Showing papers in "Biomedizinische Technik in 2016"

Random forests in non-invasive sensorimotor rhythm brain-computer interfaces: a practical and convenient non-linear classifier.

Abstract: There is general agreement in the brain-computer interface (BCI) community that although non-linear classifiers can provide better results in some cases, linear classifiers are preferable. Particularly, as non-linear classifiers often involve a number of parameters that must be carefully chosen. However, new non-linear classifiers were developed over the last decade. One of them is the random forest (RF) classifier. Although popular in other fields of science, RFs are not common in BCI research. In this work, we address three open questions regarding RFs in sensorimotor rhythm (SMR) BCIs: parametrization, online applicability, and performance compared to regularized linear discriminant analysis (LDA). We found that the performance of RF is constant over a large range of parameter values. We demonstrate - for the first time - that RFs are applicable online in SMR-BCIs. Further, we show in an offline BCI simulation that RFs statistically significantly outperform regularized LDA by about 3%. These results confirm that RFs are practical and convenient non-linear classifiers for SMR-BCIs. Taking into account further properties of RFs, such as independence from feature distributions, maximum margin behavior, multiclass and advanced data mining capabilities, we argue that RFs should be taken into consideration for future BCIs.

Magnetic resonance brain classification by a novel binary particle swarm optimization with mutation and time-varying acceleration coefficients.

Abstract: AIM To develop an automatic magnetic resonance (MR) brain classification that can assist physicians to make a diagnosis and reduce wrong decisions. METHOD This article investigated the binary particle swarm optimization (BPSO) approach and proposed its three new variants: BPSO with mutation and time-varying acceleration coefficients (BPSO-MT), BPSO with mutation (BPSO-M), and BPSO with time-varying acceleration coefficients (BPSO-T). We first extracted wavelet entropy (WE) features from both approximation and detail sub-bands of eight-level decomposition. Afterwards, we used the proposed BPSO-M, BPSO-T, and BPSO-MT to select features. Finally, the selected features were fed into a probabilistic neural network (PNN). RESULTS The proposed BPSO-MT performed better than BPSO-T and BPSO-M. It finally selected two features of entropies of the following two sub-bands (V1, D1). The proposed system "WE + BPSO-MT + PNN" yielded perfect classification on Data160 and Data66. In addition, it yielded 99.53% average accuracy for the Data255, over 10 repetitions of k-fold stratified cross validation (SCV), higher than state-of-the-art approaches. CONCLUSIONS The proposed method is effective for MR brain classification.

P wave detection and delineation in the ECG based on the phase free stationary wavelet transform and using intracardiac atrial electrograms as reference

Abstract: Robust and exact automatic P wave detection and delineation in the electrocardiogram (ECG) is still an interesting but challenging research topic. The early prognosis of cardiac afflictions such as atrial fibrillation and the response of a patient to a given treatment is believed to improve if the P wave is carefully analyzed during sinus rhythm. Manual annotation of the signals is a tedious and subjective task. Its correctness depends on the experience of the annotator, quality of the signal, and ECG lead. In this work, we present a wavelet-based algorithm to detect and delineate P waves in individual ECG leads. We evaluated a large group of commonly used wavelets and frequency bands (wavelet levels) and introduced a special phase free wavelet transformation. The local extrema of the transformed signals are directly related to the delineating points of the P wave. First, the algorithm was studied using synthetic signals. Then, the optimal parameter configuration was found using intracardiac electrograms and surface ECGs measured simultaneously. The reverse biorthogonal wavelet 3.3 was found to be optimal for this application. In the end, the method was validated using the QT database from PhysioNet. We showed that the algorithm works more accurately and more robustly than other methods presented in literature. The validation study delivered an average delineation error of the P wave onset of -0.32±12.41 ms when compared to manual annotations. In conclusion, the algorithm is suitable for handling varying P wave shapes and low signal-to-noise ratios.

Remote vital parameter monitoring in neonatology - robust, unobtrusive heart rate detection in a realistic clinical scenario.

