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    Michael Puderbach

    Proton MRI is able to visualize the major changes in CF lung disease in a similar way to CT albeit there will be shortcomings in the detection of more subtle or smaller abnormalities. Further studies are warranted to determine whether the... more
    Proton MRI is able to visualize the major changes in CF lung disease in a similar way to CT albeit there will be shortcomings in the detection of more subtle or smaller abnormalities. Further studies are warranted to determine whether the additional structural detail provided by CT is necessary for the evaluation of the severity and progression of CF lung
    The purpose of this study was to describe the use of parallel imaging technique (PAT) using dynamic MRI in lung and tumour mobility during the breathing cycle. 20 patients with stage I non-small cell lung carcinoma were investigated using... more
    The purpose of this study was to describe the use of parallel imaging technique (PAT) using dynamic MRI in lung and tumour mobility during the breathing cycle. 20 patients with stage I non-small cell lung carcinoma were investigated using two dynamic gradient echo sequences with PAT (TrueFISP (fast imaging with steady precession), and fast low angle shot (FLASH). Craniocaudal distance
    To evaluate the influence of exposure parameters and raw-data based iterative reconstruction (IR) on the performance of computer-aided detection (CAD) of pulmonary nodules on chest multidetector computed tomography (MDCT). Seven porcine... more
    To evaluate the influence of exposure parameters and raw-data based iterative reconstruction (IR) on the performance of computer-aided detection (CAD) of pulmonary nodules on chest multidetector computed tomography (MDCT). Seven porcine lung explants were inflated in a dedicated ex vivo phantom shell and prepared with n=162 artificial nodules of a clinically relevant volume and maximum diameter (46-1063μl, and 6.2-21.5mm). n=118 nodules were solid and n=44 part-solid. MDCT was performed with different combinations of 120 and 80kV with 120, 60, 30 and 12mA*s, and reconstructed with both filtered back projection (FBP) and IR. Subsequently, 16 datasets per lung were subjected to dedicated CAD software. The rate of true positive, false negative and false positive CAD marks was measured for each reconstruction. The rate of true positive findings ranged between 88.9-91.4% for FBP and 88.3-90.1% for IR (n.s.) with most exposure settings, but was significantly lower with the combination of ...
    Magnetic resonance imaging (MRI) can provide regional information about lung structural changes in cystic fibrosis (CF), albeit at lower spatial and temporal resolution than computed tomography. The lack of ionizing radiation associated... more
    Magnetic resonance imaging (MRI) can provide regional information about lung structural changes in cystic fibrosis (CF), albeit at lower spatial and temporal resolution than computed tomography. The lack of ionizing radiation associated with MRI may make MRI an attractive alternative to computed tomography in applications in which repeated or serial scanning is desired. Furthermore, MRI can provide functional information about the lung, which may prove to be a useful outcome measure in CF. In this article, the MRI findings of CF are described, and the newer functional magnetic resonance techniques for imaging the lung are discussed.
    To develop a validated post-processing routine for volumetry of the ventilated airspaces by 3He MRI. 3Helium MRI and pulmonary function tests were performed in seven healthy volunteers. After segmentation of ventilated airspaces, their... more
    To develop a validated post-processing routine for volumetry of the ventilated airspaces by 3He MRI. 3Helium MRI and pulmonary function tests were performed in seven healthy volunteers. After segmentation of ventilated airspaces, their volumes were calculated. Functional residual capacity (FRC) was used as a reference. For comparison of absolute volumes, correction factors were evaluated. Mean lung volume (+/- standard deviation) calculated from 3He MRI was 4,082 +/- 908 mL and mean FRC was 3,696 +/- 1166 mL, with a mean difference of 386 mL (r = 0.88). After correction for the relative pulmonary air content (factor 0.82), posture (0.72), and the individual tidal volume, 3He MRI volume was 3,348 +/- 744 mL and mean FRC was 3,422 +/- 817 mL, with the mean difference down to -74 mL (r = 0.9). Comparison on an individual basis confirmed an improvement in the estimation of absolute lung volume. Volumetry of ventilated lung from 3He MRI shows high correlation and good agreement with the ...
    To analyse the flow in natural geometries of central airways an interdisciplinary project by medical and engineering partners has been created. The work presented summarises necessary developments, preliminary investigations and new... more
    To analyse the flow in natural geometries of central airways an interdisciplinary project by medical and engineering partners has been created. The work presented summarises necessary developments, preliminary investigations and new insights into the unsteady flow with a focus on numerical fluid mechanics. The objective of the investigations is the analysis and physical understanding of the dynamic flow in central
    The purpose of this study was to evaluate in vivo the influence of inversion pulse slice selectivity on oxygen-enhanced magnetic resonance imaging (MRI). Thirteen healthy volunteers were studied with a two-dimensional cardiac- and... more
    The purpose of this study was to evaluate in vivo the influence of inversion pulse slice selectivity on oxygen-enhanced magnetic resonance imaging (MRI). Thirteen healthy volunteers were studied with a two-dimensional cardiac- and respiratory-gated adiabatic inversion-recovery half-Fourier single-shot turbo spin-echo (HASTE) sequence with either slice-selective or non-slice-selective inversion recovery (IR) pulse at inversion times increasing from 300 to 1400 ms. The signal-to-noise ratio (SNR) at every inversion time (TI), real signal difference (ΔSI), and relative enhancement ratio of lung parenchyma at TI ≥ 800 ms were statistically compared for oxygen-enhanced and non-oxygen-enhanced MR images with slice-selective or non-slice-selective IR pulses. The SNRs of acquisitions with slice-selective IR pulses were significantly higher than those of non-slice-selective IR pulses (P < 0.05). At TI 800 ms, the ΔSI of lung parenchyma on IR-HASTE images with slice-selective inversion pulse type was significantly higher than on that with the non-slice-selective type (P < 0.05). Relative enhancement ratios of the slice-selective IR pulses were significantly lower than those of non-slice-selective IR pulses at TIs between 800 and 1400 ms (P < 0.05). Slice selectivity of inversion pulse type affects oxygen-enhanced MRI in vivo.
