Marc-André Weber

Universität Heidelberg, Heidelburg, Baden-Württemberg, Germany

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Publications (95)257.69 Total impact

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    ABSTRACT: Digital plain radiographs of the full leg are frequently performed examinations of children and young adults. Thus, the objective of this work was to reduce the radiation exposure dependent on specific indications, and to determine objective quality-control criteria to ensure accurate assessment. Institutional review board approval and informed consent of all participants were obtained. In this prospective, randomized controlled, blinded, two-armed single-center study, 288 evaluable patients underwent plain radiography of the full leg with standard and reduced doses. The evaluation of the plain radiographs was conducted using the following criteria: mechanical axis, leg length, and maturation of the epiphyseal plate. Two blinded radiologists evaluated these criteria using a score ranging from 1 (definitely assessable) to 4 (not assessable). If a single criterion had been evaluated with a score of 3 or more points or all criteria with 2 points, the radiograph was scored as "not assessable". The study was designed as a non-inferiority trial. Eleven (3.8 %) examined X-rays were scored as not assessable. The rate of non-assessable radiographs with 33 % reduced dose was significantly not inferior to the rate of non-assessable radiographs with standard dose. The evaluation of the quality criteria was dose independent. Full-leg plain radiography in patients with knee malalignment can be performed at 33 % reduced dose without loss of relevant diagnostic information.
    Skeletal Radiology 12/2014; · 1.74 Impact Factor
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    ABSTRACT: To determine the accuracy and reliability of three-dimensional (3D) T1- and proton density (PD)-weighted turbo spin-echo (TSE) sampling perfection with application-optimized contrasts using different flip-angle evolution (SPACE) compared with conventional 2D sequences in assessment of the shoulder-joint.
    European journal of radiology. 06/2014;
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    ABSTRACT: The ability to ascertain information pertaining to peripheral perfusion through the analysis of tissues' temporal reaction to the inflow of contrast agent (CA) was first recognized in the early 1990's. Similar to other functional magnetic resonance imaging (MRI) techniques such as arterial spin labeling (ASL) and blood oxygen level-dependent (BOLD) MRI, dynamic contrast-enhanced MRI (DCE-MRI) was at first restricted to studies of the brain. Over the last two decades the spectrum of ailments, which have been studied with DCE-MRI, has been extensively broadened and has come to include pathologies of the heart notably infarction, stroke and further cerebral afflictions, a wide range of neoplasms with an emphasis on antiangiogenic treatment and early detection, as well as investigations of the peripheral vascular and musculoskeletal systems. DCE-MRI possesses an unparalleled capacity to quantitatively measure not only perfusion but also other diverse microvascular parameters such as vessel permeability and fluid volume fractions. More over the method is capable of not only assessing blood flowing through an organ, but in contrast to other noninvasive methods, the actual tissue perfusion. These unique features have recently found growing application in the study of the peripheral vascular system and most notably in the diagnosis and treatment of peripheral arterial occlusive disease (PAOD). The first part of this review will elucidate the fundamentals of data acquisition and interpretation of DCE-MRI, two areas that often remain baffling to the clinical and investigating physician because of their complexity. The second part will discuss developments and exciting perspectives of DCE-MRI regarding the assessment of perfusion in the extremities. Emerging clinical applications of DCE-MRI will be reviewed with a special focus on investigation of physiology and pathophysiology of the microvascular and vascular systems of the extremities.
    Cardiovascular diagnosis and therapy. 04/2014; 4(2):147-164.
