Symptomatic atherosclerotic occlusive disease of all supra-aortic arch vessels treated with total aortic arch rerouting.

We present an uncommon case of symptomatic atherosclerotic occlusive disease of all supra-aortic arch vessels and its surgical treatment by total aortic arch rerouting after endarteriectomy of all target vessels.

Intrapulmonary 3He gas distribution depending on bolus size and temporal bolus placement.

OBJECTIVE: Dynamic ventilation (3)He-MRI is a new method to assess pulmonary gas inflow. As differing airway diameters throughout the ventilatory cycle can influence gas inflow this study intends to investigate the influence of volume and timing of a He gas bolus with respect to the beginning of the tidal volume on inspiratory gas distribution. MATERIALS AND METHODS: An ultrafast 2-dimensional spoiled gradient echo sequence (temporal resolution 100 milliseconds) was used for dynamic ventilation (3)He-MRI of 11 anesthetized and mechanically ventilated pigs. The applied (3)He gas bolus was varied in volume between 100 and 200 mL. A 150-mL bolus was varied in its application time after the beginning of the tidal volume between 0 and 1200 milliseconds. Signal kinetics were evaluated using an in-house developed software after definition of parameters for the quantitative description of (3)He gas inflow. RESULTS: The signal rise time (time interval between signal in the parenchyma reaches 10% and 90% of its maximum) was prolonged with increasing bolus volume. The parameter was shortened with increasing delay of (3)He application after the beginning of the tidal volume. Timing variation as well as volume variation showed no clear interrelation to the signal delay time 10 (time interval between signal in the trachea reaches 50% of its maximum and signal in the parenchyma reaches 10% of its maximum). CONCLUSIONS: Dynamic ventilation (3)He-MRI is able to detect differences in bolus geometry performed by volume variation. Pulmonary gas inflow as investigated by dynamic ventilation (3)He-MRI tends to be accelerated by an increasing application delay of a (3)He gas bolus after the beginning of the tidal volume.

Oxygen-sensitive 3He-MRI in bronchiolitis obliterans after lung transplantation.

Oxygen-sensitive 3He-MRI was studied for the detection of differences in intrapulmonary oxygen partial pressure (pO2) between patients with normal lung transplants and those with bronchiolitis obliterans syndrome (BOS). Using software developed in-house, oxygen-sensitive 3He-MRI datasets from patients with normal lung grafts (n = 8) and with BOS (n = 6) were evaluated quantitatively. Datasets were acqiured on a 1.5-T system using a spoiled gradient echo pulse sequence. Underlying diseases were pulmonary emphysema (n = 10 datasets) and fibrosis (n = 4). BOS status was verified by pulmonary function tests. Additionally, 3He-MRI was assessed blindedly for ventilation defects. Median intrapulmonary pO2 in patients with normal lung grafts was 146 mbar compared with 108 mbar in patients with BOS. Homogeneity of pO2 distribution was greater in normal grafts (standard deviation pO2 34 versus 43 mbar). Median oxygen decrease rate during breath hold was higher in unaffected patients (-1.75 mbar/s versus -0.38 mbar/s). Normal grafts showed fewer ventilation defects (5% versus 28%, medians). Oxygen-sensitive 3He-MRI appears capable of demonstrating differences of intrapulmonary pO2 between normal lung grafts and grafts affected by BOS. Oxygen-sensitive 3He-MRI may add helpful regional information to other diagnostic techniques for the assessment and follow-up of lung transplant recipients.

Involvement of jugular valve insufficiency in cerebral venous air embolism.

