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  • 1
    Keywords: IN-VITRO ; AGENTS ; IN-VIVO ; PERFUSION ; THERAPY ; CT ; HEPATOCELLULAR-CARCINOMA ; liver ; TISSUE ; MRI ; CATHETER ; embolization ; X-RAY ; ARTERIOVENOUS-MALFORMATIONS ; MICROSPHERES ; ARTERY EMBOLIZATION ; ENDOVASCULAR EMBOLIZATION ; multimodal ; THERAPEUTIC EMBOLIZATION ; UTERINE FIBROID EMBOLIZATION
    Abstract: Objectives: Embolization therapy is gaining importance in the treatment of malignant lesions, and even more in benign lesions. Current embolization materials are not visible in imaging modalities. However, it is assumed that directly visible embolization material may provide several advantages over current embolization agents, ranging from particle shunt and reflux prevention to improved therapy control and follow-up assessment. X-ray-as well as magnetic resonance imaging (MRI)-visible embolization materials have been demonstrated in experiments. In this study, we present an embolization material with the property of being visible in more than one imaging modality, namely MRI and x-ray/computed tomography (CT). Characterization and testing of the substance in animal models was performed. Materials and Methods: To reduce the chance of adverse reactions and to facilitate clinical approval, materials have been applied that are similar to those that are approved and being used on a routine basis in diagnostic imaging. Therefore, x-ray-visible Iodine was combined with MRI-visible Iron (Fe3O4) in a macroparticle (diameter, 40-200 mu m). Its core, consisting of a copolymerized monomer MAOETIB (2-methacryloyloxyethyl [2,3,5-triiodobenzoate]), was coated with ultra-small paramagnetic iron oxide nanoparticles (150 nm). After in vitro testing, including signal to noise measurements in CT and MRI (n = 5), its ability to embolize tissue was tested in an established tumor embolization model in rabbits (n = 6). Digital subtraction angiography (DSA) (Integris, Philips), CT (Definition, Siemens Healthcare Section, Forchheim, Germany), and MRI (3 Tesla Magnetom Tim Trio MRI, Siemens Healthcare Section, Forchheim, Germany) were performed before, during, and after embolization. Imaging signal changes that could be attributed to embolization particles were assessed by visual inspection and rated on an ordinal scale by 3 radiologists, from 1 to 3. Histologic analysis of organs was performed. Results: Particles provided a sufficient image contrast on DSA, CT (signal to noise [SNR], 13 +/- 2.5), and MRI (SNR, 35 +/- 1) in in vitro scans. Successful embolization of renal tissue was confirmed by catheter angiography, revealing at least partial perfusion stop in all kidneys. Signal changes that were attributed to particles residing within the kidney were found in all cases in all the 3 imaging modalities. Localization distribution of particles corresponded well in all imaging modalities. Dynamic imaging during embolization provided real-time monitoring of the inflow of embolization particles within DSA, CT, and MRI. Histologic visualization of the residing particles as well as associated thrombosis in renal arteries could be performed. Visual assessment of the likelihood of embolization particle presence received full rating scores (153/153) after embolization. Conclusions: Multimodal-visible embolization particles have been developed, characterized, and tested in vivo in an animal model. Their implementation in clinical radiology may provide optimization of embolization procedures with regard to prevention of particle misplacement and direct intraprocedural visualization, at the same time improving follow-up examinations by utilizing the complementary characteristics of CT and MRI. Radiation dose savings can also be considered. All these advantages could contribute to future refinements and improvements in embolization therapy. Additionally, new approaches in embolization research may open up
    Type of Publication: Journal article published
    PubMed ID: 21263332
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  • 2