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    ABSTRACT: Purpose To implement chlorine 35 ((35)Cl) magnetic resonance (MR) at a 7-T whole-body MR system and evaluate its feasibility for imaging humans. Materials and Methods All examinations were performed with ethical review board approval; written informed consent was obtained from all volunteers. Seven examinations each of brain and muscle in healthy volunteers and four examinations of patients were performed. Two patients with histologically confirmed glioblastoma multiforme underwent brain imaging. (35)Cl MR and (35)Cl inversion-recovery (IR) MR were performed. Two patients with genetically confirmed hypokalemic periodic paralysis underwent calf muscle imaging. Seven multiecho sequences (acquisition time, 5 minutes; voxel dimension, 11 mm(3)) were applied to determine transverse relaxation time as affected by magnetic field heterogeneity (T2*) and chlorine concentration. (35)Cl and sodium 23 ((23)Na) MR were conducted with a 7-T whole-body MR system. (35)Cl longitudinal relaxation time (T1) and T2* of healthy human brain and muscle were determined with a three-dimensional density-adapted-projection reconstruction technique to achieve short echo times and high signal-to-noise ratio (SNR) efficiency. A nonlinear least squares routine and mono- (T1) and biexponential (T2*) models were used for curve fitting. Results Phantom imaging revealed 15-fold lower SNR and much shorter relaxation times for (35)Cl than (23)Na. In vivo T2* was biexponential and extremely short. Monoexponential fits of T1 revealed 9.2 and 4.0 milliseconds ± 0.7 (standard deviation) for brain and muscle, respectively. In glioblastoma tissue, increased Cl(-) concentrations and increased Cl(-) IR signal intensities were detected. Voxel dimension and acquisition time, respectively, were 6 mm(3) and 9 minutes 45 seconds ((35)Cl MR) and 10 mm(3) and 10 minutes ((35)Cl IR MR). In patients with hypokalemic periodic paralysis versus healthy volunteers, Cl(-) and Na(+) concentrations were increased. Cl(-) concentration of muscle could be determined (voxel size, 11 mm(3); total acquisition time, 35 minutes). Conclusion MR at 7 T enables in vivo imaging of (35)Cl in human brain and muscle in clinically feasible acquisition times (10-35 minutes) and voxel volumes (0.2-1.3 cm(3)). Pathophysiological changes of Cl(-) homeostasis due to cancer or muscular ion channel disease can be visualized. © RSNA, 2014 Online supplemental material is available for this article.
    Radiology 02/2014; · 6.34 Impact Factor
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    ABSTRACT: Purpose To compare sensitivity of whole-body Computed Tomography (wb-CT) and whole-body Magnetic Resonance Imaging (wb-MRI) with Projection Radiography (PR) regarding each method's ability to detect osteolyses in patients with monoclonal plasma cell disease. Patients and Methods The bone status of 171 patients was evaluated. All patients presented with multiple myeloma (MM) of all stages, monoclonal gammopathy of unknown significance (MGUS) or solitary plasmacytoma. Two groups were formed. Group A consisted of 52 patients (26 females, 26 males) with an average age of 62 years (range, 45-89 years) who received, both, PR and wb-CT as part of their diagnostic work-up. Group B comprised 119 patients (58 females, 61 males) averaging 57 years of age (range 20-80 years) who received, both, PR and wb-MRI. Two experienced radiologists were blinded regarding the disease status and assessed the number and location of osteolyses in consensus. A distinction was made between axial and extra-axial lesions. Results In group A, wb-CT revealed osteolyses in 12 patients (23%) that were not detected in PR. CT was superior in detecting lesions in patients with osteopenia and osteoporosis. Compared with PR, wb-CT was significantly more sensitive in detecting osteolyses than PR (p < 0.001). This was particularly true for axial lesions. Additionally, CT revealed clinically relevant incidental findings in 33 patients (63%). In group B, wb-MRI revealed lesions in 19 patients (16%) that were not detected in PR. All lesions detected by PR were also detected by wb-MRI and wb-CT. Wb-MRI and wb-CT are each superior to PR in detecting axial lesions. Conclusion Wb-CT can detect 23% more focal lesions than PR, especially in the axial skeleton. Therefore, this imaging method should be preferred over PR in the diagnostic work-up and staging of patients with monoclonal plasma cell disease.
