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  • magnetic resonance imaging  (5)
Keywords
  • 1
    Keywords: measurement ; BLOOD ; Germany ; VOLUME ; TIME ; BLOOD-FLOW ; SIMULATION ; blood flow ; MR ; SIGNAL ; MAGNETIC-RESONANCE ; magnetic resonance imaging ; NMR ; ARTERY ; radiology ; 2D ; interventional ; STENOSIS ; catheterization ; intra-arterial flow measurements ; MR-compatible devices ; PULSEWAVE VELOCITY ; STENT PLACEMENT ; TARDUS
    Abstract: Flow measurements can be used to quantify blood flow during MR-guided intravascular interventional procedures. In this study, a fast flow measurement technique is proposed that quantifies flow velocities in the vicinity of a small RF coil attached to an intravascular catheter. Since the small RF coil receives signal from only a limited volume around the catheter, a spatially nonselective signal reception is employed. To enhance signal from flowing blood, and suppress unwanted signal contributions from static material, a slice-selective RF excitation is used. At a velocity sensitivity of 150 cm/s, a temporal resolution of 2 x TR = 10.2 ms can be achieved. The flow measurement is combined with an automatic slice positioning to facilitate measurements during interventional procedures. The influence of the catheter position in the blood vessel on the velocity measurement was analyzed in simulations. For blood vessels with laminar flow, the simulation showed a systematic deviation between catheter measurement and true flow between -15% and 80%. In four animal experiments, the catheter velocity measurement was compared with results from a conventional ECG-triggered 2D phase-contrast (PC) technique. The shapes of the velocity time curves in the abdominal aorta were nearly identical to the conventional measurements. A relative scaling factor of 0.69-1.19 was found between the catheter velocity measurement and the reference measurement, which could be partly explained by the simulation results. (C) 2004 Wiley-Liss, Inc
    Type of Publication: Journal article published
    PubMed ID: 15334577
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  • 2
    Keywords: CANCER ; tumor ; carcinoma ; CELL ; Germany ; CT ; imaging ; DISEASE ; DIFFERENTIATION ; TISSUE ; computed tomography ; SURGERY ; PATIENT ; primary ; MRI ; MAGNETIC-RESONANCE ; magnetic resonance imaging ; NO ; DIFFERENCE ; NUMBER ; METASTASIS ; metastases ; REGION ; REGIONS ; DISSEMINATED TUMOR-CELLS ; adenocarcinoma ; COMPUTED-TOMOGRAPHY ; CELL CARCINOMA ; renal cell carcinoma ; pancreas ; ENHANCEMENT ; methods ; multidetector CT ; RENAL-CELL
    Abstract: Aims: To investigate the characteristics of metastasis to the pancreas using computed tomography (CT) and magnetic resonance imaging (MRI). Methods: Twenty-two patients with metastases to the pancreas were examined preoperatively by MRI (7/22) and/or multidetector CT (15/22). Pre- and post-contrast images were acquired and morphology, size, and contrast enhancement of the tumor analyzed. Subsequently, all patients underwent surgery, and the histopathologic findings were compared with the imaging results. Results: In 22 patients, a total of 29 metastases were found on CT and MRI. These metastases originated from renal cell carcinomas (RCC; 22/29), colorectal carcinoma (3/29), and other malignancies (4/29). The metastases differed not in size or location, but in their contrast enhancement characteristics. RCC metastases had either intense homogeneous enhancement (in small lesions) or rim enhancement (in large lesions). Outer regions of colorectal metastases showed no difference from normal pancreatic tissue, whereas the inner area showed hypo-enhancement due to central necrosis. Conclusion: Imaging features of metastases from RCC point to their primary origin. While they can be distinguished from primary adenocarcinoma of the pancreas, differentiation from endocrine carcinoma might be difficult. Differentiation of colorectal carcinoma remains to be investigated on larger numbers of cases. Copyright (C) 2008 S. Karger AG, Basel and IAP
    Type of Publication: Journal article published
    PubMed ID: 18434757
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  • 3
    Keywords: Germany ; imaging ; TISSUE ; RESOLUTION ; radiation ; PATIENT ; CONTRAST ; MR ; MRI ; MAGNETIC-RESONANCE ; magnetic resonance imaging ; ACQUISITION ; HEALTH ; RATES ; ANGIOGRAPHY ; nuclear medicine ; RECONSTRUCTION ; 2D ; CATHETER TRACKING ; 3D ; TECHNOLOGY ; COILS ; occupational health ; PLACEMENT
    Abstract: At present, interventional procedures, such as stent placement, are performed under X-ray image guidance. Unfortunately with X-ray imaging, both patient and interventionalist are exposed to ionising radiation. Furthermore, X-ray imaging is lacking soft tissue contrast and is not capable of true 3-D displays of either interventional device or tissue morphology. Magnetic resonance imaging (MRI) offers excellent soft tissue contrast, 3-D acquisition techniques, as well as rapid image acquisition and reconstruction. Despite these advantages, MR-guided interventions are challenging owing to the limited access to the patient, strong magnetic and radio-frequency fields that require special interventional devices, inferior image frame rates and spatial resolution, and high MRI scanner noise. For MR-guided intravascular interventions, where access to the target organ is achieved through catheters, dedicated hardware and automated image slice positioning techniques have been developed. We illustrate that MR-guided renal embolisations can be performed in closed-bore high-field MR scanners