    To develop a model for exactly reproducible respiration motion simulations of animal lung explants inside an MR-compatible chest phantom. The materials included a piston pump and a flexible silicone reconstruction of a porcine diaphragm... more
    To develop a model for exactly reproducible respiration motion simulations of animal lung explants inside an MR-compatible chest phantom. The materials included a piston pump and a flexible silicone reconstruction of a porcine diaphragm and were used in combination with an established MR-compatible chest phantom for porcine heart-lung preparations. The rhythmic inflation and deflation of the diaphragm at the bottom of the artificial thorax with water (1 - 1.5 L) induced lung tissue displacement resembling diaphragmatic breathing. This system was tested on five porcine heart-lung preparations using 1.5T MRI with transverse and coronal 3D-GRE (TR/TE = 3.63/1.58, 256 x 256 matrix, 350 mm FOV, 4 mm slices) and half Fourier T2-FSE (TR/TE = 545/29, 256 x 192, 350 mm, 6 mm) as well as multiple row detector CT (16 x 1 mm collimation, pitch 1.5, FOV 400 mm, 120 mAs) acquired at five fixed inspiration levels. Dynamic CT scans and coronal MRI with dynamic 2D-GRE and 2D-SS-GRE sequences (image frequencies of 10/sec and 3/sec, respectively) were acquired during continuous "breathing" (7/minute). The position of the piston pump was visually correlated with the respiratory motion visible through the transparent wall of the phantom and with dynamic displays of CT and MR images. An elastic body splines analysis of the respiratory motion was performed using CT data. Visual evaluation of MRI and CT showed three-dimensional movement of the lung tissue throughout the respiration cycle. Local tissue displacement inside the lung explants was documented with motion maps calculated from CT. The maximum displacement at the top of the diaphragm (mean 26.26 [SD 1.9] mm on CT and 27.16 [SD 1.5] mm on MRI, respectively [p = 0.25; Wilcoxon test]) was in the range of tidal breathing in human patients. The chest phantom with a diaphragmatic pump is a promising platform for multi-modality imaging studies of the effects of respiratory lung motion.
    Supplementing global spirometry with regional information could allow for earlier and more specific diagnosis of lung disease. Dynamic magnetic resonance imaging (dMRI) makes it possible to derive functional parameters from the... more
    Supplementing global spirometry with regional information could allow for earlier and more specific diagnosis of lung disease. Dynamic magnetic resonance imaging (dMRI) makes it possible to derive functional parameters from the visualization of the pulmonary motion of single lungs. The aim of this study was to compare high temporal resolution measurements of left and right thoracic diameters to simultaneously acquired spirometry. 10 healthy volunteers underwent 2-dimensional dMRI of both lungs at 1.5 T. Spirometry was performed simultaneously with an MRI-compatible spirometer. Thoracic diameters were measured semiautomatically and compared to simultaneously measured spirometric volumes. A dMRI surrogate for the Tiffeneau Index was compared to the spirometric Tiffeneau. The volume-time and flow-volume curves from dMRI were very similar to the spirometric curves. The semiautomatically measured diameters correlated well with the spirometric volumes (r > = 0.8, p < 10 - 15). Agreement between the methods at full temporal resolution was not as convincing (width of 95 % limits of agreement interval up to 56 %). Good agreement was found between the Tiffenau surrogate and spirometry (width of 95 % limits of agreement interval of 14.5 %). DMRI with semiautomatic measurement of thoracic diameters makes measurement of realistic volume-time and flow-volume curves from single lungs possible. The derived single lung Tiffeneau Index shows good agreement to spirometry and could be valuable to supplement global spirometric measurements with functional data from single lungs.
