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  • 1
    Type of Publication: Journal article epub ahead of print
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  • 2
    Keywords: ANGIOGENESIS ; CANCER ; GROWTH-FACTOR ; tumor ; carcinoma ; MODEL ; neoplasms ; THERAPY ; MICE ; magnetic resonance imaging ; BREAST ; PROGRESSION ; MR-ANGIOGRAPHY ; blood pool contrast agents ; contrast enhanced MRA ; GADOMER-17 ; POOL CONTRAST AGENTS
    Abstract: Purpose: To evaluate high-resolution three-dimensional MR angiography (MRA) for the visualization and morphologic characterization of intratumoral vasculature. Materials and Methods: Two subcutaneous rodent tumor models (human skin carcinoma HaCaT-ras-A-5RT3 grown in nude mice and rat prostate carcinoma R3327-AT1 grown in Copenhagen rats) were examined with a clinical 1.5 T MR-system. For MRA a dedicated high- resolution three-dimensional gradient echo pulse sequence with a voxel size of 166 x 206 x 320 mum(3) was performed after injection of Gadomer-17. The image analysis included a correlation of intratumoral vessels with histology. Signal intensity measurements were performed in the vena cava, the tumor underlying muscle, and in various regions of the tumor. Signal-to-noise-ratios (SNR) and contrast-to-noise-ratios (CNR) were calculated from this measurement. Results: High-resolution MRA allowed a clear distinction of intratumoral blood vessels. The mouse tumor model tended to be strongly vascularized with several intratumoral blood vessels clearly displayed by MRA. When correlated with histology, these intratumoral blood vessels had a size in the range of 300 to 400 mum. In contrast, rat tumors had only sparse capillary intratumoral blood vessels that could only be demonstrated by histology. In both tumor models, dilated blood vessels were observed in the subcutaneous tissue near the tumor. In general, areas with a strong contrast enhancement correlated with viable, well vascularized tumor regions, whereas non-enhancing tumor areas correlated with tumor necrosis or hypoxic areas. Conclusion: High-resolution three-dimensional MRA allows the visualization of intratumoral vasculature in rodent models. With minimal hardware and software modifications, high-resolution MRA could be performed on a clinical 1.5 T MRI scanner. Morphologic characterization of intratumoral blood vessels could add important insights into the process of tumor angiogenesis
    Type of Publication: Journal article published
    PubMed ID: 12815640
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  • 3
    Keywords: PERFUSION ; CT ; DIAGNOSIS ; FOLLOW-UP ; imaging ; VENTILATION ; VISUALIZATION ; EFFICIENCY ; computed tomography ; PATIENT ; MR ; MRI ; magnetic resonance ; MAGNETIC-RESONANCE ; tomography ; EMBOLISM ; COMPUTED-TOMOGRAPHY ; DIAGNOSTIC-TESTS ; MAGNETIC-RESONANCE ANGIOGRAPHY ; MR-ANGIOGRAPHY ; ANGIOGRAPHY ; CONTRAST-ENHANCED MRI ; MR angiography ; MR imaging ; MANAGEMENT ; AIRWAY-OBSTRUCTION ; DEEP VENOUS THROMBOSIS ; LUNG PERFUSION ; MOLECULAR-WEIGHT HEPARIN ; NONTRAUMATIC THORACIC EMERGENCIES ; pulmonary embolism ; SINGLE BREATH-HOLD ; SPIN-LABELING TECHNIQUES ; thrombus imaging ; VEIN THROMBOSIS
    Abstract: Pulmonary embolism (PE) is one of the most frequently encountered clinical emergencies. The diagnosis often involves multiple diagnostic tests, which need to be carried out rapidly to assist in the safe management of the patient. Recent strides in computed tomography (CT) have made big improvements in patient management and efficiency of diagnostic imaging. This review article describes the developments in magnetic resonance (MR) techniques for the diagnosis of acute PE. Techniques include MR angiography (MRA) and thrombus imaging for direct clot visualization, perfusion MR, and combined perfusion-ventilation MR. As will be demonstrated, some of these techniques are now entering the clinical arena, and it is anticipated that MR imaging (MRI) will have an increasing role in the initial diagnosis and follow-up of patients with acute PE
    Type of Publication: Journal article published
    PubMed ID: 14635147
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  • 4
