In this paper multivariate analysis is adopted to evaluate the gait of subjects submitted to surg... more In this paper multivariate analysis is adopted to evaluate the gait of subjects submitted to surgical reconstruction with complex traumas of the foot (loss of skin, crushing) due to car crashes or accidents on the job. The analysis of gait parameters are a significant barrier to the clinical application of gait analysis. Principal component modeling of gait kinetic parameters reduces
Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2001
Obstructive sleep apnea (OSA) is a common health concern associated with serious implications and... more Obstructive sleep apnea (OSA) is a common health concern associated with serious implications and increased cardiovascular morbidity and mortality. This study approaches the problem of identification OSA patients and detection of OSA phases on the basis of heart rate variability (HRV) analysis. Only a single ECG-channel is required for this purpose. We used data from the apnea ECG database:40 patients
Endangered patients with ventricular tachycardia (VT) could be identified by quantification of th... more Endangered patients with ventricular tachycardia (VT) could be identified by quantification of the low level high frequency content of their preprocessed ECG signals. For this purpose the authors developed a classification method which consists of two parts: (i) a small number of features is dimensional input patterns, preprocessed ECG signal, by wavelet transformation. A number of easily interpretable parameters in the time-frequency plane controls this feature extraction process. The calculated features are regarded as inputs to a simple artificial neural network (ANN) which is used as classifier. Because the learning phase of the ANN is expanded from training the weight coefficients to the time-frequency parameters of the input nodes, one gets optimally tuned features. The result of 96% correct classification for identifying VT patients by the described wavelet network approach confirms the efficiency of this method
Time-frequency representations describe the characteristics of time-varying signals by means of t... more Time-frequency representations describe the characteristics of time-varying signals by means of two-dimensional energy distributions in an excellent manner. Many examples in this book demonstrate the advantages of time-frequency transformations in different medical and biological applications. However, normally these methods do not automatically characterize signals with a set of meaningful parameters as is necessary for typical classification or discrimination tasks. For example, in our application, evoked potentials are used to discriminate children with attention deficit disorder with hyperactivity (ADDH) from a control group. To verify the clinical hypothesis of frontal brain lesions, the central nervous system is tested by auditory evoked potentials (AEPs). This activity is particularly useful because it is independent of an intact behavioral response system. However, the main problem of our study is to extract parameters from evoked potentials (EPs) which can be easily used to...
This study examines the utility of heart rate variability (HRV) and repolarization parameters to ... more This study examines the utility of heart rate variability (HRV) and repolarization parameters to predict the outcome of head-up tilt tests from early phases of the response to tilting in 44 young patients with syncope and 34 age-matched controls. Synchronized to the tilting events, we extracted minute-by-minute progression of time- and frequency domain HRV descriptors as well as mean QT
2011 1st Middle East Conference on Biomedical Engineering, 2011
Quantitative in silico modeling is a powerful means to enhance our understanding of complex biolo... more Quantitative in silico modeling is a powerful means to enhance our understanding of complex biological systems. Accordingly, intuitive and flexible computational tools are needed to support the development of such models. We previously developed the platform EPISIM for graphical modeling and simulation of cellular behavior in epithelia. In this work we demonstrate how computationally efficient software components for epithelial tissue
Computers in Cardiology 1999. Vol.26 (Cat. No.99CH37004), 1999
Compares different strategies for nonsupervised classification of QRS complexes and reports resul... more Compares different strategies for nonsupervised classification of QRS complexes and reports results on the MIT/BIH arrhythmia database in respect to discriminatory power and computational demand. One approach is based on a hierarchical cluster analysis procedure with three different feature sets consisting of coefficients of orthogonal series expansions. The second method uses a two step correlation technique. For several reasons, our
Quantitative assessment of myocardial perfusion by myocardial blush grade (MBG) is an angiographi... more Quantitative assessment of myocardial perfusion by myocardial blush grade (MBG) is an angiographic computer-assisted method to assess myocardial tissue-level reperfusion in patients with acute coronary syndromes and microvascular integrity in heart transplant recipients with suspected cardiac allograft vasculopathy. This review describes the ability of quantitative MBG as a simple, fast and cost effective modality for the prompt diagnosis of impaired microvascular integrity during routine cardiac catheterization. Herein, we summarize the existing evidence, its usefulness in the clinical routine, and compare this method to other techniques which can be used for the assessment of myocardial perfusion.
