Maximilian F Reiser

Ludwig-Maximilians-University of Munich, München, Bavaria, Germany

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Publications (739)1695.82 Total impact

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    ABSTRACT: The objective of this study was to evaluate the feasibility of a novel 3-dimensional turbo spin-echo technique with isotropic resolution for the diagnosis of deep vein thrombosis (DVT) in comparison with contrast-enhanced magnetic resonance imaging (CE-MRI) and sonography. Thirteen patients (8 males, 17-93 years) with proven DVT in duplex ultrasound (n = 11) or with pulmonary embolism and suspected to have DVT (n = 2) were consecutively imaged at 3.0 T with 1.2-mm isotropic-resolution volumetric isotropic turbo spin-echo acquisition (VISTA). Sensitivity (SE), specificity (SP), positive and negative predictive values (PPV and NPV, respectively), Cohen κ, as well as accuracy of VISTA-MRI were calculated and compared with CE-MRI and sonography as a standard of reference. Image quality and diagnostic confidence were assessed on a 4-point scale. Image quality and diagnostic confidence level of VISTA-MRI and CE-MRI were comparable (3.54 vs 3.55 and 3.80 vs 3.77; both P values are nonsignificant). Using CE-MRI as the criterion standard, there was a high agreement between the CE-MRI and the 3-dimensional VISTA examinations for the detection of DVT, with κ of 0.89 for reader 1 and κ of 0.88 for reader 2 (both P < 0.001). The SE, SP, PPV, NPV, as well as accuracy of VISTA-MRI were 92.5%, 97.9%, 89.3%, 98.6%, and 97.1% for reader 1 as well as 90.7%, 97.9%, 89.1%, 98.3%, and 96.8% for reader 2. For both readers, combined comparison of VISTA-MRI and sonography resulted in an SE, SP, PPV, and NPV of 77.8%, 94.8%, 85.4%, and 91.6%, respectively. Volumetric isotropic turbo spin-echo acquisition magnetic resonance imaging can be used to diagnose DVT with good to excellent agreement compared with CE-MRI and sonography. It might be useful when contrast media is prohibited and in patients with suspected thrombosis of the iliac veins, which can be hard to detect with sonography.
    Investigative radiology 03/2015; DOI:10.1097/RLI.0000000000000142 · 4.85 Impact Factor
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    ABSTRACT: To determine the feasibility of free-breathing, GRAPPA-based, real-time (RT) cine 3T cardiac magnetic resonance imaging (MRI) with high acceleration factors for the assessment of left-ventricular function in a cohort of patients as compared to conventional segmented cine imaging. In this prospective cohort study, subjects with various cardiac conditions underwent MRI involving two RT cine sequences (high resolution and low resolution) and standard segmented cine imaging. Standard qualitative and quantitative parameters of left-ventricular function were quantified. Among 25 subjects, 24 were included in the analysis (mean age: 50.5±21 years, 67% male, 25% with cardiomyopathy). RT cine derived quantitative parameters of volumes and left ventricular mass were strongly correlated with segmented cine imaging (intraclass correlation coefficient [ICC]: >0.72 for both RT cines) but correlation for peak ejection and filling rates were moderate to poor for both RT cines (ICC<0.40). Similarly, RT cines significantly underestimated peak ejection and filling rates (>103.2±178ml/s). Among patient-related factors, heart rate was strongly predictive for deviation of measurements (p<0.05). RT cine MRI at 3T is feasible for qualitative and quantitative assessment of left ventricular function for low and high-resolution sequences but results in significant underestimation of systolic function, peak ejection and filling rates. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
    European journal of radiology 02/2015; DOI:10.1016/j.ejrad.2015.02.016 · 2.65 Impact Factor
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    ABSTRACT: To investigate a multimodal, multiparametric perfusion MRI / 18F-fluoro-deoxyglucose-(18F-FDG)-PET imaging protocol for monitoring regorafenib therapy effects on experimental colorectal adenocarcinomas in rats with immunohistochemical validation. Human colorectal adenocarcinoma xenografts (HT-29) were implanted subcutaneously in n = 17 (n = 10 therapy group; n = 7 control group) female athymic nude rats (Hsd:RH-Foxn1rnu). Animals were imaged at baseline and after a one-week daily treatment protocol with regorafenib (10 mg/kg bodyweight) using a multimodal, multiparametric perfusion MRI/18F-FDG-PET imaging protocol. In perfusion MRI, quantitative parameters of plasma flow (PF, mL/100 mL/min), plasma volume (PV, %) and endothelial permeability-surface area product (PS, mL/100 mL/min) were calculated. In 18F-FDG-PET, tumor-to-background-ratio (TTB) was calculated. Perfusion MRI