    Keywords: measurement ; Germany ; LUNG ; TIME ; PATIENT ; QUALITY ; BODY-WEIGHT ; CONTRAST ; INJECTION ; MAGNETIC-RESONANCE ; DIFFERENCE ; RATES ; arteries ; VASCULATURE ; GADOPENTETATE DIMEGLUMINE ; MAGNETIC-RESONANCE ANGIOGRAPHY ; gadobenate dimeglumine ; ARTERIOVENOUS-MALFORMATION ; lung,magnetic resonance angiography,comparative study,contrast agent,time-resolved
    Abstract: Purpose: To compare contrast characteristics and image quality of 1.0 M gadobutrol with 0.5 M Gd-DTPA for time-resolved three-dimensional pulmonary magnetic resonance angiography (MRA).Materials and Methods: Thirty-one patients and five healthy volunteers were examined with a contrast-enhanced time-resolved pulmonary MRA protocol (fast low-angle shot [FLASH] three-dimensional, TR/TE=2.2/1.0 msec, flip angle: 25degrees, scan time per three-dimensional data set=5.6 seconds). Patients were randomized to receive either 0.1 mmol/kg body weight (bw) or 0.2 mmol/kg bw gadobutrol, or 0.2 mmol/kg bw Gd-DTPA. Volunteers were examined three times, twice with 0.2 mmol/kg bw gadobutrol. using two different flip angles and once with 0.2 mmol/kg bw Gd-DTPA. All contrast injections were performed at a rate of 5 mL/second. Image analysis included signal-to-noise ratio (SNR) and contrast-to-noise. ratio (CNR) measurements in lung arteries and veins, as well as a subjective analysis of image quality.Results: In patients, significantly higher SNR and CNR were observed with Gd-DTPA compared to both doses of gadobutrol (SNR: 35-42 vs. 17-25; CNR 33-39 vs. 16-23; Pless than or equal to0.05). No relevant differences were observed between 0.1 mmol/kg bw and 0.2 mmol/kg bw gadobutrol. In volunteers, gadobutrol and Gd-DTPA achieved similar SNR and CNR. A significantly higher SNR and CNR was observed for gadobutrol-enhanced MRA with an increased flip angle of 40degrees. Image quality was rated equal for both contrast agents.Conclusion: No relevant advantages of 1.0 M gadobutrol over 0.5 M Gd-DTPA were observed for time-resolved pulmonary MRA in this study. Potential explanations are T2/T2*-effects caused by the high intravascular concentration when using high injection rates
    Type of Publication: Journal article published
    PubMed ID: 14745754
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  • 5
    Keywords: evaluation ; human ; IN-VIVO ; LUNG ; DENSITY ; HIGH-RESOLUTION CT ; imaging ; INFORMATION ; VENTILATION ; DYNAMICS ; MRI ; FIELD ; PROTON ; GAS ; PARENCHYMA ; COMPUTED-TOMOGRAPHY ; THIN-SECTION CT ; functional MRI ; OXYGEN ; hyperpolarized ; helium-3 ; DIFFUSION ; AIRWAY ; PULMONARY ; pulmonary function ; TRANSPLANT RECIPIENTS ; HE-3 GAS ; lung diseases ; CYSTIC-FIBROSIS ; LASER-POLARIZED XE-129 ; NOBLE-GAS ; NUCLEAR-MAGNETIC-RESONANCE ; ultrafast imaging
    Abstract: Lung imaging has traditionally relied on x-ray methods, since proton MRI is limited to some extent by low proton density in the lung parenchyma and static field inhomogeneities in the chest. The relatively recent introduction of MRI of hyperpolarized noble gases has led to a rapidly evolving field of pulmonary MRI, revealing functional information of the lungs, which were hitherto unattainable. This review article briefly describes the physical background of the technology, and subsequently focuses on its clinical applications. Four different techniques that have been used in various human investigations are discussed: ventilation distribution, ventilation dynamics, and small airway evaluation using diffusion imaging and oxygen uptake assessment
    Type of Publication: Journal article published
    PubMed ID: 15390146
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  • 6
    Keywords: AGENTS ; Germany ; PERFUSION ; imaging ; thorax ; TIME ; CONTRAST ; DYNAMICS ; CONTRAST AGENT ; MRI ; MAGNETIC-RESONANCE ; EXPERIENCE ; arteries ; PARAMETERS ; CONTRAST AGENTS ; magnetic resonance angiography ; GD-DTPA ; HEALTHY ; contrast media ; BOLUS ; AGENT ; HEALTHY-VOLUNTEERS ; STENOSIS ; SIZE ; contrast-enhanced ; PULMONARY-ARTERIES ; bolus dispersion ; comparative study ; time-resolved magnetic resonance angiography
