Georg Rose - Academia.edu (original) (raw)

Papers by Georg Rose

Wahrend einer neurochirurgischen Intervention muss es dem Operateur moglich sein diagnostische Bi... more Wahrend einer neurochirurgischen Intervention muss es dem Operateur moglich sein diagnostische Bilder zu aktualisieren. Bei dem hier verwendeten neurochirurgischen Mikroskop konnen diagnostische Bilder als virtuelle Modelle und Schnittbilder eingeblendet werden, um einen Sichtwechsel zwischen Patient und externen Bildschirmen zu vermeiden. Um eine intraoperative Aktualisierung der Modelle zu ermoglichen, wurde im Rahmen dieser Arbeit das Mikroskop an eine C-Arm-Angiographieanlage uber einen PACS-Server angebunden. Auserdem wird ein effizienter Workflow vorgestellt, der u. a. die Modellgenerierung aus den DICOM-Bildern mit Hilfe der Entwicklungsumgebung MeVisLab vorsieht. Unter Laborbedingungen durchgefuhrte Experimente ergaben eine mittlere Dauer der Modellaktualisierung von maximal 18,5 ± 2,5 min. Die Abweichung der virtuellen Uberlagerung von realen Strukturen im Mikroskop liegt im Wesentlichen im Submillimeterbereich. Das Mikroskopsystem bildet mit diesem Workflow eine solide For...

Physiological Measurement, Feb 27, 2017

In life-threatening diseases and in several clinical interventions, monitoring of vital parameter... more In life-threatening diseases and in several clinical interventions, monitoring of vital parameters is essential to guarantee the safety of patients. Besides monitoring the electrocardiogram (ECG), it is helpful to assess respiratory activity. If the respiration signal itself is not recorded, it can be extracted from the ECG (i.e. ECG derived respiration, EDR). In the present paper, we compared six EDR approaches, namely RS-decline quantified by central moments, respiratory sinus arrhythmia (RSA), R-wave amplitude, QRS area, RS-distance and maximum RS-slope. In order to evaluate the performance of each approach, we applied each method to a database of ECGs and reference respiration signals of 41 healthy subjects. All considered methods revealed relatively small absolute mean errors of the breathing rate (BR) at rest (0.75-1.3 Bpm). The method based on higher order central moments revealed a minimum mean absolute error of 0.75Bpm (4.40%) and a maximum correlation and concordance with the reference BR (rp=0.97, rc=0.97). Using this technique, we analyzed changes of respiration in patients suffering from acute schizophrenia. An increased respiration rate of about 4Bpm was found. Additionally, alteration of respiratory ratio and reduced respiratory sinus arrhythmia was demonstrated. We conclude that a precise dynamic monitoring of breathing and the investigation of changes in breathing patterns is possible without recording respiration per se.

Current Directions in Biomedical Engineering, Sep 1, 2016

The arterial blood pressure (ABP) holds a lot of information about the cardiovascular system. To ... more The arterial blood pressure (ABP) holds a lot of information about the cardiovascular system. To analyse the ABP signal, at first the pulse wave has to be detected correctly. Due to influences, e.g. of noise, an accurate beat detection is a challenging task. In this work, a novel real-time ABP detector based on higher-order statistics is presented. The method uses the 4 th order cumulants for ABP-peak detection. To evaluate this detector, the Fantasia database freely available at physionet was used. In this database, 142,936 systolic peaks were available to check the efficiency of the beat detector. A sensitivity of 99.91% and a positive predictive value of 99.50% were achieved with the novel method.

Current Directions in Biomedical Engineering, Sep 1, 2016

Evaluating individual aerobic exercise capacity is fundamental in sports and exercise medicine bu... more Evaluating individual aerobic exercise capacity is fundamental in sports and exercise medicine but associated with organizational and instrumental effort. Here, we extract an index related to common performance markers, the aerobic and anaerobic thresholds enabling the estimation of exercise capacity from a conventional sports watch supporting beatwise heart rate tracking. Therefore, cardiac vagal threshold (CVT) was determined in 19 male subjects performing an incremental maximum exercise test. CVT varied around the anaerobic threshold AnT with mean deviation of 7.9 ± 17.7 W. A high correspondence of the two thresholds was indicated by Bland-Altman plots with limits of agreement −27.5 W and 43.4 W. Additionally, CVT was strongly correlated AnT (r p = 0.86, p < 0.001) and reproduced this marker well (r c = 0.81). We conclude, that cardiac vagal threshold derived from compression entropy time course can be useful to assess physical fitness in an uncomplicated way.