parameters were correlated with TTB and immunohistochemical assessments of tumor microvascular density (CD-31) and cell proliferation (Ki-67). Regorafenib significantly (p<0.01) suppressed PF (81.1±7.5 to 50.6±16.0 mL/100mL/min), PV (12.1±3.6 to 7.5±1.6%) and PS (13.6±3.2 to 7.9±2.3 mL/100mL/min) as well as TTB (3.4±0.6 to 1.9±1.1) between baseline and day 7. Immunohistochemistry revealed significantly (p<0.03) lower tumor microvascular density (CD-31, 7.0±2.4 vs. 16.1±5.9) and tumor cell proliferation (Ki-67, 434.0 ± 62.9 vs. 663.0 ± 98.3) in the therapy group. Perfusion MRI parameters ΔPF, ΔPV and ΔPS showed strong and significant (r = 0.67-0.78; p<0.01) correlations to the PET parameter ΔTTB and significant correlations (r = 0.57-0.67; p<0.03) to immunohistochemical Ki-67 as well as to CD-31-stainings (r = 0.49-0.55; p<0.05). A multimodal, multiparametric perfusion MRI/PET imaging protocol allowed for non-invasive monitoring of regorafenib therapy effects on experimental colorectal adenocarcinomas in vivo with significant correlations between perfusion MRI parameters and 18F-FDG-PET validated by immunohistochemistry.
    PLoS ONE 02/2015; 10(2):e0115543. DOI:10.1371/journal.pone.0115543 · 3.53 Impact Factor
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    ABSTRACT: To prospectively assess current limitations and complication rates of the transbrachial access technique for endovascular treatment of peripheral vascular pathologies. In total, 150 patients (112 men; mean age 66.3±10.0 years) with arterial occlusive disease underwent endovascular therapy via a transbrachial access. Periprocedure data (sheath size, dose area product, fluoroscopy time, and procedure duration) were analyzed. Postprocedure complications of the puncture sites were categorized as minor (local hematoma, pseudoaneurysm, embolization, dissection, minor bleeding) and major (thrombotic occlusion, hematoma requiring surgery, major bleeding, nerve injury). The minor and major complication rates were 14.0% (n=21) and 2.7% (n=4). The most frequent major complication was thrombotic occlusion of the brachial artery requiring surgical treatment (3/150, 2%). There was only one temporary palsy of the median nerve and no stroke. Local hematoma (15, 10%), pseudoaneurysm (3, 2%), or a combination of both (3, 2%) dominated the minor complications. The average dose area product and fluoroscopy time were 12,752.1±9524.5 cGy*cm(2) and 24.3±18.4 minutes, respectively, though procedure duration was acceptable (121.8±48.9 minutes). Complication rates of the transbrachial access for endovascular treatment of peripheral or visceral artery occlusive disease are tolerably low, making it a safe and an important alternative to the transfemoral access in selected cases, though the radiation exposure is rather high. © The Author(s) 2015.
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    ABSTRACT: The purpose of this study was to develop a new method of displaying dynamic cerebral computed tomographic (CT) angiography (CTA) data sets in which the time delay to maximum enhancement (Tdelay) is displayed in a range of colors (color-coded CT angiography [cCTA]). This institutional review board-approved study included multiparametric CT data sets from 16 patients with different types of supra-aortic large vessel occlusions. Color-coded CT angiography was reconstructed from CT perfusion raw data sets. All voxel enhancement curves were fitted to f(t) = α · AIFmtt(t - Δt), with AIFmtt(t), indicating enhancement of AIF dilated by convolution with boxcar function (with mean transit time [mtt]); α, scaling factor; and Δt, transition along the time. The time delay to maximum enhancement was defined as Tdelay = Δt +0.5 · mtt. Values of Tdelay were color-coded and superimposed on temporal maximum intensity projections CTA resulting in colored angiographic composite images. For a pilot clinical evaluation, diagnostic confidence in determining the pathology, quality of the visualization of leptomeningeal collaterals, and additional diagnostic information were assessed. The reconstruction of cCTA was technically feasible in all 16 patients. Both diagnostic confidence (P < 0.01) and the quality of the visualization of collaterals (P < 0.0001) were significantly higher when using the combination of single-phase CTA and cCTA compared with single-phase CTA alone. Additional diagnostic information was obtained with cCTA regarding occlusion type (reader 1: 5 cases and reader 2: 4 cases), differentiation between arteries and veins (11/13), differentiation between antegrade and retrograde filling (12/13), as well as leptomeningeal collateralization (13/14). Color-coded CT angiography is a technically feasible technique that provides additional information on cerebral hemodynamics in ischemic stroke patients.
