R König

University of Bonn, Bonn, North Rhine-Westphalia, Germany

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Publications (48)173.01 Total impact

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    ABSTRACT: In patients with drug-refractory focal epilepsy, nonlesional magnetic resonance imaging (MRI) or discordant data of presurgical standard investigations leads to failure generating a sufficient hypothesis for electrode implantation or epilepsy surgery. The seizure-onset zone can be further investigated by subtraction ictal single-photon emission computed tomography (SPECT) coregistered to MRI (SISCOM). This is an observational study of a large consecutive cohort of patients undergoing prospective SISCOM to generate hypothesis for electrode implantation or site of epilepsy surgery. One hundred seventy-five consecutive patients undergoing presurgical evaluation with either nonlesional MRI or discordant data of standard investigations preventing the generation of hypothesis for seizure onset were evaluated with SISCOM. Results were compared to gold standard for seizure onset detection, either electrocorticography (ECoG) and/or postoperative outcome. One hundred thirty patients had successful SPECT injection. Hypothesis for electrode implantation/site of surgery was generated in 74 patients. Forty patients had gold standard comparison. Twenty-eight patients underwent resective surgery. SISCOM was concordant to site of surgery in 82%. An additional 12 patients underwent invasive EEG monitoring but were not suitable for surgery. SISCOM was concordant multifocal in 75%. Two years postsurgical follow-up of 26 patients showed favorable outcome in 22 (Engel class I and class II). SISCOM is a highly valuable diagnostic tool to localize the seizure-onset zone in nonlesional and extratemporal epilepsies. Outcome in this patient group was unexpectedly good, even in patients with nonlesional MRI. The high correlation with ECoG and site of successful surgery is a strong indicator that outcome prediction in this patient group should be adapted accordingly, which may encourage more patients to undergo electrode implantation and subsequent successful surgery. Statistical analysis showed that SISCOM with shorter duration of seizures, focal seizures, and lesional MRI was more likely to generate implantation hypothesis.
    Full-text · Article · Dec 2011 · Epilepsia
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    ABSTRACT: To investigate the response in R2* relaxation rate of human intracranial tumours during hyperoxic and hypercapnic respiratory challenges. In seven patients with different intracranial tumours, cerebral R2* changes during carbogen and CO(2)/air inhalation were monitored at 3 T using a dynamic multigradient-echo sequence of high temporal and spatial resolution. The R2* time series of each voxel was tested for significant change. Regions of interest were analysed with respect to response amplitude and velocity. The tumours showed heterogeneous R2* responses with large interindividual variability. In the 'contrast-enhancing' area of five patients and in the 'non-tumoral' tissue most voxels showed a decrease in R2* for carbogen. For the 'contrast-enhancing' area of two patients hardly any responses were found. In areas of 'necrosis' and perifocal 'oedema' typically voxels with R2* increase and no response were found for both gases. For tissue responding to CO(2)/air, the R2* changes were of the same order of magnitude as those for carbogen. The response kinetic was generally attenuated in tumoral tissue. The spatially resolved determination of R2* changes reveals the individual heterogeneous response characteristic of intracranial human tumours during hyperoxic and hypercapnic respiratory challenges.
    Full-text · Article · Apr 2011 · European Radiology
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    ABSTRACT: Childhood onset of epilepsy has long been associated with an adverse impact on brain development and cognition. In this study it is proposed that earlier (vs later) onset of temporal lobe epilepsy (TLE) has a negative developmental impact on distant brain structures. One hundred ten patients with TLE were assigned to early (≤14 years, N=58) and late (>15 years, N=52) age at onset of epilepsy groups. Voxel-based morphometry revealed onset-dependent abnormalities (in terms of a gray matter excess in the early-onset group), which were found mainly in frontal regions. An excess of gray matter is not a usual finding in TLE. However, within a neurodevelopmental framework, retained gray matter is discussed as reflecting neurodevelopmental disruption. The findings indicate the importance of quantitative MRI for the detection of subtle secondary abnormalities in focal TLE and once more underline the importance of early seizure management in children with intractable TLE.
    No preview · Article · Mar 2011 · Epilepsy & Behavior

