Binary Local Fractal Dimension: a Precise Structure Parameter for 3D High Resolution Computed Tomography Images of the Human Spongiosa

We present the Binary Local Fractal Dimension (LFD) to analyze osteoporosis induced fracture risk with clinical 3D high resolution quantitative computed tomographic (HRCT) images of human vertebrae. We test if LFD parameters provide precise additional information besides bone mineral density (BMD) and standard descriptors of bone quality, for example bone surface ratio (BS/BV). We define a weighted LFD (wLFD) using the ¯R2 of the H¨older exponents. We compare the LFD with standard methods (distance transform, direct secant method and run-length method) on 5 vertebrae × 8 volumes of interest and 5 repeated scans. The wLFD contains the highest direct and BMD-independent precision (R2 = 0.985 and R2 = 0.949), followed by BS/BV (R2 = 0.977 and R2 = 0.920) including low correlation with BMD (wLFD: R2 = 0.704, BS/BV: R2 = 0.814). LFD improves the translation from reference μCT- to clinical HRCT-resolution. In conclusion, LFD provides a strong diagnostic tool to characterize bone quality to predict osteoporosis induced fracture risk.Sociedad Argentina de Informática e Investigación Operativ

Binary Local Fractal Dimension: a Precise Structure Parameter for 3D High Resolution Computed Tomography Images of the Human Spongiosa

We present the Binary Local Fractal Dimension (LFD) to analyze osteoporosis induced fracture risk with clinical 3D high resolution quantitative computed tomographic (HRCT) images of human vertebrae. We test if LFD parameters provide precise additional information besides bone mineral density (BMD) and standard descriptors of bone quality, for example bone surface ratio (BS/BV). We define a weighted LFD (wLFD) using the ¯R2 of the H¨older exponents. We compare the LFD with standard methods (distance transform, direct secant method and run-length method) on 5 vertebrae × 8 volumes of interest and 5 repeated scans. The wLFD contains the highest direct and BMD-independent precision (R2 = 0.985 and R2 = 0.949), followed by BS/BV (R2 = 0.977 and R2 = 0.920) including low correlation with BMD (wLFD: R2 = 0.704, BS/BV: R2 = 0.814). LFD improves the translation from reference μCT- to clinical HRCT-resolution. In conclusion, LFD provides a strong diagnostic tool to characterize bone quality to predict osteoporosis induced fracture risk.Sociedad Argentina de Informática e Investigación Operativ

Binary Local Fractal Dimension: a Precise Structure Parameter for 3D High Resolution Computed Tomography Images of the Human Spongiosa

We present the Binary Local Fractal Dimension (LFD) to analyze osteoporosis induced fracture risk with clinical 3D high resolution quantitative computed tomographic (HRCT) images of human vertebrae. We test if LFD parameters provide precise additional information besides bone mineral density (BMD) and standard descriptors of bone quality, for example bone surface ratio (BS/BV). We define a weighted LFD (wLFD) using the ¯R2 of the H¨older exponents. We compare the LFD with standard methods (distance transform, direct secant method and run-length method) on 5 vertebrae × 8 volumes of interest and 5 repeated scans. The wLFD contains the highest direct and BMD-independent precision (R2 = 0.985 and R2 = 0.949), followed by BS/BV (R2 = 0.977 and R2 = 0.920) including low correlation with BMD (wLFD: R2 = 0.704, BS/BV: R2 = 0.814). LFD improves the translation from reference μCT- to clinical HRCT-resolution. In conclusion, LFD provides a strong diagnostic tool to characterize bone quality to predict osteoporosis induced fracture risk.Sociedad Argentina de Informática e Investigación Operativ

Bone-marrow densitometry: Assessment of marrow space of human vertebrae by single energy high resolution-quantitative computed tomography