Physiological measurement, Jan 10, 2017

In life-threatening diseases and in several clinical interventions, monitoring of vital parameter... more In life-threatening diseases and in several clinical interventions, monitoring of vital parameters is essential to guarantee the safety of patients. Besides monitoring the electrocardiogram (ECG), it is helpful to assess respiratory activity. If the respiration signal itself is not recorded, it can be extracted from the ECG (i.e. ECG derived respiration, EDR). In the present paper, we compared six EDR approaches, namely RS-decline quantified by central moments, respiratory sinus arrhythmia (RSA), R-wave amplitude, QRS area, RS-distance and maximum RS-slope. In order to evaluate the performance of each approach, we applied each method to a database of ECGs and reference respiration signals of 41 healthy subjects. All considered methods revealed relatively small absolute mean errors of the breathing rate (BR) at rest (0.75-1.3 Bpm). The method based on higher order central moments revealed a minimum mean absolute error of 0.75Bpm (4.40%) and a maximum correlation and concordance with ...

Biomedical Engineering / Biomedizinische Technik, 2012

American Journal of Neuroradiology, 2014

BACKGROUND AND PURPOSE: Endovascular therapy is an emerging treatment option in patients with acu... more BACKGROUND AND PURPOSE: Endovascular therapy is an emerging treatment option in patients with acute ischemic stroke and especially in cases presenting late after symptom onset. Information about remaining viable tissue as measured with perfusion imaging is crucial for proper patient selection. The aim of this study was to investigate whether perfusion imaging with C-arm CT in the angiography suite is feasible and provides measurements comparable with ones made by CTP. MATERIALS AND METHODS: The MCA was occluded surgically in 6 sheep. Perfusion studies were performed before surgery, immediately after, and at 3 hours after MCA occlusion by using a robotic flat panel detector C-arm angiographic system. For comparison, conventional CTP was performed at the same time points. Two different protocols with the C-arm CT were tested. Images were analyzed by 2 readers with regard to the presence and size of perfusion abnormalities. RESULTS: With C-arm CT, perfusion abnormalities were detected with a high sensitivity and specificity when vessel occlusion was confirmed by criterion standard DSA. No difference was found between lesions sizes measured with the 2 C-arm CT protocols and CTP. Growth of the CBV lesions with time was captured with C-arm CT and CTP. CONCLUSIONS: In this small study, it was feasible to qualitatively measure CBV and CBF by using a flat panel detector angiographic system. S troke is a major cause of death and disability throughout the world. IV thrombolysis within 4.5 hours of symptom onset remains the only therapy with benefit for patients so far, as proved by randomized trials. 1-3 However, the results of studies investigating endovascular approaches indicate that the outcome of patients with large-artery occlusions may be improved in comparison with IV thrombolysis. 4-8 Perfusion measurements are useful in selecting patients most likely to benefit from revascularization because they provide information about the ratio of infarct core to penumbra. This is especially true for those patients presenting outside the therapeutic time window for IV thrombolysis.

Biomedical Engineering / Biomedizinische Technik, 2012

Biomedical Engineering / Biomedizinische Technik, 2012

Current Directions in Biomedical Engineering, 2021

Performing minimal invasive interventions under real-time image guidance proves problematic in a ... more Performing minimal invasive interventions under real-time image guidance proves problematic in a closed-bore magnetic resonance imaging scanner. To enable better usability in MRI guided interventions, robotic systems could be used for additional assistance. However, the integration of such devices into the clinical workflow relates to many technical challenges in order to increase precision of the procedure while ensuring the overall safety. In this work, an MR compatible, compact, ultra-light and remotely controllable micropositioning system called μRIGS is presented. The instrument positioning unit can be operated in a 5-DoF range within a working volume of 2100 cm3with an instrument feed of 120 mm. The kinematics are actuated with a combination of non-metallic Bowden cables and electric stepper motors from a safe distance inside the scanner room, while their control is initiated from the control room via a custom-fitted GUI. Thereby, the precision of the positioning reproducibili...