Fundamental changes were achieved with the introduction of minimally invasive surgery. In this co... more Fundamental changes were achieved with the introduction of minimally invasive surgery. In this context, innovations in microtechnology played a significant role in the deployment of new tools. Developments for further integration are still ongoing. Furthermore, decisive progress was made by the timely provision of individual patient data prior to surgery. These comprise imaging data, electrophysiological or functional recordings, and synthetic data gained by modeling and simulation of anatomical or physiological conditions. Aside from the technical aspects of supporting surgery, effective quality management and optimized workflow are essential for therapeutic success. The vision of autonomously operating robots has been dropped in favor of permanently conducted and supervised interventions with the support of intelligent tools for the surgeon. Recent advances in reconstruction and transplantation surgery by tissue engineering and molecular biology are only the beginning of new promi...
Studies in health technology and informatics, 2007
We introduce a computer based algorithm for objective quantification of myocardial perfusion to s... more We introduce a computer based algorithm for objective quantification of myocardial perfusion to support the diagnosis of cad patients. This new method is based on conventional cine angiographic films. In order to achieve maximal quality of the digital subtraction angiography images, the sequence is synchronized with the ECG. Optionally, the digital images can be motion compensated by a two step matching method. The spatio-temporal spread of blood, or the so-called blush, through the microvasculature to the myocardium--indicated by dye injection--represents a characteristic pattern for the myocardial perfusion. This dynamic temporal pattern is characterized by typical features as the maximal value of blush intensity, of increase and of decrease velocity which correspond with the different phases of flooding in and washout. On the basis of 100 different temporal blush profiles, an algorithm is established which classifies the acquired blush patterns into 4 different grades.
Studies in health technology and informatics, 2007
The long QT syndrome (LQTS) belongs to the family of hereditary diseases and can cause life-threa... more The long QT syndrome (LQTS) belongs to the family of hereditary diseases and can cause life-threatening arrhythmias and leads to sudden cardiac death. Mutations on six genes are responsible for changes in the electrophysiological properties of myocardial cells that are involved in the repolarization phase. In the surface ecg this is expressed by a prolonged QT interval and genotypespecific shapes for the T-Wave. The aim of the study was to find parameters that quantify properties of the repolarization phase which can be used in addition to the established Schwartz score in the process of diagnosing LQTS. Furthermore, ecg features were evaluated for the separation of the LQT subtypes LQT1, LQT2 and LQT3. The combination of the features PtA50 and QTc yielded with 93% sensitivity and 100% specificity the best results in the field of patient identification. Despite the small dataset consisting of 14 patients that was available for the second aim, the achieved results for the morphology ...
Studies in health technology and informatics, 2006
Modelling in systems biology currently lacks clinical applications. As a possible approach leadin... more Modelling in systems biology currently lacks clinical applications. As a possible approach leading to clinical relevance the modelling of tissue homeostasis is proposed. As an example a model of epidermal homeostasis is presented which reproduces central morphological and kinetic characteristics of epidermal tissue. Each individual cell is modelled as an agent. The tissue arises as an emergent phenomenon from the interactions of agents. Each agent's behaviour is qualitatively modelled by a simple differentiation state-flow program. Epithelialisation under the influence of parameters concerning stem-cell location is briefly demonstrated.
