S Rheinheimer

Universität Heidelberg, Heidelberg, Baden-Wuerttemberg, Germany

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Publications (4)5.29 Total impact

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    ABSTRACT: To evaluate the effect of cold ischemia time (CIT) of renal allografts on diffusion and perfusion using intravoxel incoherent motion (IVIM) derived parameters. A total of 37 patients with renal allografts (CIT: 27 <15 h, 10 ≥15 h) and 30 individuals with healthy kidneys were examined at 1.5 T using a single-shot echo-planar diffusion-weighted pulse sequence with nine b-values ranging from 0 to 800 s/mm(2). ADC, perfusion fraction f, and the diffusion coefficient D were calculated using the IVIM model. Parameters of allografts stratified by CIT were compared with healthy kidney groups using the Mann-Whitney U test for unpaired data. We computed the Spearman correlation coefficient for correlation with creatinine values. ADC, D, and f of transplanted kidneys were significantly lower than in the healthy controls. The long-CIT group showed significantly lower diffusion parameters compared with the short-CIT group [mean±SD]: ADC: 1.63±0.14 μm(2)/ms, f: 11.90±5.22%, D: 1.55±0.25 μm(2)/ms versus ADC: 1.79±0.13 μm(2)/ms, f: 16.12±3.43%, D: 1.73±0.14 μm(2)/ms, P(ADC), (f), (D)<0.05. Our results suggest that diffusion parameters, especially the ADC, depend on the CIT of the kidney allograft. Potentially, this stands for functional changes in renal allografts. Diffusion-weighted imaging could be used for follow-up examinations. Thus, diffusion parameters may help guide therapy in patients with delayed graft function.
    European journal of radiology 07/2012; 81(9):e951-6. · 2.65 Impact Factor
  • Der Nephrologe 06/2012; 29:306-314.
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    ABSTRACT: Usefulness of biexponentially fitted signal attenuation at different b-values for differentiating the histological characteristics of renal tumors. A total of 26 patients with 28 renal masses (histologically proven: 20 clear cell renal cell carcinomas [ccRCC], three transitional cell carcinomas, two oncocytomas, and one papillary RCC) and 30 volunteers with healthy kidneys were examined at 1.5 Tesla using an echo-planar DWI sequence. Using the IVIM model, we calculated the perfusion fraction f and the diffusion coefficient D. Furthermore, the ADC was obtained. These tumor parameters were compared to healthy renal tissue nonparametrically, and a receiver operating characteristic (ROC) analysis was performed. Healthy renal parenchyma showed higher ADC and D values (p<0.001) than ccRCC (ADC 1.95±0.10 [SD] μm2/ms, f 18.32±2.52%, and D 1.88±0.11 μm2/ms versus ADC 1.45±0.38 μm2/ms, f 18.59±6.16%, and D 1.34±0.38 μm2/ms). When detecting malignancies the area under the curve for D was higher than for ADC. The f values for ccRCC were higher (p<0.001) than for non-ccRCC (ADC 1.52±0.47 μm2/ms, f 8.44±1.24%, and D 1.30±0.18 μm2/ms). Both f and D correlated with ccRCC grading. IVIM imaging is able to provide reliable diffusion values in the human kidney and may enhance the accuracy of tumor diagnosis. The D value was the best parameter to distinguish renal tumors from healthy renal tissue. The f value is promising for determining the histological subgroups.
    European journal of radiology 11/2011; 81(3):e310-6. · 2.65 Impact Factor
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    ABSTRACT: Die häufige Anwendung bildgebender Verfahren hat zu einem Anstieg der Zahl der zufällig entdeckten Nierenzellkarzinome („renal cell carcinomas“, RCC) geführt. Insbesondere die Inzidenz kleiner asymptomatischer Nierenmassen hat signifikant zugenommen. Infolge erheblicher Fortschritte im Therapiemanagement der RCC, z.B. neue Ansätze in der „Nephron-sparing“-Chirurgie für lokalisierte Tumoren, die <4cm groß sind, wird die Schnittbildgebung für eine detailliertere präoperative Charakterisierung der Nierenmassen erforderlich. Die meisten Nierentumoren (80%) werden zufällig bei Ultraschalluntersuchungen (US) diagnostiziert. Die Detektionsrate kann mithilfe der farbcodierten Duplexsonographie oder des kontrastverstärkten Ultraschalls („contrast-enhanced