Purpose: Accurate noninvasive assessment of vertebral bone marrow fat fraction is important for diagnostic assessment of a variety of disorders and therapies known to affect marrow composition. Moreover, it provides a means to correct fat‐induced bias of single energy quantitative computed tomography (QCT) based bone mineral density (BMD) measurements. The authors developed new segmentation and calibration methods to obtain quantitative surrogate measures of marrow‐fat density in the axial skeleton. Methods: The authors developed and tested two high resolution‐QCT (HR‐QCT) based methods which permit segmentation of bone voids in between trabeculae hypothesizing that they are representative of bone marrow space. The methods permit calculation of marrow content in units of mineral equivalent marrow density (MeMD). The first method is based on global thresholding and peeling (GTP) to define a volume of interest away from the transition between trabecular bone and marrow. The second method, morphological filtering (MF), uses spherical elements of different radii (0.1–1.2 mm) and automatically places them in between trabeculae to identify regions with large trabecular interspace, the bone‐void space. To determine their performance, data were compared ex vivo to high‐resolution peripheral CT (HR‐pQCT) images as the gold‐standard. The performance of the methods was tested on a set of excised human vertebrae with intact bone marrow tissue representative of an elderly population with low BMD. Results: 86% (GTP) and 87% (MF) of the voxels identified as true marrow space on HR‐pQCT images were correctly identified on HR‐QCT images and thus these volumes of interest can be considered to be representative of true marrow space. Within this volume, MeMD was estimated with residual errors of 4.8 mg/cm3 corresponding to accuracy errors in fat fraction on the order of 5% both for GTP and MF methods. Conclusions: The GTP and MF methods on HR‐QCT images permit noninvasive localization and densitometric assessment of marrow fat with residual accuracy errors sufficient to study disorders and therapies known to affect bone marrow composition. Additionally, the methods can be used to correct BMD for fat induced bias. Application and testing in vivo and in longitudinal studies are warranted to determine the clinical performance and value of these methods.Fil: Peña, Jaime A.. Christian‐Albrechts‐Universität zu Kiel; AlemaniaFil: Thomsen, Felix Sebastian Leo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur; ArgentinaFil: Damm, Timo. Christian‐Albrechts‐Universität zu Kiel; AlemaniaFil: Campbell, Graeme M.. Christian‐Albrechts‐Universität zu Kiel; Alemania. Technische Universität Hamburg‐Harburg; AlemaniaFil: Bastgen, Jan. Christian‐Albrechts‐Universität zu Kiel; AlemaniaFil: Barkmann, Reinhard. Christian‐Albrechts‐Universität zu Kiel; AlemaniaFil: Glüer, Claus C.. Christian‐Albrechts‐Universität zu Kiel; Alemani

Neue Horizonte für die in vivo Bestimmung wesentlicher Aspekte der Knochenqualität: Mikrostruktur und Materialeigenschaften, bestimmt mit Quantitativer Computertomographie und Quantitativen Ultrasound Methoden, entwickelt durch das BioAsset Konsortium