    Investigative Radiology 01/2015; DOI:10.1097/RLI.0000000000000134 · 4.45 Impact Factor
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    ABSTRACT: The aim of this study was to assess the diagnostic performance of a dynamic, multiphasic contrast-enhanced volume-interpolated sequence with advanced parallel imaging techniques, Dixon fat saturation, and view sharing with 5 hepatic arterial subphases for the detection of focal liver lesions. Twenty-four consecutive patients (13 females, 11 males; mean [SD] age, 58 [15] years) with focal liver lesions were included in this prospective study. The examination was performed at a 3-T magnetic resonance imaging system (MAGNETOM Skyra; Siemens Healthcare, Erlangen, Germany). Five dynamic arterial subphases with a temporal resolution of 2.6 seconds, starting 17 seconds after injection of the hepatobiliary contrast agent gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Eovist; Bayer HealthCare, Leverkusen, Germany), were acquired using an accelerated parallel imaging volume-interpolated sequence with view sharing (multiarterial controlled aliasing in parallel imaging results in higher acceleration-Dixon-time-resolved angiography with interleaved stochastic trajectories-volumetric interpolated breath-hold examination [MA-CDT-VIBE]). The fourth of the 5 arterial acquisition phases (ie, at 24.8 seconds after the start of contrast agent injection) was considered the equivalent of a standard hepatic arterial phase (equivalent standard arterial phase [ESAP]). The diagnostic value of all 5 dynamic arterial phases for the detection of focal liver lesions, as compared with the single ESAP, was judged in 2 independent consensus readings. The 2 consensus reading groups were blinded to each others' results. The complete, comprehensive multisequence magnetic resonance imaging examination, including T1-weighted, T2-weighted, and multiphasic contrast-enhanced sequences, served as the standard of reference for lesion detection. Forty-six percent of the patients (11/24) had hypervascular lesions. In 79 % of all patients (19/24), the best arterial parenchymal contrast of one of the MA-CDT-VIBE acquisition phases was considered better than that of the ESAP. In one third of all cases (8/24 for the first and 6/24 for the second consensus reading), MA-CDT-VIBE showed an improved lesion detection rate compared with ESAP, especially in hypervascular lesions (4/11, representing 36% of all patients with hypervascular lesions). There was a high degree of interrater agreement between the 2 consensus reading groups (the Cohen κ, 0.71-1.00; P < 0.001). Compared with a standard hepatic arterial phase, MA-CDT-VIBE with 5 hepatic arterial subphases demonstrated greater diagnostic accuracy for the detection of hypervascular focal liver lesions and provided a robust and optimized hepatic arterial acquisition phase.
    Investigative Radiology 12/2014; DOI:10.1097/RLI.0000000000000118 · 4.45 Impact Factor
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    ABSTRACT: We aimed to evaluate the accuracy of multidetector computed tomography (MDCT) venous mapping for the localization of the right adrenal veins (RAV) in patients suffering from primary aldosteronism. MDCT scans of 75 patients with primary aldosteronism between March 2008 and November 2011 were evaluated by two readers (a junior [R1] and a senior [R2] radiologist) according to the following criteria: quality of RAV depiction (scale, 1-5), localization of the RAV confluence with regard to the inferior vena cava, and depiction of anatomical variants. Results were compared with RAV venograms obtained during adrenal vein sampling and corroborated by laboratory testing of cortisol in selective RAV blood samples. Kappa statistics were calculated for interobserver agreement and for concordance of MDCT mapping with the gold standard. Successful RAV sampling was achieved in 69 of 75 patients (92%). Using MDCT mapping, adrenal veins could be visualized in 78% (R1, 54/69) and 77% (R2, 53/69) of patients. MDCT mapping led to correct identification of RAV in 70% (R1, 48/69) and 88% (R2, 61/69) of patients. Venograms revealed five cases of anatomical variants, which were correctly identified in 60% (R1, R2). MDCT-based localizations were false or misleading in 16% (R1, 11/69) and 7% (R2, 5/69) of cases. Preinterventional MDCT mapping may facilitate successful catheterization in adrenal vein sampling.