  • No preview · Article · Dec 2010 · RöFo - Fortschritte auf dem Gebiet der R
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    ABSTRACT: To prospectively and intraindividually compare single-source radiofrequency (RF) excitation and dual-source parallel RF excitation in 3.0-T magnetic resonance (MR) imaging of the spine. Institutional review board approval and written informed patient consent were obtained. The RF power of a 3.0-T MR imaging system was distributed to two ports of the body coil of the system by using independent RF transmit channels. The maximum B(1) field strength for dual-source parallel RF excitation was maintained, as compared with single-source RF excitation. The repetition time was reduced according to the revised RF setup with dual-source parallel RF excitation while maintaining specific energy absorption limitations. Thirty patients were examined with and without dual-source parallel RF excitation. Diagnostic quality was assessed independently by two radiologists according to a four-point grading system. Image contrast ratios (CRs) were calculated between reference tissues and vertebrae for single-source RF excitation and dual-source parallel RF excitation. The mean acceleration achieved with dual-source parallel RF excitation was 36% (range, 18%-50%). The total imaging duration of a three-station total spinal examination was reduced by one-third by using dual-source parallel RF transmission. For all cases investigated, diagnostic image quality without significant differences between the two methods and with a good interobserver agreement was achieved (Kendall tau-b, 0.50-0.84). The observed image contrast changes were predominantly small (<0.10 in 15 of 24 CRs), though they were significantly different (P < .05). While shortening examination times by approximately one-third, the dual-source parallel RF transmission mode in MR imaging of the spine yielded diagnostic image quality comparable to that with the conventional single-source RF transmission mode.
    No preview · Article · Dec 2010 · Radiology
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    ABSTRACT: PURPOSE Prospective intra-individual comparison of single and dual source parallel RF excitation in 3.0T MR imaging (MRI) of the spine. METHOD AND MATERIALS A 3.0T MR system (Achieva 3.0T TX, Philips Healthcare) equipped with fully flexible multi-source RF transmission (dual source) was used. The root mean square magnitude of RF fields was increased whereas the time of repetition was reduced according to the revised RF setup while maintaining specific energy absorption limitations. 30 patients underwent MRI of the spinal cord. A total of 77 sequences with and without parallel transmission were available for an intraindividual comparison. Diagnostic quality of examinations was scored as follows: Score of 4, excellent (sharp depiction of vertebrae, the thecal sac and traversing nerve roots). Score of 3, adequate for diagnosis (minor artifacts (e.g. CSF pulsation), or noise present not interfering with image interpretation). Score of 2, questionable for diagnosis (impaired by artifacts, noise and / or changes in contrast). Score of 1, nondiagnostic. Contrast ratios (CRs) were calculated between reference tissues and vertebrae for single and parallel transmission. RESULTS A mean speed-up of 36% was achieved with dual source RF excitation. The total scan duration of a three-station whole spine examination including axial imaging stacks in all three stations could be reduced by 31 % (30:16 min. vs. 44:00 min.) using parallel RF transmission, as compared to single transmit mode. Spinal 3T MRI with parallel transmission yielded a median assessment of at least adequate image quality in all of the compared sequences. There was no case with a nondiagnostic image quality. The observed contrast changes were predominantly small (< 0.10 in 15 out of 24 CRs), though of statistical significance. CONCLUSION While shortening examination times by approximately one-third, dual-source RF transmission in 3T MRI of the spinal cord exhibits a diagnostic image quality readily comparable to that of standard single transmission sequences. CLINICAL RELEVANCE/APPLICATION Parallel RF transmission yields an effective gain of time in 3T spine examinations.
    No preview · Conference Paper · Nov 2010
