Publications by authors named "Karl Ludwig"

32 Publications

Probing the subcellular nanostructure of engineered human cardiomyocytes in 3D tissue.

Microsyst Nanoeng 2021 27;7:10. Epub 2021 Jan 27.

Department of Mechanical Engineering, Boston University, Boston, MA 02215 USA.

The structural and functional maturation of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) is essential for pharmaceutical testing, disease modeling, and ultimately therapeutic use. Multicellular 3D-tissue platforms have improved the functional maturation of hiPSC-CMs, but probing cardiac contractile properties in a 3D environment remains challenging, especially at depth and in live tissues. Using small-angle X-ray scattering (SAXS) imaging, we show that hiPSC-CMs matured and examined in a 3D environment exhibit a periodic spatial arrangement of the myofilament lattice, which has not been previously detected in hiPSC-CMs. The contractile force is found to correlate with both the scattering intensity (  = 0.44) and lattice spacing (  = 0.46). The scattering intensity also correlates with lattice spacing (  = 0.81), suggestive of lower noise in our structural measurement than in the functional measurement. Notably, we observed decreased myofilament ordering in tissues with a myofilament mutation known to lead to hypertrophic cardiomyopathy (HCM). Our results highlight the progress of human cardiac tissue engineering and enable unprecedented study of structural maturation in hiPSC-CMs.
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http://dx.doi.org/10.1038/s41378-020-00234-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8433147PMC
January 2021

de Gennes Narrowing and Relationship between Structure and Dynamics in Self-Organized Ion-Beam Nanopatterning.

Phys Rev Lett 2021 Jan;126(1):016101

Department of Physics and Materials Science Program, University of Vermont, Burlington, Vermont 05405, USA.

Investigating the relationship between structure and dynamical processes is a central goal in condensed matter physics. Perhaps the most noted relationship between the two is the phenomenon of de Gennes narrowing, in which relaxation times in liquids are proportional to the scattering structure factor. Here, a similar relationship is discovered during the self-organized ion-beam nanopatterning of silicon using coherent x-ray scattering. However, in contrast to the exponential relaxation of fluctuations in classic de Gennes narrowing, the dynamic surface exhibits a wide range of behaviors as a function of the length scale, with a compressed exponential relaxation at lengths corresponding to the dominant structural motif-self-organized nanoscale ripples. These behaviors are reproduced in simulations of a nonlinear model describing the surface evolution. We suggest that the compressed exponential behavior observed here is due to the morphological persistence of the self-organized surface ripple patterns which form and evolve during ion-beam nanopatterning.
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http://dx.doi.org/10.1103/PhysRevLett.126.016101DOI Listing
January 2021

MITF and TFEB cross-regulation in melanoma cells.

PLoS One 2020 3;15(9):e0238546. Epub 2020 Sep 3.

Department of Biochemistry and Molecular Biology, Faculty of Medicine, BioMedical Center, University of Iceland, Reykjavík, Iceland.

The MITF, TFEB, TFE3 and TFEC (MiT-TFE) proteins belong to the basic helix-loop-helix family of leucine zipper transcription factors. MITF is crucial for melanocyte development and differentiation, and has been termed a lineage-specific oncogene in melanoma. The three related proteins MITF, TFEB and TFE3 have been shown to be involved in the biogenesis and function of lysosomes and autophagosomes, regulating cellular clearance pathways. Here we investigated the cross-regulatory relationship of MITF and TFEB in melanoma cells. Like MITF, the TFEB and TFE3 genes are expressed in melanoma cells as well as in melanoma tumors, albeit at lower levels. We show that the MITF and TFEB proteins, but not TFE3, directly affect each other's mRNA and protein expression. In addition, the subcellular localization of MITF and TFEB is subject to regulation by the mTOR signaling pathway, which impacts their cross-regulatory relationship at the transcriptional level. Our work shows that the relationship between MITF and TFEB is multifaceted and that the cross-regulatory interactions of these factors need to be taken into account when considering pathways regulated by these proteins.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0238546PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7470386PMC
October 2020

Coherent X-ray measurement of step-flow propagation during growth on polycrystalline thin film surfaces.

Nat Commun 2019 06 14;10(1):2638. Epub 2019 Jun 14.

Division of Materials Science and Engineering, Boston University, Boston, MA, 02215, USA.

The properties of artificially grown thin films are strongly affected by surface processes during growth. Coherent X-rays provide an approach to better understand such processes and fluctuations far from equilibrium. Here we report results for vacuum deposition of C on a graphene-coated surface investigated with X-ray Photon Correlation Spectroscopy in surface-sensitive conditions. Step-flow is observed through measurement of the step-edge velocity in the late stages of growth after crystalline mounds have formed. We show that the step-edge velocity is coupled to the terrace length, and that there is a variation in the velocity from larger step spacing at the center of crystalline mounds to closely-spaced, more slowly propagating steps at their edges. The results extend theories of surface growth, since the behavior is consistent with surface evolution driven by processes that include surface diffusion, the motion of step-edges, and attachment at step edges with significant step-edge barriers.
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http://dx.doi.org/10.1038/s41467-019-10629-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6570654PMC
June 2019

Sawtooth structure formation under nonlinear-regime ion bombardment.

J Phys Condens Matter 2018 Jul 14;30(29):294004. Epub 2018 May 14.

The Charles Stark Draper Laboratory, Inc., Cambridge, MA 02139, United States of America.