Abstract: Vital parameter monitoring of term and preterm infants during incubator care with self-adhesive electrodes or sensors directly positioned on the skin [e.g. photoplethysmography (PPG) for oxygen saturation or electrocardiography (ECG)] is an essential part of daily routine care in neonatal intensive care units. For various reasons, this kind of monitoring contains a lot of stress for the infants. Therefore, there is a need to measure vital parameters (for instance respiration, temperature, pulse, oxygen saturation) without mechanical or conductive contact. As a non-contact method of monitoring, we present an adapted version of camera-based photoplethysmography imaging (PPGI) according to neonatal requirements. Similar to classic PPG, the PPGI camera detects small temporal changes in the term and preterm infant's skin brightness due to the cardiovascular rhythm of dermal blood perfusion. We involved 10 preterm infants in a feasibility study [five males and five females; mean gestational age: 26 weeks (24-28 weeks); mean biological age: 35 days (8-41 days); mean weight at the time of investigation: 960 g (670-1290 g)]. The PPGI camera was placed directly above the incubators with the infant inside illuminated by an infrared light emitting diode (LED) array (850 nm). From each preterm infant, 5-min video sequences were recorded and analyzed post hoc. As the measurement scenario was kept as realistic as possible, the infants were not constrained in their movements in front of the camera. Movement intensities were assigned into five classes (1: no visible motion to 5: heavy struggling). PPGI was found to be significantly sensitive to movement artifacts. However, for movement classes 1-4, changes in blood perfusion according to the heart rate (HR) were recovered successfully (Pearson correlation: r=0.9759; r=0.765 if class 5 is included). The study was approved by the Ethics Committee of the Universal Hospital of the RWTH Aachen University, Aachen, Germany (EK 254/13).

Assessment of calibration methods on impedance pneumography accuracy.

Abstract: The aim was to assess accuracy of tidal volumes (TV) calculated by impedance pneumography (IP), reproducibility of calibration coefficients (CC) between IP and pneumotachometry (PNT), and their relationship with body posture, breathing rate and depth. Fourteen students performed three sessions of 18 series: normal and deep breathing at 6, 10, 15 breaths/min rates, while supine, sitting and standing; 18 CC were calculated for every session. Session 2 was performed 2 months after session 1, session 3 1-3 days after session 2. TV were calculated using full or limited set of CC from current session, in case of sessions 2 and 3 also using CC from session 1 and 2, respectively. When using full set of CC from current session, IP underestimated TV by -3.2%. Using CC from session 2 for session 3 measurements caused decrease of relative difference: -3.9%, from session 1 for session 2: -5.3%; for limited set of CC: -5.0%. The body posture had significant effect on CC. The highest accuracy was obtained when all factors influencing CC were considered. The application of CC related only to body posture may result in shortening of calibration and moderate accuracy loss. Using CC from previous session compromises accuracy moderately.

Biomechanical effect of different femoral neck blade position on the fixation of intertrochanteric fracture: A finite element analysis

Abstract: Medial migration or cutout of the neck helical blade has commonly occurred in the treatment of trochanteric fracture of the femur The position of the helical blade within the femoral head is one of the influencing factors that cause the blade to perforate the intact joint surface; however, the ideal placement of the helical blade is not currently known A finite element model of a femur/nail construct was utilized to analyze five possible blade positions in the femoral head Normal strain at the fracture surface, the minimum principal strain in the cancellous bone, and the von Mises stress in the implant itself were calculated and compared between different blade positions The results showed that a large area of normal compressive strain at the fracture surface was observed in the inferior and posterior blade positions The volume of cancellous bone strained to yielding in the femoral head and neck was lower for the inferior and posterior positions, whereas it was the highest for the superior position The inferior and posterior positions had lower von Mises stress in the implant itself The inferior and posterior positions may be the ideal position for the intramedullary nail with a helical neck blade

Thermodynamic effects after Diode and Er:YAG laser irradiation of grade IV and V titanium implants placed in bone – an ex vivo study. Preliminary report

