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    Keywords: Germany ; LUNG ; PERFUSION ; DIAGNOSIS ; imaging ; INFORMATION ; VOLUME ; DISEASE ; TIME ; PATIENT ; BLOOD-FLOW ; primary ; HIGH-RESOLUTION MEASUREMENT ; MRI ; TRACER BOLUS PASSAGES ; SEQUENCE ; LUNG PERFUSION
    Abstract: Purpose: To assess the use of time-resolved parallel 3D MRI for a quantitative analysis of pulmonary perfusion in patients with cardiopulmonary disease. Materials and Methods: Eight patients with pulmonary embolism or pulmonary hypertension were examined with a time-resolved 3D gradient echo pulse sequence with parallel imaging techniques (FLASH 3D, TE/TR: 0.81 1.9 ms; flip angle: 40degrees; GRAPPA). A quantitative perfusion analysis based on indicator dilution theory was performed using a dedicated software. Results: Patients with pulmonary embolism or chronic thromboembolic pulmonary hypertension revealed characteristic wedge-shaped perfusion defects at perfusion MRI. They were characterized by a decreased pulmonary blood flow (PBF) and pulmonary blood volume (PBV) and increased mean transit time (MTT). Patients with primary pulmonary hypertension or Eisenmenger syndrome showed a more homogeneous perfusion pattern. The mean MTT of all patients was 3.3 +/- 4.7 s. The mean PBF and PBV showed a broader interindividual variation (PBF: 104-322ml/100ml/min; PBV: 8-21ml/100 ml). Conclusion: Time-resolved parallel 3D MRI allows at least a semi-quantitative assessment of lung perfusion. Future studies will have to assess the clinical value of this quantitative information for the diagnosis and management of cardiopulmonary disease
    Type of Publication: Journal article published
    PubMed ID: 14872369
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  • 4
    Keywords: measurement ; evaluation ; Germany ; LUNG ; PERFUSION ; imaging ; QUANTIFICATION ; VENTILATION ; TIME ; BLOOD-FLOW ; MR ; MRI ; SEQUENCE ; SIGNAL ; ACQUISITION ; DIFFERENCE ; REGION ; arteries ; REGIONS ; EMBOLISM ; ANGIOGRAPHY ; PULMONARY PERFUSION ; LUNG PERFUSION ; PULMONARY ; HEALTHY-VOLUNTEERS ; CINE-MRI ; perfusion,lung,phase-contrast,MRI,parallel imaging
    Abstract: Purpose: Evaluation of lung perfusion by contrast-enhanced 3D MRI using partial parallel imaging techniques. Materials and Methods: Eight healthy volunteers were examined using a contrast-enhanced dynamic FLASH 3D sequence with partial parallel imaging technique at 1.5 T MRI with a TA of 1.5 sec. The whole lung was covered by 36 coronal slices. A ventral, middle and dorsal, slice of each lung was manually segmented and signal-to-time curves were computed. For absolute quantification of blood flow through the right and left pulmonary artery, phase-contrast flow measurements were performed. Results: No significant difference was found between the signal intensity in the right (8.9 +/- 2.6) and left (8.0 +/- 3.5) lung, corresponding to a left-to-right signal intensity ratio of 0.9. A significantly higher signal intensity was found in the dorsal regions of the lungs (p = 0.01) compared to the ventral regions. The time to peak of the signal intensity was significantly shorter in the dorsal (15.3 sec) and middle (15.7 sec) regions of the lungs (p = 0.03 and p = 0.04, respectively) than in the ventral regions (16.3 sec). The ratio between blood flow through the left (2.2 L/min) and right (2.7 L/min) lung was 0.84. Conclusion: Partial parallel image acquisition can assess the perfusion of the lungs at high temporal resolution. The perfusion is slightly higher on the right than on the left. The signal increases faster and has a higher peak in the dorsal lung regions
    Type of Publication: Journal article published
    PubMed ID: 15026945
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    Keywords: BLOOD ; Germany ; LUNG ; PERFUSION ; imaging ; QUANTIFICATION ; VOLUME ; TIME ; BLOOD-FLOW ; blood flow ; FLOW ; HIGH-RESOLUTION MEASUREMENT ; MRI ; TRACER BOLUS PASSAGES ; MAGNETIC-RESONANCE ; magnetic resonance imaging ; AGE ; PARAMETERS ; SCINTIGRAPHY ; CONTRAST-ENHANCED MRI ; magnetic resonance imaging (MRI) ; QUANTITATIVE-ANALYSIS ; HEALTHY ; LUNG PERFUSION ; TRANSIT-TIME ; HEALTHY-VOLUNTEERS ; ARTERIAL ; INFLATION ; contrast-enhanced
    Abstract: Rationale and Objectives: 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). Methods and Results: Nine healthy volunteers (median age, 28 years; range, 20-45 years) were examined with contrast-enhanced time-resolved 3-dimensional pulmonary perfusion MRI (FLASH 313, TR/TE: 1.9/0.8 ms; flip angle: 40degrees; 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. Results: There was a statistically significant increase of the PBF (Delta = 182 mL/100mL/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 less than or equal to0.008) with inspiratory PABF. Conclusion: Pulmonary perfusion during breathhold depends on the inspiratory level. Higher perfusion is observed at expiratory breathhold