The Biomechanically founded individualised osteoporosis Assessment and treatment (BioAsset) consortium pursues experimental and clinical studies in the context of skeletal effects of bisphosphonate treatment. Here, first results using newly developed diagnostic methods in a set of vertebral bone specimen obtained from donors with documented bisphosphonate history ranging from 0 to more than 5 years of treatment are presented. A new thoracolumbar quantitative computed tomography (QCT) protocol covering T6 to L4 plus high-resolution QCT (HRQCT) assessment of T12 were compared with high-resolution peripheral QCT (HRpQCT) and micro-CT scans of excised specimens serving as gold standard techniques. Finite element (FE) modelling was performed. Material, ultrastructural, and micromechanical properties were tested on a set of single trabeculae obtained from the donor specimens. A newly developed quantitative ultrasound (QUS) device for measuring the anisotropy of cortical material properties was designed and built. The thoracolumbar QCT protocol permitted in situ imaging with good image quality and automated segmentation of vertebral bodies in the whole range from T6 to L4. The duration of bisphosphonate treatment was significantly associated with increased levels of mineralization and this effect could be measured with HRQCT performed on excised specimens. Microstructural parameters contributed to vertebral bone strength modelled by FE analysis independently of bone mineral density. The new QUS scanner permitted measuring the acoustical anisotropy of reference materials. Taken together, these results document that new methods developed in BioAsset permit a more comprehensive assessment of bone fragility. The set of donor specimens with a documented history of bisphosphonate treatment allows for the assessment of the effects of long-term treatment from the organ down to the tissue and material level. These results will ultimately be linked to the parallel clinical study to provide guidance for determining the optimum duration of bisphosphonate treatment to reduce the incidence of osteoporotic fractures.Das Biomechanically founded individualised osteoporosis Assessment and treatment (BioAsset) Konsortium führt experimentelle und klinische Studien zu skelettalen Effekten von Bisphosphonaten durch. Neue diagnostische Verfahren zur Analyse von Wirbelkörperproben von Spendern mit dokumentierter Bisphosphonateinnahme über 0 bis >5 Jahre wurden entwickelt. Mittels thorakolumbaler Quantitativer Computertomographie (QCT) und hochauflösender QCT (HRQCT) wurden Knochenmineraldichte (BMD), Mikrostrukturvariablen und Materialeigenschaften, insbesondere Mineralisierung, untersucht. Finite Element (FE) Modellierung dient der Bestimmung der Wirbelkörperbruchlast. Ein neues Quantitatives Ultraschall (QUS) Gerät zur Messung anisotroper kortikaler Materialeigenschaften wurde konstruiert. Ein signifikanter Zusammenhang von Mineralisierung und (Dauer der) Bisphosphonattherapie konnte mit Mikro-CT und HRQCT nachgewiesen werden. Das thorakolumbale QCT Protokoll ermöglichte eine Dosisreduktion von 60% gegenüber Standardprotokollen. Eine Finite Elemente Analyse zeigte BMD und Trabekelanzahl als unabhängige Determinanten der Bruchlast. Mit dem neuen QUS Gerät konnte die akustische Anisotropie von Referenzmaterialien bestimmt werden. Die Daten dokumentieren erweitere Diagnosemöglichkeiten zur Abschätzung von Knochenfragilität durch die neuen Verfahren. Parallel durchgeführte klinische Studien sollen die Frage der optimalen Dauer von Bisphosphonattherapie klären.Fil: Glüer, Claus C.. Universitätsklinikum Schleswig-Holstein; AlemaniaFil: Krausse, Matthias. Universitätsklinikum Hamburg-Eppendorf. Institut für Osteologie und Biomechanik; Alemania. Universitat Hamburg; AlemaniaFil: Museyko, Oleg. Universität Erlangen. Institut für Medizinische Physik; AlemaniaFil: Wulff, Birgit. Universitätsklinikum Hamburg-Eppendorf. Institut für Rechtsmedizin; AlemaniaFil: Campbell, Graeme. Universitätsklinikum Schleswig-Holstein; AlemaniaFil: Damm, Timo. Universitätsklinikum Schleswig-Holstein; AlemaniaFil: Daugschies, Melanie. Universitätsklinikum Schleswig-Holstein; AlemaniaFil: Huber, Gerd. Technische Universität Hamburg-Harburg. Institut für Biomechanik; AlemaniaFil: Lu, Yongtao. Technische Universität Hamburg-Harburg. Institut für Biomechanik; AlemaniaFil: Peña, Jaime. Universitätsklinikum Schleswig-Holstein; AlemaniaFil: Waldhausen, Sonja. Universitätsklinikum Schleswig-Holstein; AlemaniaFil: Bastgen, Jan. Universitätsklinikum Schleswig-Holstein; AlemaniaFil: Rodhe, Kerstin. Universitätsklinikum Schleswig-Holstein; AlemaniaFil: Steinebach, Inga. Alfried Krupp Krankenhaus Steele. Osteologisches Forschungszentrum Essen; AlemaniaFil: Thomsen, Felix Sebastian Leo. Universitätsklinikum Schleswig-Holstein; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahia Blanca; ArgentinaFil: Amling, Michael. Universitätsklinikum Hamburg-Eppendorf. Institut für Osteologie und Biomechanik; AlemaniaFil: Barkmann, Reinhard. Universitätsklinikum Schleswig-Holstein; AlemaniaFil: Engelke, Klaus. Universität Erlangen. Institut für Medizinische Physik; AlemaniaFil: Morlock, Michael M.. Technische Universität Hamburg-Harburg. Institut für Biomechanik; AlemaniaFil: Pfeilschifter, Johannes. Alfried Krupp Krankenhaus Steele. Osteologisches Forschungszentrum Essen; AlemaniaFil: Püschel, Klaus. Universitätsklinikum Hamburg-Eppendorf. Institut für Rechtsmedizin; Alemani