Abstract: Many inserted implants are affected by peri-implantitis. The aim of our study was to evaluate increases in implant temperature, depending on the diameter and chemical composition of implants. In particular we measured the time it takes for the temperature of an implant to rise by 10°C and evaluated laser power settings required to prevent thermal injury when an implant surface is decontaminated during the treatment of peri-implantitis. The study analysed six implants placed in porcine ribs and divided into two groups according to their diameter and chemical composition (grade IV and grade V titanium). The implants were irradiated with Diode and Er:YAG lasers using different laser parameters. The temperature was measured with a K-type thermocouple. The temperature on the implant surface rose as the laser power increased and the implant diameter decreased. The time required to increase the temperature of an implant by 10°C was less than it was for titanium grade IV. The temperature gradient was below 10°C for all implants treated using a laser power up to 1 W. It is important to choose the correct laser parameters, depending on the chemical composition and diameter of the implant, so that decontamination of the implant surface is thorough, effective and safe.

Calcium phosphate/microgel composites for 3D powderbed printing of ceramic materials.

Abstract: Composites of microgels and calcium phosphates are promising as drug delivery systems and basic components for bone substitute implants. In this study, we synthesized novel composite materials consisting of pure β-tricalcium phosphate and stimuli-responsive poly(N-vinylcaprolactam-co-acetoacetoxyethyl methacrylate-co-vinylimidazole) microgels. The chemical composition, thermal properties and morphology for obtained composites were extensively characterized by Fourier transform infrared, X-ray photoelectron spectroscopy, IGAsorp moisture sorption analyzer, thermogravimetric analysis, granulometric analysis, ESEM, energy dispersive X-ray spectroscopy and TEM. Mechanical properties of the composites were evaluated by ball-on-three-balls test to determine the biaxial strength. Furthermore, initial 3D powderbed-based printing tests were conducted with spray-dried composites and diluted 2-propanol as a binder to evaluate a new binding concept for β-tricalcium phosphate-based granulates. The printed ceramic bodies were characterized before and after a sintering step by ESEM. The hypothesis that the microgels act as polymer adhesive agents by efficient chemical interactions with the β-tricalcium phosphate particles was confirmed. The obtained composites can be used for the development of new scaffolds.

Analysis of wrist bone motion before and after SL-ligament resection

Abstract: The analysis of the three-dimensional motion of wrist joint components in the physiological and injured wrist is of high clinical interest. Therefore, the purpose of this in vitro study was to compare the motion of scaphoid, lunate and triquetrum during physiological wrist motion in flexion and extension, and in radial- and ulnar-deviation, with those motion patterns after complete resection of the scapho-lunate-ligament. Eight fresh frozen cadaver wrists were carefully thawed and prepared for the investigation with an electromagnetic tracking system by implantation of measurement coils with 6 degrees of freedom. Electromagnetic tracking enabled the motion analysis of the scaphoid, lunate, and triquetrum bones with respect to the fixed radius in three planes of passive motion. After scapho-lunate-ligament injury changes in the translational and rotational motion pattern especially of the scaphoid bone occurred in dorsal-volar directions during flexion and extension, radial- and ulnar-deviation, and during rotation around the radio-ulnar- and longitudinal-axis of the wrist.

Brain tumor classification and segmentation using sparse coding and dictionary learning.

Abstract: This paper presents a novel fully automatic framework for multi-class brain tumor classification and segmentation using a sparse coding and dictionary learning method. The proposed framework consists of two steps: classification and segmentation. The classification of the brain tumors is based on brain topology and texture. The segmentation is based on voxel values of the image data. Using K-SVD, two types of dictionaries are learned from the training data and their associated ground truth segmentation: feature dictionary and voxel-wise coupled dictionaries. The feature dictionary consists of global image features (topological and texture features). The coupled dictionaries consist of coupled information: gray scale voxel values of the training image data and their associated label voxel values of the ground truth segmentation of the training data. For quantitative evaluation, the proposed framework is evaluated using different metrics. The segmentation results of the brain tumor segmentation (MICCAI-BraTS-2013) database are evaluated using five different metric scores, which are computed using the online evaluation tool provided by the BraTS-2013 challenge organizers. Experimental results demonstrate that the proposed approach achieves an accurate brain tumor classification and segmentation and outperforms the state-of-the-art methods.

