe MRI for evaluation of lung microstructure and ventilation at 1.5T.

Background: To support translational lung MRI research with hyperpolarized Xe gas, comprehensive evaluation of derived quantitative lung function measures against established measures from He MRI is required. Few comparative studies have been performed to date, only at 3T, and multisession repeatability of Xe functional metrics have not been reported.

Purpose/hypothesis: To compare hyperpolarized Xe and He MRI-derived quantitative metrics of lung ventilation and microstructure, and their repeatability, at 1.

Supine posture changes lung volumes and increases ventilation heterogeneity in cystic fibrosis.

Introduction: Lung Clearance Index (LCI) is recognised as an early marker of cystic fibrosis (CF) lung disease. The effect of posture on LCI however is important when considering longitudinal measurements from infancy and when comparing LCI to imaging studies.

Methods: 35 children with CF and 28 healthy controls (HC) were assessed.

Spatial fuzzy c-means thresholding for semiautomated calculation of percentage lung ventilated volume from hyperpolarized gas and H MRI.

Purpose: To develop an image-processing pipeline for semiautomated (SA) and reproducible analysis of hyperpolarized gas lung ventilation and proton anatomical magnetic resonance imaging (MRI) scan pairs. To compare results from the software for total lung volume (TLV), ventilated volume (VV), and percentage lung ventilated volume (%VV) calculation to the current manual "basic" method and a K-means segmentation method.

Materials And Methods: Six patients were imaged with hyperpolarized He and same-breath lung H MRI at 1.

Regional Ventilation Changes in the Lung: Treatment Response Mapping by Using Hyperpolarized Gas MR Imaging as a Quantitative Biomarker.

Purpose To assess the magnitude of regional response to respiratory therapeutic agents in the lungs by using treatment response mapping (TRM) with hyperpolarized gas magnetic resonance (MR) imaging. TRM was used to quantify regional physiologic response in adults with asthma who underwent a bronchodilator challenge. Materials and Methods This study was approved by the national research ethics committee and was performed with informed consent.

Detection of early subclinical lung disease in children with cystic fibrosis by lung ventilation imaging with hyperpolarised gas MRI.

Hyperpolarised He ventilation-MRI, anatomical lung MRI, lung clearance index (LCI), low-dose CT and spirometry were performed on 19 children (6-16 years) with clinically stable mild cystic fibrosis (CF) (FEV>-1.96), and 10 controls. All controls had normal spirometry, MRI and LCI.

Multiple breath washout of hyperpolarized Xe and He in human lungs with three-dimensional balanced steady-state free-precession imaging.

Purpose: To compare quantitative fractional ventilation measurements from multiple breath washout imaging (MBW-I) using hyperpolarized He with both spoiled gradient echo (SPGR) and balanced steady-state free precession (bSSFP) three-dimensional (3D) pulse sequences and to evaluate the feasibility of MBW-I with hyperpolarized Xe.

Methods: Seven healthy subjects were scanned using He MBW-I with 3D SPGR and bSSFP sequences. Five also underwent MBW-I with Xe.

Reproducibility of quantitative indices of lung function and microstructure from Xe chemical shift saturation recovery (CSSR) MR spectroscopy.

Purpose: To evaluate the reproducibility of indices of lung microstructure and function derived from Xe chemical shift saturation recovery (CSSR) spectroscopy in healthy volunteers and patients with chronic obstructive pulmonary disease (COPD), and to study the sensitivity of CSSR-derived parameters to pulse sequence design and lung inflation level.

Methods: Preliminary data were collected from five volunteers on three occasions, using two implementations of the CSSR sequence. Separately, three volunteers each underwent CSSR at three different lung inflation levels.

Comparison of CT-based Lobar Ventilation with 3He MR Imaging Ventilation Measurements.

Purpose: To compare lobar lung ventilation computed from expiratory and inspiratory computed tomographic (CT) data with direct measurements of ventilation at hyperpolarized helium 3 ((3)He) magnetic resonance (MR) imaging by using same-breath hydrogen 1 ((1)H) MR imaging examinations to coregister the multimodality images.

Materials And Methods: The study was approved by the national research ethics committee, and written patient consent was obtained. Thirty patients with asthma underwent breath-hold CT at total lung capacity and functional residual capacity.

Quantification of regional fractional ventilation in human subjects by measurement of hyperpolarized 3He washout with 2D and 3D MRI.

Multiple-breath washout hyperpolarized (3)He MRI was used to calculate regional parametric images of fractional ventilation (r) as the ratio of fresh gas entering a volume unit to the total end inspiratory volume of the unit. Using a single dose of inhaled hyperpolarized gas and a total acquisition time of under 1 min, gas washout was measured by dynamic acquisitions during successive breaths with a fixed delay. A two-dimensional (2D) imaging protocol was investigated in four healthy subjects in the supine position, and in a second protocol the capability of extending the washout imaging to a three-dimensional (3D) acquisition covering the whole lungs was tested.