    European journal of radiology 01/2014; · 2.65 Impact Factor
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    ABSTRACT: PURPOSE To quantitatively and qualitatively compare both image quality and diagnostic performance of 2D and 3D sequences for dedicated wrist imaging. METHOD AND MATERIALS 16 healthy volunteers (mean age, 26.4 years) and 18 patients (mean age, 36.2 years) with wrist pain were examined using an 8-channel wrist-coil at 3 Tesla MRI. The imaging protocol consisted of 2D-proton-density fat-saturated (PDfs), isotropic 3D MEDIC, 3D-TrueFISP and 3D-PDfs-SPACE sequences. Signal-to-noise-ratios (SNR) and contrast-to-noise-ratios (CNR) of cartilage/bone/muscle/fluid and mean overall SNR/CNR were calculated using region-of-interest analysis. Qualitative analysis included overall image quality (OIQ), visibility of important structures and degree of artifacts rated on a five-point scale (0-4). ANOVA and adjusted Wilcoxon-signed-rank tests were applied. The study was approved by the institutional review board and all patients gave informed consent prior to inclusion. RESULTS Mean overall SNR/CNR for 2dPDfs; 3D-PDfs-SPACE; 3D-TrueFISP; 3D-MEDIC was 96/73; 43/28; 61/53; 77/45. SNR and CNR were higher (p<0.01) for 2D-PDfs and 3D-MEDIC for all single items except fluid and fluid/cartilage contrast, where 2D-PDfs and 3D-TrueFISP were superior. 3D-PDfs-SPACE was inferior (p<0.05) in all comparisons. In volunteers OIQ was not different between 3D-TrueFISP (3.5), 3D-MEDIC (3.4) and 2D-PDfs (3.3), but all were superior to 3D-SPACE (2.2, p<0.01). The best sequence for cartilage was the 3D-TrueFISP (3.6), for ligaments/TFCC the 2D-PDfs (3.2/3.4) and the 3D-MEDIC (3.1/3.2). In 18/20 items image quality measures were worse in the patient group (mean, 0.3) with 3D-TrueFISP having the strongest decrease (mean, 0.5), and 2D-PDfs the lowest (mean, 0.1). Overall artifacts were most pronounced in 3D-TrueFISP (mean, 2.3) compared to 2D-PDfs (3.3), 3D PDfs-SPACE (3.4), and 3D-MEDIC (3.3). CONCLUSION Standard 2D-PDfs sequence provides high SNR/CNR, image quality and robustness when compared to 3D sequences. Isotropic 3D-TrueFISP (cartilage) and 3D-MEDIC (ligaments/TFCC) exhibit additional advantages, while 3D-PDfs-SPACE is currently not advantageous. CLINICAL RELEVANCE/APPLICATION When imaging the wrist at 3 Tesla, the sequence protocol should include 2D-PDfs. An additional 3D-TrueFISP sequence can be recommended for assessing cartilage and a 3D-MEDIC for ligaments and TFCC.
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
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    ABSTRACT: We studied a two-generation family presenting with conditions that included progressive permanent weakness, myopathic myopathy, exercise-induced contracture before normokalaemic periodic paralysis or, if localized to the tibial anterior muscle group, transient compartment-like syndrome (painful acute oedema with neuronal compression and drop foot). (23)Na and (1)H magnetic resonance imaging displayed myoplasmic sodium overload, and oedema. We identified a novel familial Cav1.1 calcium channel mutation, R1242G, localized to the third positive charge of the domain IV voltage sensor. Functional expression of R1242G in the muscular dysgenesis mouse cell line GLT revealed a 28% reduced central pore inward current and a -20 mV shift of the steady-state inactivation curve. Both changes may be at least partially explained by an outward omega (gating pore) current at positive potentials. Moreover, this outward omega current of 27.5 nS/nF may cause the reduction of the overshoot by 13 mV and slowing of the upstroke of action potentials by 36% that are associated with muscle hypoexcitability (permanent weakness and myopathic myopathy). In addition to the outward omega current, we identified an inward omega pore current of 95 nS/nF at negative membrane potentials after long depolarizing pulses that shifts the R1242G residue above the omega pore constriction. A simulation reveals that the inward current might depolarize the fibre sufficiently to trigger calcium release in the absence of an action potential and therefore cause an electrically silent depolarization-induced muscle contracture. Additionally, evidence of the inward current can be found in (23)Na magnetic resonance imaging-detected sodium accumulation and (1)H magnetic resonance imaging-detected oedema. We hypothesize that the episodes are normokalaemic because of depolarization-induced compensatory outward potassium flux through both delayed rectifiers and omega pore. We conclude that the position of the R1242G residue before elicitation of the omega current is decisive for its conductance: if the residue is located below the gating pore as in the resting state then outward currents are observed; if the residue is above the gating pore because of depolarization, as in the inactivated state, then inward currents are observed. This study shows for the first time that functional characterization of omega pore currents is possible using a cultured cell line expressing mutant Cav1.1 channels. Likewise, it is the first calcium channel mutation for complicated normokalaemic periodic paralysis.