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    ABSTRACT: To prospectively compare the image quality and homogeneity of magnetic resonance (MR) images obtained by using a dual-source parallel radiofrequency (RF) excitation body MR imaging system with parallel transmission and independent RF shimming with the image quality and homogeneity of single-source MR images obtained by using standard sequences for routine clinical use in patients at 3.0 T. After institutional review board approval and informed patient consent were obtained, a dual-source parallel RF excitation 3.0-T MR system with independent RF shimming and parallel transmission technology was used to examine 28 patients and was compared with a standard 3.0-T MR system with single RF transmission. The RF power was distributed to the independent ports of the system body coil by using two RF transmission sources with full software control, enabling independent control of the phase and amplitude of the RF waveforms. Axial T2-weighted fast spin-echo (SE) and diffusion-weighted (DW) liver images, axial T2-weighted fast SE pelvic images, and sagittal T1- and T2-weighted fast SE spinal images were obtained by using dual- and single-source RF excitation. Two radiologists independently evaluated the images for homogeneity and image quality. Statistical significance was calculated by using the nonparametric Wilcoxon signed rank test. Interobserver agreement was determined by using Cohen kappa and Kendall tau-b tests. Image quality comparisons revealed significantly better results with dual-source rather than single-source RF excitation at T2-weighted liver MR imaging (P = .001, kappa = 1.00) and better results at DW liver imaging at a statistical trend level (P = .066, tau-b > 0.7). Owing to reduced local energy deposition, fewer acquisitions and shorter repetition times could be implemented with dual-source RF excitation pelvic and spinal MR imaging, with image acquisition accelerating by 18%, 33%, and 50% compared with the acquisitions with single-source RF excitation. Image quality did not differ significantly between the two MR techniques (P > .05, tau-b > 0.5). Dual-source parallel RF excitation body MR imaging enables reduced dielectric shading, improved homogeneity of the RF magnetic induction field, and accelerated imaging at 3.0 T.
    No preview · Article · Sep 2010 · Radiology
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    ABSTRACT: To compare two DeltaR2* quantification methods for analyzing the response of intracranial tumors to different breathing gases. The determination of changes in the magnetic resonance imaging (MRI) relaxation rate R2* (DeltaR2*), induced by hyperoxic and hypercapnic respiratory challenges, enables the noninvasive assessment of blood oxygenation changes and vasoreactivity. Sixteen patients with various intracranial tumors were examined at 3.0 T. The response to respiratory challenges was registered using a dynamic multigradient-echo sequence with high temporal and spatial resolution. At each dynamic step, DeltaR2* was derived in two different ways: 1) by subtraction of R2* values obtained from monoexponential decay functions, 2) by computing DeltaR2* echo-wise from signal intensity ratios. The sensitivity for detection of responding voxels and the behavior of the "global" response were investigated. Significantly more responding voxels (about 4%) were found for method (1). The "global" response was independent from the chosen quantification method but showed slightly larger changes (about 6%) when DeltaR2* was derived from method (1). Similar results were observed for the two methods, with a slightly higher detection sensitivity of responding voxels when DeltaR2* was obtained from monoexponential approximation.
    No preview · Article · Jul 2010 · Journal of Magnetic Resonance Imaging
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    ABSTRACT: To compare two magnetic resonance (MR) contrast mechanisms, R*(2) BOLD and balanced SSFP, for the dynamic monitoring of the cerebral response to (C)O(2) respiratory challenges. Carbogen and CO(2)-enriched air were delivered to 9 healthy volunteers and 1 glioblastoma patient. The cerebral response was recorded by two-dimensional (2D) dynamic multi-gradient-echo and passband-balanced steady-state free precession (bSSFP) sequences, and local changes of R*(2) and signal intensity were investigated. Detection sensitivity was analyzed by statistical tests. An exponential signal model was fitted to the global response function delivered by each sequence, enabling quantitative comparison of the amplitude and temporal behavior. The bSSFP signal changes during carbogen and CO(2)/air inhalation were lower compared with R*(2) BOLD (ca. 5% as opposed to 8-13%). The blood-oxygen-level-dependent (BOLD) response amplitude enabled differentiation between carbogen and CO(2)/air by a factor of 1.4-1.6, in contrast to bSSFP, where differentiation was not possible. Furthermore, motion robustness and detection sensitivity were higher for R*(2) BOLD. Both contrast mechanisms are well suited to dynamic (C)O(2)-enhanced MR imaging, although the R*(2) BOLD mechanism was demonstrated to be superior in several respects for the chosen application. This study suggests that the R*(2) BOLD and bSSFP-response characteristics are related to different physiologic mechanisms.
    No preview · Article · Jun 2010 · Journal of Magnetic Resonance Imaging
  • M Nelles · R König · J Gieseke · H Urbach · H Schild · WA Willinek