Current Directions in Biomedical Engineering, 2018

Conventional computed tomography (CT) systems are encapsulated in hardware and software. Integrat... more Conventional computed tomography (CT) systems are encapsulated in hardware and software. Integration of further imaging modalities and sensors which can acquire prior knowledge for dose saving image acquisition and reconstruction techniques are barely possible. Within the scope of our research project, an open interface and freely configurable CT system is now being developed. The integration of further modalities and sensors into this system is a main target. A subproject deals with a multi sensor patient table, which provides additional information through integrated sensors. In particular, force sensors are installed inside the patient table to determine the patient’s mass. This value can be used to specify the required tube voltage, so that a more precise setting can be made in comparison to today‘s clinical practice. Studys show that a more precise kVp estimation can significantly reduce patient dose. Sensors for the monitoring of respiration and pulse are also integrated into ...

Current Directions in Biomedical Engineering, 2016

The arterial blood pressure (ABP) holds a lot of information about the cardiovascular system. To ... more The arterial blood pressure (ABP) holds a lot of information about the cardiovascular system. To analyse the ABP signal, at first the pulse wave has to be detected correctly. Due to influences, e.g. of noise, an accurate beat detection is a challenging task. In this work, a novel real-time ABP detector based on higher-order statistics is presented. The method uses the 4

Electromagnetic tracking systems (EMTS) are utilized to track surgical instruments during navigat... more Electromagnetic tracking systems (EMTS) are utilized to track surgical instruments during navigated interventions. Compared to optical tracking technologies, the non-line-of-sight feature is the biggest advantage of EMTS. However, significant distortions due to nearby metallic objects and a small working volume are serious drawbacks preventing ETMS from being widely used. We worked on developing new methods to improve the accuracy of EMTS even in the vicinity of large metal objects while speeding up the position estimation frame rate. Therefore, we proposed a method to realize frequency deviation multiplexing (FDM) for EMTS in order to speed up the frame rate, and a quadratic-rectangular (QR) excitation method to remove the distorted voltage induced by the nearby conductive distorter. The results show that the measurement speed and robustness to nearby metal objects of our EMTS were improved by the FDM and QR method. Keyword: Electromagnetic Tracking, Image-guided Interventions, Nav...

Sensors, 2020

Functional electrical stimulation and robot-assisted gait training are techniques which are used ... more Functional electrical stimulation and robot-assisted gait training are techniques which are used in a clinical routine to enhance the rehabilitation process of stroke patients. By combining these technologies, therapy effects could be further improved and the rehabilitation process can be supported. In order to combine these technologies, a novel algorithm was developed, which aims to extract gait events based on movement data recorded with inertial measurement units. In perspective, the extracted gait events can be used to trigger functional electrical stimulation during robot-assisted gait training. This approach offers the possibility of equipping a broad range of potential robot-assisted gait trainers with functional electrical stimulation. In particular, the aim of this study was to test the robustness of the previously developed algorithm in a clinical setting with patients who suffered a stroke. A total amount of N = 10 stroke patients participated in the study, with written ...

Sensors, 2019

Technologies such as robot-assisted gait trainers or functional electrical stimulation can improv... more Technologies such as robot-assisted gait trainers or functional electrical stimulation can improve the rehabilitation process of people affected with gait disorders due to stroke or other neurological defects. By combining both technologies, the potential disadvantages of each technology could be compensated and simultaneously, therapy effects could be improved. Thus, an algorithm was designed that aims to detect the gait cycle of a robot-assisted gait trainer. Based on movement data recorded with inertial measurement units, gait events can be detected. These events can further be used to trigger functional electrical stimulation. This novel setup offers the possibility of equipping a broad range of potential robot-assisted gait trainers with functional electrical stimulation. The aim of this paper in particular was to test the feasibility of a system using inertial measurement units for gait event detection during robot-assisted gait training. Thus, a 39-year-old healthy male adult...