    Keywords: measurement ; BLOOD ; COMBINATION ; Germany ; human ; MODEL ; PERFUSION ; QUANTIFICATION ; VOLUME ; DISEASE ; DIFFERENTIATION ; TISSUE ; RESOLUTION ; TIME ; PATIENT ; kidney ; BLOOD-FLOW ; animals ; blood flow ; CONTRAST AGENT ; FLOW ; intravascular contrast agent ; MR ; RAT-KIDNEY ; SEQUENCE ; DAMAGE ; arteries ; MR-ANGIOGRAPHY ; ABNORMALITIES ; MR angiography ; HYPERTENSION ; PREVALENCE ; TRANSPLANTS ; BREATH-HOLD ; parenchymal disease ; renal artery stenosis ; 3-DIMENSIONAL MR-ANGIOGRAPHY ; ischemic kidney disease ; renal autoregulation ; renal perfusion ; RENOGRAPHY ; SWINE MODEL
    Abstract: The interrelation between the morphologic degree of renal artery stenosis and changes in parenchymal perfusion is assessed using an intravascular contrast agent. In seven adult foxhounds, different degrees of renal artery stenosis were created with an inflatable clamp implanted around the renal artery. Dynamic susceptibility-weighted gradient-echo imaging was used to measure signal-time curves in the renal artery and the renal parenchyma during administration of 1.5 mg/kg BW of an intravascular ultrasmall particle iron oxide (USPIO) contrast agent. From the dynamic series, regional renal blood volume (rRBV), regional renal blood flow (rRBF), and mean transit time (MTT) were calculated. The morphologic degree of stenosis was measured in the steady state using a high- resolution 3D contrast-enhanced (CE) MR angiography (MRA) sequence (voxel size = 0.7 x 0.7 x 1 mm(3)). Five patients with renoparenchymal damage due to long-standing renal artery stenosis were evaluated. In the animal stenosis model, cortical perfusion remained unchanged for degrees of renal artery stenosis up to 80%. With degrees of stenoses 〉 80%, cortical perfusion dropped to 151 +/- 54 ml/100 g of tissue per minute as compared to a baseline of 513 +/- 76 ml/100 g/min. In the patients, a substantial difference in the cortical perfusion of more than 200 +/- 40 ml/100 g/min between the normal and the ischemic kidneys was found. The results show that quantitative renal perfusion measurements in combination with 3D-CE-MRA allow the functional significance of a renal artery stenosis to be determined in a single MR exam. Differentiation between renovascular and renoparenchymal disease thus becomes feasible. (C) 2003 Wiley-Liss, Inc
    Type of Publication: Journal article published
    PubMed ID: 12541249
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  • 3
    Keywords: measurement ; BLOOD ; COMBINATION ; evaluation ; Germany ; PERFUSION ; CLASSIFICATION ; DIAGNOSIS ; imaging ; QUANTIFICATION ; DISEASE ; ACCURACY ; PATIENT ; kidney ; BLOOD-FLOW ; renal ; RISK-FACTORS ; blood flow ; CANINE MODEL ; FLOW ; MR ; QUANTITATION ; SEQUENCE ; magnetic resonance ; MAGNETIC-RESONANCE ; magnetic resonance imaging ; DIFFERENCE ; arteries ; sensitivity ; REJECTION ; MR-ANGIOGRAPHY ; ANGIOGRAPHY ; ARTERY ; PREVALENCE ; HEALTHY ; resonance imaging ; perfusion study ; INVERSION ; ARTERY STENOSIS ; renal arteries ; RENOVASCULAR HYPERTENSION ; STENOSIS ; vascular studies
    Abstract: Purpose: To differentiate healthy kidneys from diseased kidneys, we propose a combined magnetic resonance (MR) examination that includes measurements of renal arterial blood flow and parenchymal perfusion. Materials and Methods: A total of 130 kidneys (patients/healthy volunteers: 83/47) were examined using renal artery MR flow measurements and renal parenchymal perfusion measurements, as well as contrast-enhanced MR angiography. Cine phase-contrast-flow measurements were performed using an ECG-gated fast low angle shot pulse sequence; perfusion was measured with an arterial spin labeling flow-sensitive alternating inversion recovery technique. Contrast-enhanced MR angiography was performed with a fast 3D gradient echo sequence in a single breath hold. For evaluation, kidneys were divided into groups based on nephrologic diagnosis of the patient. Recursive partitioning and Wilcoxon rank-sum tests were used to separate the different groups. Results: Significant differences in mean renal artery flow and parenchymal