    Assessment of lung cancer perfusion is impaired by respiratory motion. Imaging times for contrast agent wash-out studies often exceed breath hold capabilities, and respiration triggering reduces temporal resolution. Temporally resolved... more
    Assessment of lung cancer perfusion is impaired by respiratory motion. Imaging times for contrast agent wash-out studies often exceed breath hold capabilities, and respiration triggering reduces temporal resolution. Temporally resolved volume acquisition of entire tumors is required to assess heterogeneity. Therefore, we developed and evaluated an MR measurement technique that exceeds a single breath hold, and provides a variable temporal resolution during acquisition while suspending breath-dependent motion. 20 patients with suspected lung cancer were subjected to perfusion studies using a spoiled 3D gradient echo sequence after bolus injection of 0.07 mmol/kg body weight of Gd-DTPA. 10 acquisitions in expiratory breath hold were followed by 50 navigator-triggered acquisitions under free breathing. Post-processing allowed for co-registration of the 3D data sets. An ROI-based visualization of the signal-time curves was performed. In all cases motion-suspended, time-resolved volume data sets (40 x 33 x 10 cm(3), voxel size: 2.1 x 2.1 x 5.0 mm(3)) were generated with a variable, initially high temporal resolution (2.25 sec) that was synchronized with the breath pattern and covered up to 8 1/2 min. In 7 / 20 cases a remaining offset could be reduced by rigid co-registration. The tumors showed fast wash-in, followed by rapid signal decay (8 / 20) or a plateau. The feasibility of a perfusion study with hybrid breath hold and navigator-triggered time-resolved 3D MRI which combines high initial temporal resolution during breath hold with a long wash-out period under free breathing was demonstrated.
    To assess the influence of tumor diameter on tumor mobility and motion of the tumor bearing hemithorax during the whole breathing cycle in patients with stage I non-small-cell lung cancer (NSCLC) using dynamic MRI. Breathing cycles of... more
    To assess the influence of tumor diameter on tumor mobility and motion of the tumor bearing hemithorax during the whole breathing cycle in patients with stage I non-small-cell lung cancer (NSCLC) using dynamic MRI. Breathing cycles of thirty-nine patients with solitary NSCLCs were examined using a trueFISP sequence (three images per second). Patients were divided into three groups according to the maximal tumor diameter in the transverse plane (<3, 3-5 and >5 cm). Continuous time-distance curves and deep inspiratory and expiratory positions of the chest wall, the diaphragm and the tumor were measured in three planes. Motion of tumor-bearing and corresponding contralateral non-tumor bearing regions was compared. Patients with a tumor >3 cm showed a significantly lower diaphragmatic motion of the tumor bearing compared with the non-tumor bearing hemithorax in the craniocaudal (CC) directions (tumors 3-5 cm: 23.4+/-1.2 vs 21.1+/-1.5 cm (P<0.05); tumors >5 cm: 23.4+/-1.2 vs 20.1+/-1.6 cm (P<0.01). Tumors >5 cm in the lower lung region showed a significantly lower mobility compared with tumors <3 cm (1.8+/-1.0 vs 3.8+/-0.7 cm, P<0.01) in the CC directions. Dynamic MRI is a simple non-invasive method to differentiate mobility of tumors with different diameters and its influence on the surrounding tissue. Tumor diameter has a significant influence on tumor mobility and this might be taken into account in future radiotherapy planning.
    To evaluate partially parallel three-dimensional (3D) magnetic resonance (MR) imaging for assessment of regional lung perfusion in healthy volunteers and patients suspected of having lung cancer or metastasis. Seven healthy volunteers and... more
    To evaluate partially parallel three-dimensional (3D) magnetic resonance (MR) imaging for assessment of regional lung perfusion in healthy volunteers and patients suspected of having lung cancer or metastasis. Seven healthy volunteers and 20 patients suspected of having lung cancer or metastasis were examined with 3D gradient-echo MR imaging with partially parallel image acquisitions (fast low-angle shot 3D imaging; repetition time msec/echo time msec, 1.9/0.8; flip angle, 40 degrees; acceleration factor, two; number of reference k-space lines for calibration, 24; field of view, 500 x 440 mm; matrix, 256 x 123; slab thickness, 160 mm; number of partitions, 32; voxel size, 3.6 x 2.0 x 5.0 mm(3); acquisition time, 1.5 seconds) after administration of 0.1 mmol/kg of gadobenate dimeglumine. In volunteers, 3D MR perfusion data sets were assessed for topographic and temporal distribution of regional lung perfusion. Sensitivity, specificity, accuracy, and positive and negative predictive values for perfusion MR imaging for detecting perfusion abnormalities in patients were calculated, with conventional radionuclide perfusion scintigraphy as the standard of reference. Interobserver and intermodality agreement was determined by using kappa statistics. Topographic analysis of lung perfusion in volunteers revealed a significantly higher signal-to-noise ratio (SNR) of up to 327% in gravity-dependent lung areas. Temporal analysis similarly revealed much shorter lag time to peak enhancement in gravity-dependent lung areas. In patients, perfusion MR imaging achieved high sensitivity (88%-94%), specificity (100%), and accuracy (90%-95%) for detection of perfusion abnormalities. Interobserver agreement (kappa = 0.86) was very good and intermodality agreement (kappa = 0.69-0.83) was good to very good for detection of perfusion defects. A significant difference (P <.0001) in SNR was observed between normally perfused lung (14 +/- 7 [SD]) and perfusion defects (7 +/- 4) in patients. Partially parallel MR imaging with high spatial and temporal resolution allows assessment of regional lung perfusion and has high diagnostic accuracy for detecting perfusion abnormalities.