Linear-regime Ar bombardment of Si produces symmetrical ripple structures at ion incidence angles above 45° measured off-normal (Madi 2009 J. Phys.: Condens. Matter 21). In the nonlinear regime, new behaviors emerge. In this paper, we present experimental results of ion bombardment that continues into the nonlinear regime until pattern saturation at multiple ion incidence angles, showing the evolution of their grazing incidence small-angle x-ray scattering (GISAXS) spectra as well as atomic force microscopy topographs of the final, saturated structures. Asymmetric structures emerge parallel to the direction of the projected ion beam on the sample surface, constituting a height asymmetry not found in the linear regime. We then present simulations of surface height evolution under ion bombardment using a nonlinear partial differential equation developed by Pearson and Bradley (2015 J. Phys.: Condens. Matter 27 015010). We present simulated GISAXS spectra from these simulations, as well as simulated scattering from a sawtooth structure using the FitGISAXS software package (Babonneau 2010 J. Appl. Crystallogr. 43 929-36), and compare the simulated spectra to those observed experimentally. We find that these simulations reproduce many features of the sawtooth structures, as well as the nearly-flat final GISAXS spectra observed experimentally perpendicular to the sawtooth structures. However, the model fails to reproduce the final GISAXS spectra observed parallel to the sawtooth structures.
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http://dx.doi.org/10.1088/1361-648X/aac460DOI Listing
July 2018

Simulations of Co-GISAXS during kinetic roughening of growth surfaces.

J Synchrotron Radiat 2017 Nov 5;24(Pt 6):1187-1194. Epub 2017 Oct 5.

Division of Materials Science and Engineering, Boston University, Boston, MA 02215, USA.

The recent development of surface growth studies using X-ray photon correlation spectroscopy in a grazing-incidence small-angle X-ray scattering (Co-GISAXS) geometry enables the investigation of dynamical processes during kinetic roughening in greater detail than was previously possible. In order to investigate the Co-GISAXS behavior expected from existing growth models, calculations and (2+1)-dimension simulations of linear Kuramoto-Sivashinsky and non-linear Kardar-Parisi-Zhang surface growth equations are presented which analyze the temporal correlation functions of the height-height structure factor. Calculations of the GISAXS intensity auto-correlation functions are also performed within the Born/distorted-wave Born approximation for comparison with the scaling behavior of the height-height structure factor and its correlation functions.
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http://dx.doi.org/10.1107/S1600577517011924DOI Listing
November 2017

Distinguishing physical mechanisms using GISAXS experiments and linear theory: the importance of high wavenumbers.

Sci Rep 2017 05 17;7(1):2016. Epub 2017 May 17.

Department of Physics, Boston University, Boston Massachusetts, 02215, USA.

In this work we analyze GISAXS measurements of the structure factor of Si surfaces evolving during 1 keV Ar+ ion bombardment. Using newly-developed methods sensitive to the full range of experimentally-available wavenumbers q, we extract the linear amplification rate R(q) governing surface stability over a range of wavenumbers 4-5 times larger than has previously been obtained. Comparing with theoretical models also retaining full wavenumber-dependence, we find an excellent fit of the experimental data over the full range of irradiation angles and wavenumbers. Moreover, the fitted parameter values represent experimental evaluation of the magnitudes of most physical mechanisms currently believed to be important to the pattern-formation process. In all cases, the extracted values agree well with direct observations or atomistic simulations of the same quantities, suggesting that GISAXS analysis may allow more powerful comparison between experiment and theory than had previously been thought.
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http://dx.doi.org/10.1038/s41598-017-01059-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5435725PMC
May 2017

Effect of Sr Content and Strain on Sr Surface Segregation of LaSrCoFeO as Cathode Material for Solid Oxide Fuel Cells.

ACS Appl Mater Interfaces 2016 Oct 28;8(40):26704-26711. Epub 2016 Sep 28.

Division of Materials Science and Engineering, Boston University , Brookline, Massachusetts 02446, United States.

Strontium-doped lanthanum cobalt ferrite (LSCF) is a widely used cathode material due to its high electronic and ionic conductivity, and reasonable oxygen surface exchange coefficient. However, LSCF can have long-term stability issues such as surface segregation of Sr during solid oxide fuel cell (SOFC) operation, which can adversely affect the electrochemical performance. Thus, understanding the nature of the Sr surface segregation phenomenon and how it is affected by the composition of LSCF and strain are critical. In this research, heteroepitaxial thin films of La SrCoFeO with varying Sr content (x = 0.4, 0.3, 0.2) were deposited by pulsed laser deposition (PLD) on single-crystal NdGaO, SrTiO, and GdScO substrates, leading to different levels of strain in the films. The extent of Sr segregation at the film surface was quantified using synchrotron-based total-reflection X-ray fluorescence (TXRF) and atomic force microscopy (AFM). The electronic structure of the Sr-rich phases formed on the surface was investigated by hard X-ray photoelectron spectroscopy (HAXPES). The extent of Sr segregation was found to be a function of the Sr content in bulk. Lowering the Sr content from 40% to 30% reduced the surface segregation, but further lowering the Sr content to 20% increased the segregation. The strain of LSCF thin films on various substrates was measured using high-resolution X-ray diffraction (HRXRD), and the Sr surface segregation was found to be reduced with compressive strain and enhanced with tensile strain present within the thin films. A model was developed correlating the Sr surface segregation with Sr content and strain effects to explain the experimental results.
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http://dx.doi.org/10.1021/acsami.6b07118DOI Listing
October 2016

Atomic layer deposition-based tuning of the pore size in mesoporous thin films studied by in situ grazing incidence small angle X-ray scattering.

Nanoscale 2014 Dec 3;6(24):14991-8. Epub 2014 Nov 3.

Department of Solid State Sciences, COCOON, Ghent University, Krijgslaan 281/S1, B-9000 Ghent, Belgium.