perfusion were found in kidneys with renal artery stenosis as well as parenchymal disease as compared with healthy kidneys. Using a classification tree derived from the recursive partitioning, a specificity of 99% and sensitivity of 69% with a positive/negative predictive value of 97%/84% was achieved for the separation of healthy kidneys from kidneys with vascular, parenchymal or combined disease. The overall accuracy was 88%. Conclusion: The combination of cine PC flow measurements and MR perfusion measurements offers a comprehensive assessment of both renovascular and renoparenchymal disease and provide a noninvasive approach to differentiate between these kidneys and normal kidneys
    Type of Publication: Journal article published
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  • 4
    Keywords: Germany ; QUANTIFICATION ; TIME ; PATIENT ; kidney ; BLOOD-FLOW ; CANINE MODEL ; intravascular contrast agent ; AGE ; MAGNETIC-RESONANCE ANGIOGRAPHY ; FEASIBILITY ; BREATH-HOLD ; GLOMERULAR-FILTRATION ; LEVEL ; LUMEN VISUALIZATION ; NONINVASIVE MEASUREMENT
    Abstract: Purpose: To prospectively assess feasibility of renal magnetic resonance (MR) perfusion measurement method based, on turbo fast low-angle shot sequences for grading effect of renal artery stenosis (RAS) on parenchymal perfusion. Materials and Methods: Institutional review board approved this study, and patients gave written consent. Seventy-three patients (34 male, 39 female; age range, 17-84 years) who were clinically suspected of having RAS underwent contrast material- enhanced (gadodiamide) saturation-recovery turbo fast low-angle shot imaging for measurement of renal perfusion and high-spatial-resolution MR angiograpby for RAS detection and grading. Degree of stenosis was evaluated as high grade (〉= 75% stenosis), low to intermediate grade (〉 0% to 〈 75% stenosis), or absent. High temporal resolution of the turbo fast low-angle shot sequence allowed acquisition of an exact first-pass tracing of the contrast agent bolus from which a signal intensity (SI)-time curve was derived. On the basis of this curve, mean transit time (MTT) of the contrast agent bolus, maximal upslope (MUS) of the curve, maximum SI, and time to SI peak (TTP) were calculated with a gamma variate fit. Wilcoxon rank sum test, Pearson product moment correlation, and paired t test were used for statistical analysis. Results: Twenty-four renal arteries had high-grade RAS, 12 renal arteries had low- to intermediate-grade RAS, and 104 renal arteries had no RAS. Significant differences between patients without stenoses or with low- to intermediate-grade stenoses and patients with high-grade stenoses were found for MTT, MUS, and TTP (P 〈.001). Perfusion parameters were correlated with patients' serum creatinine levels, and significant correlations were found for MTT (r = 0.41), MUS (r = 0.48), and TTP (r = 0.4), with P 〈.001. Conclusion: MR perfusion parameters can be used to assess effect of RAS on parenchymal perfusion. Perfusion measurements reflect renal function as measured with serum creatinine levels. (c) RSNA, 2006
    Type of Publication: Journal article published
    PubMed ID: 16436819
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  • 5
    Keywords: 3D MR-ANGIOGRAPHY, ANGIOGRAPHY, CHEST CT, COMMON, comparison, CONTRAST, CONTRAST-ENHANCED MR, contra
    Abstract: Pulmonary embolism (PE) is a very common and potentially life-threatening disease. In comparison with CT, the clinical relevance of magnetic resonance imaging (MRI) for the assessment of PE is low. Nevertheless, as there are some potential advantages of MRI over CT (e.g. radiation free method, better safety profile of MR contrast media, capability of functional imaging). In certain patient, groups MRI might therefore be considered as a valuable alternative in the assessment of suspected PE. This article reviews the relevant MRI techniques for the evaluation of PE and gives an overview of the current literature for contrast-enhanced MR angiography of PE
    Type of Publication: Journal article published