Modular user interface design for integrated surgical workplaces

Abstract: Severe bottlenecks in usability and human technology interaction (HTI) of existing surgical workplaces and operating room (OR) equipment can occur today: lack of space, cable as trip hazard, communication problems between sterile and non-sterile staff, and operating errors in the handling of the medical devices. In fact, risks that are caused by poor usability can be critical, and studies show that most are preventable. This issue gets even more challenging in the context of open-OR networks regarding consistent and usable integration of user interfaces (UIs) of independently designed systems in one integrated surgical work system. In this work, a concept of generic UI profiles for the modular integration of a UI has been developed and first prototypes have been implemented. The concept is essentially based on the approach of device profiles developed in the context of the Bundesministerium fur Bildung und Forschung project OR.NET (www.ornet.org). We developed generic UI profiles to map the different interfaces of the medical devices on an integrated surgical UI. The integrated UI design shall be automatically verified according to agreed usability criteria, guidelines, and human error taxonomies.

Nonlinear analysis of pupillary dynamics.

Abstract: Pupil size reflects autonomic response to different environmental and behavioral stimuli, and its dynamics have been linked to other autonomic correlates such as cardiac and respiratory rhythms. The aim of this study is to assess the nonlinear characteristics of pupil size of 25 normal subjects who participated in a psychophysiological experimental protocol with four experimental conditions, namely “baseline”, “anger”, “joy”, and “sadness”. Nonlinear measures, such as sample entropy, correlation dimension, and largest Lyapunov exponent, were computed on reconstructed signals of spontaneous fluctuations of pupil dilation. Nonparametric statistical tests were performed on surrogate data to verify that the nonlinear measures are an intrinsic characteristic of the signals. We then developed and applied a piecewise linear regression model to detrended fluctuation analysis (DFA). Two joinpoints and three scaling intervals were identified: slope α0, at slow time scales, represents a persistent nonstationary long-range correlation, whereas α1 and α2, at middle and fast time scales, respectively, represent long-range power-law correlations, similarly to DFA applied to heart rate variability signals. Of the computed complexity measures, α0 showed statistically significant differences among experimental conditions (p<0.001). Our results suggest that (a) pupil size at constant light condition is characterized by nonlinear dynamics, (b) three well-defined and distinct long-memory processes exist at different time scales, and (c) autonomic stimulation is partially reflected in nonlinear dynamics.

Recognition of amyotrophic lateral sclerosis disease using factorial hidden Markov model.

Abstract: Amyotrophic lateral sclerosis (ALS) is a common disease among neurological disorders that can change the pattern of gait in human. One of the effective methods for recognition and analysis of gait patterns in ALS patients is utilizing stride interval time series. With proper preprocessing for removing unwanted artifacts from the raw stride interval times and then extracting meaningful features from these data, the factorial hidden Markov model (FHMM) was used to distinguish ALS patients from healthy subjects. The results of classification accuracy evaluated using the leave-one-out (LOO) cross-validation algorithm showed that the FHMM method provides better recognition of ALS and healthy subjects compared to standard HMM. Moreover, comparing our method with a state-of-the art method named least square support vector machine (LS-SVM) showed the efficiency of the FHMM in distinguishing ALS subjects from healthy ones.

Adhesive strength of total knee endoprostheses to bone cement - analysis of metallic and ceramic femoral components under worst-case conditions.