2006 International Conference of the IEEE Engineering in Medicine and Biology Society, 2006
This study aims at characterizing the short-term time-courses of time- and frequency-domain heart... more This study aims at characterizing the short-term time-courses of time- and frequency-domain heart rate variability (HRV) parameters during head-up tilt test (HUTT). Data from 44 young patients with a history of syncope and 34 age-matched controls was analysed in two age-groups related to puberty (< or =13 and > or =14 years), and separately for gender, by extracting minute-by-minute progression of mean RR-interval, standard deviation of RR-intervals (SDNN) and their first difference (SDSD) as well as low-frequency (LF, 0.05-0.15 Hz) energy, high-frequency (HF, 0.15-0.4 Hz) energy and the LF/HF-ratio. Time-courses were individually normalized and averaged after synchronization to the events of tilt and tilt-back/syncope. We observed remarkable age-related differences not only with respect to response to tilting but also regarding the differentiation of patients with positive HUTT from controls with negative HUTT. ROC-analysis in three regions of interest (0-2 min after tilt, 2-5 min after tilt, 5-2 min before tilt-back) revealed generally much weaker and less persistent differences in younger subjects whereas in elders the differences were clearer and often most pronounced immediately before syncope. For both age-groups, the relative change of mean RR provided best separation, however in elders in the ROI just before syncope (sensitivity: 74%, specificity 80%) in young immediately after tilt (sens.: 71%, spec.: 74%). In elder subjects, the relative reduction of SDNN 2-5 minute after tilt achieved almost the same performance (sens.: 74%, spec. 80%) as in the ROI before syncope (sens. 78%, spec. 73%), indicating the existence of rather early precursors of syncope that might help to predict the outcome of the HUTT in subjects in or after puberty.
Evaluation of spontaneous infant movements is an important tool for the detection of neurological... more Evaluation of spontaneous infant movements is an important tool for the detection of neurological impairments. It is necessary to automatically detect movement phases which exhibit certain complex characteristics in order to quantitatively assess these movements. This article presents a method to extract segments of complex movements from multivariate kinematic tracking data. Expert knowledge is represented in a principal component model.
In this paper multivariate analysis is adopted to evaluate the gait of subjects submitted to surg... more In this paper multivariate analysis is adopted to evaluate the gait of subjects submitted to surgical reconstruction with complex traumas of the foot (loss of skin, crushing) due to car crashes or accidents on the job. The analysis of gait parameters are a significant barrier to the clinical application of gait analysis. Principal component modeling of gait kinetic parameters reduces
In this paper multivariate analysis is adopted to evaluate the gait of subjects submitted to surg... more In this paper multivariate analysis is adopted to evaluate the gait of subjects submitted to surgical reconstruction with complex traumas of the foot (loss of skin, crushing) due to car crashes or accidents on the job. The analysis of gait parameters are a significant barrier to the clinical application of gait analysis. Principal component modeling of gait kinetic parameters reduces
Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2001
Obstructive sleep apnea (OSA) is a common health concern associated with serious implications and... more Obstructive sleep apnea (OSA) is a common health concern associated with serious implications and increased cardiovascular morbidity and mortality. This study approaches the problem of identification OSA patients and detection of OSA phases on the basis of heart rate variability (HRV) analysis. Only a single ECG-channel is required for this purpose. We used data from the apnea ECG database:40 patients
Endangered patients with ventricular tachycardia (VT) could be identified by quantification of th... more Endangered patients with ventricular tachycardia (VT) could be identified by quantification of the low level high frequency content of their preprocessed ECG signals. For this purpose the authors developed a classification method which consists of two parts: (i) a small number of features is dimensional input patterns, preprocessed ECG signal, by wavelet transformation. A number of easily interpretable parameters in the time-frequency plane controls this feature extraction process. The calculated features are regarded as inputs to a simple artificial neural network (ANN) which is used as classifier. Because the learning phase of the ANN is expanded from training the weight coefficients to the time-frequency parameters of the input nodes, one gets optimally tuned features. The result of 96% correct classification for identifying VT patients by the described wavelet network approach confirms the efficiency of this method
Time-frequency representations describe the characteristics of time-varying signals by means of t... more Time-frequency representations describe the characteristics of time-varying signals by means of two-dimensional energy distributions in an excellent manner. Many examples in this book demonstrate the advantages of time-frequency transformations in different medical and biological applications. However, normally these methods do not automatically characterize signals with a set of meaningful parameters as is necessary for typical classification or discrimination tasks. For example, in our application, evoked potentials are used to discriminate children with attention deficit disorder with hyperactivity (ADDH) from a control group. To verify the clinical hypothesis of frontal brain lesions, the central nervous system is tested by auditory evoked potentials (AEPs). This activity is particularly useful because it is independent of an intact behavioral response system. However, the main problem of our study is to extract parameters from evoked potentials (EPs) which can be easily used to...