ultrasound“, CEUS) sogar noch verbessert werden. Ist eine genaue US-Diagnose nicht möglich, kann die Computertomographie (CT) helfen, komplizierte zystische Nierenläsionen weiterzucharakterisieren. Heute ist die CT immer noch der Goldstandard für die Beurteilung der primären Tumorausdehnung und des Staging. Das wichtigste Kriterium für die Bewertung der Malignität von Nierenläsionen ist der durch Kontrastverstärkung gewonnene Beweis. Die CT kann auch eine Differenzierung zwischen nichtbösartigen soliden Massen, wie Angiomyolipomen und Adenomen, sowie bösartigen Nierentumoren unterstützen. Auch die Diagnose von Lymphomen ist möglich. Die Magnetresonanztomographie (MRT) bietet einen besseren Weichteilkontrast und ist der CT in der Diagnose möglicher vaskulärer Beteiligung und einer Bewertung von Tumorzapfen der V.cava inferior überlegen. Die Differenzierung in RCC-Subtypen, Angiomyolipome und eine Unterscheidung zwischen einfachen sowie komplexen Nierenzysten sind ebenfalls möglich. Das Grading der verschiedenen Nierenzellkarzinome kann präoperativ mithilfe der dynamischen kontrastverstärkten MRT oder durch eine Messung der Perfusion und Diffusion innerhalb des Nierentumors beurteilt werden. Die Kombination Positronen-Emissions-Tomographie/Computertomographie (PET/CT) ist aufgrund der niedrigen Sensitivität und Verlässlichkeit für diagnostische Routineuntersuchungen ungeeignet. Dennoch kann die PET eine wichtige Rolle für die Diagnose von Fernmetastasen und die postoperative Überwachung von fortgeschrittenen Nierentumoren spielen. In einigen Fällen ist eine komplementäre Anwendung radiologischer Bildgebungsmodalitäten (US, CT, MRT oder PET/CT) für die genaue Differenzierung der Nierenmassen und eine Diagnose von Nierenzellkarzinomen notwendig. The frequent use of imaging modalities has led to a rising number of incidentally detected renal cell carcinomas (RCC). Especially the incidence of small asymptomatic renal masses has significantly increased. Due to considerable progress in disease management of RCC, for example new approaches in nephron-sparing surgery for localized tumors less than 4cm, cross-sectional imaging is required for a more detailed preoperative characterization of renal masses. Most renal tumors (80%) are diagnosed incidentally by ultrasound examination (US). The detection rate can even be improved using duplex sonography or contrast-enhanced ultrasound (CEUS). If an accurate diagnosis is not possible with ultrasound, computed tomography (CT) examination may help to further qualify complicated cystic lesions of the kidneys. Computed tomography (CT) is still the reference standard for diagnosing primary tumor extent as well as for tumor staging. The most important criterion for assessing malignancy in a renal lesion is the evidence supplied by contrast-enhancement. Computed tomography also facilitates a differentiation of benign solid masses, such as angiomyolipomas and adenomas from malignant renal tumors and even the diagnosis of lymphomas is possible. Magnetic resonance imaging offers a better soft tissue contrast and is superior to a CT examination in diagnosing possible venous involvement and in the evaluation of inferior vena cava tumor thrombi. The differentiation of RCC subtypes, angiomyolipomas as well as distinguishing simple from complex renal cysts is also possible. The grading of different RCCs can be preoperatively estimated using dynamic contrast-enhanced MRI or measuring perfusion and diffusion within renal tumors. Due to a low sensitivity positron emission tomography/computed tomography (PET/CT) is not part of the routine diagnostic management for RCC. Nevertheless it plays an important role in the diagnosis of distant metastases and postoperative surveillance of advanced renal tumors. In some cases a complementary application of radiological imaging modalities, such as US, CT, MRI or PET/CT is required for an accurate differentiation of renal masses and for the diagnosis of RCCs. SchlüsselwörterNierenzellkarzinom–Nierenerkrankungen, zystisch–Diagnostische Bildgebung–Klassifikation–Tumor-Staging KeywordsRenal cell carcinoma–Kidney diseases, cystic–Diagnostic imaging–Classification–Tumor staging
    Der Nephrologe 07/2011; 6(4):306-314.