Atomic layer deposition (ALD) enables the conformal coating of porous materials, making the technique suitable for pore size tuning at the atomic level, e.g., for applications in catalysis, gas separation and sensing. It is, however, not straightforward to obtain information about the conformality of ALD coatings deposited in pores with diameters in the low mesoporous regime (<10 nm). In this work, it is demonstrated that in situ synchrotron based grazing incidence small angle X-ray scattering (GISAXS) can provide valuable information on the change in density and internal surface area during ALD of TiO(2) in a porous titania film with small mesopores (3-8 nm). The results are shown to be in good agreement with in situ X-ray fluorescence data representing the evolution of the amount of Ti atoms deposited in the porous film. Analysis of both datasets indicates that the minimum pore diameter that can be achieved by ALD is determined by the size of the Ti-precursor molecule.
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http://dx.doi.org/10.1039/c4nr05049eDOI Listing
December 2014

Atomic layer deposition of TiO2 on surface modified nanoporous low-k films.

Langmuir 2013 Oct 17;29(39):12284-9. Epub 2013 Sep 17.

Department of Solid State Sciences, COCOON, Ghent University , Krijgslaan 281/S1, B-9000 Ghent, Belgium.

This paper explores the effects of different plasma treatments on low dielectric constant (low-k) materials and the consequences for the growth behavior of atomic layer deposition (ALD) on these modified substrates. An O2 and a He/H2 plasma treatment were performed on SiCOH low-k films to modify their chemical surface groups. Transmission FTIR and water contact angle (WCA) analysis showed that the O2 plasma changed the hydrophobic surface completely into a hydrophilic surface, while the He/H2 plasma changed it only partially. In a next step, in situ X-ray fluorescence (XRF), ellipsometric porosimetry (EP), and Rutherford backscattering spectroscopy (RBS) were used to characterize ALD growth of TiO2 on these substrates. The initial growth of TiO2 was found to be inhibited in the original low-k film containing only Si-CH3 surface groups, while immediate growth was observed in the hydrophilic O2 plasma treated film. The latter film was uniformly filled with TiO2 after 8 ALD cycles, while pore filling was delayed to 17 ALD cycles in the hydrophobic film. For the He/H2 plasma treated film, containing both Si-OH and Si-CH3 groups, the in situ XRF data showed that TiO2 could no longer be deposited in the He/H2 plasma treated film after 8 ALD cycles, while EP measurements revealed a remaining porosity. This can be explained by the faster deposition of TiO2 in the hydrophilic top part of the film than in the hydrophobic bulk which leaves the bulk porous, as confirmed by RBS depth profiling. The outcome of this research is not only of interest for the development of advanced interconnects in ULSI technology, but also demonstrates that ALD combined with RBS analysis is a handy approach to analyze the modifications induced by a plasma treatment on a nanoporous thin film.
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http://dx.doi.org/10.1021/la4027738DOI Listing
October 2013

CT-guided radiofrequency ablation of osteoid osteoma: correlation of clinical outcome and imaging features.

Diagn Interv Radiol 2013 Jul-Aug;19(4):330-9

Departments of Diagnostic and Interventional Radiology, University of Heidelberg, Heidelberg, Germany.

Purpose: We aimed to retrospectively evaluate the computed tomography (CT) and magnetic resonance imaging (MRI) findings of patients with osteoid osteoma treated with CT-guided radiofrequency 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 postprocedural 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 correlation with markers of clinical success.

Results: The primary technique effectiveness rate was 71/72 (99%). One relapse was successfully retreated, leading to a secondary 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 assessed 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, including 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 correlated with the clinical outcome.

Conclusion: The long-term outcome of CT-guided RFA of osteoid osteoma is excellent. There is no correlation of the CT and MRI patterns with the clinical outcome. Thus, the treatment decisions should not be solely based on the imaging findings. Investigators should also be aware of the variety of imaging patterns after RFA.
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http://dx.doi.org/10.5152/dir.2013.096DOI Listing
May 2014

Evidence for Family-Meakin dynamical scaling in island growth and coalescence during vapor phase deposition.

Phys Rev Lett 2012 Sep 7;109(10):106102. Epub 2012 Sep 7.

Department of Physics, Boston University, Boston, Massachusetts 01770, USA.

Using real-time grazing-incidence small-angle x-ray scattering, we find that the processes of island formation and coalescence during the room-temperature vapor phase deposition of aluminum lead to dynamical scaling of the evolving surface morphology. The scaling is quantitatively consistent with the self-similarity predicted by the Family-Meakin model, which was developed to describe liquid droplet deposition, growth, and coalescence. The Family-Meakin model assumes only that atomic diffusion over the substrate between islands or droplets is negligible and that diffusion between impinging islands or droplets is sufficient to give complete coalescence. Therefore the dynamical scaling morphology evolution identified here may be common in the initial stages of those solid film growth processes which proceed by island formation and growth.
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http://dx.doi.org/10.1103/PhysRevLett.109.106102DOI Listing
September 2012

CT-guided radiofrequency ablation of osteoid osteoma and osteoblastoma: clinical success and long-term follow up in 77 patients.

Eur J Radiol 2012 Nov 6;81(11):3426-34. Epub 2012 Jul 6.

Department of Diagnostic and Interventional Radiology, University of Heidelberg, Im Neuenheimer Feld 110, D-69120 Heidelberg, Germany.

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 3-6 months 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, 38.5 months; 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.
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http://dx.doi.org/10.1016/j.ejrad.2012.04.037DOI Listing
November 2012

X-ray photon correlation spectroscopy in systems without long-range order: existence of an intermediate-field regime.