    Type of Publication: Journal article published
    PubMed ID: 16464829
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  • 4
    Keywords: GROWTH ; INVASION ; tumor ; carcinoma ; CELL ; Germany ; CT ; FOLLOW-UP ; imaging ; SUPPORT ; SYSTEM ; VISUALIZATION ; TUMORS ; computed tomography ; RESOLUTION ; SURGERY ; NUCLEAR-MEDICINE ; kidney ; MRI ; treatment ; magnetic resonance ; MAGNETIC-RESONANCE ; magnetic resonance imaging ; PERFORMANCE ; tomography ; PROGNOSTIC-SIGNIFICANCE ; FAT ; COMPUTED-TOMOGRAPHY ; nuclear medicine ; MR imaging ; staging ; HELICAL CT ; radiology ; CELL CARCINOMA ; renal cell carcinoma ; INFILTRATION ; review ; TUMOR-GROWTH ; EXTENSION ; HIGH-RESOLUTION ; methods ; NUCLEAR ; COMPUTERIZED-TOMOGRAPHY ; multidetector CT ; abdomen ; CT high resolution ; MEDICINE ; imaging modalities ; RESONANCE ; 1997 TNM CLASSIFICATION ; FAT INVASION ; NEPHRON-SPARING SURGERY ; therapy planning ; TUMOR THROMBUS EXTENSION
    Abstract: Modern imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI) allow high-resolution imaging of the abdomen. Modern scanners made high temporal as well as high spatial resolution available. Therapeutic approaches to the treatment of renal cell carcinoma have been improved over the recent years. Besides conventional and open laparoscopic tumor nephrectomy and nephron sparing, surgical approaches such as local tumor cryotherapy and radiofrequency ablation (RF) are ablative modalities and are used increasingly. Improved anesthesiological methods and new surgical approaches also allow curative treatment in extended tumors. Prerequisites for preoperative imaging modalities include visualization of the kidney tumor as well as its staging. Tumor-related infiltration of the renal pelvis or invasion of the perinephric fat and the renal hilus has to be excluded prior to nephron sparing surgery. In cases with extended tumors with infiltration of the inferior vena cava, it is necessary to visualize the exact extension of the tumor growth towards the right atrium in the vena cava. The radiologist should be informed about the diagnostic possibilities and limitations of the imaging modalities of CT and MRI in order to support the urologist in the planning and performance Of Surgical therapeutical approaches
    Type of Publication: Journal article published
    PubMed ID: 18004691
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  • 5
    Keywords: CANCER ; tumor ; carcinoma ; CELL ; Germany ; MODEL ; PERFUSION ; imaging ; DIFFERENTIATION ; TUMORS ; SURGERY ; PATIENT ; IMPACT ; CONTRAST ; MRI ; SEQUENCE ; MAGNETIC-RESONANCE ; magnetic resonance imaging ; NUMBER ; tomography ; CARCINOMAS ; CONTRAST-ENHANCED MRI ; CELL CARCINOMA ; renal cell carcinoma ; ONCOLOGY ; dynamic contrast enhanced MRI ; SUBTYPES ; dCE MRI ; PHARMACOKINETIC PARAMETERS ; NEPHRON-SPARING SURGERY ; FUNCTIONAL ASSESSMENT ; grading ; AREA ; CELL CARCINOMAS
    Abstract: In this study, we investigated whether assessment of the tumor perfusion by dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) enables to estimate the morphologic grading of renal cell carcinomas. A total of 21 patients with suspected renal cell cancer were examined using a Gadobutrol-enhanced, dynamic saturation-recovery, turbo-fast, low-angle shot sequence. Tumor perfusion and the tissue-blood ratio within the entire tumor and the most highly vascularized part of the tumor were calculated according to the model of Miles. Immediately after examination, patients underwent surgery, and the results from imaging were compared with the morphological analysis of the histologic grading. Fourteen patients had G2 tumors, and seven patients had G3 tumors. Significantly higher perfusion values (p 〈 0.05) were obtained in G3 tumors than in G2 tumors when the entire tumor area was considered (1.59 +/- 0.44 (ml/g/min) vs. 1.08 +/- 0.38 (ml/g/min)) or its most highly vascularized part (2.14 + 0.89 (ml/g/min) vs. 1.40 + 0.49 (ml/g/min)). By contrast, the tissue-blood ratios did not differ significantly between the two groups. In conclusion, unlike tissue-blood ratio, surrogate parameters of the tumor perfusion determined by DCE MRI seem to allow an estimation of the grading of renal cell carcinoma. However, further studies with high case numbers and including patients with G1 tumors are required to evaluate the full potential and clinical impact. (C) 2009 Elsevier Ireland Ltd. All rights reserved
    Type of Publication: Journal article published
    PubMed ID: 19540690
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