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  • magnetic resonance imaging  (9)
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  • 1
    Keywords: brain ; Germany ; MODEL ; MODELS ; PERFUSION ; imaging ; SYSTEM ; CONTRAST ; MAGNETIC-RESONANCE ; magnetic resonance imaging ; NERVOUS-SYSTEM ; CEREBRAL-BLOOD-FLOW ; CENTRAL-NERVOUS-SYSTEM ; CONTRAST-ENHANCED MRI ; functional MRI ; ENHANCEMENT ; INVERSION ; ARTERIAL ; contrast-enhanced ; functional imaging ; ARTERIAL WATER ; ASL ; BALLOON MODEL ; BOLD-fMRI ; BRAIN PERFUSION ; dynamic contrast enhanced-MRI ; dynamic susceptibility contrast-MRI ; FMRI ; HIGH-SPATIAL-RESOLUTION ; OXYGEN-CONSUMPTION ; QUIPSS II
    Abstract: This review presents the basic principles of functional imaging of the central nervous system utilizing magnetic resonance imaging. The focus is set on visualization of different functional aspects of the brain and related pathologies. Additionally, clinical cases are presented to illustrate the applications of functional imaging techniques in the clinical setting. The relevant physics and physiology of contrast-enhanced and non-contrast-enhanced methods are discussed. The two main functional MR techniques requiring contrast-enhancement are dynamic T1 - and T2(*)-MRI to image perfusion. Based on different pharmacokinetic models of contrast enhancement diagnostic applications for neurology and radio-oncology are discussed. The functional non-contrast enhanced imaging techniques are based on "blood oxygenation level dependent (BOLD)-fMRI and arterial spin labeling (ASL) technique. They have gained clinical impact particularly in the fields of psychiatry and neurosurgery
    Type of Publication: Journal article published
    PubMed ID: 15871087
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  • 2
    Keywords: MODEL ; MODELS ; PROSTATE ; THERAPY ; imaging ; VOLUME ; DRUG ; ACCURACY ; TIME ; MRI ; treatment ; MAGNETIC-RESONANCE ; magnetic resonance imaging ; TRIAL ; BENIGN ; nuclear medicine ; LOCATION ; monitoring ; EXTENSION ; HYPERPLASIA ; BENIGN PROSTATIC HYPERPLASIA ; ACCURATE ; COIL ; prostate volume ; THERMOTHERAPY ; TRANSRECTAL ULTRASOUND
    Abstract: Objectives: We sought to evaluate the capabilities of different magnetic resonance imaging (MRI)-based methodologies for measuring prostate volume. Materials and Methods: Twenty-four male beagles with benign prostatic hyperplasia were enrolled in a drug trial and imaged at 5 time points. A total of 120 prostate volumes were determined by MRI-based semiautomated segmentation. For planimetric assessment, 8 diameter locations were determined in the axial and coronal plane of the MRI slice with maximum extension of the prostate. Thirteen calculation models based on these diameters were determined by comparison to the reference volume and evaluated during treatment. Results: The segmented MRI prostate volume significantly correlated with post necropsy Volume. The best diameter-based model also worked very well for monitoring prostate volume of dogs under treatment. Conclusions: MRI-based segmentation is highly accurate in assessing prostate volume. Diameter-based measurements are closely correlated to the segmented prostate volume and are feasible to monitor therapy
    Type of Publication: Journal article published
    PubMed ID: 15770143
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  • 3
    Keywords: ANGIOGENESIS ; CANCER ; SURVIVAL ; tumor ; Germany ; THERAPY ; DENSITY ; DIAGNOSIS ; imaging ; liver ; NEW-YORK ; SAMPLE ; SAMPLES ; TISSUE ; TUMORS ; NUCLEAR-MEDICINE ; PATIENT ; BIOMARKERS ; TISSUES ; MAGNETIC-RESONANCE ; magnetic resonance imaging ; BREAST ; immunohistochemistry ; REGION ; REGIONS ; MUSCLE ; PARAMETERS ; NORMAL TISSUE ; SERIES ; CONTRAST-ENHANCED MRI ; nuclear medicine ; ASBESTOS ; mesothelioma ; MALIGNANT MESOTHELIOMA ; LUNG-CARCINOMA ; HETEROGENEITY ; radiology ; RE ; THERAPIES ; monitoring ; dynamic contrast enhanced MRI ; biomarker ; analysis ; methods ; SUBTYPES ; NUCLEAR ; USA ; correlation ; spleen ; Aorta ; microvascular density ; MEDICINE ; quantitative ; PHARMACOKINETIC ANALYSIS ; DCE-MRI ; neoplasm ; CD-34 ; IMAGING BIOMARKER