    Type of Publication: Journal article published
    PubMed ID: 15654250
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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: carcinoma ; Germany ; human ; MODEL ; FOLLOW-UP ; IMAGES ; imaging ; TISSUE ; TUMORS ; TIME ; kidney ; MR ; SEQUENCE ; SEQUENCES ; treatment ; MAGNETIC-RESONANCE ; magnetic resonance imaging ; LESIONS ; RESECTION ; RENAL-CELL CARCINOMA ; renal cell carcinoma ; PHASE ; SIZE ; human renal cell carcinoma ; EXTENT ; PORCINE MODEL ; viability ; CLINICAL-EXPERIENCE ; RADIO-FREQUENCY ABLATION ; THERMAL ABLATION
    Abstract: Background and Purpose: Radiofrequency ablation (RFA) is an attractive minimally invasive treatment option for small renal masses. The purpose of this study was to investigate the morphologic imaging appearance of RF lesions immediately after the ablation of kidney tissue using standard clinical MR sequences, as well as to investigate the correlation between MR and gross lesion size. Materials and Methods: Ablations were performed 17 times in a standardized model of ex-vivo perfused porcine kidneys using a resistance-controlled RF device (250 W, 470 kHz) and a nonexpandable bipolar applicator inserted into the center of healthy renal parenchyma. The RF current was applied for 9 minutes at 20 W. Imaging was performed after ablation using standard clinical MR sequences: morphologic T-1/T(2-)weighted images and an isotropic post-contrast T-1 high-resolution measurement (VIBE). Maximum lesion diameters were measured in three directions and were compared with the measurements of the gross lesions. Histologic (hematoxylin + eosin and nicotinamide adenine dinucleotide staining) and statistical analyses were performed. Results: The gross pathologic examination showed a firm, white-yellow ablation zone sharply demarcated from the untreated tissue. The histologic examination confirmed cellular viability outside but not in the treatment zone. The RF lesions were hyperintense on T-1-weighted images and hypointense on T-2-weighted images. The lesion size measured in the VIBE images correlated best with the macroscopic lesion size (N = 16). Conclusions: Morphologic MR T-1 and T-2 sequences of RF lesions immediately after ablation produce reliable and consistent imaging characteristics. The post-contrast, high-resolution sequence (VIBE) enables the extent of the lesion to be determined accurately. The potential uses of this imaging strategy in clinical practise warrant further investigation on human renal-cell carcinoma
    Type of Publication: Journal article published
    PubMed ID: 16724901
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  • 8
    Keywords: ABNORMALITIES, ALGORITHM, ALIGNMENT, chest, CT, evaluation, Germany, IMAGE REGISTRATION, imaging, IN
    Abstract: Recently it has been shown that regional lung perfusion can be assessed using time-resolved contrast-enhanced magnetic resonance (MR) imaging. Quantification of the perfusion images has been attempted, based on definition of small regions of interest (ROIs). Use of complete lung segmentations instead of ROIs could possibly increase quantification accuracy. Due to the low signal-to-noise ratio, automatic segmentation algorithms cannot be applied. On the other hand, manual segmentation of the lung tissue is very time consuming and can become inaccurate, as the borders of the lung to adjacent tissues are not always clearly visible. We propose a new workflow for semi-automatic segmentation of the lung from additionally acquired morphological HASTE MR images. First the lung is delineated semi-automatically in the HASTE image. Next the HASTE image is automatically registered with the perfusion images. Finally, the transformation resulting from the registration is used to align the lung segmentation from the morphological dataset with the perfusion images. We evaluated rigid, affine and locally elastic transformations, suitable optimizers and different implementations of mutual information (MI) metrics to determine the best possible registration algorithm. We located the shortcomings of the registration procedure and under which conditions automatic registration will succeed or fail. Segmentation results were evaluated using overlap and distance measures. Integration of the new workflow reduces the time needed for post-processing of the data, simplifies the perfusion quantification and reduces interobserver variability in the segmentation process. In addition, the matched morphological data set can be used to identify morphologic changes as the source for the perfusion abnormalities