    Abstract: Purpose: To compare the signal characteristics and bolus dynamics of 1.0 M gadobutrol and 0.5 M Gd-DTPA for time-resolved, three-dimensional, contrast-enhanced (CE) MRA of the upper torso. Materials and Methods: Ten healthy volunteers were examined with time-resolved three-dimensional CE-MRA (scan time per three-dimensional data set: 0.86 second; voxel size: 3.6 x 2 x 6.3 mm(3)). Each volunteer underwent eight individual examinations after intravenous injection of 0.05 and 0.1 mmol/kg body weight (b.w.) of 1.0 M gadobutrol and 0.5 M Gd-DTPA using two injection rates (2.5 and 5 mL/second). The data analysis included quantitative measurements of the peak signal-to-noise ratio (SNR) and bolus dispersion (full width at half maximum (FWHM)) in the pulmonary artery, left atrium, and thoracic and abdominal aortas. Results: No significant differences in the peak SNR and bolus dispersion were observed between gadobutrol and Gd-DTPA for all dose levels and injection rates in any of the vascular segments. For both contrast agents a dose of 0.1 mmol/kg b.w. injected with 5 mL/second achieved the highest SNR in all vascular segments. Conclusion: For the imaging parameters used in this study, higher-concentrated gadolinium chelates offer no relevant advantages for time-resolved three-dimensional CE-MRA of the upper torso
    Type of Publication: Journal article published
    PubMed ID: 16028246
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  • 7
    Keywords: Germany ; IN-VIVO ; LUNG ; MODEL ; EMPHYSEMA ; IMAGES ; imaging ; TIME ; PATIENT ; MRI ; SEQUENCE ; MAGNETIC-RESONANCE ; REPRODUCIBILITY ; GAS ; PARAMETERS ; Jun ; helium ; FUNCTION TESTS ; HEALTHY ; DIFFUSION ; STANDARD ; SINGLE ; hyperpolarized gas ; COEFFICIENT ; BM ; lung microstructure ; RICIAN DISTRIBUTION
    Abstract: Purpose: To determine the reproducibility of several parameters of the ADC measurement by calculating the scan-to-scan intrasubject variability., Materials and Methods: Measurements were performed using a gradient-echo sequence with a bipolar gradient for diffusion weighting (b = 3.89 sec/cm(2)). Five patients with pulmonary emphysema, and six healthy-lung volunteers were included in the study. Images were acquired after inspiration of He-3 during a single inspiratory breath-hold. To assess the reproducibility, the measurement was performed twice (time between measurements = 20 minutes) without repositioning the subjects. Analysis was performed on the basis of region-of-interest (ROI)l analysis and global lung ADC histograms. Results: The mean ADC of a ROI varied by 5.1% between two measurements for volunteers and by 6.1% for patients. In the global evaluation, the 75th percentile demonstrated the best reproducibility (2%), while other parameters showed variations up to 12%. Only the variation of the standard deviation (SD) and the measure of homogeneity of the ADC map showed a significant difference between patients and volunteers. Conclusion: Diffusion-weighted imaging (DWI) is a well-reproducible method for assessing the lung microstructure
    Type of Publication: Journal article published
    PubMed ID: 15906344
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  • 8
    Keywords: AGE, ALGORITHM, ALGORITHMS, analysis, ANGIOGRAPHY, CARDIOVASCULAR MR, CHILDREN, comparison, COMPUTED
    Abstract: Purpose: To evaluate three-dimensional (3D), free-breathing, steady-state free precession (SSFP) magnetic resonance angiography (MRA) for volumetric assessment of ventricular function. Materials and Methods: In 18 subjects (mean age = 21.5 years) 3D datasets of the heart and great vessels were acquired using an ECG-triggered, free-breathing SSFP technique with a T2-preparation prepulse. Data were acquired during end-systole (ES) and end-diastole (ED) for assessment of stroke volumes (SVs). Through-plane flow measurements of the great arteries were performed as well as 2D-cine SSFP imaging for comparison. For image analysis of the 3D SSFP datasets a simplex mesh model was used. Papillary muscles were excluded from ventricular volumes using thresholds. Intra- and interobserver variability (Bland-Alt-man analysis) and correlations (Pearson's coefficient) between volumetric and flow measurements were assessed. Results: ES and ED datasets were acquired successfully in all subjects. The best correlation was observed between flow vs. 3D SSFP SV for the LV (r = 0.85, mean difference = -1.0 mL) and the RV (r = 0.89, mean difference = -2.2 mL) with high intra- (LV: r = 0.93; RV: r = 0.94) and interobserver (LV: r 0.91; RV: r 0.93) reproducibility. Conclusion: 3D SSFP datasets combined with semiautomatic segmentation algorithms allow highly accurate and reproducible assessment of left (LV) and right ventricular (RV) SVs in free-breathing subjects