    Abstract: Rationale and Objectives. Malignant mesothelioma (MM) of the pleura is an aggressive and often fatal neoplasm. Because MM frequently demonstrates marked angiogenesis, it may be responsive to antiangiogenic therapy, but effective methods for selecting and monitoring of patients are further needed. We employed dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and quantitative immunohistochemistry (IHC) to characterize the microvascularity of MM using both a physiologic and ultrastructural method. Materials and Methods. Nineteen patients diagnosed with MM were enrolled and DCE-MRI was performed before antiangiogenic treatment. For each patient, tumor regions were characterized by their DCE-MRI-derived pharmacokinetic parameters (Amp, k(ep), k(el)), which were also compared to those of normal tissue (aorta, liver, spleen, and muscle). In addition, quantitative ITIC of representative samples was performed with CD-34 staining to compare the calculated microvessel density (MVD) results with DCE-MRI results. Results. MM demonstrated markedly abnormal pharmacokinetic properties compared with normal tissues. Among the parameters tested, Amp was significantly different in MM (P :5.001) compared to normal organs. Despite the observation that the MVD of mesotheliomas in this series was high compared to other tumors, DCE-MRI pharmacokinetic parameters had a moderately positive correlation with MVD (r = 0.5). Conclusions. DCE-MRI and IHC can be used in patients with MM to visualize tumor microvascularity and to characterize tumor heterogeneity. DCE-MRI and IHC results positively correlated, though moderately, but these two methods present as essential tumor biomarkers. This multimodal characterization may be useful in selecting possible tumor subtypes that would benefit from antiangiogenic therapy
    Type of Publication: Journal article published
    PubMed ID: 18423312
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  • 4
    Keywords: MODEL ; VISUALIZATION ; DISEASE ; BLOOD-FLOW ; MAGNETIC-RESONANCE ; magnetic resonance imaging ; SURVEILLANCE ; ANGIOGRAPHY ; endovascular repair ; endovascular ; ANEURYSM REPAIR ; Aorta ; stent graft ; phase-contrast flow ; blood flow velocity
    Abstract: PURPOSE: To validate flow measurements within an aortic nickel-titanium (nitinol) stent graft using velocity-encoded cine magnetic resonance imaging (VEC MRI) and to assess intraobserver agreement of repeated flow measurements. MATERIALS AND METHODS: An elastic tube phantom mimicking the descending aorta was developed with the possibility to insert an aortic nitinol stent graft. Different flow patterns (constant, sinusoidal and pulsatile aortic flow) were applied by a gear pump. A two-dimensional phase-contrast sequence was used to acquire VEC perpendicular cross-sections at six equidistant levels along the phantom. Each acquisition was performed twice with and without stent graft, and each dataset was analysed twice by the same reader. The percental difference of the measured flow volume to the gold standard (pump setting) was defined as the parameter for accuracy. Furthermore, the intraobserver agreement was assessed. RESULTS: Mean accuracy of flow volume measurements was -0.45+/- 1.63% without stent graft and -0.18+/- 1.45% with stent graft. Slightly lower accuracy was obtained for aortic flow both without (-2.31%) and with (-1.29%) stent graft. Accuracy was neither influenced by the measurement position nor by repeated acquisitions. There was significant intraobserver agreement with an intraclass correlation coefficient of 0.87 (without stent graft, p〈0.001) and 0.80 (with stent graft, p〈0.001). The coefficient of variance was 0.25% without stent graft and 0.28% with stent graft. CONCLUSION: This study demonstrated high accuracy and excellent intraobserver agreement of flow measurements within an aortic nitinol stent graft using VEC MRI. VEC MRI may give new insights into the haemodynamic consequences of endovascular aortic repair.
    Type of Publication: Journal article published
    PubMed ID: 20888719
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  • 5
    Keywords: VISUALIZATION ; MRI ; magnetic resonance imaging ; ANEURYSMS ; ARCH ; FLOW PATTERNS ; VOLUNTEERS
    Abstract: This report describes flow patterns derived by three-dimensional (3D) three-directional velocity-encoded cine (VEC) magnetic resonance imaging (MRI), in a patient with chronic Stanford type B aortic dissection. Acquired 3D VEC MRI data illustrated an acceleration of blood flow through the primary entry toward the vessel wall of the false lumen, leading to disturbed intraluminal flow. Furthermore, accelerated blood flow was observed in the partially compressed true lumen. 3D VEC MRI data may be helpful to guide physicians for a more comprehensive preoperative and postoperative assessment of complex aortic pathologies.