    Diagnostic and interventional radiology (Ankara, Turkey) 11/2014; 21(1). DOI:10.5152/dir.2014.14026 · 1.43 Impact Factor
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    ABSTRACT: The velocity of collateral filling can be assessed in dynamic time-resolved computed tomography (CT) angiographies and may predict initial CT perfusion (CTP) and follow-up lesion size. We included all patients with an M1± internal carotid artery (ICA) occlusion and follow-up imaging from an existing cohort of 1791 consecutive patients who underwent multimodal CT for suspected stroke. The velocity of collateral filling was quantified using the delay of time-to-peak (TTP) enhancement of the M2 segment distal to the occlusion. Cerebral blood volume (CBV) and mean transit time (MTT)-CBV mismatch were assessed in initial CTP. Follow-up lesion size was assessed by magnetic resonance imaging (MRI) or non-enhanced CT (NECT). Multivariate analyses were performed to adjust for extent of collateralization and type of treatment. Our study comprised 116 patients. Multivariate analysis showed a short collateral blood flow delay to be an independent predictor of a small CBV lesion (P<0.001) and a large relative mismatch (P<0.001) on initial CTP, of a small follow-up lesion (P<0.001), and of a small difference between initial CBV and follow-up lesion size (P=0.024). Other independent predictors of a small lesion on follow-up were a high morphologic collateral grade (P=0.001), lack of an additional ICA occlusion (P=0.009), and intravenous thrombolysis (P=0.022). Fast filling of collaterals predicts initial CTP and follow-up lesion size and is independent of extent of collateralization.Journal of Cerebral Blood Flow & Metabolism advance online publication, 5 November 2014; doi:10.1038/jcbfm.2014.182.
    Journal of Cerebral Blood Flow & Metabolism 11/2014; DOI:10.1038/jcbfm.2014.182 · 5.34 Impact Factor
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    ABSTRACT: To evaluate the benefits of dual-energy computed tomography (CT) colonography (DECTC) as a preoperative staging tool in patients with clinically suspected colorectal cancer (CRC). Twenty-two patients with colorectal neoplasia underwent preoperative abdominal DECTC on a dual-source scanner (SOMATOM Definition Flash; Siemens) operated at tube potentials of Sn140/100 kVp. Scans were evaluated for local tumor stage and the presence of synchronous intracolonic and extracolonic findings using dual-energy color-coded images. An enhancement ≥25 Hounsfield units (HU) was defined to indicate malignancy. Patients' effective doses were calculated. Preoperative DECTC allowed for complete bowel evaluation in all patients, including subjects with stenosing CRC. DECTC revealed 22 carcinomas (mean enhancement, 47 ± 12 HU). In total, 22 synchronous intracolonic lesions were detected, including 19 adenomas (mean enhancement, 51 ± 19 HU). Benign structures showed enhancement <25 HU. Comparing DECTC to histopathology, 95% carcinomas and 71% synchronous lesions proximal to stenosing CRC could be verified. Mean estimated effective dose was 13.0 ± 5.2 mSv. Preoperative DECTC can be used as an accurate and dose-efficient primary-staging examination. Especially after incomplete optical colonoscopy, virtual colonoscopy enables full preoperative colonic assessment on the same day. Dual-energy CT enables distinction between neoplasia and non-neoplastic findings within and outside the colon. Therefore, DECTC can be regarded as a promising "one-stop" staging examination in patients with clinically suspected CRC. Copyright © 2014 AUR. Published by Elsevier Inc. All rights reserved.