Authors:
Karl Ludwig

J Synchrotron Radiat 2012 Jan 15;19(Pt 1):66-73. Epub 2011 Nov 15.

Physics Department, Boston University, Boston, MA 02215, USA.

Successful X-ray photon correlation spectroscopy studies often require that signals be optimized while minimizing power density in the sample to decrease radiation damage and, at free-electron laser sources, thermal impact. This suggests exploration of scattering outside the Fraunhofer far-field diffraction limit d(2)/λ << R, where d is the incident beam size, λ is the photon wavelength and R is the sample-to-detector distance. Here it is shown that, in an intermediate regime d(2)/λ > R >> dξ/λ, where ξ is the structural correlation length in the material, the ensemble averages of the scattered intensity and of the structure factor are equal. Similarly, in the regime d(2)/λ > R >> dξ(τ)/λ, where ξ(τ) is a time-dependent dynamics length scale of interest, the ensemble-averaged correlation functions g(1)(τ) and g(2)(τ) of the scattered electric field are also equal to their values in the far-field limit. This broadens the parameter space for X-ray photon correlation spectroscopy experiments, but detectors with smaller pixel size and variable focusing are required to more fully exploit the potential for such studies.
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http://dx.doi.org/10.1107/S0909049511040532DOI Listing
January 2012

Direct measurement of microstructural avalanches during the martensitic transition of cobalt using coherent x-ray scattering.

Phys Rev Lett 2011 Jul 30;107(1):015702. Epub 2011 Jun 30.

Department of Physics, Boston University, Massachusetts 02215, USA.

Heterogeneous microscale dynamics in the martensitic phase transition of cobalt is investigated with real-time x-ray scattering. During the transformation of the high-temperature face-centered cubic phase to the low-temperature hexagonal close-packed phase, the structure factor evolution suggests that an initial rapid local transformation is followed by a slower period during which strain relaxes. Coherent x-ray scattering measurements performed during the latter part of the transformation show that the kinetics is dominated by discontinuous sudden changes-avalanches. The spatial size of observed avalanches varies widely, from 100 nm to 10 μm, the size of the x-ray beam. An empirical avalanche amplitude quantifies this behavior, exhibiting a power-law distribution. The avalanche rate decreases with inverse time since the onset of the transformation.
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http://dx.doi.org/10.1103/PhysRevLett.107.015702DOI Listing
July 2011

Tailoring nanoporous materials by atomic layer deposition.

Chem Soc Rev 2011 Nov 22;40(11):5242-53. Epub 2011 Jun 22.

Ghent University, Dept. of Solid State Sciences, Krijgslaan 281/S1, Gent B-9000, Belgium.

Atomic layer deposition (ALD) is a cyclic process which relies on sequential self-terminating reactions between gas phase precursor molecules and a solid surface. The self-limiting nature of the chemical reactions ensures precise film thickness control and excellent step coverage, even on 3D structures with large aspect ratios. At present, ALD is mainly used in the microelectronics industry, e.g. for growing gate oxides. The excellent conformality that can be achieved with ALD also renders it a promising candidate for coating porous structures, e.g. for functionalization of large surface area substrates for catalysis, fuel cells, batteries, supercapacitors, filtration devices, sensors, membranes etc. This tutorial review focuses on the application of ALD for catalyst design. Examples are discussed where ALD of TiO(2) is used for tailoring the interior surface of nanoporous films with pore sizes of 4-6 nm, resulting in photocatalytic activity. In still narrower pores, the ability to deposit chemical elements can be exploited to generate catalytic sites. In zeolites, ALD of aluminium species enables the generation of acid catalytic activity.
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http://dx.doi.org/10.1039/c1cs15091jDOI Listing
November 2011

Mass redistribution causes the structural richness of ion-irradiated surfaces.

Phys Rev Lett 2011 Feb 8;106(6):066101. Epub 2011 Feb 8.

Harvard School of Engineering and Applied Sciences, Cambridge Massachusetts 02138, USA.

We show that the "sputter patterning" topographical instability is determined by the effects of ion impact-induced prompt atomic redistribution and that erosion--the consensus predominant cause--is essentially irrelevant. We use grazing incidence small angle x-ray scattering to measure in situ the damping of noise or its amplification into patterns via the linear dispersion relation. A model based on the effects of impact-induced redistribution of those atoms that are not sputtered away explains both the observed ultrasmoothening at low angles from normal incidence and the instability at higher angles.
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http://dx.doi.org/10.1103/PhysRevLett.106.066101DOI Listing
February 2011

Radiological and clinical outcome after operations in patients with congenital deficiencies of the wrist and hand.

Eur J Radiol 2011 Feb 17;77(2):261-8. Epub 2010 Nov 17.

Department of Orthopedic Surgery, University of Heidelberg, Germany.

Purpose: To evaluate the incidence, therapy results, complications and radiologic workup of operatively treated congenital disorders of the hand and wrist in a large university center during a 10-year period.

Methods: The institutional database was retrospectively analysed for patients with congenital disorders of the hand and wrist treated operatively during a 10-year period (1998-2007). Disorders were classified according to Van Schoonhoven into 11 different entities. For each entity the incidence, the patients' age at the time of operation, the pre- and postoperative clinical and radiological workup and the frequency of complications and reoperations were evaluated.

Results: A total of 278 patients was treated operatively for congenital disorders of the hand and wrist with syndactyly being present in 112, thumb hypoplasia in 15, polydactyly in 11, radial clubhand in 7, radioulnar synostosis in 6, clinodactyly in 6, thumb duplication in 6, brachydactyly in 4 and macrodactyly in 4 cases. Patients' age at the time of operation varied substantially between the different entities with a mean age between 0.9 and 6.2 years. There were 9 complications (3%, n = 278)--all of them infections. There were 28 reoperations (10%, n = 278), 13 of them (5%, n = 278) due to reoccurring webs in syndactyly.