    Type of Publication: Journal article published
    PubMed ID: 21658891
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  • 6
    Keywords: POPULATION ; magnetic resonance imaging ; AGE ; NECK ; COMPUTED-TOMOGRAPHY ; ANGIOGRAPHY ; physiology ; CONFORMATIONAL-CHANGES ; THORACIC AORTA ; endovascular repair ; endovascular ; ANEURYSMS ; stent graft ; ARTERIAL STIFFNESS ; WAVE REFLECTION
    Abstract: PURPOSE: To test our hypothesis that distension and displacement in various segments of the healthy thoracic aorta are significant and can be predicted based on clinical characteristics. MATERIALS AND METHODS: Sixty-one Caucasian volunteers without cardiovascular disease (49 +/- 16 years, range 19-82; 28 men, 33 women) divided into two age groups (A: 〈50, B: 〉/= 50 years) underwent 1.5-T MRI. ECG-gated dynamic data sets were acquired at five locations perpendicular to the thoracic aorta. Aortic distension and Centre of Mass (CoM) displacement were determined as percentages of diastolic aortic diameter. A multiple linear regression model including age group, gender, location, mean arterial blood pressure, heart rate and body mass index was tested. RESULTS: Mean aortic distension averaged over all locations was 11.2 +/- 4.1% (age group A) and 6.7 +/- 3.3% (age group B), mean displacement 15.1 +/- 8.3% (A) and 11.0 +/- 6.2% (B). Systolic and diastolic aortic diameter and CoM position significantly differed at all locations (p〈0.001). Distension and displacement could be predicted based on the regression model (p〈0.001). Age group A and women exhibited significantly greater distension and displacement compared to age group B (p〈0.001) and men (p〈0.01), respectively. Distension increased, displacement decreased from proximal to distal. CONCLUSION: Distension and translational displacement are significant at all levels of the thoracic aorta and can be predicted based on clinical characteristics.
    Type of Publication: Journal article published
    PubMed ID: 20850234
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  • 7
    Keywords: MODEL ; VISUALIZATION ; HEART ; BLOOD-FLOW ; blood flow ; magnetic resonance imaging ; PATTERNS ; 2D ; three-dimensional imaging ; 3D ; endovascular repair ; ANEURYSM REPAIR ; phase-contrast MRI ; Aorta ; stent graft
    Abstract: RATIONALE AND OBJECTIVES: Three-dimensional (3D) velocity-encoded cine (VEC) magnetic resonance imaging (MRI) has the potential to quantify 3D hemodynamic aspects known from computational fluid dynamics and to be used to identify hemodynamic risk factors for complications of endovascular aortic repair. The purpose of this study was to investigate the impact of an aortic nickel-titanium (nitinol) stent graft on the accuracy of flow measurements by 3D VEC MRI. MATERIALS AND METHODS: A pump generated pulsatile aortic flow in an elastic tube phantom mimicking the aorta. Stacked two-dimensional three-directional VEC MRI (stacked-2D-3dir-MRI), 3D three-directional VEC MRI (3D-3dir-MRI), and gold-standard 2D through-plane VEC MRI were applied before and after the insertion of an aortic nitinol stent graft. Six equidistant levels were analyzed twice by the same reader. The percentage difference of the measured flow rate from the gold standard was defined as the parameter of accuracy. RESULTS: The overall accuracy of in-stent flow measurements related to the gold standard was -5.4% for stacked-2D-3dir-MRI and -4.1% for 3D-3dir-MRI, demonstrating significant overall underestimation compared to the gold standard (P = .016 and P = .013). However, flow measurements with the stent graft were significantly overestimated by 4.1% using stacked-2D-3dir-MRI (P 〈 .001) and by 5.4% using 3D-3dir-MRI (P = .003) compared to identical measurements without the stent graft. In stacked-2D-3dir-MRI, this positive bias was significantly greater at the proximal and distal ends of the stent graft (P = .025). In 3D-3dir-MRI, measurements along the whole length of the stent graft were affected (P = .006). Intraobserver agreement was excellent, with intraclass correlation coefficients of 0.94 for stacked-2D-3dir-MRI (P 〈 .001) and 0.90 for 3D-3dir-MRI (P 〈 .001). CONCLUSIONS: Flow measurements within an aortic nitinol stent graft by 3D VEC MRI are feasible, but stent grafts may cause a significant positive bias.