    No preview · Article · Mar 2010 · RöFo - Fortschritte auf dem Gebiet der R
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    ABSTRACT: We investigated the respective contribution (in terms of cancer yield and stage at diagnosis) of clinical breast examination (CBE), mammography, ultrasound, and quality-assured breast magnetic resonance imaging (MRI), used alone or in different combination, for screening women at elevated risk for breast cancer. Prospective multicenter observational cohort study. Six hundred eighty-seven asymptomatic women at elevated familial risk (> or = 20% lifetime) underwent 1,679 annual screening rounds consisting of CBE, mammography, ultrasound, and MRI, read independently and in different combinations. In a subgroup of 371 women, additional half-yearly ultrasound and CBE was performed more than 869 screening rounds. Mean and median follow-up was 29.18 and 29.09 months. Twenty-seven women were diagnosed with breast cancer: 11 ductal carcinoma in situ (41%) and 16 invasive cancers (59%). Three (11%) of 27 were node positive. All cancers were detected during annual screening; no interval cancer occurred; no cancer was identified during half-yearly ultrasound. The cancer yield of ultrasound (6.0 of 1,000) and mammography (5.4 of 1,000) was equivalent; it increased nonsignificantly (7.7 of 1,000) if both methods were combined. Cancer yield achieved by MRI alone (14.9 of 1,000) was significantly higher; it was not significantly improved by adding mammography (MRI plus mammography: 16.0 of 1,000) and did not change by adding ultrasound (MRI plus ultrasound: 14.9 of 1,000). Positive predictive value was 39% for mammography, 36% for ultrasound, and 48% for MRI. In women at elevated familial risk, quality-assured MRI screening shifts the distribution of screen-detected breast cancers toward the preinvasive stage. In women undergoing quality-assured MRI annually, neither mammography, nor annual or half-yearly ultrasound or CBE will add to the cancer yield achieved by MRI alone.
    No preview · Article · Feb 2010 · Journal of Clinical Oncology