Conclusion: Congenital disorders of the hand and wrist include various rare diseases with syndactyly and thumb hypoplasia being the most frequent entities. As a rule, diagnosis is obtained clinically. Radiologic workup typically consists of plain radiography. Complications are rare, whereas reoperations are frequent, mostly due to reoccurring webs in syndactyly.
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http://dx.doi.org/10.1016/j.ejrad.2010.10.023DOI Listing
February 2011

Clinical course and spectrum of intensive care unit patients reactivating herpes simplex-1 virus: a retrospective analysis.

Indian J Crit Care Med 2008 Oct;12(4):145-52

Department of Medicine, Utah Valley Reginal Medical Center, Provo, Utah, USA.

Background: Herpes simplex-1 virus (HSV-1) reactivation in the respiratory tract is common in intensive care unit (ICU) patients. However, susceptible ICU populations are poorly defined. Clinical recognition of HSV infection of the respiratory tract is difficult and the impact of such reactivation is not understood.

Materials And Methods: A retrospective analysis of HSV-1 positive patients encountered over a 5-year period at a multispecialty ICU was carried out. HSV-1 was identified in respiratory secretions using a qualitative polymerase chain reaction (PCR) technique. Patient charts were reviewed for clinical features that would typify HSV-1 respiratory involvement, and the morbidity and mortality risks found with HSV-1 respiratory involvement.

Results: A review of 48 HSV-1 positive ICU patients showed that patients reactivating HSV in the respiratory tract fell into one of the three categories: (1) septic elderly patients with and without ARDS, (2) immunosuppressed patients, especially those receiving high-dose steroids, and (3) post-thoracotomy patients. Abnormalities suggestive of HSV-1 reactivation in the respiratory tract included, haemorrhagic or excessive respiratory secretions, concomitant orofacial herpes (42%), and bronchoscopic abnormalities (hemorrhagic ulcers and mucosal friability) (83%). Twenty eight percent of the HSV-1 infected patients experienced postextubation stridor. HSV-1 reactivation was associated with extended ventilator stays, significant mortality (42%), and ventilator-associated pneumonias (52%).

Conclusions: Identification of susceptible populations and definition of clinical features of HSV-1 related respiratory disease can enable diagnosis of HSV-1 infection in ICU patients. Although detection by a PCR technique can rapidly diagnose HSV-1 reactivation, prospective studies are required to clarify HSV disease versus mere shedding, and understand the impact of HSV-1 reactivation in hospitalized patients.
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http://dx.doi.org/10.4103/0972-5229.45073DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2738328PMC
October 2008

Depiction of the triangular fibro-cartilage in patients with ulnar-sided wrist pain: comparison of direct multi-slice CT arthrography and direct MR arthrography.

Eur Radiol 2009 Jan 30;19(1):147-51. Epub 2008 Jul 30.

Department of Hand and Elbow Surgery, Orthopaedic University Hospital, Heidelberg, Germany.

To compare direct multi-slice CT arthrography (MSCT-AG) and direct MR arthrography (MR-AG) of the wrist with regard to the depiction of the triangular fibro-cartilage (TFC). Fifteen consecutive patients with ulnar-sided wrist pain suspicious for TFC tear underwent both MSCT-AG and MR-AG of the wrist. Images obtained were evaluated by two radiologists in a blinded fashion for the depiction of six anatomical areas (radial, central and ulnar portion on the proximal and distal side) of the TFC by means of a five-point scoring system (1 = excellent visibility to 5 = not visible). Scores for MSCT-AG and MR-AG were compared using the Student's t-test. Mean scores for MSCT-AG and MR-AG, respectively, were 2.5/2.0, 3.2/2.5 and 2.8/2.4 for the radial, central and ulnar portion of the TFC on its proximal side, and 2.7/2.0, 3.1/2.3 and 2.9/2.4 for the radial, central and ulnar portion on its distal side (n = 15). Paired Student's t-test showed no significant difference between MSCT-AG and MR-AG (P > 0.05). In a first, small series, depiction of the TFC with MSCT-AG is comparable to that of MR-AG. Further evaluation of direct multi-slice CT arthrography of the wrist in a larger patient population would be promising.
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http://dx.doi.org/10.1007/s00330-008-1118-3DOI Listing
January 2009

Osteoid osteoma in an ex vivo animal model: temperature changes in surrounding soft tissue during CT-guided radiofrequency ablation.

Radiology 2006 Jan 17;238(1):107-12. Epub 2005 Nov 17.

Department of Radiology, Stiftung Orthopädische Universitätsklinik, Schlierbacher Landstr 200A, 69118 Heidelberg, Germany.

Purpose: To assess temperature changes in the soft tissue surrounding bone during radiofrequency (RF) ablation of osteoid osteoma in an ex vivo animal model.

Materials And Methods: Intracortical cavities were created in fresh bovine long bone specimens obtained from a slaughterhouse as models for osteoid osteoma. Three groups of three specimens each were defined according to the thickness (1, 3, and 5 mm) of the cortical bone lamella separating the nidus from the periosteum. Three thermocouples were applied to the soft tissue surrounding the bone in defined distances (0, 5, and 10 mm) from the periosteum. Before RF ablation, the thickness of the cortical bone lamella was documented at computed tomography. Specimens were heated in a 37 degrees C basin. As soon as the measured temperature in the cavity of the specimen reached 35 degrees C, RF ablation was performed for 400 seconds, with a target temperature of 95 degrees C. During RF ablation, continuous measurements were performed simultaneously with digital thermometers. No simulation of vessel perfusion was used. The effect of the thickness of residual osseous lamella and the effect of the distance between the thermocouple and the periosteum were tested with an analysis of variance. Post hoc Bonferroni tests were performed.