    Academic Radiology 11/2014; 21(12). DOI:10.1016/j.acra.2014.07.019 · 2.08 Impact Factor
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    ABSTRACT: Rationale and Objectives The purpose of this study was to provide normal values of volumetry and linear dimensions of adrenal glands. Materials and Methods Contrast-enhanced multidetector computed tomography scans of 105 patients were evaluated in this retrospective study. Imaging software was used both to measure the adrenal gland volume and to determine linear dimensions and density. For interobserver reliability, determination was repeated by a second reader in 10 patients selected at random. Results The mean adrenal volume was 4.84 (±1.67) cm³ on the left side and 3.62 (±1.23) cm³ on the right side. The total adrenal volume was mainly influenced by body weight (P < .001) and gender with women having smaller glands on average. The total width of the adrenal gland was 15.80 (±3.05) mm on the right side and 18.96 (±3.37) mm on the left side. There was a significant correlation between volume and linear measurements (P < .001). The mean density of both adrenal glands was 32.66 (±19.64) HU. Overall, interobserver reliability was high for volumetry (left adrenal, r = 0.98; right adrenal, r = 0.90) and low for linear dimensions. Conclusions Normal data for volumetry and linear dimensions are provided. There is a concordance between volumetric and linear assessment. However, volumetry is more reproducible.
    Academic Radiology 11/2014; 21(11):1465–1474. DOI:10.1016/j.acra.2014.06.008 · 2.08 Impact Factor
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    ABSTRACT: BACKGROUND: The purpose of this prospective study was to perform a head-to-head comparison of the two methods most frequently used for evaluation of carotid plaque characteristics: Multi-detector Computed Tomography Angiography (MDCTA) and black-blood 3 T-cardiovascular magnetic resonance (bb-CMR) with respect to their ability to identify symptomatic carotid plaques. METHODS: 22 stroke unit patients with unilateral symptomatic carotid disease and >50% stenosis by duplex ultrasound underwent MDCTA and bb-CMR (TOF, pre- and post-contrast fsT1w-, and fsT2w- sequences) within 15 days of symptom onset. Both symptomatic and contralateral asymptomatic sides were evaluated. By bb-CMR, plaque morphology, composition and prevalence of complicated AHA type VI lesions (AHA-LT6) were evaluated. By MDCTA, plaque type (non-calcified, mixed, calcified), plaque density in HU and presence of ulceration and/or thrombus were evaluated. Sensitivity (SE), specificity (SP), positive and negative predictive value (PPV, NPV) were calculated using a 2-by-2-table. RESULTS: To distinguish between symptomatic and asymptomatic plaques AHA-LT6 was the best CMR variable and presence / absence of plaque ulceration was the best CT variable, resulting in a SE, SP, PPV and NPV of 80%, 80%, 80% and 80% for AHA-LT6 as assessed by bb-CMR and 40%, 95%, 89% and 61% for plaque ulceration as assessed by MDCTA. The combined SE, SP, PPV and NPV of bb-CMR and MDCTA was 85%, 75%, 77% and 83%, respectively. CONCLUSIONS: Bb-CMR is superior to MDCTA at identifying symptomatic carotid plaques, while MDCTA offers high specificity at the cost of low sensitivity. Results were only slightly improved over bb-CMR alone when combining both techniques.
    Journal of Cardiovascular Magnetic Resonance 10/2014; 16(1):84. DOI:10.1186/s12968-014-0084-y · 5.11 Impact Factor
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    ABSTRACT: OBJECTIVE. Beta-2-microglobulin is a serum maker of tumor burden in hematologic malignancies. We aimed to correlate serum β2-microglobulin levels in patients with multiple myeloma (MM) to tumor mass determined by whole-body MRI. MATERIALS AND METHODS. We retrospectively included patients with newly diagnosed, untreated MM who underwent whole-body MRI at our institution between 2003 and 2011. Patients with a glomerular filtration rate of less than 60 mL/min were excluded from analysis because β2-microglobulin levels are increased in renal failure. Thirty patients could be included. Whole-body MRI examinations (T1-weighted turbo spin-echo and STIR sequences) were assessed by two musculoskeletal radiologists in consensus for focal lesions and the presence of diffuse myeloma infiltration. The presence of diffuse infiltration was confirmed by histology as the reference standard. MM was staged according to the Durie and Salmon PLUS staging system. RESULTS. According to whole-body MRI findings, MM was classified as Durie and Salmon PLUS stage I (low grade) in 13 patients, stage II (intermediate grade) in six patients, and stage III (high grade) in 11 patients. As we expected, most patients with stage I disease (12/13) had normal β2-microglobulin levels (≤ 3 mg/L). Higher β2-microglobulin values were associated with a higher stage of disease (p < 0.05). However, five of six patients with stage II MM and five of 11 patients with stage III MM showed normal β2-microglobulin levels. Thus, 10 of 17 patients (58.8%) with substantial infiltration in the bone marrow showed false-negative β2-microglobulin levels. CONCLUSION. Serum β2-microglobulin levels correlate with tumor stage in MM. However, it may be misleading as a marker of tumor load in a subset of patients with substantial myeloma infiltration in the bone marrow. Whole-body MRI may display the full tumor load and correctly show the extension of myeloma infiltrates.