    MRI with hyperpolarized helium-3 ((3)He) provides high-resolution imaging of ventilated airspaces. The first aim of this (3)He-study was to compare observations of localized signal defects in healthy smokers and non-smokers. A second aim... more
    MRI with hyperpolarized helium-3 ((3)He) provides high-resolution imaging of ventilated airspaces. The first aim of this (3)He-study was to compare observations of localized signal defects in healthy smokers and non-smokers. A second aim was to describe relationships between parameters of lung function, volume of inspired (3)He and signal-to-noise ratio. With Ethics Committee approval and informed consent, 12 healthy volunteers (seven smokers and five non-smokers) were studied. Imaging was performed in a 1.5 T scanner using a two-dimensional FLASH sequence at 30V transmitter amplitude (TR/TE/alpha = 11 ms/4.2 ms/<10 degrees ). Known amounts of (3)He were inhaled from a microprocessor-controlled delivery device and imaged during single breath-holds. Images were evaluated visually, and scored using a prospectively defined 'defect-index'. Signal-to-noise ratio of the images were correlated with localization, (3)He volumes and static lung volumes. Due to poor image quality studies of two smokers were not eligible for the evaluation. Smokers differed from non-smokers in total number and size of defects: the 'defect-index' of smokers ranged between 0.8 and 6.0 (median = 1.1), that of non-smokers between 0.1 and 0.8 (median = 0.4). Intraindividually, an anteroposterior gradient of signal-to-noise ratio was apparent. Signal-to-noise ratio correlated with the estimated amount of hyperpolarization administered (r = 0. 77), but not with static lung volumes. We conclude that (3)He MRI is a sensitive measure to detect regional abnormalities in the distribution of ventilation in clinically healthy persons with normal pulmonary function tests.
    Acute voluntary lung hyperinflation provoked by glossopharyngeal insufflation (GI) elicits numerous, possibly deleterious, effects on the cardiopulmonary system by increasing intrathoracic pressures far above normal values. This study... more
    Acute voluntary lung hyperinflation provoked by glossopharyngeal insufflation (GI) elicits numerous, possibly deleterious, effects on the cardiopulmonary system by increasing intrathoracic pressures far above normal values. This study quantifies acute pulmonary hemodynamics during GI using phase-contrast magnetic resonance imaging (MRI). Hemodynamic parameters were measured in nine elite male breath hold divers with a mean age of 30 yr (range = 20-43 yr) by velocity-encoding cine (VEC)-MRI of the main pulmonary artery (PA) before, during, and after GI. Simultaneously, GI-lung volume (GIVEC-MRI) was measured by MR-compatible spirometry. Hemodynamic parameters were associated with GIVEC-MRI. Highly significant changes during GI were shown for the mean flow in the PA, which decreased by 45% (P < 0.007), and right ventricular output and cardiac index, which decreased by 41% and 40%, respectively (P < 0.007). Acceleration time also decreased highly significant by 36% during GI (P < 0.007). All hemodynamic parameters except acceleration time returned to baseline after GI. Acute voluntary lung hyperinflation mimics changes seen in pulmonary arterial hypertension, but unlike the latter, these changes are fully reversible shortly after cessation of voluntary lung hyperinflation. Persistent changes due to repetitive GI could not be detected.
    To demonstrate the influence of inversion pulse type and inversion time for assessment of oxygen-enhancement on centrically-reordered non-slice-selective inversion-recovery (IR) half-Fourier single-shot turbo spin-echo (HASTE) sequence.... more
    To demonstrate the influence of inversion pulse type and inversion time for assessment of oxygen-enhancement on centrically-reordered non-slice-selective inversion-recovery (IR) half-Fourier single-shot turbo spin-echo (HASTE) sequence. Phantoms with and without 100% oxygen and three healthy volunteers were studied with two-dimensional (2D) centrically-reordered non-slice selective IR-HASTE sequence with either composite or block inversion-recovery pulse at increasing inversion times from 200 to 1800 msec. Signal-to-noise ratios (SNRs) of phantom, real signal differences, and relative enhancement ratios of lung parenchyma between oxygen-enhanced and non-oxygen-enhanced MR images on composite and block pulse type were statistically compared at each TI. SNRs at TIs of 200 and 400 msec using the composite inversion pulse type were significantly lower than those with the block inversion pulse in the in vivo study (P < 0.05), although no significant differences were observed in the phantom study and in the in vivo study at inversion times greater than or equal to 600 msec. Real signal intensity (SI) differences at 400 and 600 msec of the composite inversion pulse type were significantly higher than those with the block inversion pulse type (P < 0.05). Relative enhancement ratio at 800 msec with the composite inversion pulse were significantly lower than that with the block inversion pulse (P < 0.05). IR pulse type and inversion time have influence on assessment of oxygen-enhancement by centrically-reordered non-slice-selective IR-HASTE sequence.