Results: Mean maximum temperatures of 69.1 degrees, 51.3 degrees, and 42.5 degrees C for 1-mm lamella; 59.2 degrees, 46.5 degrees, and 41.1 degrees C for 3-mm lamella; and 50.6 degrees, 44.8 degrees, and 40.0 degrees C for 5-mm lamella were measured 0, 5, and 10 mm, respectively, from the periosteum. Significant temperature differences were shown with analysis of variance and post hoc tests for the three groups of bone lamella thickness and distance (P < .001).

Conclusion: In the model of osteoid osteoma, the surrounding temperature (soft tissue) during RF ablation was shown to depend on the thickness of the cortical bone lamella and the distance from the periosteum.
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http://dx.doi.org/10.1148/radiol.2381041500DOI Listing
January 2006

Reconstruction of the pelvic ring using an autologous free non-vascularized fibula graft in a patient with benign fibrous histiocytoma.

World J Surg Oncol 2004 Nov 23;2:38. Epub 2004 Nov 23.

Orthopedic University Hospital, Heidelberg, Germany.

Background: Benign fibrous histiocytomas (BFH) usually presents as a small benign lesion that predominantly occurs in the skin. Only few cases of BFH arising from bone have been reported, its occurrence in pelvic bones is even rarer.

Case Presentation: A 34-year-old female presented with BFH at a rare anatomical location on both sides of the os ilium which was larger than earlier reported BFH of the bone. Surgical resection was performed successfully including resection of the inner pelvic ring and reconstruction of the linea terminalis using a non-vascularized fibular autograft. At 18 months after tumor resection and reconstruction of the pelvic ring, with interposition of a free vascularized fibula graft patient has an excellent clinical oncological and functional outcome.

Conclusion: Non vascularized fibular autograft is a useful reconstructive procedure in select patients.
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http://dx.doi.org/10.1186/1477-7819-2-38DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC538289PMC
November 2004

Detection of pulmonary nodules at multirow-detector CT: effectiveness of double reading to improve sensitivity at standard-dose and low-dose chest CT.

Eur Radiol 2005 Jan 4;15(1):14-22. Epub 2004 Nov 4.

Department of Clinical Radiology, University Hospital Münster, Albert-Schweitzer-Strasse 33, 48149 Münster, Germany.

The purpose of this study was to assess the effectiveness of double reading to increase the sensitivity of lung nodule detection at standard-dose (SDCT) and low-dose multirow-detector CT (LDCT). SDCT (100 mAs effective tube current) and LDCT (20 mAs) of nine patients with pulmonary metastases were obtained within 5 min using four-row detector CT. Softcopy images reconstructed with 5-mm slice thickness were read by three radiologists independently. Images with 1.25-mm slice thickness served as the gold standard. Sensitivity was assessed for single readers and combinations. The effectiveness of double reading was expressed as the increase of sensitivity. Average sensitivity for detection of 390 nodules (size 3.9+/-3.2 mm) for single readers was 0.63 (SDCT) and 0.64 (LDCT). Double reading significantly increased sensitivity to 0.74 and 0.79, respectively. No significant difference between sensitivity at SDCT and LDCT was observed. The percentage of nodules detected by all three readers concordantly was 52% for SDCT and 47% for LDCT. Although double reading increased the detection rate of pulmonary nodules from 63% to 74-79%, a considerable proportion of nodules remained undetected. No difference between sensitivities at LDCT and SDCT for detection of small nodules was observed.
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http://dx.doi.org/10.1007/s00330-004-2527-6DOI Listing
January 2005

Low-voltage digital selenium radiography: detection of simulated interstitial lung disease, nodules, and catheters--a phantom study.

Radiology 2004 Sep 23;232(3):693-700. Epub 2004 Jul 23.

Department of Clinical Radiology, University of Muenster, Albert-Schweitzer-Str 33, 48129 Muenster, Germany.

Purpose: To compare three tube voltages in digital selenium radiography for the detection of simulated interstitial lung disease, nodules, and catheters.

Materials And Methods: Simulated catheters, nodules, and ground-glass, linear, miliary, and reticular patterns were superimposed over an anthropomorphic chest phantom. Digital selenium radiography was performed with different tube voltages (70, 90, and 150 kVp). Hard-copy images were generated. Detection performance of five radiologists was compared by using receiver operating characteristic (ROC) analysis involving 54,000 observations.

Results: The detection of ground-glass, linear, miliary, and reticular patterns over lucent lung and of nodules equal to, smaller than, and larger than 10 mm increased when 70 kVp and/or 90 kVp was used. However, only the reticular pattern was significantly better detected at lower peak voltage (P <.05). Simulated catheters and nodules over the mediastinum showed smaller areas under the ROC curve at lower peak voltage. These results were not statistically significant (P >.05).

Conclusion: The diagnostic performance of digital selenium radiography at lower peak voltage is at least as good as that at higher peak voltage for interstitial lung disease over lucent lung. Performance is equivalent for nodules and catheters over obscured chest regions at lower peak voltages compared with that at 150 kVp. Our results implicate that the use of high-voltage technique in digital selenium radiography should be reassessed.
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http://dx.doi.org/10.1148/radiol.2323030187DOI Listing
September 2004

Diagnostic performance of a flat-panel detector at low tube voltage in chest radiography: a phantom study.