    Brain 11/2013; · 10.23 Impact Factor
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    ABSTRACT: To prospectively evaluate whether dynamic contrast-enhanced (DCE) MRI can assess vascularity within non-unions and predicts clinical outcome in combination with the clinical Non-Union Scoring System (NUSS). Fifty-eight patients with non-unions of extremities on CT underwent 3-T DCE MRI. Signal intensity curves obtained from a region-of-interest analysis were subdivided into those with more intense contrast agent uptake within the non-union than in adjacent muscle (vascularised non-union) and those with similar or less contrast uptake. The pharmacokinetic parameters of the Tofts model K trans, K ep, iAUC and V e were correlated with union at CT 1 year later (n = 49). Despite inserted osteosynthetic material, DCE parameters could be evaluated in 57 fractures. The sensitivity/specificity of vascularised non-unions as an indicator of good outcome was 83.9 %/50.0 % compared to 96.8 %/33.3 % using NUSS (n = 49). Logistic regression revealed a significant impact of NUSS on outcome (P = 0.04, odds ratio = 0.93). At first examination, median iAUC (initial area under the enhancement curve) for the ratio non-union/muscle was 10.28 in patients with good outcome compared with 3.77 in non-responders (P = 0.023). K trans, K ep and Ve within the non-union were not significantly different initially (n = 57) or 1 year later (n = 19). DCE MRI can assess vascularity in fracture non-unions. A vascularised non-union correlates with good outcome. • Dynamic contrast-enhanced magnetic resonance imaging can assess vascularity within bony non-unions. • Vascularised ununited fractures appear better at 1-year CT than poorly vascularised fractures. • Non-union healing after osteosynthesis or osteoinductive drugs fundamentally requires vascularity. • DCE MRI predicts treatment outcome better than the clinical Non-Union Scoring System. • DCE MRI is clinically feasible to predict treatment outcome in bony non-unions.
    European Radiology 10/2013; · 4.34 Impact Factor
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    ABSTRACT: Purpose:To investigate muscular micro-perfusion by employing dynamic contrast-enhanced ultrasound (CEUS) and performing transient arterial occlusion in patients with type 2 diabetes mellitus (DM-2).Methods:Twenty DM-2 patients (mean age, 58 ± 8.6 years; duration of diabetes, 15.4 ± 12.1 years) and 20 healthy volunteers (mean age, 54 ± 5.4 years) participated. CEUS was applied to the calf, while 4.8 mL of SonoVue(®) was injected intravenously. At the thigh level, arterial occlusion (60 s) was performed. CEUS parameters (tmax, max, AUCpost and m) were evaluated and Pearson-product-moment correlation coefficients were computed.Results:A moderate negative correlation of HbA1c and max was established (-0.53). Max in patients with DM-2 >10 years was 79.89 ± 37.4. Max in patients with DM-2 duration <10 years was 137.62 ± 71.72 (p = 0.04). AUCpost in patients with DM-2 duration >10 years was 3924.01 ± 1630.52. AUCpost in patients with DM-2 duration <10 years was 6453.59 ± 3206.23 (p = 0.04).Conclusion:Patients with long history of DM-2 present with impaired muscular perfusion. CEUS and transient arterial occlusion may provide appropriate methods for semi-quantitative evaluation of muscular micro-perfusion in patients with DM-2.
    Diabetes & Vascular Disease Research 05/2013; · 2.59 Impact Factor
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    ABSTRACT: PURPOSE: We aimed to retrospectively evaluate the computed tomog- raphy (CT) and magnetic resonance imaging (MRI) findings of patients with osteoid osteoma treated with CT-guided ra- diofrequency ablation (RFA) along with the clinical outcome and long-term success. MATERIALS AND METHODS: Seventy-three CT-guided RFA procedures were performed in 72 patients. The long-term success was assessed using a questionnaire including several visual analog scale scores. The CT evaluation included pre- and immediate postproce- dural imaging of all 72 patients, and MRI was performed in 18 patients with follow-up imaging (mean, 3.4±2.2 months). The evaluation criteria included nidus morphology and a cor- relation with markers of clinical success. RESULTS: The primary technique effectiveness rate was 71/72 (99%). One relapse was successfully retreated, leading to a second- ary technique effectiveness rate of 72/72 (100%). The long- term follow-up (mean, 51.2±31.2 months; range, 3-109 months) revealed a highly significant reduction of all as- sessed limitation scores (P < 0.001). The CT morphology was typical in all cases and did not change during the short-term follow-up. The follow-up MRI patterns varied considerably, in- cluding persistent nidus contrast enhancement in one-third (6/18) and persistent marrow edema in half (9/18) of the patients. None of the investigated MRI and CT patterns cor- related with the clinical outcome. CONCLUSION: The long-term outcome of CT-guided RFA of osteoid oste- oma is excellent. There is no correlation of the CT and MRI patterns with the clinical outcome. Thus, the treatment de- cisions should not be solely based on the imaging findings. Investigators should also be aware of the variety of imaging patterns after RFA.