    To compare different unenhanced magnetic resonance angiography (MRA) techniques for quantitative evaluation of vessel lumen in an experimental setting in young pigs whose dimensions allow for a comparison with a pediatric population.... more
    To compare different unenhanced magnetic resonance angiography (MRA) techniques for quantitative evaluation of vessel lumen in an experimental setting in young pigs whose dimensions allow for a comparison with a pediatric population. Magnetic resonance imaging was performed in 5 healthy ventilated pigs at 1.5 T. Three different electrocardiogram (ECG)-triggered sequences were applied for MRA: [TSE-Db] T2-weighted dark-blood TurboSpinEcho (2.0 x 1.1 x 4 mm3); [trueFISP] 2D-steady-state-free-precession (2.2 x 1.8 x 2 mm3); [NAV] respiratory-gated, T2-prepared 3D-trueFISP (1.3 x 1.3 x 1.3 mm3). ECG-gated-CT angiography (CTA) (16-row CT, 1 mm collimation) served as the standard of reference. The vessel lumen was measured at 7 positions perpendicularly angulated to the vessel wall on multiplanar reformations: ascending aorta (P1), the aortic arch before (P2) and after (P3) the origin of the first supraaortic branch, the aortic arch after the origin of the second supraaortic branch (P4), the descending aorta at the level of the diaphragm (P5), and the first and second supraaortic branches (P6, P7). Percentage differences in the vessel area determined by MRA reformation compared with CTA-reformation were 10% +/- 20% and 35% +/- 27% (TSE-Db), -4% +/- 13% and 20% +/- 24% (trueFISP), and -3% +/- 13% and -10% +/- 19% (NAV), for positions P1 to P5 and P6 to P7, respectively. A significant difference from CTA was found for TSE-Db at all positions, and for trueFISP only at positions P6 and P7. Unenhanced MRA techniques allow for a reliable assessment of the dimensions of the thoracic aorta compared with CTA as the standard of reference. Using ECG-gating and navigator techniques, the free-breathing approach showed the best agreement with CTA. This technique may therefore be the most useful in the pediatric age group allowing for true 3D data acquisition with its inherent postprocessing possibilities.
    To investigate diaphragm and chest wall motion during the whole breathing cycle using magnetic resonance imaging (MRI) and a volumetric model in correlation with spirometry. Breathing cycles of 15 healthy volunteers were examined using a... more
    To investigate diaphragm and chest wall motion during the whole breathing cycle using magnetic resonance imaging (MRI) and a volumetric model in correlation with spirometry. Breathing cycles of 15 healthy volunteers were examined using a trueFISP sequence (5 slices in 3 planes, 3 images per second). Time-distance curves were calculated and correlated to spirometry. A model for vital capacity (VC), continuous time-dependent vital capacity (tVC), and investigating the influence of horizontal and vertical parameters on tVC was introduced. Time-distance curves of the breathing cycle using MRI correlated highly significant with spirometry (P < 0.0001). VC calculated by the model was similar to VC measured in spirometry (5.00 L vs. 5.15 L). tVC correlated highly significantly with spirometry (P < 0.0001). Vertical parameters had a more profound influence on tVC change than horizontal parameters. Dynamic MRI is a simple noninvasive method to evaluate local chest wall motion and respiratory mechanics. It widens the repertoire of tools for lung examination with a high temporal resolution.
    As pulmonary complications are life limiting in patients with cystic fibrosis (CF), repeated chest imaging [chest x-ray, computed tomography (CT)] is needed for follow up. With the continuously rising life expectancy of CF patients,... more
    As pulmonary complications are life limiting in patients with cystic fibrosis (CF), repeated chest imaging [chest x-ray, computed tomography (CT)] is needed for follow up. With the continuously rising life expectancy of CF patients, magnetic resonance imaging (MRI) as a radiation-free imaging modality might become more and more attractive. The goal of this study was to prospectively assess the value of MRI for evaluation of morphologic pulmonary CF-changes in comparison to established imaging modalities. Thirty-one CF patients (19 female, 12 male; mean age 16.7 years) with stable lung disease were examined by MRI: HASTE, coronal/transversal (TR/TE/alpha/TA: infinite/28 ms/180 degrees /18 s), multi-detector computed tomography (MDCT) (30 patients): 120 kV, dose modulated mAs, and chest x-ray (21 patients). Image evaluation: random order, 4 chest radiologists in consensus; chest x-ray: modified Chrispin-Norman score; CT and MRI: modified Helbich score. The maximal attainable score for chest x-ray was 34, for MRI and CT 25. Median scores, Pearson correlation coefficients, Bland-Altman plots, and concordance of MRI to CT on a lobar and segmental basis were calculated. The median MRI and MDCT scores were 13 (min 3, max 20) respectively 13.5 (min 0, max 20). The median chest x-ray score was 14 (min 5, max 32). Pearson correlation coefficients: MRI/CT = 0.80, P < 0.0001; MRI/chest x-ray = 0.63, P < 0.0018; chest x-ray/CT = 0.75, P < 0.0001. The median lobe related concordance was 80% for bronchiectasis, 77% for mucus plugging, 93%, for sacculation/abscesses, and 100% for collapse/consolidation. Morphologic MRI of the lung in CF patients demonstrates comparable results to MDCT and chest x-ray. Because radiation exposure is an issue in CF patients, MRI might have the ability to be used as an appropriate alternative method for pulmonary imaging.