  • No preview · Article · Jan 2010 · RöFo - Fortschritte auf dem Gebiet der R

  • No preview · Article · Apr 2009 · RöFo - Fortschritte auf dem Gebiet der R

  • No preview · Article · Jan 2009 · RöFo - Fortschritte auf dem Gebiet der R
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    ABSTRACT: Magnetic resonance imaging (MRI) volumetry has evolved to a highly sensitive method for presurgical detection of hippocampal sclerosis in temporal lobe epilepsy (TLE). Seizure resolution and neuropsychological sequelae are believed to correlate with extent of resection. Therefore an easy volumetric method to determine extent of resection is desirable. The purpose of this work is to evaluate and compare two different measurement techniques for hippocampal resection length. Sixty-one patients with a mean seizure history of 25.1 years and medically intractable TLE were included. They underwent MRI with sagittal acquired 3D T1-weighted spoiled gradient recalled echo sequence in 1 mm(3) isotropic voxel. Hippocampal resection length was calculated with two different methods. In the slice counting method (SCM) the number of consecutive 1-mm-thick slices containing resected hippocampus formation was counted. In the vector method (VM) the sum of the oblique and thus longer distances between the centre points of segmented hippocampal areas on each MRI slice were calculated. Since the hippocampus is a curved body, the resection lengths measured with VM were always larger than measured with SCM. The comparison of resection length expressed in "percent of total length" showed good agreement between the two methods, because unlike the absolute values of resection length, the percentage values are unaffected by the three-dimensional shape of the hippocampus. The easier and quicker method of "slice counting" may be used to determine resection length expressed in "percent of total length", giving reliable values for resection length but causing less volumetric work.
    No preview · Article · May 2008 · Acta Neurochirurgica
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    ABSTRACT: To develop a method for the coregistration of digital photographs of the human cortex with head magnetic resonance imaging (MRI) scans for invasive diagnostics and resective neocortical epilepsy surgery. Six chronically epileptic patients (two women, four men; mean age, 34 yr; age range, 20-43 yr) underwent preoperative three-dimensional (3D) T1-weighted MRI scans. Digital photographs of the exposed cortex were taken during implantation of subdural grid electrodes. Rendering software (Analyze 3.1; Biomedical Imaging Resource, Mayo Foundation, Rochester, MN) was used to create an MRI-based 3D model of the brain surface. Digital photographs were manually coregistered with the brain surface MRI model using the registration tool in the Analyze software. By matching the digital photograph and the brain surface model, the position of the subdural electrodes was integrated into the coordinate system of the preoperatively acquired 3D MRI dataset. In all patients, the position of the labeled electrode contacts in relation to the cortical anatomy could be visualized on the 3D models of the cortical surface. At the time of resection, the resulting image of the coregistration process provides a realistic view of the cortex and the position of the subdural electrode. The coregistration of digital photographs of the brain cortex with the results of 3D MRI data sets is possible. This allows for identification of anatomic details underlying the subdural grid electrodes and enhances the orientation of the surgeon.
    No preview · Article · Dec 2007 · Neurosurgery
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    ABSTRACT: Diagnosing breast cancer in its intraductal stage might be helpful to prevent the development of invasive cancer. Our aim was to investigate the sensitivity with which ductal carcinoma in situ (DCIS) is diagnosed by mammography and by breast MRI. During a 5-year period, 7319 women who were referred to an academic national breast centre received MRI in addition to mammography for diagnostic assessment and screening. Mammograms and breast MRI studies were assessed independently by different radiologists. We investigated the sensitivity of each method of detection and compared the biological profiles of mammography-diagnosed DCIS versus DCIS detected by MRI alone. We also compared the risk profiles of women with mammography-detected DCIS with those of MRI-detected DCIS. 193 women received a final surgical pathology diagnosis of pure DCIS. Of those, 167 had undergone both imaging tests preoperatively. 93 (56%) of these cases were diagnosed by mammography and 153 (92%) by MRI (p<0.0001). Of the 89 high-grade DCIS, 43 (48%) were missed by mammography, but diagnosed by MRI alone; all 43 cases missed by mammography were detected by MRI. By contrast, MRI detected 87 (98%) of these lesions; the two cases missed by MRI were detected by mammography. Age, menopausal status, personal or family history of breast cancer or of benign breast disease, and breast density of women with MRI-only diagnosed DCIS did not differ significantly from those of women with mammography-diagnosed DCIS. MRI could help improve the ability to diagnose DCIS, especially DCIS with high nuclear grade.
    Full-text · Article · Aug 2007 · The Lancet