This study examines the utility of heart rate variability (HRV) and repolarization parameters to ... more This study examines the utility of heart rate variability (HRV) and repolarization parameters to predict the outcome of head-up tilt tests from early phases of the response to tilting in 44 young patients with syncope and 34 age-matched controls. Synchronized to the tilting events, we extracted minute-by-minute progression of time- and frequency domain HRV descriptors as well as mean QT
2011 1st Middle East Conference on Biomedical Engineering, 2011
Quantitative in silico modeling is a powerful means to enhance our understanding of complex biolo... more Quantitative in silico modeling is a powerful means to enhance our understanding of complex biological systems. Accordingly, intuitive and flexible computational tools are needed to support the development of such models. We previously developed the platform EPISIM for graphical modeling and simulation of cellular behavior in epithelia. In this work we demonstrate how computationally efficient software components for epithelial tissue
Computers in Cardiology 1999. Vol.26 (Cat. No.99CH37004), 1999
Compares different strategies for nonsupervised classification of QRS complexes and reports resul... more Compares different strategies for nonsupervised classification of QRS complexes and reports results on the MIT/BIH arrhythmia database in respect to discriminatory power and computational demand. One approach is based on a hierarchical cluster analysis procedure with three different feature sets consisting of coefficients of orthogonal series expansions. The second method uses a two step correlation technique. For several reasons, our
Quantitative assessment of myocardial perfusion by myocardial blush grade (MBG) is an angiographi... more Quantitative assessment of myocardial perfusion by myocardial blush grade (MBG) is an angiographic computer-assisted method to assess myocardial tissue-level reperfusion in patients with acute coronary syndromes and microvascular integrity in heart transplant recipients with suspected cardiac allograft vasculopathy. This review describes the ability of quantitative MBG as a simple, fast and cost effective modality for the prompt diagnosis of impaired microvascular integrity during routine cardiac catheterization. Herein, we summarize the existing evidence, its usefulness in the clinical routine, and compare this method to other techniques which can be used for the assessment of myocardial perfusion.
Fundamental changes were achieved with the introduction of minimally invasive surgery. In this co... more Fundamental changes were achieved with the introduction of minimally invasive surgery. In this context, innovations in microtechnology played a significant role in the deployment of new tools. Developments for further integration are still ongoing. Furthermore, decisive progress was made by the timely provision of individual patient data prior to surgery. These comprise imaging data, electrophysiological or functional recordings, and synthetic data gained by modeling and simulation of anatomical or physiological conditions. Aside from the technical aspects of supporting surgery, effective quality management and optimized workflow are essential for therapeutic success. The vision of autonomously operating robots has been dropped in favor of permanently conducted and supervised interventions with the support of intelligent tools for the surgeon. Recent advances in reconstruction and transplantation surgery by tissue engineering and molecular biology are only the beginning of new promi...
Studies in health technology and informatics, 2007
We introduce a computer based algorithm for objective quantification of myocardial perfusion to s... more We introduce a computer based algorithm for objective quantification of myocardial perfusion to support the diagnosis of cad patients. This new method is based on conventional cine angiographic films. In order to achieve maximal quality of the digital subtraction angiography images, the sequence is synchronized with the ECG. Optionally, the digital images can be motion compensated by a two step matching method. The spatio-temporal spread of blood, or the so-called blush, through the microvasculature to the myocardium--indicated by dye injection--represents a characteristic pattern for the myocardial perfusion. This dynamic temporal pattern is characterized by typical features as the maximal value of blush intensity, of increase and of decrease velocity which correspond with the different phases of flooding in and washout. On the basis of 100 different temporal blush profiles, an algorithm is established which classifies the acquired blush patterns into 4 different grades.