    To compare the image quality and lesion contrast of lung MRI using 5 different pulse sequences at 1.5 T and 3 T. Lung MRI was performed at 1.5 T and 3 T using 5 pulse sequences which have been previously proposed for lung MRI: 3D... more
    To compare the image quality and lesion contrast of lung MRI using 5 different pulse sequences at 1.5 T and 3 T. Lung MRI was performed at 1.5 T and 3 T using 5 pulse sequences which have been previously proposed for lung MRI: 3D volumetric interpolated breath-hold examination (VIBE), true fast imaging with steady-state precession (TrueFISP), half-Fourier single-shot turbo spin-echo (HASTE), short tau inversion recovery (STIR), T2-weighted turbo spin-echo (TSE). In addition to 4 healthy volunteers, 5 porcine lungs were examined in a dedicated chest phantom. Lung pathology (nodules and infiltrates) was simulated in the phantom by intrapulmonary and intrabronchial injections of agarose. CT was performed in the phantom for correlation. Image quality of the sequences was ranked in a side-by-side comparison by 3 blinded radiologists regarding the delineation of pulmonary and mediastinal anatomy, conspicuity of pulmonary nodules and infiltrates, and presence of artifacts. The contrast of nodules and infiltrates (CNODULES and CINFILTRATES) defined by the ratio of the signal intensities of the lesion and adjacent normal lung parenchyma was determined. There were no relevant differences regarding the preference for the individual sequences between both field strengths. TSE was the preferred sequence for the visualization of the mediastinum at both field strengths. For the visualization of lung parenchyma the observers preferred TrueFISP in volunteers and TSE in the phantom studies. At both field strengths VIBE achieved the best rating for the depiction of nodules, whereas HASTE was rated best for the delineation of infiltrates. TrueFISP had the fewest artifacts in volunteers, whereas STIR showed the fewest artifacts in the phantom. For all but the TrueFISP sequence the lesion contrast increased from 1.5 T to 3 T. At both field strengths VIBE showed the highest CNODULES (6.6 and 7.1) and HASTE the highest CINFILTRATES (6.1 and 6.3). The imaging characteristics of different pulse sequences used for lung MRI do not substantially differ between 1.5 T and 3 T. A higher lesion contrast can be expected at 3 T.
    We sought to investigate lung volume and surface measurements during the breathing cycle using dynamic three-dimensional magnetic resonance imaging (3D MRI). Breathing cycles of 20 healthy volunteers were examined using a 2D trueFISP... more
    We sought to investigate lung volume and surface measurements during the breathing cycle using dynamic three-dimensional magnetic resonance imaging (3D MRI). Breathing cycles of 20 healthy volunteers were examined using a 2D trueFISP sequence (3 images/second) in combination with a model and segmented 3D FLASH sequence (1 image/second) MR images using view sharing. Segmentation was performed semiautomatically using an interactive region growing technique. Vital capacity (VC) was calculated from MRI using the model (2D) and counting the voxels (3D) and was compared with spirometry. VC from spirometry was 4.9+/-0.9 L, 4.4+/-1.2 L from 2D MRI measurement, and 4.7+/-0.9 L for 3D MRI. Using the 3D technique, correlation to spirometry was higher than using the 2D technique (r>0.95 vs. r>0.83). Using the 3D technique, split lung volumes and lung surface could be calculated. There was a significant difference between the left and right lung volume in expiration (P<0.05). Dynamic 3D MRI is a noninvasive tool to evaluate split lung volumes and lung surfaces during the breathing cycle with a high correlation to spirometry.
    To compare 1.0 M gadobutrol and 0.5 M Gd-DTPA for contrast-enhanced three-dimensional pulmonary perfusion magnetic resonance imaging (3D MRI). Ten healthy volunteers (3 females; 7 males; median age, 27 years; age range, 18-31 years) were... more
    To compare 1.0 M gadobutrol and 0.5 M Gd-DTPA for contrast-enhanced three-dimensional pulmonary perfusion magnetic resonance imaging (3D MRI). Ten healthy volunteers (3 females; 7 males; median age, 27 years; age range, 18-31 years) were examined with contrast-enhanced dynamic 3D MRI with parallel acquisition technique (FLASH 3D; reconstruction algorithm: generalized autocalibrating partially parallel acquisitions; acceleration factor: 2; TE/TR/alpha: 0.8/1.9 milliseconds/40 degrees; FOV: 500 x 375 mm; matrix: 256 x 86; slab thickness: 180 mm; 36 partitions; voxel size: 4.4 x 2 x 5 mm; TA: 1.48 seconds). Twenty-five consecutive data sets were acquired after intravenous injection of 0.025, 0.05, and 0.1 mmol/kg body weight of gadobutrol and Gd-DTPA. Quantitative measurements of peak signal-to-noise ratios (SNR) of both lungs were performed independently by 3 readers. Bolus transit times through the lungs were assessed from signal intensity time curves. The peak SNR in the lungs was comparable between gadobutrol and Gd-DTPA at all dose levels (15.7 vs. 15.5 at 0.1 mmol/kg bw; 12.9 vs. 12.5 at 0.05 mmol/kg bw; 7.6 vs. 8.9 at 0.025 mmol/kg bw). A dose of 0.1 mmol/kg achieved the highest peak SNR compared with all other dose levels (P < 0.05). A higher peak SNR was observed in gravity dependent lung (P < 0.05). Despite different injection volumes, transit times of the contrast bolus did not differ between both agents. Higher concentrated gadolinium chelates offer no advantage over standard 0.5 M Gd-DTPA for contrast-enhanced 3D MRI of lung perfusion.