Invest Radiol 2004 Feb;39(2):97-103

Department of Clinical Radiology, University of Münster, Germany.

Rationale And Objectives: To evaluate a large area, cesium iodide amorphous silicon flat-panel detector (CsI/a-Si) at 3 tube voltages to detect simulated interstitial lung disease, nodules, and catheters.

Methods: Simulated interstitial lung disease, nodules, and catheters were superimposed over a chest phantom. Images were generated at 125 kVp, 90 kVp, and 70 kVp at the same surface dose and reduced effective dose equivalent for 90 kVp and 70 kVp and printed on hard copies. Fifty-four thousand observations were analyzed by receiver operating characteristic (ROC).

Results: Detectability of linear, miliary, reticular pattern, and nodules over lucent lung as well as of catheters and nodules over obscured chest areas increased at 90 and/or 70 kVp with higher Az values; however, only it was statistically significant for reticular pattern at 70 kVp and nodules at 90 kVp compared with 125 kVp (P < 0.05). The detection of ground-glass pattern was worse at lower kVp (P > 0.05).

Conclusion: For most simulated patterns, differences in diagnostic performance at 70 kVp/90 kVp and 125 kVp were not significant, except for reticular pattern and nodules over lucent lung.
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http://dx.doi.org/10.1097/01.rli.0000110566.23154.81DOI Listing
February 2004

CT colonography: Protocol optimization with multi-detector row CT--study in an anthropomorphic colon phantom.

Radiology 2003 Sep;228(3):753-9

Department of Clinical Radiology, University of Muenster, Albert-Schweitzer-Strasse 33, 48 149 Muenster, Germany.

Purpose: To determine optimal detector collimation, section thickness, and tube current for multi-detector row computed tomography (CT) colonography.

Materials And Methods: An anthropomorphic colon phantom with simulated polyps of varying size (2, 6, 8, 10, and 12 mm) was examined by using multi-detector row CT with varying combinations of detector collimation (4 x 1.0 mm and 4 x 2.5 mm), dose per section (10, 20, 40, 60, 80, 100, and 140 mAs), and section thickness/reconstruction interval (1.25/0.6, 2.0/1.0, 3.0/1.0, and 5.0/2.0 mm). Polyp depiction, longitudinal polyp distortion, and presence of rippling artifacts were assessed on reformatted three-dimensional endoluminal images by three reviewers.

Results: Longitudinal distortion and rippling artifacts increased with increasing section thickness and use of broader detector collimation. Polyps 8 mm or larger were depicted with any combination of section thickness, detector collimation, and tube current. Depiction of polyps 6 mm or smaller depended on the detector collimation/reconstructed section thickness and was rated optimal for the 4 x 1.0-mm detector collimation with a section thickness of 1.25 mm. This was also observed for low-dose protocols. Polyps 6 mm or smaller that were not detected with 3-mm section thickness and 4 x 2.5-mm detector collimation were detected with 1.25-mm section thickness and 10 mAs.

Conclusion: A narrow detector collimation with thin-section imaging (4 x 1.0-mm detector collimation, 1.25-mm section thickness) is a prerequisite for low-dose (10-mAs) multi-detector row CT colonography.
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http://dx.doi.org/10.1148/radiol.2283020928DOI Listing
September 2003

Lumbar spine radiography: digital flat-panel detector versus screen-film and storage-phosphor systems in monkeys as a pediatric model.

Radiology 2003 Oct 18;229(1):140-4. Epub 2003 Aug 18.

Department of Clinical Radiology, University of Münster, Germany.

Purpose: To assess image quality and exposure dose requirements of a flat-panel detector system versus screen-film and storage-phosphor systems for radiographic depiction of the lumbar spine in Cynomolgus monkeys as a pediatric model.

Materials And Methods: Twenty Cynomolgus monkeys underwent anteroposterior radiography of the lumbar spine. The size and weight of these monkeys are comparable to those of infants 3-4 months of age. Images were acquired with speed class 400 screen-film, flat-panel, and storage-phosphor systems with identical exposure dose. All other conditions were matched exactly. Additional images were acquired with the flat-panel and storage-phosphor systems at exposure doses equivalent to speed classes 800 and 1600. All images were obtained at 66 kVp without antiscatter grid. Images were assessed independently by three radiologists for visibility of 60 anatomic structures by using a five-point confidence scale. Scores were calculated for the seven combinations of imaging mode and exposure dose and were compared by using the Friedman test.

Results: Scores were 1.70 (speed class 400), 1.97 (speed class 800), and 2.27 (speed class 1600) for the flat-panel system; 2.50 (speed class 400) for the screen-film system; and 2.58 (speed class 400), 2.77 (speed class 800), and 3.13 (speed class 1600) for the storage-phosphor system. Scores for the flat-panel system at speed classes 400 and 800 were significantly lower (indicating better visibility) than those of the screen-film and storage-phosphor systems (P <.05).

Conclusion: The flat-panel system is superior to screen-film and storage-phosphor systems in lumbar spine radiography in monkeys. With the flat-panel system, exposure dose can be reduced by 75% without loss in image quality.
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http://dx.doi.org/10.1148/radiol.2291020717DOI Listing
October 2003

Performance of a flat-panel detector in the detection of artificial erosive changes: comparison with conventional screen-film and storage-phosphor radiography.

Eur Radiol 2003 Jun 29;13(6):1316-23. Epub 2002 Nov 29.

Department of Clinical Radiology, University of Münster, Albert-Schweitzer-Strasse 33, 48129, Münster, Germany.