PLOS ONE, 2018

The aim of this study was the development and evaluation of a real-time guidance support using op... more The aim of this study was the development and evaluation of a real-time guidance support using optical Moiré Phase Tracking (MPT) for magnetic resonance (MR) guided percutaneous interventions. A gradient echo sequence, capable of real-time position updates by the MPT system, was modified to enable needle guidance based on four rigidly attached MPT markers at the back of a needle. Two perpendicular imaging planes were automatically aligned along the calibrated needle and centered at its tip. For user guidance, additional information about the needle trajectory and the tip to target distance were added as image overlay. Both, images and guiding information were displayed on the in-room monitor to facilitate MR guided interventions. The guidance support was evaluated by four experienced interventional radiologists and four novices targeting rubber O-rings embedded in a custommade phantom on a 3T wide-bore MRI system (80 punctures). The skin to target time, user error, system error and total error were analyzed. The mean skin to target time was 146s ±68s with no statistically significant difference between experts and novices. A low mean user error (0.91mm±0.43mm), system error (0.53mm±0.27mm) and total error (0.99mm ±0.47mm) was reached in all directions. No statistically significant difference in user error, system error and total error could be found between experts and novices. The presented tracking and image guidance system combined with the user interface offers continuous and interactive control of the imaging plane while puncturing in the magnet enabling accurate real-time feedback for both, experienced and non-experienced users.

Biomedical Engineering / Biomedizinische Technik, 2012

International Journal of Computer Assisted Radiology and Surgery, 2017

Purpose To assess the accuracy of medical electromagnetic tracking systems, reference positioning... more Purpose To assess the accuracy of medical electromagnetic tracking systems, reference positioning systems are generally required. Errors are unavoidable in such systems, and despite how tiny they may be, prevent the ground truth from being known. In this work, a simulator was developed and used to analyze the theoretical system performances in electromagnetic tracking. Methods To simulate the entire tracking process, the magnetic dipole model, Faraday's law, and a mathematical optimization algorithm are applied. With the simulator, we optimized the spatial placement of the transmitter coils, analyzed the tracking accuracy by applying stochastic and optimized coil placement. Additionally, the performance of the calibration of transmitter coils' measurement error and Kalman filtering was tested. Results The results show that, after optimizing the spatial arrangement of the transmitter coils, the tracking accuracy is significantly improved to a much higher level compared with applying statistical arrangement. The measurement errors of the transmitter coils' positions and orientations can be totally rectified by the developed calibration algorithm when no noises are introduced. The Kalman filter reduces the sensor jitter errors caused by noise, which potentially allows the EM tracking system to reach a larger volume of interest. Conclusions We proposed a simulator for advanced anal

Wahrend einer neurochirurgischen Intervention muss es dem Operateur moglich sein diagnostische Bi... more Wahrend einer neurochirurgischen Intervention muss es dem Operateur moglich sein diagnostische Bilder zu aktualisieren. Bei dem hier verwendeten neurochirurgischen Mikroskop konnen diagnostische Bilder als virtuelle Modelle und Schnittbilder eingeblendet werden, um einen Sichtwechsel zwischen Patient und externen Bildschirmen zu vermeiden. Um eine intraoperative Aktualisierung der Modelle zu ermoglichen, wurde im Rahmen dieser Arbeit das Mikroskop an eine C-Arm-Angiographieanlage uber einen PACS-Server angebunden. Auserdem wird ein effizienter Workflow vorgestellt, der u. a. die Modellgenerierung aus den DICOM-Bildern mit Hilfe der Entwicklungsumgebung MeVisLab vorsieht. Unter Laborbedingungen durchgefuhrte Experimente ergaben eine mittlere Dauer der Modellaktualisierung von maximal 18,5 ± 2,5 min. Die Abweichung der virtuellen Uberlagerung von realen Strukturen im Mikroskop liegt im Wesentlichen im Submillimeterbereich. Das Mikroskopsystem bildet mit diesem Workflow eine solide For...

Physiological Measurement, Feb 27, 2017

In life-threatening diseases and in several clinical interventions, monitoring of vital parameter... more In life-threatening diseases and in several clinical interventions, monitoring of vital parameters is essential to guarantee the safety of patients. Besides monitoring the electrocardiogram (ECG), it is helpful to assess respiratory activity. If the respiration signal itself is not recorded, it can be extracted from the ECG (i.e. ECG derived respiration, EDR). In the present paper, we compared six EDR approaches, namely RS-decline quantified by central moments, respiratory sinus arrhythmia (RSA), R-wave amplitude, QRS area, RS-distance and maximum RS-slope. In order to evaluate the performance of each approach, we applied each method to a database of ECGs and reference respiration signals of 41 healthy subjects. All considered methods revealed relatively small absolute mean errors of the breathing rate (BR) at rest (0.75-1.3 Bpm). The method based on higher order central moments revealed a minimum mean absolute error of 0.75Bpm (4.40%) and a maximum correlation and concordance with the reference BR (rp=0.97, rc=0.97). Using this technique, we analyzed changes of respiration in patients suffering from acute schizophrenia. An increased respiration rate of about 4Bpm was found. Additionally, alteration of respiratory ratio and reduced respiratory sinus arrhythmia was demonstrated. We conclude that a precise dynamic monitoring of breathing and the investigation of changes in breathing patterns is possible without recording respiration per se.