    Type of Publication: Journal article published
    PubMed ID: 17654727
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  • 9
    Keywords: CARBON, DIFFUSING-CAPACITY, DIFFUSION, DISEASE, DISEASES, EVALUATE, EXCHANGE, fibrosis, function, FU
    Abstract: Purpose: To evaluate an optimized method for oxygen-enhanced MRI of the lung, using simultaneous electrocardiograph (ECG) and navigator triggering. To correlate oxygen-enhanced MRI with lung function tests assessing alveolar-capillary gas exchange. Materials and Methods: A total of 12 healthy volunteers (aged 20-32 years) and 10 patients (aged 37-87 years) with interstitial lung diseases (ILD) underwent oxygen-enhanced MRI and pulmonary functional tests (PFTs) assessing alveolar-capillary gas exchange. The paradigm room-air-oxygen-room-air was acquired with a nonselective inversion-recovery half-Fourier single-shot turbo spin-echo sequence (inversion time = 1200 msec; acquisition time = 134.5 msec; slice thickness = 20 mm; matrix size = 128 X 128), using simultaneous double triggering (navigator plus ECG trigger). Cross-correlation was performed in regions of interest (ROIs) encompassing both lungs. The number of oxygen-activated pixels over the total number of pixels in the ROIs (OAP%) of volunteers and patients was compared. OAP%s were correlated with PFTs. Results: The mean OAP% of patients was significantly lower than that of volunteers (36.7 vs. 81.7, P = 0.001). OAP% correlated with the transfer lung factor for carbon monoxide (Tlco) (r = 0.64; P = 0.002), the transfer coefficient (Kco) (r = 0.75; P = 0.001), the arterial partial pressure (r = 0.77; P 〈 0.001), and the saturation (r = 0.70; P 〈 0.001) of oxygen. Conclusion: Navigator-triggered oxygen-enhanced MRI of the lung may have a potential role in the quantitative assessment of lung function in ILD
    Type of Publication: Journal article published
    PubMed ID: 17968900
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  • 10
    Keywords: brain ; IN-VIVO ; MODEL ; NETWORK ; validation ; susceptibility contrast ; BEHAVIOR ; DIFFUSION ; phantom ; BOLD ; DEOXYGENATED BLOOD-VOLUME ; diffusion dephasing ; OXYGEN EXTRACTION FRACTION ; qBOLD ; static dephasing
    Abstract: Purpose: To experimentally verify a theoretical model describing the MR signal dephasing under nonstatic conditions in a voxel containing a vascular network, and to estimate the stability of the model for qBOLD measurements. Materials and Methods: Measurement phantoms reflecting the properties of the theoretical model, i.e., statistically distributed and randomly oriented cylinders in a homogeneous medium were constructed by randomly coiled polyamide fibers immersed in a NiSO4 solution. The resemblance between measured and theoretical signal curves was investigated by calculation of root mean squared error maps. Simulated nonstatic dephasing data were evaluated using the static dephasing model to estimate the stability of the model and the influence of input parameters. Results: The theoretical model describing the MR signal dephasing under nonstatic conditions was experimentally verified in phantom measurements. In simulations, it was found that, by neglecting the effect of diffusion when predicting the MR signal-time course expected in an in vivo measurement of the tissue oxygenation, errors of 10-30% would be introduced into the parameter estimation. The simulations indicate unpredictable results for simultaneous evaluation of blood oxygenation level and blood volume fraction. Conclusion: Neglecting the effects of diffusion in quantitative BOLD measurements could give rise to substantial errors in the parameter estimation
    Type of Publication: Journal article published
    PubMed ID: 21274984
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