BACKGROUND: Cerebral venous air entrapment is a rare finding on cranial computed tomography (CT) scan. Peripheral air embolism is discussed as a potential cause. However, the mechanism of retrograde passage through internal jugular valves and veins is unclear. CASE REPORT: The case of a patient is reported, who had air entrapment in the left cavernous sinus. Prior to CT scanning, a peripheral intravenous line had been placed. Ultrasound revealed excessive insufficiency of the left internal jugular valve. To further study the mechanism of embolism, an echo contrast agent was injected into the cubital vein. A Valsalva maneuver resulted in retrograde transition of microbubbles across the insufficient valve. Valvular function on the unaffected right side was intact. CONCLUSIONS: This case report gives insight into the mechanism of cerebral venous air embolism. This is the firstcase describing jugular valve insufficiency as the missing link between peripheral air embolism and cerebral venous air entrapment.

Two-dimensional and three-dimensional oxygen mapping by 3He-MRI validation in a lung phantom.

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.

Respiratory lumenal change of the pharynx and trachea in normal subjects and COPD patients: assessment by cine-MRI.

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.

Functional evaluation of emphysema using diffusion-weighted 3Helium-magnetic resonance imaging, high-resolution computed tomography, and lung function tests.

PURPOSE: To assess the emphysematous enlargement of distal airspaces and concomitant large and small airway disease using diffusion-weighted Helium-magnetic resonance imaging (MRI), high-resolution computed tomography (HRCT), and lung function tests (LFT). METHODS: Seven patients were examined after single lung transplantation (LTx) and 1 before double LTx for various forms of emphysema. Five patients after double LTx served as controls. Patients were assessed by Helium-MRI (apparent diffusion coefficient [ADC]), HRCT (mean lung density [MLD], emphysema index [EI]), and LFT. RESULTS: Transplanted lungs: mean ADC = 0.17 cm/s, MLD = -848 H, EI = 22%. Emphysematous lungs: mean ADC = 0.33 cm/s, MLD = -922 H; EI = 54%. Good correlations were found between ADC and MLD (r = 0.6), EI (r = 0.8), intrathoracic gas volume (r = 0.7), forced expiratory volume in 1 second (r = 0.7), and forced expiratory flows (r = 0.7). In contrast, HRCT only provided moderate correlations with LFT (EI: r = 0.5; MLD: r [le] 0.4). CONCLUSION: In this initial study, He-MRI yield good correlations with HRCT and agrees better than HRCT with the functional characterization of emphysema regarding hyperinflation, large and small airway disease as provided by LFT.

Functional analysis in single-lung transplant recipients: a comparative study of high-resolution CT, 3He-MRI, and pulmonary function tests.

OBJECTIVE: To develop and evaluate a postprocessing tool to quantify ventilated split-lung volumes on the basis of (3)He-MRI and to apply it in patients after single-lung transplantation (SLTX). High-resolution CT (HRCT) was employed as a reference modality providing split air-filled lung volumes. Lung volumes derived from pulmonary function test results served as clinical parameters and were used as the "gold standard." MATERIAL AND METHODS: Eight patients (mean age, 54 years) with emphysema and six patients (mean age, 58 years) with idiopathic pulmonary fibrosis. All patients were evaluated following SLTX. HRCT was performed during inspiration (slice thickness, 1 mm; increment, 10 mm). For correlation with (3)He-MRI, HRCT images were reconstructed in coronal orientation to match the same anatomic levels. Aerated lung was determined by threshold-based segmentation of CT. (3)He-MRI was performed on a 1.5-T scanner using a two-dimensional, fast low-angle shot sequence in coronal orientation covering the whole lung after inhalation of a 300-mL bolus of hyperpolarized (3)He gas followed by normal room air for the rest of the tidal volume. Lung segmentation on (3)He-MRI was done using different thresholds. RESULTS: In emphysematous patients, (3)He-MRI showed excellent correlation (r = 0.9) with vital capacity, while CT correlated (r = 0.8) with total lung capacity. (3)He-MRI correlated well with CT (r > 0.8) for grafts and native fibrotic lungs. In emphysematous lungs, MRI showed a good correlation (r = 0.7) with the nonemphysematous lung volume from CT. Increasing thresholds in (3)He-MRI reveal differences between aerated and ventilated lung areas with a different distribution in emphysema and fibrosis. CONCLUSIONS: (3)He-MRI is superior to CT in emphysema to demonstrate ventilated lung areas that participate in gas exchange. In fibrosis, (3)He-MRI and CT have a similar impact. The decrease pattern and the intraindividual ratio between ventilation of native and transplanted lungs will have to be investigated as a new surrogate for the ventilatory follow-up in patients undergoing SLTX.