Current Directions in Biomedical Engineering, Sep 1, 2016

The arterial blood pressure (ABP) holds a lot of information about the cardiovascular system. To ... more The arterial blood pressure (ABP) holds a lot of information about the cardiovascular system. To analyse the ABP signal, at first the pulse wave has to be detected correctly. Due to influences, e.g. of noise, an accurate beat detection is a challenging task. In this work, a novel real-time ABP detector based on higher-order statistics is presented. The method uses the 4 th order cumulants for ABP-peak detection. To evaluate this detector, the Fantasia database freely available at physionet was used. In this database, 142,936 systolic peaks were available to check the efficiency of the beat detector. A sensitivity of 99.91% and a positive predictive value of 99.50% were achieved with the novel method.

Current Directions in Biomedical Engineering, Sep 1, 2016

Evaluating individual aerobic exercise capacity is fundamental in sports and exercise medicine bu... more Evaluating individual aerobic exercise capacity is fundamental in sports and exercise medicine but associated with organizational and instrumental effort. Here, we extract an index related to common performance markers, the aerobic and anaerobic thresholds enabling the estimation of exercise capacity from a conventional sports watch supporting beatwise heart rate tracking. Therefore, cardiac vagal threshold (CVT) was determined in 19 male subjects performing an incremental maximum exercise test. CVT varied around the anaerobic threshold AnT with mean deviation of 7.9 ± 17.7 W. A high correspondence of the two thresholds was indicated by Bland-Altman plots with limits of agreement −27.5 W and 43.4 W. Additionally, CVT was strongly correlated AnT (r p = 0.86, p < 0.001) and reproduced this marker well (r c = 0.81). We conclude, that cardiac vagal threshold derived from compression entropy time course can be useful to assess physical fitness in an uncomplicated way.

Physiological measurement, Jan 10, 2017

In life-threatening diseases and in several clinical interventions, monitoring of vital parameter... more In life-threatening diseases and in several clinical interventions, monitoring of vital parameters is essential to guarantee the safety of patients. Besides monitoring the electrocardiogram (ECG), it is helpful to assess respiratory activity. If the respiration signal itself is not recorded, it can be extracted from the ECG (i.e. ECG derived respiration, EDR). In the present paper, we compared six EDR approaches, namely RS-decline quantified by central moments, respiratory sinus arrhythmia (RSA), R-wave amplitude, QRS area, RS-distance and maximum RS-slope. In order to evaluate the performance of each approach, we applied each method to a database of ECGs and reference respiration signals of 41 healthy subjects. All considered methods revealed relatively small absolute mean errors of the breathing rate (BR) at rest (0.75-1.3 Bpm). The method based on higher order central moments revealed a minimum mean absolute error of 0.75Bpm (4.40%) and a maximum correlation and concordance with ...