    Type of Publication: Journal article published
    PubMed ID: 22177284
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  • 8
    Keywords: brain ; AGENTS ; Germany ; human ; DISEASE ; SITE ; PROTEIN ; PROTEINS ; TUMORS ; MR ; BINDING ; magnetic resonance imaging ; NUMBER ; RATES ; CRYSTAL-STRUCTURE ; CONTRAST AGENTS ; GADOPENTETATE DIMEGLUMINE ; gadobenate dimeglumine ; GD-DTPA ; contrast media ; albumin ; SERUM ; RE ; INCREASE ; ENHANCED MR-ANGIOGRAPHY ; human serum albumin ; MS-325 ; relaxation rate
    Abstract: Objectives: Exogenous magnetic resonance (MR) contrast media (CM) are used to improve detection and delineation of physiological and pathologic structures. Temporary binding between CM and proteins such as human serum albumin (HSA) may alter the relaxation-enhancing properties of specific contrast agents. In this study, the presence and strength of HSA interaction with different CM was investigated. Material and Methods: Three contrast agents were chosen: GdDTPA, Gd-BT-DO3A, and Gd-BOPTA, each of which is known to have a different protein interaction. Samples were prepared using 7 different HSA concentrations, all at a constant CM concentration of 0.5 mmol/L. The relaxation rates, R1 and R2, of each sample were measured at 1.5 T. Virtual docking studies were performed to estimate the number of high affinity-binding sites of Gd-BOPTA and the surface of the HSA dimer. Results: Gd-BOPTA caused the greatest increase in R1 and R2, which followed an exponential dependency with increasing HSA concentration. Between the range of 0 and 7 g/dL of HSA, GdDTPA and Gd-BT-DO3A showed a relative change in both relaxation rates of approximately 13% and 22% for R1 and 26% and 30% for R2, respectively. In contrast, Gd-BOPTA demonstrated a relative increase of approximately 108% and 363% for R1 and R2, respectively. Changes of HSA concentration within physiological range (3.5-5.5 g/dL) resulted in an increase of RI and R2 of approximately 40% when using Gd-BOPTA. The docking study revealed that approximately 10 small hydrophobic pockets exist on the HSA surface where the aromatic tail of Gd-BOPTA can fit in and a stronger noncovalent binding can occur compared with Gd-DTPA and Gd-BT-DO3A. Conclusion: Relaxation rates of Gd-BOPTA showed a strong dependency on HSA. In contrast, Gd-DTPA and Gd-BT-DO3A demonstrated little or no relevant dependency. On the basis of these results, the influence of serum protein concentration should be considered in both research studies and in clinical use
    Type of Publication: Journal article published
    PubMed ID: 16481904
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  • 9
    Keywords: brain ; tumor ; AGENTS ; neoplasms ; PERFUSION ; THERAPY ; DIAGNOSIS ; FOLLOW-UP ; imaging ; SYSTEM ; MORTALITY ; DRUG ; TISSUE ; TUMORS ; MECHANISM ; CONTRAST ; mechanisms ; MRI ; SIGNAL ; FIELD ; MAGNETIC-RESONANCE ; magnetic resonance imaging ; NERVOUS-SYSTEM ; EXPERIENCE ; CENTRAL-NERVOUS-SYSTEM ; pathology ; CONTRAST-ENHANCED MRI ; contrast media ; DIFFERENTIAL-DIAGNOSIS ; YOUNG ; ADULT ; ADULTS ; BRAIN-TUMORS ; dynamic contrast enhanced MRI ; ENHANCEMENT ; blood-brain barrier ; brain tumors ; TUMOR TISSUE ; technique ; functional imaging ; BARRIER ; nervous system ; central nervous system ; BLOOD-BRAIN-BARRIER ; CLINICAL-EXPERIENCE ; PITFALLS
    Abstract: Brain tumors are one of the most common neoplasms in young adults and are associated with a high mortality and disability rate. Magnetic resonance imaging (MRI) is widely accepted to be the most sensitive imaging modality in the assessment of cerebral neoplasms. Because the detection, characterization, and exact delineation of brain tumors require a high lesion contrast that depends on the signal of the lesion in relation to the surrounding tissue, contrast media is given routinely. Anatomical and functional, contrast agent-based MRI techniques allow for a better differential diagnosis, grading, and especially therapy decision, planing, and follow-up. In this article, the basics of contrast enhancement of brain tumors will be reviewed. The underlying pathology of a disrupted blood-brain barrier and drug influences will be discussed. An overview of the currently available contrast media and the influences of dosage, field strength, and application on the tumor tissue contrast will be given. Challenging, contrast-enhanced, functional imaging techniques, such as perfusion MRI and dynamic contrast-enhanced MRI, are presented both from the technical side and the clinical experience in the assessment of brain tumors. The advantages over conventional, anatomical MRI techniques will be discussed as well as possible pitfalls and drawbacks.
    Type of Publication: Journal article published
    PubMed ID: 17198225
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