    American Journal of Roentgenology 10/2014; 203(4):854-862. DOI:10.2214/AJR.13.10724 · 2.74 Impact Factor
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    ABSTRACT: Objectives To find out whether the use of accelerated 2D-selective parallel-transmit excitation MRI for diffusion-weighted EPI (pTX-EPI) offers advantages over conventional single-shot EPI (c-EPI) with respect to different aspects of image quality in the MRI of the pancreas. Materials and methods The MRI examinations of 33 consecutive patients were evaluated in this prospective and IRB-approved study. PTX-EPI was performed with a reduced (zoomed) FOV of 230 × 118 mm2. The 2D-RF pulse of pTX-EPI was accelerated, i. e. shortened by a factor of 1.7 (pTX-acceleration factor). C-EPI used a full-FOV of 380 × 285 mm2. In a qualitative analysis, two experienced readers evaluated 3 different aspects of image quality on 3- to 5-point Likert scales. Additionally, apparent diffusion coefficients (ADCs) were determined in both c-EPI and pTX-EPI in normal-appearing pancreatic tissue using regions of interests (ROIs). Mean ADC values and standard deviations were compared between the two techniques. Results The reduced-FOV pTX-EPI was superior to c-EPI with respect to overall image quality (p < 0.0001) and identifiability of the pancreatic ducts (p < 0.01). Artifacts were significantly less severe in pTX-EPI (p < 0.01). The mean ADC values of c-EPI (1.29 ± 0.19 × 10−3 mm2/s) and pTX-EPI (1.27 ± 0.17 × 10−3 mm2/s) did not differ significantly between the two techniques (p = 0.44). The variation within the ROIs as measured by the standard deviation was significantly lower in pTX-EPI (0.095 × 10−3 mm2/s) than in c-EPI (0.135 × 10−3 mm2/s), p < 0.05. Conclusions PTX-accelerated EPI with spatially-selective excitation and reduced FOV leads to substantial improvements in DWI of the pancreas with respect to different aspects of image quality without significantly influencing the ADC values.
    European Journal of Radiology 10/2014; 83(10):1709-1714. DOI:10.1016/j.ejrad.2014.06.006 · 2.16 Impact Factor
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    ABSTRACT: The purpose of this study was to assess the influence of region of interest (ROI) size and positioning on perfusion and permeability parameters as well as on interobserver and intraobserver variability of dynamic contrast-enhanced (DCE-MRI) of primary renal cell carcinoma (RCC) and metastases.
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    ABSTRACT: To evaluate the use of diffusion-weighted MRI (DW-MRI) and volume measurements for early monitoring of antiangiogenic therapy in an experimental tumor model.
    PLoS ONE 09/2014; 9(9):e106970. DOI:10.1371/journal.pone.0106970 · 3.53 Impact Factor
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    ABSTRACT: While penumbra assessment has become an important part of the clinical decision making for acute stroke patients, there is a lack of studies measuring the reliability and reproducibility of defined assessment techniques in the clinical setting. Our aim was to determine reliability and reproducibility of different types of three-dimensional penumbra assessment methods in stroke patients who underwent whole brain CT perfusion imaging (WB-CTP).