(3)He-MRI in follow-up of lung transplant recipients.

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.

Magnetic resonance imaging using hyperpolarized 3He-Gas.

RATIONALE AND OBJECTIVES: Current imaging procedures of the lung concentrate on visualization of morphology. Computed tomography is the imaging method of choice for the majority of pulmonary diseases. Functional data are commonly obtained from arterial blood gas analysis, spirometry, and body plethysmography, which all suffer from lack of regional information. MATERIALS AND METHODS: Magnetic resonance imaging (MRI) of the lung has been advanced recently by the use of hyperpolarized 3He as a new contrast mechanism. Four different image acquisition modes are performed during a typical patient study. RESULTS: 3He-MRI yields functional information about the lung with a high spatial and temporal resolution, avoiding the risks of ionizing radiation. The method is currently limited by high costs and restricted availability of the gas. CONCLUSION: In this article, the experience obtained at the University of Mainz, being Europe's most experienced center performing 3He-MRI in humans, is reviewed against the international background.

Distribution of ventilation in lung transplant recipients: evaluation by dynamic 3He-MRI with lung motion correction.

RATIONALE AND OBJECTIVES: The ability of motion corrected dynamic 3He-magnetic resonance imaging (MRI) to discriminate distributional patterns of inhaled hyperpolarized 3He between different groups of lung transplant recipients was evaluated. METHODS: An ultrafast low-angle shot 2D sequence (temporal resolution 128 ms) was used for ventilation 3He-MRI of 11 single and 6 double lung transplant recipients. After digital motion correction, signal kinetics were evaluated in a tracheal and 7 pulmonary regions of interest. Results from grafts and native lungs as well as from normal and rejected grafts were compared with each other and to reference values from healthy subjects. RESULTS: In emphysema patients, median alveolar rise time, a parameter for increase of alveolar signal, was 0.28 seconds for the graft and 0.48 seconds for the native lung, in fibrosis patients its median was 0.46 seconds for the graft and 0.21 seconds for the native lung. In double lung recipients, alveolar rise time was 0.29 seconds in normal and clinically rejected grafts. CONCLUSIONS: Dynamic ventilation 3He-MRI discriminated normal lung grafts from diseased native lungs in single lung recipients. Graft rejection in double lung recipients could not be discriminated.

Dynamic ventilation (3)He-magnetic resonance imaging with lung motion correction: gas flow distribution analysis.

RATIONALE AND OBJECTIVES: Software was developed to correct for lung motion to improve the description of hyperpolarized (3)He gas distribution in the lung. METHODS: Five volunteers were studied by dynamic ventilation (3)He-MRI using an ultrafast FLASH 2D sequence with a temporal resolution of 128 milliseconds. Signal kinetics were evaluated in the trachea and seven parenchymal Regions of Interest. Reference ranges for healthy subjects were defined for motion-corrected and uncorrected images. RESULTS: Motion correction was successfully performed. Reference ranges were 0.11-1.21 seconds for tracheal transit time, 0-0.02 seconds for trachea-alveolar interval, 0.22-0.62 seconds for alveolar rise time and 0-76.6 arbitrary units for alveolar amplitude for motion corrected images, and 0-1.09 seconds, 0-0.11 seconds, 0.26-0.85 seconds, 46.4-99.8 arbitrary units for uncorrected images. CONCLUSIONS: Evaluation of (3)He-distribution in the lung using motion correction of dynamic (3)He-ventilation imaging is feasible and gives more narrow reference ranges.