Biomedical Engineering / Biomedizinische Technik, 2012

American Journal of Neuroradiology, 2014

BACKGROUND AND PURPOSE: Endovascular therapy is an emerging treatment option in patients with acu... more BACKGROUND AND PURPOSE: Endovascular therapy is an emerging treatment option in patients with acute ischemic stroke and especially in cases presenting late after symptom onset. Information about remaining viable tissue as measured with perfusion imaging is crucial for proper patient selection. The aim of this study was to investigate whether perfusion imaging with C-arm CT in the angiography suite is feasible and provides measurements comparable with ones made by CTP. MATERIALS AND METHODS: The MCA was occluded surgically in 6 sheep. Perfusion studies were performed before surgery, immediately after, and at 3 hours after MCA occlusion by using a robotic flat panel detector C-arm angiographic system. For comparison, conventional CTP was performed at the same time points. Two different protocols with the C-arm CT were tested. Images were analyzed by 2 readers with regard to the presence and size of perfusion abnormalities. RESULTS: With C-arm CT, perfusion abnormalities were detected with a high sensitivity and specificity when vessel occlusion was confirmed by criterion standard DSA. No difference was found between lesions sizes measured with the 2 C-arm CT protocols and CTP. Growth of the CBV lesions with time was captured with C-arm CT and CTP. CONCLUSIONS: In this small study, it was feasible to qualitatively measure CBV and CBF by using a flat panel detector angiographic system. S troke is a major cause of death and disability throughout the world. IV thrombolysis within 4.5 hours of symptom onset remains the only therapy with benefit for patients so far, as proved by randomized trials. 1-3 However, the results of studies investigating endovascular approaches indicate that the outcome of patients with large-artery occlusions may be improved in comparison with IV thrombolysis. 4-8 Perfusion measurements are useful in selecting patients most likely to benefit from revascularization because they provide information about the ratio of infarct core to penumbra. This is especially true for those patients presenting outside the therapeutic time window for IV thrombolysis.

Biomedical Engineering / Biomedizinische Technik, 2012

Biomedical Engineering / Biomedizinische Technik, 2012

Current Directions in Biomedical Engineering, 2021

Performing minimal invasive interventions under real-time image guidance proves problematic in a ... more Performing minimal invasive interventions under real-time image guidance proves problematic in a closed-bore magnetic resonance imaging scanner. To enable better usability in MRI guided interventions, robotic systems could be used for additional assistance. However, the integration of such devices into the clinical workflow relates to many technical challenges in order to increase precision of the procedure while ensuring the overall safety. In this work, an MR compatible, compact, ultra-light and remotely controllable micropositioning system called μRIGS is presented. The instrument positioning unit can be operated in a 5-DoF range within a working volume of 2100 cm3with an instrument feed of 120 mm. The kinematics are actuated with a combination of non-metallic Bowden cables and electric stepper motors from a safe distance inside the scanner room, while their control is initiated from the control room via a custom-fitted GUI. Thereby, the precision of the positioning reproducibili...

Current Directions in Biomedical Engineering, 2018

Conventional computed tomography (CT) systems are encapsulated in hardware and software. Integrat... more Conventional computed tomography (CT) systems are encapsulated in hardware and software. Integration of further imaging modalities and sensors which can acquire prior knowledge for dose saving image acquisition and reconstruction techniques are barely possible. Within the scope of our research project, an open interface and freely configurable CT system is now being developed. The integration of further modalities and sensors into this system is a main target. A subproject deals with a multi sensor patient table, which provides additional information through integrated sensors. In particular, force sensors are installed inside the patient table to determine the patient’s mass. This value can be used to specify the required tube voltage, so that a more precise setting can be made in comparison to today‘s clinical practice. Studys show that a more precise kVp estimation can significantly reduce patient dose. Sensors for the monitoring of respiration and pulse are also integrated into ...

Current Directions in Biomedical Engineering, 2016

The arterial blood pressure (ABP) holds a lot of information about the cardiovascular system. To ... more The arterial blood pressure (ABP) holds a lot of information about the cardiovascular system. To analyse the ABP signal, at first the pulse wave has to be detected correctly. Due to influences, e.g. of noise, an accurate beat detection is a challenging task. In this work, a novel real-time ABP detector based on higher-order statistics is presented. The method uses the 4

Electromagnetic tracking systems (EMTS) are utilized to track surgical instruments during navigat... more Electromagnetic tracking systems (EMTS) are utilized to track surgical instruments during navigated interventions. Compared to optical tracking technologies, the non-line-of-sight feature is the biggest advantage of EMTS. However, significant distortions due to nearby metallic objects and a small working volume are serious drawbacks preventing ETMS from being widely used. We worked on developing new methods to improve the accuracy of EMTS even in the vicinity of large metal objects while speeding up the position estimation frame rate. Therefore, we proposed a method to realize frequency deviation multiplexing (FDM) for EMTS in order to speed up the frame rate, and a quadratic-rectangular (QR) excitation method to remove the distorted voltage induced by the nearby conductive distorter. The results show that the measurement speed and robustness to nearby metal objects of our EMTS were improved by the FDM and QR method. Keyword: Electromagnetic Tracking, Image-guided Interventions, Nav...

