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The aim of this study was to validate oxygen-sensitive 3He-MRI in noninvasive determination of the regional, two- and three-dimensional distribution of oxygen partial pressure. In a gas-filled elastic silicon ventilation bag used as a lung phantom, oxygen sensitive two- and three-dimensional 3He-MRI measurements were performed at different oxygen concentrations which had been equilibrated in a range of normal and pathologic values. The oxygen partial pressure distribution was determined from 3He-MRI using newly developed software allowing for mapping of oxygen partial pressure. The reference bulk oxygen partial pressure inside the phantom was measured by conventional respiratory gas analysis. In two-dimensional measurements, image-based and gas-analysis results correlated with r=0.98; in three-dimensional measurements the between-methods correlation coefficient was r=0.89. The signal-to-noise ratio of three-dimensional measurements was about half of that of two-dimensional measurements and became critical (below 3) in some data sets. Oxygen-sensitive 3He-MRI allows for noninvasive determination of the two- and three-dimensional distribution of oxygen partial pressure in gas-filled airspaces. [ABSTRACT FROM AUTHOR]

The purpose of this study was to use cine-MRI during continuous respiration to measure the respiratory lumenal diameter change in the pharynx and at an upper tracheal level. Fifteen non-smokers and 23 chronic obstructive pulmonary disease (COPD) patients with smoking history (median 50 pack-years) were included. Cine-MRI with seven frames/s was performed during continuous respiration. Minimal and maximal cross-sectional lumenal diameters within the pharynx and the upper tracheal lumen area were measured. The median diameter change in the pharynx (tracheal area) was 70% (1.4 cm(2)) in volunteers and 76% (1.7 cm(2)) in smokers (P=0.98, P=0.04). Tracheal lumenal collapse was a median of 43% in volunteers and 64% in smokers (P=0.011). No clear disease-related difference of the pharynx-lumen was found. The maximal cross-sectional area of the upper trachea lumen as well as the respiratory collapse was larger in COPD patients than in normal subjects. This information is important for the modelling of ventilation and prediction of drug deposition, which are influenced by the airway diameter. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the possible contribution of (3)He-MRI to detect obliterative bronchiolitis (OB) in the follow-up of lung transplant recipients. Nine single- and double-lung transplanted patients were studied by an initial and a follow-up (3)He-MRI study. Images were evaluated subjectively by estimation of ventilation defect area and quantitatively by individually adapted threshold segmentation and subsequent calculation of ventilated lung volume. Bronchiolitis obliterans syndrome (BOS) was diagnosed using pulmonary function tests. At (3)He-MRI, OB was suspected if ventilated lung volume had decreased by 10% or more at the follow-up MRI study compared with the initial study. General accordance between pulmonary function testing and (3)He-MRI was good, although subjective evaluation of (3)He-MRI underestimated improvement in ventilation as obtained by pulmonary function tests. The (3)He-MRI indicated OB in 6 cases. According to pulmonary function tests, BOS was diagnosed in 5 cases. All diagnoses of BOS were also detected by (3)He-MRI. In 2 of these 5 cases, (3)He-MRI indicated OB earlier than pulmonary function tests. The results support the hypothesis that (3)He-MRI may be sensitive for early detection of OB and emphasize the need for larger prospective follow-up studies. [ABSTRACT FROM AUTHOR]