    To monitor lung motion in patients with malignant pleural mesothelioma (MPM) before and after chemotherapy (CHT) using 2-dimensional (2D) and 3-dimensional (3D) dynamic MRI (dMRI) in comparison with spirometry. Twenty-two patients with... more
    To monitor lung motion in patients with malignant pleural mesothelioma (MPM) before and after chemotherapy (CHT) using 2-dimensional (2D) and 3-dimensional (3D) dynamic MRI (dMRI) in comparison with spirometry. Twenty-two patients with MPM were examined before CHT, as well as after 3 and 6 CHT cycles (3 months and 6 months) using 2D dMRI (trueFISP; 3 images/s) and 3D dMRI (FLASH 3D, 1 slab (52 slices)/s) using parallel imaging in combination with view-sharing technique. Maximum craniocaudal lung dimensions (2D) and lung volumes (3D) were monitored, separated into the tumor-bearing and nontumor-bearing hemithorax. Vital capacity (VC) was measured for comparison using spirometry. Using 2D technique, there was a significant difference between the tumor-bearing and the nontumor-bearing hemithorax before CHT (P < 0.01) and after 3 CHT cycles (P < 0.05), whereas difference was not significant in the second control. In the tumor-bearing hemithorax, mobility increased significantly from the status before versus after 3 CHT cycles (4.1 +/- 1.1 cm vs. 4.8 +/- 1.4 cm, P < 0.05). Using 3D technique, at maximum inspiration, the volume of the tumor-bearing hemithorax was 0.6 +/- 0.4 L and of the nontumor-bearing hemithorax 1.25 +/- 0.4 L before CHT. In the follow-up exams, these volumes changed to 1.05 +/- 0.4 L (P < 0.05) and 1.4 +/- 0.5 L, respectively. Using spirometry, there was no significant change in VC (1.9 +/- 0.4 L vs. 2.2 +/- 0.7 L vs. 2.2 +/- 0.9 L). dMRI is capable of monitoring changes in lung motion and volumetry in patients with MPM not detected by global spirometry. Thus, dMRI is proposed for use as a further measure of therapy response.
    The effect of breathholding on pulmonary perfusion remains largely unknown. The aim of this study was to assess the effect of inspiratory and expiratory breathhold on pulmonary perfusion using quantitative pulmonary perfusion magnetic... more
    The effect of breathholding on pulmonary perfusion remains largely unknown. The aim of this study was to assess the effect of inspiratory and expiratory breathhold on pulmonary perfusion using quantitative pulmonary perfusion magnetic resonance imaging (MRI). Nine healthy volunteers (median age, 28 years; range, 20-45 years) were examined with contrast-enhanced time-resolved 3-dimensional pulmonary perfusion MRI (FLASH 3D, TR/TE: 1.9/0.8 ms; flip angle: 40 degrees; GRAPPA) during end-inspiratory and expiratory breathholds. The perfusion parameters pulmonary blood flow (PBF), pulmonary blood volume (PBV), and mean transit time (MTT) were calculated using the indicator dilution theory. As a reference method, end-inspiratory and expiratory phase-contrast (PC) MRI of the pulmonary arterial blood flow (PABF) was performed. There was a statistically significant increase of the PBF (delta = 182 mL/100 mL/min), PBV (delta = 12 mL/100 mL), and PABF (delta = 0.5 L/min) between inspiratory and expiratory breathhold measurements (P < 0.0001). Also, the MTT was significantly shorter (delta = -0.5 sec) at expiratory breathhold (P = 0.03). Inspiratory PBF and PBV showed a moderate correlation (r = 0.72 and 0.61, P < or = 0.008) with inspiratory PABF. Pulmonary perfusion during breathhold depends on the inspiratory level. Higher perfusion is observed at expiratory breathhold.
    To analyse the dynamic flow in central airways, a workflow has been established which finally enables numerical simulation with simultaneous consideration of natural deformed geometries and inversion of flow direction. A comprehensive... more
    To analyse the dynamic flow in central airways, a workflow has been established which finally enables numerical simulation with simultaneous consideration of natural deformed geometries and inversion of flow direction. A comprehensive description of the radiologic experiments, the segmentation methods and the simulation procedure is given. Finally results gained from simulations in static and dynamic airways are presented and discussed.
    Goals of our study were to compare the pulmonary hemodynamics between healthy volunteers and patients with pulmonary arterial hypertension (PAH) and correlate MR flow measurements with echocardiography. Twenty-five patients with PAH and... more
    Goals of our study were to compare the pulmonary hemodynamics between healthy volunteers and patients with pulmonary arterial hypertension (PAH) and correlate MR flow measurements with echocardiography. Twenty-five patients with PAH and 25 volunteers were examined at 1.5 T. Phase-contrast flow measurements were performed in the ascending aorta and pulmonary trunk, resulting in the following parameters: peak velocity (cm/s), average blood flow (l/min), time to peak velocity (ms), velocity rise gradient and pulmonary distensibility (cm(2)). The bronchosystemic shunt was calculated. In PAH patients transthoracic echocardiography and right-heart catheterization (RHC) served as the gold standard. In comparison to volunteers, the PAH patients showed significantly reduced pulmonary velocities (P = 0.002), blood flow (P = 0.002) and pulmonary distensibility (P = 0.008). In patients, the time to peak velocity was shorter (P<0.001), and the velocity rise gradient was steeper (P = 0.002) than in volunteers. While in volunteers the peak velocity in the aorta was reached earlier, it was the reverse in patients. Patients showed a significant bronchosystemic shunt (P = 0.01). No meaningful correlation was found between MRI measurements and echocardiography or RHC. MRI is a feasible technique for the differentiation between PAH and volunteers. Further studies have to be conducted for the absolute calculation of pressure estimates.