Studies in health technology and informatics, 2007
The long QT syndrome (LQTS) belongs to the family of hereditary diseases and can cause life-threa... more The long QT syndrome (LQTS) belongs to the family of hereditary diseases and can cause life-threatening arrhythmias and leads to sudden cardiac death. Mutations on six genes are responsible for changes in the electrophysiological properties of myocardial cells that are involved in the repolarization phase. In the surface ecg this is expressed by a prolonged QT interval and genotypespecific shapes for the T-Wave. The aim of the study was to find parameters that quantify properties of the repolarization phase which can be used in addition to the established Schwartz score in the process of diagnosing LQTS. Furthermore, ecg features were evaluated for the separation of the LQT subtypes LQT1, LQT2 and LQT3. The combination of the features PtA50 and QTc yielded with 93% sensitivity and 100% specificity the best results in the field of patient identification. Despite the small dataset consisting of 14 patients that was available for the second aim, the achieved results for the morphology ...
Studies in health technology and informatics, 2006
Modelling in systems biology currently lacks clinical applications. As a possible approach leadin... more Modelling in systems biology currently lacks clinical applications. As a possible approach leading to clinical relevance the modelling of tissue homeostasis is proposed. As an example a model of epidermal homeostasis is presented which reproduces central morphological and kinetic characteristics of epidermal tissue. Each individual cell is modelled as an agent. The tissue arises as an emergent phenomenon from the interactions of agents. Each agent's behaviour is qualitatively modelled by a simple differentiation state-flow program. Epithelialisation under the influence of parameters concerning stem-cell location is briefly demonstrated.
2006 International Conference of the IEEE Engineering in Medicine and Biology Society, 2006
This study aims at characterizing the short-term time-courses of time- and frequency-domain heart... more This study aims at characterizing the short-term time-courses of time- and frequency-domain heart rate variability (HRV) parameters during head-up tilt test (HUTT). Data from 44 young patients with a history of syncope and 34 age-matched controls was analysed in two age-groups related to puberty (< or =13 and > or =14 years), and separately for gender, by extracting minute-by-minute progression of mean RR-interval, standard deviation of RR-intervals (SDNN) and their first difference (SDSD) as well as low-frequency (LF, 0.05-0.15 Hz) energy, high-frequency (HF, 0.15-0.4 Hz) energy and the LF/HF-ratio. Time-courses were individually normalized and averaged after synchronization to the events of tilt and tilt-back/syncope. We observed remarkable age-related differences not only with respect to response to tilting but also regarding the differentiation of patients with positive HUTT from controls with negative HUTT. ROC-analysis in three regions of interest (0-2 min after tilt, 2-5 min after tilt, 5-2 min before tilt-back) revealed generally much weaker and less persistent differences in younger subjects whereas in elders the differences were clearer and often most pronounced immediately before syncope. For both age-groups, the relative change of mean RR provided best separation, however in elders in the ROI just before syncope (sensitivity: 74%, specificity 80%) in young immediately after tilt (sens.: 71%, spec.: 74%). In elder subjects, the relative reduction of SDNN 2-5 minute after tilt achieved almost the same performance (sens.: 74%, spec. 80%) as in the ROI before syncope (sens. 78%, spec. 73%), indicating the existence of rather early precursors of syncope that might help to predict the outcome of the HUTT in subjects in or after puberty.
Evaluation of spontaneous infant movements is an important tool for the detection of neurological... more Evaluation of spontaneous infant movements is an important tool for the detection of neurological impairments. It is necessary to automatically detect movement phases which exhibit certain complex characteristics in order to quantitatively assess these movements. This article presents a method to extract segments of complex movements from multivariate kinematic tracking data. Expert knowledge is represented in a principal component model.
In this paper multivariate analysis is adopted to evaluate the gait of subjects submitted to surg... more In this paper multivariate analysis is adopted to evaluate the gait of subjects submitted to surgical reconstruction with complex traumas of the foot (loss of skin, crushing) due to car crashes or accidents on the job. The analysis of gait parameters are a significant barrier to the clinical application of gait analysis. Principal component modeling of gait kinetic parameters reduces
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Papers by Hartmut Dickhaus