    Diagnostic and interventional radiology (Ankara, Turkey) 03/2013; · 1.03 Impact Factor
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    ABSTRACT: To prospectively assess whether changes in apparent diffusion coefficient (ADC) values or standardized uptake value (SUV) changes in 18F-fluorodeoxyglucose (FDG) PET correlate with treatment response under neoadjuvant chemotherapy in patients with locally advanced adenocarcinoma of the esophagogastric junction (AEG). Fifteen patients (median age, 64 years) with histologically proven AEG type I and II received 1.5 Tesla MRI including "diffusion-weighted imaging" and FDG PET/CT before and 14 days after neoadjuvant EOX chemotherapy. The FDG uptake of the tumor was quantified by calculating the SUV in static PET scans. ADC values within the tumor tissue were quantitatively assessed using a region-of-interest analysis excluding necrotic areas. Early metabolic response was defined as a decrease in the SUVmean > /= 35% in FDG PET two weeks following the start of neoadjuvant chemotherapy, which had been reported to be predictive of histopathological response and survival. Concordance between ADC and SUV changes, differences at first examination and overall survival were assessed. The ADC within the AEG tumors was significantly lower than in normal esophagus and increased following neoadjuvant chemotherapy by 16.0 +/- 1.1% (p=0.007). Tumor glucose SUV decreased by 29.1 +/- 23.2% (p=0.002). Initial ADC and SUV were comparable in both groups (p=0.65, p=0.82). ADC increase and metabolic PET-response were concordant in 73.3% of all patients. The median overall survival was 757 days for PET-responders and 623 days for PET-non-responders (p=0.138). The ADC increase in AEG tumors following chemotherapy is concordant in the majority of cases to PET-response, but not correlated to prognosis in this study.
    Journal of gastrointestinal and liver diseases: JGLD 03/2013; 22(1):45-52. · 1.86 Impact Factor
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    ABSTRACT: This paper proposes to employ a detailed tumor growth model to synthesize labelled images which can then be used to train an efficient data-driven machine learning tumor predictor. Our MR image synthesis step generates images with both healthy tissues as well as various tumoral tissue types. Subsequently, a discriminative algorithm based on random regression forests is trained on the simulated ground truth to predict the continuous latent tumor cell density, and the discrete tissue class associated with each voxel. The presented method makes use of a large synthetic dataset of 740 simulated cases for training and evaluation. A quantitative evaluation on 14 real clinical cases diagnosed with low-grade gliomas demonstrates tissue class accuracy comparable with state of the art, with added benefit in terms of computational efficiency and the ability to estimate tumor cell density as a latent variable underlying the multimodal image observations. The idea of synthesizing training data to train data-driven learning algorithms can be extended to other applications where expert annotation is lacking or expensive.
    MICCAI Workshop on Medical Computer Vision; 10/2012
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    ABSTRACT: The purpose of this study was to retrospectively evaluate long-term success of CT-guided radiofrequency ablation (RFA) in patients with osteoid osteoma (OO) and osteoblastoma (OB) including tumors in critical locations. Eighty-one CT-guided RFA procedures were performed in 77 patients with OO (65 patients) and OB (12) including 6 spinal and 15 intra/periarticular tumors. Procedural techniques included multiple needle positions, three-dimensional access planning, as well as, thermal protection techniques. Long-term success was assessed using a questionnaire including, among others, several VAS (visual analogue scale) scores. All patients completed 3-6months follow-up, overall response to the questionnaire was 64/77 (83.1%). Primary success rate was 74/77 (96.1%) of all patients. Retreatment with RFA in 3 patients resulted in a secondary success rate of 77/77 (100%). Long-term follow-up (mean, 38.5months; range, 3-92) revealed a highly significant (p<0.001) reduction of all assessed limitation scores reaching normal or almost normal values. One major complication, a cannula break leading to a secondary short hospital stay, occurred. In conclusion, RFA is a safe and effective long-lasting treatment of OO and OB. Advanced procedural techniques aid treating tumors in critical locations and in the coverage of larger tumors. Besides night pain, RFA also greatly improves other factors negatively affecting the quality of life.