    A frequent side effect after radiotherapy of lung tumors is a decrease of pulmonary function accompanied by dyspnea due to developing lung fibrosis. The aim of this study was to monitor lung motion as a correlate of pulmonary function and... more
    A frequent side effect after radiotherapy of lung tumors is a decrease of pulmonary function accompanied by dyspnea due to developing lung fibrosis. The aim of this study was to monitor lung motion as a correlate of pulmonary function and intrathoracic tumor mobility before and after radiotherapy (RT) using dynamic MRI (dMRI). Thirty-five patients with stage I non-small-cell lung carcinoma were examined using dMRI (trueFISP; three images/s). Tumors were divided into T1 and T2 tumors of the upper, middle and lower lung region (LR). Maximum craniocaudal (CC) lung dimensions and tumor mobility in three dimensions were monitored. Vital capacity (VC) was measured and correlated using spirometry. Before RT, the maximum CC motion of the tumor-bearing hemithorax was 5.2 +/- 0.9 cm if the tumor was located in the lower LR (middle LR: 5.5 +/- 0.8 cm; upper LR: 6.0 +/- 0.6 cm). After RT, lung motion was significantly reduced in the lower LR (P < 0.05). Before RT, the maximum CC tumor mobility was significantly higher in tumors of the lower LR 2.5 +/- 0.6 vs. 2.0 +/- 0.3 cm (middle LR; P < 0.05) vs. 0.7 +/- 0.2 cm (upper LR; P < 0.01). After RT, tumor mobility was significantly reduced in the lower LR (P < 0.01) and in T2 tumor patients (P < 0.05). VC showed no significant changes. dMRI is capable of monitoring changes in lung motion that were not suspected from spirometry. This might make the treatment of side effects possible at a very early stage. Changes of lung motion and tumor mobility are highly dependent on the tumor localization and tumor diameter.
    The purpose of this study was to assess the feasibility of contrast-enhanced 3D perfusion MRI and MR angiography (MRA) of pulmonary embolism (PE) in pigs using a single injection of the blood pool contrast Gadomer. PE was induced in five... more
    The purpose of this study was to assess the feasibility of contrast-enhanced 3D perfusion MRI and MR angiography (MRA) of pulmonary embolism (PE) in pigs using a single injection of the blood pool contrast Gadomer. PE was induced in five domestic pigs by injection of autologous blood thrombi. Contrast-enhanced first-pass 3D perfusion MRI (TE/TR/FA: 1.0 ms/2.2 ms/40 degrees; voxel size: 1.3 x 2.5 x 4.0 mm3; TA: 1.8 s per data set) and high-resolution 3D MRA (TE/TR/FA: 1.4 ms/3.4 ms/40 degrees; voxel size: 0.8 x 1.0 x 1.6 mm3) was performed during and after a single injection of 0.1 mmol/kg body weight of Gadomer. Image data were compared to pre-embolism Gd-DTPA-enhanced MRI and post-embolism thin-section multislice CT (n = 2). SNR measurements were performed in the pulmonary arteries and lung. One animal died after induction of PE. In all other animals, perfusion MRI and MRA could be acquired after a single injection of Gadomer. At perfusion MRI, PE could be detected by typical wedge-shaped perfusion defects. While the visualization of central PE at MRA correlated well with the CT, peripheral PE were only visualized by CT. Gadomer achieved a higher peak SNR of the lungs compared to Gd-DTPA (21 +/- 8 vs. 13 +/- 3). Contrast-enhanced 3D perfusion MRI and MRA of PE can be combined using a single injection of the blood pool contrast agent Gadomer.
    Differentiation between different forms of pulmonary hypertension (PH) is essential for correct disease management. The goal of this study was to elucidate the clinical impact of high spatial resolution MR angiography (SR-MRA) and... more
    Differentiation between different forms of pulmonary hypertension (PH) is essential for correct disease management. The goal of this study was to elucidate the clinical impact of high spatial resolution MR angiography (SR-MRA) and time-resolved MRA (TR-MRA) to differentiate between patients with chronic thromboembolic PH (CTEPH) and idiopathic pulmonary arterial hypertension (IPAH). Ten PH patients and five volunteers were examined. Twenty TR-MRA data sets (TA 1.5 s) and SR-MRA (TA 23 s) were acquired. TR-MRA data sets were subtracted as angiography and perfusion images. Evaluation comprised analysis of vascular pathologies on a segmental basis, detection of perfusion defects, and bronchial arteries by two readers in consensus. Technical evaluation comprised evaluation of image quality, signal-to-noise ratio (SNR) measurements, and contrast-media passage time. Visualization of the pulmonary arteries was possible down to a subsegmental (SR-MRA) and to a segmental (TR-MRA) level. SR-MRA outperformed TR-MRA in direct visualization of intravascular changes. Patients with IPAH predominantly showed tortuous pulmonary arteries while in CTEPH wall irregularities and abnormal proximal-to-distal tapering was found. Perfusion images showed a diffuse pattern in IPAH and focal defects in CTEPH. TR-MRA and SR-MRA resulted in the same final diagnosis. Both MRA techniques allowed for differentiation between IPAH and CTEPH. Therefore, TR-MRA can be used in the clinical setting, especially in dyspneic patients.

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