    PLoS ONE 08/2014; 9(8):e105413. DOI:10.1371/journal.pone.0105413 · 3.53 Impact Factor
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    ABSTRACT: Background/Objectives: To evaluate the predictive value of CT-derived measurements of the aortic annulus for prosthesis sizing in transcatheter aortic valve implantation (TAVI) and to calculate optimal cutoff values for the selection of various prosthesis sizes. Methods: The local IRB waived approval for this single-center retrospective analysis. Of 441 consecutive TAVI-patients, 90 were excluded (death within 30 days: 13; more than mild aortic regurgitation: 10; other reasons: 67). In the remaining 351 patients, the CoreValve (Medtronic) and the Edwards Sapien XT valve (Edwards Lifesciences) were implanted in 235 and 116 patients. Optimal prosthesis size was determined during TAVI by inflation of a balloon catheter at the aortic annulus. All patients had undergone CT-angiography of the heart or body trunk prior to TAVI. Using these datasets, the diameter of the long and short axis as well as the circumference and the area of the aortic annulus were measured. Multi-Class Receiver-Operator-Curve analyses were used to determine the predictive value of all variables and to define optimal cutoff-values. Results: Differences between patients who underwent implantation of the small, medium or large prosthesis were significant for all except the large vs. medium CoreValve (all p's<0.05). Furthermore, mean diameter, annulus area and circumference had equally high predictive value for prosthesis size for both manufacturers (multi-class AUC's: 0.80, 0.88, 0.91, 0.88, 0.88, 0.89). Using the calculated optimal cutoff-values, prosthesis size is predicted correctly in 85% of cases. Conclusion: CT-based aortic root measurements permit excellent prediction of the prosthesis size considered optimal during TAVI.
    PLoS ONE 08/2014; 9(8):e103481. DOI:10.1371/journal.pone.0103481 · 3.53 Impact Factor
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    ABSTRACT: To evaluate the diagnostic accuracy of dynamic-contrast-enhanced (DCE) MRI in comparison to both (18) F-FDG- and (68) Ga-DOTATATE-PET/CT in patients with liver metastases of neuroendocrine neoplasms (NEN). Thirty-two patients with hepatic metastases from NEN were examined both in DCE-MRI and positron emission tomography/computed tomography (PET/CT), using either (18) F-fluorodeoxyglucose ((18) F-FDG) or (68) Ga-DOTATATE as tracer. DCE-MRI was performed at 3 Tesla with Gd-EOB-DTPA acquiring 48 slices every 2.2 s for 5 min. Three regions of interest (ROIs) representing liver background and liver metastases were defined in fat-saturated T1w three-dimensional GRE MRI sequences in the hepatobiliary phase. Corresponding ROIs were then defined in the DCE-MRI- and in the PET/CT-dataset. Area under the curve (AUC) was calculated for the differentiation between metastases and liver background for DCE-MRI and PET-CT parameters. AUC was very high for SUVmean (mean standardized uptake value) derived from (68) Ga-DOTATATE- (AUC = 0.966), and (18) F-FDG-PET/CT (AUC = 0.989). For DCE-MRI parameters, arterial flow fraction and intracellular uptake fraction showed the highest AUCs (AUC = 0.826, AUC = 0.819, respectively). The combination of those two had an AUC of 0.949. The combination of DCE-MRI and PET-CT parameters resulted in the highest AUC. Both PET/CT parameters and DCE-MRI perfusion parameters show a high diagnostic accuracy in the distinction between liver metastases and liver tissue. Our data suggest that both modalities provide complementary information.J. Magn. Reson. Imaging 2013. © 2013 Wiley Periodicals, Inc.
    Journal of Magnetic Resonance Imaging 08/2014; 40(2). DOI:10.1002/jmri.24363 · 2.57 Impact Factor
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    ABSTRACT: Purpose To evaluate technical success, complications, and effective dose in patients undergoing CT fluoroscopy-guided iliosacral screw placement for the fixation of unstable posterior pelvic ring injuries. Materials and methods Our retrospective analysis includes all consecutive patients with vertical sacral fractures and/or injury of the iliosacral joint treated with CT fluoroscopy-guided screw placement in our department from 11/2005 to 03/2013. Interventions were carried out under general anesthesia and CT fluoroscopy (10–20 mAs; 120 kV; 16- or 128-row scanner, Siemens Healthcare, Erlangen, Germany). Technical outcome, major and minor complications, and effective patient dose were analyzed. Results We treated 99 consecutive patients (mean age 53.1 ± 21.7 years, 50 male, 49 female) with posterior pelvic ring instability with CT fluoroscopy-guided screw placement. Intervention was technically successful in all patients (n = 99). No major and one minor local complication occurred (1 %, secondary screw dislocation). General complications included three cases of death (3 %) due to pulmonary embolism (n = 1), hemorrhagic shock (n = 1), or cardiac event (n = 1) during a follow-up period of 30 days. General complications were not related to the intervention. Mean effective patient radiation dose per intervention was 12.28 mSv ± 7.25 mSv. Mean procedural time was 72.1 ± 37.4 min. Conclusions CT fluoroscopy-guided screw placement for the treatment of posterior pelvic ring instabilities can be performed with high technical success and a low complication rate. This method provides excellent intrainterventional visualization of iliac and sacral bones, as well as the sacral neuroforamina for precise screw placement by applying an acceptable effective patient dose.