    European journal of radiology 07/2012; 81(11):3426-34. · 2.65 Impact Factor
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    ABSTRACT: By magnetic resonance imaging in multiple myeloma, focal lesions as well as diffuse and variegated infiltration patterns can be detected. In the current study we compared treatment response in 100 myeloma patients with changes in infiltration patterns in whole body magnetic resonance imaging before and after autologous stem cell transplantation. We found an agreement between serological response and changes in imaging (p<0.001). In detail, a significant agreement of treatment response was observed for diffuse (p=0.004) as well as for focal (p=0.01) infiltration patterns. The number of focal lesions at second magnetic resonance imaging was of prognostic significance for overall survival (p=0.001). We conclude that treatment response in myeloma goes along with a decrease in imaging findings. We suggest that residual disease after high dose chemotherapy detected by magnetic resonance imaging increases the risk of relapse. Therefore, myeloma patients with such findings after treatment might benefit from further cytoreduction.
    Haematologica 06/2012; · 5.94 Impact Factor
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    ABSTRACT: Recently we reported a cytoplasmic sodium overload to cause a severe osmotic oedema in Duchenne muscular dystrophy (DMD). Our results suggested that this dual overload of sodium ions and water precedes the dystrophic process and persists until fatty muscle degeneration is complete. The present paper addresses the questions as to whether these overloads are important for the pathogenesis of the disease, and if so, whether they can be treated. As a first step, we investigated the effects of various diuretic drugs on a cell model of DMD, i.e. rat diaphragm strips previously exposed to amphotericin B. We found that both carbonic anhydrase inhibitors and aldosterone antagonists were able to repolarise depolarised muscle fibres. Since carbonic anhydrase inhibitors are known to have acidifying effects and this might be detrimental to the ventilation of DMD patients, we mainly concentrated on the modern spironolactone derivative, eplerenone. This drug had a very high repolarizing power, the parameter considered by us as being most relevant for a beneficial effect. In a pilot study we administered this drug to a 22-yr-old female DMD patient who was bound to an electric wheelchair and has had no corticosteroid therapy before. Eplerenone decreased both cytoplasmic sodium and water overload and increased muscle strength and mobility. We conclude that eplerenone has beneficial effects on DMD muscle. In our opinion the cytoplasmic oedema is cytotoxic and should be treated before fatty degeneration takes place.
    Acta myologica: myopathies and cardiomyopathies: official journal of the Mediterranean Society of Myology / edited by the Gaetano Conte Academy for the study of striated muscle diseases 05/2012; 31(1):31-9.
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    ABSTRACT: To assess whether myoplasmic ionic sodium (Na+) is increased in muscles of patients with hyperkalemic periodic paralysis (HyperPP) with 3-T sodium 23 (23Na) magnetic resonance (MR) imaging and to evaluate the effect of medical treatment on sodium-induced muscle edema. This study received institutional review board approval; written informed consent was obtained. Proton (hydrogen 1 [1H]) and 23Na MR of both calves were performed in 12 patients with HyperPP (mean age, 48 years±14 [standard deviation]) and 12 healthy volunteers (mean age, 38 years±12) before and after provocation (unilateral cooling, one calf). 23Na MR included spin-density, T1-weighted, and inversion-recovery (IR) sequences. Total sodium concentration and normalized signal intensities (SIs) were evaluated within regions of interest (ROIs). Muscle strength was measured with the British Medical Research Council (MRC) grading scale. Five patients underwent follow-up MR after diuretic treatment. During rest, mean myoplasmic Na+ concentration was significantly higher in HyperPP with permanent weakness (40.7 μmol/g±3.9) compared with HyperPP with transient weakness (31.3 μmol/g±4.8) (P=.004). Mean SI in 23Na IR MR was significantly higher in HyperPP with permanent weakness (0.83±0.04; median MRC, grade 4; range, 3-5) compared with HyperPP without permanent weakness (0.67±0.05; median MRC, grade 5; range, 4-5) (P=.002). Provocation reduced muscle strength in HyperPP (before provocation, median MRC, 5; range, 3-5; after provocation, median MRC, 3; range, 1-4) and increased SI in 23Na IR from 0.75±0.09 to 0.86±0.10 (P=.004). Spin-density and T1-weighted sequences were less sensitive, particularly to cold-induced Na+ changes. 23Na IR SI remained unchanged in volunteers (0.53±0.06 before and 0.54±0.06 after provocation, P=.3). Therapy reduced mean SI in 23Na IR sequence from 0.85±0.04 to 0.64±0.11. 23Na MR imaging depicts increased myoplasmic Na+ in HyperPP with permanent weakness. Na+ overload may cause muscle degeneration developing with age. 23Na MR imaging may have potential to aid monitoring of medical treatment that reduces this overload.