    Type of Publication: Journal article published
    PubMed ID: 17301453
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    Keywords: BLOOD, blood flow, blood volume, BLOOD-FLOW, CONTRAST, correlation, DIAGNOSIS, FLOW, Germany, HYPERT
    Abstract: Purpose: Pathological changes of the peripheral pulmonary arteries induce pulmonary arterial hypertension (PAH). Ann of this study was to quantitatively assess the effect of PAH on pulmonary perfusion by 3D-MR-perfusion techniques and to compare findings to healthy controls. Furthermore, quantitative perfusion data were correlated with invasive pressure measurements. Material and methods: Five volunteers and 20 PAH patients (WHO class II or III) were examined using a 1.5 T MR scanner. Measurement of pulmonary perfusion was done in an inspiratory breathhold (FLASH3D; 3.5 min x 1.9 mm x 4 min; TA per 3D dataset 1.5 s). Injection of contrast media (0. 1 mmol Gd-DTPA/k, BW) and image acquisition were started simultaneously. Evaluation of 3D perfusion was done using singular value decomposition. Lung borders were outlined manually. Each lung Volume was divided into three regions (anterior, middle, posterior), and the following parameters were assessed: Time-to-Peak (TTP), blood flow (PBF), blood volume (PBV), and mean transit time (NITT). In 10 patients invasive pulmonary artery pressure measurements were available and correlated to the perfusion measurements. Results: In both, controls and patients, an anterior-to-posterior gradient with higher PBF and PBV posterior was observed. In the posterior lung region, a significant difference (p 〈 0.05) was found for TTP (12 s versus 16 s) and MTT (4 s versus 6 s) between volunteers and patients. PBF and PBV were lower in patients than in Volunteers (i.e. dorsal regions: 124 versus 180 ml/100 ml/min and 10 versus 12 ml/ 100 ml), but the difference failed to be significant. The ratio of PBF and PBV between the posterior and the middle or ventral regions showed no difference between both groups. A moderate linear correlation between mean pulmonary arterial pressure (mPAP) and PBV (r= 0.51) and MTT (r = 0.56) was found. Conclusion: The only measurable effect of PAH on pulmonary perfusion is a prolonging of the MTT. There is only it moderate linear correlation of invasive mPAP with PBV and MTT. (c) 2006 Elsevier Ireland Ltd. All rights reserved
    Type of Publication: Journal article published
    PubMed ID: 17045440
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  • 10
    Keywords: -, BLOOD, blood flow, blood volume, BLOOD-FLOW, CONTRAST, CONTRAST-ENHANCED MRI, FLOW, Germany, HEAL
    Abstract: Purpose: Oxygen-enhanced magnetic resonance (MR)-ventilation imaging of the lung is based on the inhalation of a high concentration of oxygen (hyperoxia). However, the effect of hyperoxia on the pulmonary circulation is not yet fully understood. In this study the impact of hyperoxia on the pulmonary circulation was evaluated. Materials and Methods: Ten healthy volunteers were examined in a 1.5 T MRI system with contrast-enhanced perfusion MRI (saturation recovery 2D turboFLASH) of the lung and phase-contrast flow measurements in the pulmonary trunk. Both measurements were performed breathing room air (R-A) and, subsequently, 100% oxygen (15 L/mm) (O-2). Results: The perfusion measurements showed a significant difference between RA and 02 for the pulmonary blood flow (181 vs. 257 mL/min/100 mL, P = 0.04) and blood volume (14 vs. 21 mL/100 mL, P = 0.008). The mean transit time of the contrast bolus was not changed (P = 0.4) in the dorsal part of the lung, whereas it was significantly prolonged (P = 0.006) in the central part. The mean heart rate during flow measurements breathing RA (67 +/- 11 beats/min) and O-2 (61 +/- 12 beats/min) were not significantly different (P = 0.055). The average cardiac output (pulmonary trunk) was not significantly lower while breathing O-2 (R-A: 5.9 vs. O-2: 5.5 L/min, P = 0.054). Conclusion: Hyperoxia causes a significant increase and redistribution of the pulmonary perfusion, whereas it leads to a not significant decrease in cardiac output. Thus, for MR-perfusion and MR-flow measurements oxygen inhalation should be avoided, if possible. In the context of oxygen-enhanced MR-ventilation imaging of the lung the contribution of this effect needs to be further evaluated
    Type of Publication: Journal article published
    PubMed ID: 17414523
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