    PubMed ID: 17486344
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  • 6
    Keywords: AGENTS ; Germany ; imaging ; DISEASE ; MORTALITY ; NEW-YORK ; NUCLEAR-MEDICINE ; TIME ; PATIENT ; kidney ; CONTRAST ; CONTRAST AGENT ; ASSOCIATION ; PATHOGENESIS ; HIGH-RISK ; STABILITY ; CONTRAST AGENTS ; MAGNETIC-RESONANCE ANGIOGRAPHY ; magnetic resonance imaging (MRI) ; nuclear medicine ; AGENT ; radiology ; fibrosis ; case control study ; review ; ENHANCED MR-ANGIOGRAPHY ; case control studies ; NUCLEAR ; USA ; function ; RECOMMENDATIONS ; odds ratio ; retrospective ; systemic ; MEDICINE ; case control ; medical imaging ; - ; German ; case-control ; gadolinium ; OCCURS ; CONTRAST-MEDIA ; review article ; DERMOPATHY ; GADODIAMIDE ; HIGH-RISK PATIENTS ; NEPHROGENIC SYSTEMIC FIBROSIS ; nephrogenic systemic fibrosis (NSF) ; RATIO ; SUBTRACTION ; TRANSMETALATION
    Abstract: Nephrogenic systemic fibrosis (NSF) is a systemic disease with a 5% mortality which was first described in 1997 and which only occurs in patients with severely impaired renal function (GFR 〈 30 ml/min per 1.73 m(2)) and for which an association with previous administration of several Gd-chelates has been observed. According to retrospective case control studies the odds ratio for a patient with severely impaired renal function to develop NSF was increased by a factor of 22-32 when gadodiamide was administered. At this time there are approximately 250 confirmed cases of NSF of which 177 are associated with the administration of gadodiamide and 78 are associated with gadopentetate dimeglumine. This review article elucidates the postulated pathogenesis of NSF and provides an overview of the published statements and recommendations from international regulatory authorities and from international advisory boards. Even though the pathogenesis is not completely understood at this time, the European Pharmacovigilance Working Party has decided that gadodiamide and gadopentetate dimeglumine must not be used in high-risk patients. Other Gd-containing contrast agents should only be administered after thorough assessment of the indication and with minimized Gd dose. In the USA, the FDA has issued a black box warning for Gd-containing contrast agents
    Type of Publication: Journal article published
    PubMed ID: 17624507
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  • 7
    Keywords: BREAST-CANCER ; COMPUTED-TOMOGRAPHY ; LIVER METASTASES ; SOLID TUMORS ; PULMONARY NODULES ; EMISSION-TOMOGRAPHY ; SKELETAL SCINTIGRAPHY ; METASTATIC-DISEASE ; OBSERVER VARIATION ; BONE-SCINTIGRAPHY
    Abstract: Abstract: Background: Malignant melanoma (MM) is dramatically increasing in light-skinned populations worldwide. Staging and regular follow-up examinations are essential. The purpose of this study was to compare the diagnostic accuracy of whole-body MRI with the standard diagnostic algorithm (whole-body CT and brain MRI) in patients with stage III/IV MM. Patients and methods: A group of 50 consecutively admitted patients with stage III/IV MM were included in the study. Whole-body CT and brain MRI scans were performed. Additionally, all patients underwent a whole-body MRI (1.5 Tesla Magnetom Avanto, Siemens Healthcare Sector, Erlangen). The findings were compared on a lesion-by-lesion basis as part of clinical routine follow-up. Results: 33 patients received a follow-up CT and were evaluated. Overall, 824 lesions were detected. The sensitivity of whole-body MRI was observer-dependent. MRI was slightly less sensitive than CT according to the findings of the two most experienced observers (73.4% vs. 78.2%, p = 0.0744). CT was significantly more sensitive in the detection of small (1-5 mm) pulmonary nodules (2.9% vs. 66.9%, p 〈 0.0001). Yet overall, MRI was significantly more specific than CT (83.4% vs. 50.4%, p 〈 0.0001). Conclusions: Whole-body MRI in compliance with standard requirements for the observers (high level of experience) should be considered as an appropriate alternative to CT without ionizing radiation, particularly for young patients with advanced MM.