Sensors, 2020

Functional electrical stimulation and robot-assisted gait training are techniques which are used ... more Functional electrical stimulation and robot-assisted gait training are techniques which are used in a clinical routine to enhance the rehabilitation process of stroke patients. By combining these technologies, therapy effects could be further improved and the rehabilitation process can be supported. In order to combine these technologies, a novel algorithm was developed, which aims to extract gait events based on movement data recorded with inertial measurement units. In perspective, the extracted gait events can be used to trigger functional electrical stimulation during robot-assisted gait training. This approach offers the possibility of equipping a broad range of potential robot-assisted gait trainers with functional electrical stimulation. In particular, the aim of this study was to test the robustness of the previously developed algorithm in a clinical setting with patients who suffered a stroke. A total amount of N = 10 stroke patients participated in the study, with written ...

Sensors, 2019

Technologies such as robot-assisted gait trainers or functional electrical stimulation can improv... more Technologies such as robot-assisted gait trainers or functional electrical stimulation can improve the rehabilitation process of people affected with gait disorders due to stroke or other neurological defects. By combining both technologies, the potential disadvantages of each technology could be compensated and simultaneously, therapy effects could be improved. Thus, an algorithm was designed that aims to detect the gait cycle of a robot-assisted gait trainer. Based on movement data recorded with inertial measurement units, gait events can be detected. These events can further be used to trigger functional electrical stimulation. This novel setup offers the possibility of equipping a broad range of potential robot-assisted gait trainers with functional electrical stimulation. The aim of this paper in particular was to test the feasibility of a system using inertial measurement units for gait event detection during robot-assisted gait training. Thus, a 39-year-old healthy male adult...

PLOS ONE, 2018

The aim of this study was the development and evaluation of a real-time guidance support using op... more The aim of this study was the development and evaluation of a real-time guidance support using optical Moiré Phase Tracking (MPT) for magnetic resonance (MR) guided percutaneous interventions. A gradient echo sequence, capable of real-time position updates by the MPT system, was modified to enable needle guidance based on four rigidly attached MPT markers at the back of a needle. Two perpendicular imaging planes were automatically aligned along the calibrated needle and centered at its tip. For user guidance, additional information about the needle trajectory and the tip to target distance were added as image overlay. Both, images and guiding information were displayed on the in-room monitor to facilitate MR guided interventions. The guidance support was evaluated by four experienced interventional radiologists and four novices targeting rubber O-rings embedded in a custommade phantom on a 3T wide-bore MRI system (80 punctures). The skin to target time, user error, system error and total error were analyzed. The mean skin to target time was 146s ±68s with no statistically significant difference between experts and novices. A low mean user error (0.91mm±0.43mm), system error (0.53mm±0.27mm) and total error (0.99mm ±0.47mm) was reached in all directions. No statistically significant difference in user error, system error and total error could be found between experts and novices. The presented tracking and image guidance system combined with the user interface offers continuous and interactive control of the imaging plane while puncturing in the magnet enabling accurate real-time feedback for both, experienced and non-experienced users.

Biomedical Engineering / Biomedizinische Technik, 2012

International Journal of Computer Assisted Radiology and Surgery, 2017

Purpose To assess the accuracy of medical electromagnetic tracking systems, reference positioning... more Purpose To assess the accuracy of medical electromagnetic tracking systems, reference positioning systems are generally required. Errors are unavoidable in such systems, and despite how tiny they may be, prevent the ground truth from being known. In this work, a simulator was developed and used to analyze the theoretical system performances in electromagnetic tracking. Methods To simulate the entire tracking process, the magnetic dipole model, Faraday's law, and a mathematical optimization algorithm are applied. With the simulator, we optimized the spatial placement of the transmitter coils, analyzed the tracking accuracy by applying stochastic and optimized coil placement. Additionally, the performance of the calibration of transmitter coils' measurement error and Kalman filtering was tested. Results The results show that, after optimizing the spatial arrangement of the transmitter coils, the tracking accuracy is significantly improved to a much higher level compared with applying statistical arrangement. The measurement errors of the transmitter coils' positions and orientations can be totally rectified by the developed calibration algorithm when no noises are introduced. The Kalman filter reduces the sensor jitter errors caused by noise, which potentially allows the EM tracking system to reach a larger volume of interest. Conclusions We proposed a simulator for advanced anal