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    ABSTRACT: The aim of this study was to test a modified radial semiautomated volumetry technique (radial divider technique, RDT) versus the manual volumetry technique (MVT) for proportionality of temporal subvolumes in 30 patients with drug-resistant temporal lobe epilepsy. Included in the study were 30 patients (15 female, 15 male; mean age 39.6 years) with pharmacoresistant epilepsy (mean duration 26.6 years). MRI studies were performed preoperatively on a 1.5-T scanner. All image processing steps and volume measurements were performed using ANALYZE software. The volumes of six subregions were measured bilaterally; these included the superior temporal gyrus (STG), middle + inferior temporal gyrus (MITG), fusiform gyrus (FG), parahippocampal gyrus (PHG), amygdala (AM), and hippocampus (HP). Linear regression was used to investigate the relationship between the comparable subvolumes obtained with MVT and RDT. Very high correlations (R (2) >0.95) between RDT and MVT were observed for the STG + MITG and the STG + MITG + FG, but low correlations for the PHG subvolumes and the combined PHG + HP + AM subvolumes. These observations were independent of the side of the pathology and of hemisphere. The two measurement techniques provided highly reliable proportional results. This series in a homogeneous group of TLE patients suggests that the much quicker RDT is suitable for determining the volume of temporolateral and laterobasal temporal lobe compartments, of both the affected and the non-affected side and the right and left hemisphere.
    No preview · Article · Apr 2007 · Neuroradiology
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    ABSTRACT: For technical reasons, T2-weighted and fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) sequences do not allow morphological orientation with high anatomic resolution, but they may show small epileptogenic lesions. Considering the peculiarities of diagnostic and resective epilepsy surgery the present study focused on the co-registration of various magnetic resonance sequences for guided epilepsy surgery. Fifty patients (24 men; 26 women) aged 2 to 74 years (mean, 32 yr), in whom epileptogenic lesions were not readily identifiable on three-dimensional T1-weighted MRI scans underwent additional two-dimensional T2-weighted and FLAIR sequences before diagnostic and/or resective epilepsy surgery. FLAIR and/or T2-weighted images were co-registered to the T1-weighted data set and were displayed on the navigation station on site for guided invasive diagnostics and for resection according to an individualized resection plan. Postoperative MRI scanning was routinely performed for assessment of resection extent. Co-registered T1- and FLAIR-/T2-images allowed for image-guided intraoperative identification of all lesions (n = 50). Control MRI scans revealed that complete resection was performed as planned before the operation in 49 patients and incomplete resection was performed in one patient. Preliminary seizure outcome with a mean follow up of 14 months (range, 7-24 mo) was assigned according to the Engel classification: Class I, 78%; Class II, 12%; Class III, 4%; Class IV, 6%. Image guidance on the basis of image fusion/co-registration of T1- and FLAIR-/T2-images allows for intraoperative identification of otherwise poorly visible lesions on standard MRI sequences in good spatial resolution. Recall of this information during surgery from the navigation system's screen assists in achieving the goal of precise electrode placement, or complete resection of the lesion as well as of the perilesional epileptogenic tissue and improves the surgeon's intraoperative orientation.
    No preview · Article · Mar 2006 · Neurosurgery
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    ABSTRACT: To evaluate whether limbic system abnormalities associated with Ammon's horn sclerosis alter seizure outcome after selective amgydalohippocampectomy. In 45 patients with unilateral mesial temporal lobe epilepsy, histologically proven Ammon's horn sclerosis, and uneventful postoperative course, volumes of the hippocampus, hemisphere, amygdala, entorhinal cortex, mamillary body, and fornix were measured by using a T(1)-weighted 3-D gradient-echo sequence with roughly isotropic (1.17 x 1.17 x 1-mm) voxels. In addition, signal intensity of the hippocampus and of the temporal lobe white matter was visually assessed and graded on a coronal T(2)-weighted fast-spin-echo sequence with 2-mm-thick slices. Volumetric measurements and visual analysis were compared between seizure-free and non-seizure-free patients examined 12 months after surgery. Hippocampal, hemispheric, entorhinal cortex, mamillary body, and fornix volumes, but not amygdalar volumes, were significantly smaller on the operated-on than on the non-operated-on side and significantly smaller in patients compared with controls. No volume differences of the hippocampus, hemisphere, amygdala, entorhinal cortex, mamillary body, and fornix existed between seizure-free (Engel class IA) and non-seizure-free patients (Engel class IB-IV). Increased temporal lobe white matter signal was observed in 15 patients but did not alter seizure outcome. Limbic system abnormalities are not a surrogate marker to predict postsurgical seizure outcome in patients with unilateral Ammon's horn sclerosis.
    Full-text · Article · May 2005 · Epilepsia

Publication Stats

1k Citations
173.01 Total Impact Points


  • 1997-2011
    • University of Bonn
      • Department of Neurobiology
      Bonn, North Rhine-Westphalia, Germany
  • 2010
    • Universität Ulm
      Ulm, Baden-Württemberg, Germany
  • 1999-2000
    • University of Bonn - Medical Center
      Bonn, North Rhine-Westphalia, Germany