    Skeletal Radiology 08/2014; 43(8). DOI:10.1007/s00256-014-1890-x · 1.74 Impact Factor
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    ABSTRACT: Purpose The purpose of this study was to investigate intracranial pressure and associated hemo- and hydrodynamic parameters in patients with cerebral arteriovenous malformations AVMs. Methods Thirty consecutive patients with arteriovenous malformations (median age 38.7 years, 27/30 previously treated with radiosurgery) and 30 age- and gender-matched healthy controls were investigated on a 3.0 Tesla MR scanner. Nidus volume was quantified on dynamic MR angiography. Total arterial cerebral blood flow (tCBF), venous outflow as well as aqueductal and craniospinal stroke volumes were obtained using velocity-encoded cine-phase contrast MRI. Intracranial volume change during the cardiac cycle was calculated and intracranial pressure (ICP) was derived from systolic intracranial volume change (ICVC) and pulse pressure gradient. Results TCBF was significantly higher in AVM patients as compared to healthy controls (median 799 vs. 692 mL/min, p = 0.007). There was a trend for venous flow to be increased in both the ipsilateral internal jugular vein (IJV, 282 vs. 225 mL/min, p = 0.16), and in the contralateral IJV (322 vs. 285 mL/min, p = 0.09), but not in secondary veins. There was no significant difference in median ICP between AVM patients and control subjects (6.9 vs. 8.6 mmHg, p = 0.30) and ICP did not correlate with nidus volume in AVM patients (ρ=-0.06, p = 0.74). There was a significant positive correlation between tCBF and craniospinal CSF stroke volume (ρ=0.69, p = 0.02). Conclusions The elevated cerebral blood flow in patients with AVMs is drained through an increased flow in IJVs but not secondary veins. ICP is maintained within ranges of normal and does not correlate with nidus volume.
    European Journal of Radiology 08/2014; 83(8). DOI:10.1016/j.ejrad.2014.05.011 · 2.16 Impact Factor

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Institutions

  • 1995–2015
    • Ludwig-Maximilians-University of Munich
      • • Department of Clinical Radiology
      • • Department of Urology
      • • Department of Ear, Nose and Throat Medicine
      München, Bavaria, Germany
  • 2003–2013
    • University Hospital München
      München, Bavaria, Germany
  • 2012
    • University of Leeds
      • Division of Medical Physics
      Leeds, ENG, United Kingdom
  • 1996–2012
    • Technische Universität München
      • Institute of Radiology
      München, Bavaria, Germany
  • 2011
    • NYU Langone Medical Center
      • Department of Radiology
      New York City, NY, United States
  • 2003–2011
    • Harvard University
      Cambridge, Massachusetts, United States
  • 2010
    • Trinity College Dublin
      • School of Medicine
      Dublin, L, Ireland
  • 2009–2010
    • University of Rostock
      Rostock, Mecklenburg-Vorpommern, Germany
    • Scott & White
      Temple, Texas, United States
    • Memorial Sloan-Kettering Cancer Center
      • Department of Radiology
      New York City, NY, United States
  • 2008–2010
    • Universität Heidelberg
      • • Faculty of Medicine Mannheim and Clinic Mannheim
      • • Institute of Clinical Radiology
      Heidelberg, Baden-Wuerttemberg, Germany
  • 2007
    • Florida State University
      Tallahassee, Florida, United States
    • University of Wisconsin, Madison
      • Department of Radiology
      Mississippi, United States
  • 2002
    • Huazhong University of Science and Technology
      Wu-han-shih, Hubei, China
  • 2001
    • Tongji Medical University
      China
  • 1992–1993
    • University of Bonn
      • Radiologische Klinik
      Bonn, North Rhine-Westphalia, Germany