    Type of Publication: Journal article published
    PubMed ID: 21352483
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  • 8
    Keywords: TUMORS ; RESOLUTION ; MAGNETIC-RESONANCE ; RELAXATION ; COMPONENT ; SKELETAL-MUSCLE ; human brain ; TISSUE SODIUM CONCENTRATION ; ECHO TIMES ; PROJECTION TECHNIQUE
    Abstract: Purpose: To qualitatively and quantitatively assess the corticomedullary sodium 23 ((23)Na) concentration in human kidneys before and after oral administration of a water load by using 3-T magnetic resonance (MR) imaging. Materials and Methods: Fourteen healthy volunteers (mean age, 28 years; range, 24-34 years) were included in this institutional review board-approved study between July and December 2009. For (23)Na MR imaging, a density-adapted three-dimensional radial gradient echo sequence (echo time, 0.55 msec; repetition time, 120 msec; spatial resolution, 5 x 5 x 5 mm) was used with a dedicated (23)Na-tuned coil. Beforehand, the coil profile was assessed by using phantom measurements, and the volunteer images were mathematically corrected accordingly. Images of the volunteers were obtained before and 30 minutes after oral ingestion of 1 L of water. As internal reference, (23)Na concentration of the cerebrospinal fluid (CSF) was calculated. Well-defined corticomedullary complexes in each kidney were assessed, with (23)Na concentrations in the cortex and medulla assessed at various standardized points. From these values, quantitative (23)Na concentrations were derived, and the slopes of the linear portion of the concentration gradient were calculated. Paired t tests were performed. Results: Mean calculated (23)Na concentrations of CSF before (135.2 mmol/L +/- 10.4) and after water load (135.5 mmol/L +/- 11.0) fell within physiologic ranges (P = .95). An increase in average (23)Na concentration from 63.5 mmol/L +/- 9.3 in the cortex to 108.0 mmol/L +/- 10.9 in the medulla was identified. After the water load, this gradient was preserved, although (23)Na concentrations decreased significantly (P 〈 .0001) to 48.6 mmol/L +/- 5.3 in the cortex and 81.9 mmol/L +/- 10.1 in the medulla-declines of 23.4% and 24.7%, respectively. Conclusion: This study demonstrates the physiologic evaluation of human kidneys with 3-T (23)Na MR imaging. The (23)Na imaging technique used allows the quantification of the corticomedullary (23)Na concentration and the assessment of its change with differing physiologic conditions.
    Type of Publication: Journal article published
    PubMed ID: 21771954
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  • 9
    Keywords: measurement ; BLOOD ; Germany ; MODEL ; PERFUSION ; IMAGES ; QUANTIFICATION ; VOLUME ; TIME ; kidney ; blood flow ; CANINE MODEL ; CEREBRAL BLOOD-FLOW ; CONTRAST AGENT ; dynamic T-2*-weighted imaging ; FLOW ; HIGH-RESOLUTION MEASUREMENT ; INJECTION ; intravascular contrast agent ; MR ; MRI ; QUANTITATION ; RAT-KIDNEY ; susceptibility contrast ; time series deconvolution ; TRACER BOLUS PASSAGES
    Abstract: In this work absolute values of regional renal blood volume (rRBV) and flow (rRBF) are assessed by means of contrast- enhanced (CE) MRI using an intravascular superparamagnetic contrast agent. In an animal study, eight foxhounds underwent dynamic susceptibility-weighted MRI upon injection of contrast agent. Using principles of indicator dilution theory and deconvolution analysis, parametric images of rRBV, rRBF, and mean transit time (MTT) were computed. For comparison, whole- organ blood flow was determined invasively by means of an implanted flow probe, and the weight of the kidneys was evaluated postmortem. A mean rBV value of 28 ml/100 g was found in the renal cortex, with a corresponding mean rBF value of 524 ml/100 g/min and an average MTT of about 3.4 s. Although there was a systematic difference between the absolute blood flow values determined by MRI and the ultrasonic probe, a significant correlation (r(s) = 0.72, P 〈 0.05) was established. The influence of the arterial input function (AIF), T-1 relaxation effects, and repeated measurements on the precision of the perfusion quantitation is discussed. (C) 2003 Wiley-Liss, Inc
    Type of Publication: Journal article published
    PubMed ID: 12541248
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  • 10
    Keywords: brain ; Germany ; MRI ; ALZHEIMERS-DISEASE ; DEMENTIA ; AD ; Alzheimer's disease,magnetic resonance imaging,computed tomography,fMRI,structural imaging ; ATROPHY ; CEREBRAL WHITE-MATTER ; DIFFUSION TENSOR ; MILD COGNITIVE IMPAIRMENT ; VASCULAR DEMENTIA ; WORKING-MEMORY
    Type of Publication: Journal article published
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