The purpose of this study was to compare a large-area, direct-readout, flat-panel detector system with a conventional screen-film system, a storage-phosphor system, and a mammography screen-film system with regard to the detection of artificial bone erosions simulating rheumatoid disease, and to assess its diagnostic performance with decreasing exposure dose. Six hundred forty regions were defined in 160 metacarpophalangeal and proximal interphalangeal joint specimens from 20 monkey paws (4 regions per joint). Artificial bone erosions were created in 320 of these 640 regions. Specimens were enclosed in containers filled with water to obtain absorption and scatter radiation conditions similar to those of a human hand. Imaging was performed using a flat-panel system, a speed class 200 screen-film system, a mammography screen-film system, and a storage-phosphor system under exactly matched conditions. Different exposure doses equivalent to speed classes of S=100, 200, 400, 800, 1600, and 3200 were used. In all images the presence or absence of a lesion was assessed by three radiologists using a five-level confidence scale. Receiver operating characteristic (ROC) analysis was performed for a total of 21,120 observations (1920 for each imaging modality and exposure level) and diagnostic performance estimated by the area under the ROC curve (A(z)). The significance of differences in diagnostic performance was tested with analysis of variance. The ROC analysis showed A(z) values of 0.809 (S=200), 0.768 (S=400), 0.737 (S=800), 0.710 (S=1600), and 0.685 (S=3200) for the flat-panel system, 0.770 for the speed class 200 screen-film system, 0.781 (S=200), 0.739 (S=400), 0.724 (S=800), 0.680 (S=1600) for the storage-phosphor system, and 0.798 for the mammography screen-film system. Analysis of variance showed significant differences between different combinations of imaging modalities and exposure doses ( p<0.05). The diagnostic performance of the flat-panel detector system is superior to that of a screen-film system and a storage-phosphor system for the detection of erosive lesions at clinical exposure settings (S=200). Using the flat-panel system the exposure dose can be reduced by 50% to obtain a diagnostic performance comparable to a speed class 200 screen-film system.
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http://dx.doi.org/10.1007/s00330-002-1763-xDOI Listing
June 2003

Injuries and overuse syndromes in golf.

Am J Sports Med 2003 May-Jun;31(3):438-43

Departments of Orthopaedics, University of Muenster, Muenster, Germany.

Background: Although golf is becoming more popular, there is a lack of reliable epidemiologic data on golf injuries and overuse syndromes, especially regarding their severity.

Objective: To perform an epidemiologic study of the variety of different musculoskeletal problems in professional and amateur golfers and to find associations of age, sex, physical stature (body mass index), warm-up routine, and playing level with the occurrence of reported injuries.

Study Design: Retrospective cohort study.

Methods: We analyzed the injury data from a total of 703 golfers who were randomly selected over two golfing seasons and interviewed with the use of a six-page questionnaire.

Results: Overall, 82.6% (N = 526) of reported injuries involved overuse and 17.4% (N = 111) were single trauma events. Professional golfers were injured more often, typically in the back, wrist, and shoulder. Amateurs reported many elbow, back, and shoulder injuries. Severity of reported injuries was minor in 51.5%, moderate in 26.8%, and major in 21.7% of cases. Carrying one's bag proved to be hazardous to the lower back, shoulder, and ankle. Warm-up routines were found to have a positive effect if they were at least 10 minutes long.

Conclusions: Overall, golf may be considered a rather benign activity, if overuse can be avoided. If not, golf can result in serious, chronic musculoskeletal problems.
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http://dx.doi.org/10.1177/03635465030310031901DOI Listing
October 2003

Detection of subtle undisplaced rib fractures in a porcine model: radiation dose requirement--digital flat-panel versus screen-film and storage-phosphor systems.

Radiology 2003 Apr 28;227(1):163-8. Epub 2003 Feb 28.

Department of Clinical Radiology, University of Munster, Albert-Schweitzer-Strasse 33, D-48129 Munster, Germany.

Purpose: To compare a large-area direct read-out flat-panel detector radiography system with screen-film and storage-phosphor systems with regard to detection of subtle undisplaced rib fractures and to assess the diagnostic performance of the flat-panel system with decreasing exposure level.

Materials And Methods: Subtle fractures were created artificially in 100 of 200 porcine rib specimens. Specimens were enclosed in containers of water to generate absorption and scatter radiation conditions similar to those of a human chest wall. Imaging was performed with flat-panel, screen-film, and storage-phosphor systems with conditions that were exactly matched. Different exposure levels equivalent to speed classes (S) of 400, 800, 1,600, and 6,400 were used. All images were independently assessed for the presence of fracture by three radiologists with a five-level confidence scale. Receiver operating characteristic (ROC) analysis was performed for a total of 4,200 observations (600 for each imaging system and exposure level). Diagnostic performance was estimated with area under the ROC curve (Az). Significance of differences in diagnostic performance was tested with analysis of variance.

Results: ROC analysis yielded mean Az values for the flat-panel system of 0.879 (S = 400), 0.833 (S = 800), 0.765 (S = 1,600), and 0.576 (S = 6,400). Az values were 0.834 (S = 400) for the screen-film system and 0.789 (S = 400) and 0.729 (S = 800) for the storage-phosphor system. Analysis of variance revealed significant differences in diagnostic performance between various combinations of imaging system and exposure levels (P <.05).

Conclusion: The flat-panel system is superior to the screen-film and storage-phosphor systems for detection of subtle undisplaced rib fractures at clinical exposure settings (eg, S = 400). With the flat-panel system, radiation dose can be reduced by 50% to achieve diagnostic performance comparable to that of a speed class 400 screen-film system.
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http://dx.doi.org/10.1148/radiol.2271020378DOI Listing
April 2003
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