    Radiology 04/2012; 264(1):154-63. · 6.34 Impact Factor
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    ABSTRACT: The prevalence of osteoarthritis of the hand and wrist is high, and a thorough assessment of even subtle cartilage injuries is necessary before surgical interventions. Although magnetic resonance imaging (MRI) has been established as an important diagnostic tool for the evaluation of hand and wrist disorders, the focus has been on the assessment of the triangular fibrocartilage complex, tendons, ligaments, and the detection of avascular necrosis or occult fractures rather than on cartilage imaging. 3-T MR systems have become more and more widely available and yield an improved signal-to-noise ratio and thus a higher spatial resolution than 1.5-T systems. In principle, this should be especially beneficial for depicting the thin cartilage layers of the hand and wrist. This review focuses on cartilage imaging of the hand and wrist with 3-T MRI and addresses these four topics: (1) the advantages of 3-T versus 1.5- and 1-T MRI, (2) dedicated sequence protocols at 3 T including novel three-dimensional sequences, (3) imaging findings in common cases of overuse or sports injury, and (4) functional cartilage imaging techniques of the hand and wrist, for instance, delayed gadolinium-enhanced MRI of the cartilage.
    Seminars in Musculoskeletal Radiology 04/2012; 16(2):71-87. · 1.40 Impact Factor
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    ABSTRACT: The apparent diffusion coefficient (ADC) derived from diffusion-weighted imaging (DWI) correlates inversely with tumor proliferation rates. High-grade gliomas are typically heterogeneous and the delineation of areas of high and low proliferation is impeded by partial volume effects and blurred borders. Commonly used manual delineation is further impeded by potential overlap with cerebrospinal fluid and necrosis. Here we present an algorithm to reproducibly delineate and probabilistically quantify the ADC in areas of high and low proliferation in heterogeneous gliomas, resulting in a reproducible quantification in regions of tissue inhomogeneity. We used an expectation maximization (EM) clustering algorithm, applied on a Gaussian mixture model, consisting of pure superpositions of Gaussian distributions. Soundness and reproducibility of this approach were evaluated in 10 patients with glioma. High- and low-proliferating areas found using the clustering correspond well with conservative regions of interest drawn using all available imaging data. Systematic placement of model initialization seeds shows good reproducibility of the method. Moreover, we illustrate an automatic initialization approach that completely removes user-induced variability. In conclusion, we present a rapid, reproducible and automatic method to separate and quantify heterogeneous regions in gliomas.
    Cancer Imaging 01/2012; 12:89-99. · 1.59 Impact Factor

Publication Stats

936 Citations
257.69 Total Impact Points

Institutions

  • 2003–2014
    • Universität Heidelberg
      • • Department of Diagnostic and Interventional Radiology
      • • Interdisciplinary Center for Scientific Computing
      • • Abteilung Neurologie und Poliklinik
      Heidelburg, Baden-Württemberg, Germany
  • 2009–2013
    • Universität Ulm
      • • Division of Neurophysiology
      • • Institute of Applied Physiology
      Ulm, Baden-Württemberg, Germany
  • 2003–2013
    • German Cancer Research Center
      • Division of Radiology
      Heidelburg, Baden-Württemberg, Germany
  • 2010–2011
    • Massachusetts Institute of Technology
      • Computer Science and Artificial Intelligence Laboratory
      Cambridge, MA, United States
  • 2006
    • University of Tuebingen
      Tübingen, Baden-Württemberg, Germany