Abstract: Evaluation of the adhesive strength of femoral components to the bone cement is a relevant parameter for predicting implant safety. In the present experimental study, three types of cemented femoral components (metallic, ceramic and silica/silane-layered ceramic) of the bicondylar Multigen Plus knee system, implanted on composite femora were analysed. A pull-off test with the femoral components was performed after different load and several cementing conditions (four groups and n=3 components of each metallic, ceramic and silica/silane-layered ceramic in each group). Pull-off forces were comparable for the metallic and the silica/silane-layered ceramic femoral components (mean 4769 N and 4298 N) under standard test condition, whereas uncoated ceramic femoral components showed reduced pull-off forces (mean 2322 N). Loading under worst-case conditions led to decreased adhesive strength by loosening of the interface implant and bone cement using uncoated metallic and ceramic femoral components, respectively. Silica/silane-coated ceramic components were stably fixed even under worst-case conditions. Loading under high flexion angles can induce interfacial tensile stress, which could promote early implant loosening. In conclusion, a silica/silane-coating layer on the femoral component increased their adhesive strength to bone cement. Thicker cement mantles (>2 mm) reduce adhesive strength of the femoral component and can increase the risk of cement break-off.

Multi-modal signal acquisition using a synchronized wireless body sensor network in geriatric patients.

Abstract: Wearable home-monitoring devices acquiring various biosignals such as the electrocardiogram, photoplethysmogram, electromyogram, respirational activity and movements have become popular in many fields of research, medical diagnostics and commercial applications. Especially ambulatory settings introduce still unsolved challenges to the development of sensor hardware and smart signal processing approaches. This work gives a detailed insight into a novel wireless body sensor network and addresses critical aspects such as signal quality, synchronicity among multiple devices as well as the system's overall capabilities and limitations in cardiovascular monitoring. An early sign of typical cardiovascular diseases is often shown by disturbed autonomic regulations such as orthostatic intolerance. In that context, blood pressure measurements play an important role to observe abnormalities like hypo- or hypertensions. Non-invasive and unobtrusive blood pressure monitoring still poses a significant challenge, promoting alternative approaches including pulse wave velocity considerations. In the scope of this work, the presented hardware is applied to demonstrate the continuous extraction of multi modal parameters like pulse arrival time within a preliminary clinical study. A Schellong test to diagnose orthostatic hypotension which is typically based on blood pressure cuff measurements has been conducted, serving as an application that might significantly benefit from novel multi-modal measurement principles. It is further shown that the system's synchronicity is as precise as 30 μs and that the integrated analog preprocessing circuits and additional accelerometer data provide significant advantages in ambulatory measurement environments.

Segmentation and classification of bright lesions to diagnose diabetic retinopathy in retinal images.

Abstract: In view of predicting bright lesions such as hard exudates, cotton wool spots, and drusen in retinal images, three different segmentation techniques have been proposed and their effectiveness is compared with existing segmentation techniques. The benchmark images with annotations present in the structured analysis of the retina (STARE) database is considered for testing the proposed techniques. The proposed segmentation techniques such as region growing (RG), region growing with background correction (RGWBC), and adaptive region growing with background correction (ARGWBC) have been used, and the effectiveness of the algorithms is compared with existing fuzzy-based techniques. Images of eight categories of various annotations and 10 images in each category have been used to test the consistency of the proposed algorithms. Among the proposed techniques, ARGWBC has been identified to be the best method for segmenting the bright lesions based on its sensitivity, specificity, and accuracy. Fifteen different features are extracted from retinal images for the purpose of identification and classification of bright lesions. Feedforward backpropagation neural network (FFBPNN) and pattern recognition neural network (PRNN) are used for the classification of normal/abnormal images. Probabilistic neural network (PNN), radial basis exact fit (RBE), radial basis fewer neurons (RB), and FFBPNN are used for further bright lesion classification and achieve 100% accuracy.

Initial experience with imaging of the lower extremity arteries in an open 1.0 Tesla MRI system using the triggered angiography non-contrast-enhanced sequence (TRANCE) compared to digital subtraction angiography (DSA).

Abstract: PURPOSE The aim of this study was to evaluate the feasibility and validity of arterial lower limb imaging with triggered angiography non-contrast enhanced (TRANCE) in an open MRI at 1.0 Tesla (T) compared to digital subtraction angiography (DSA). MATERIAL AND METHODS ECG-gated, non-contrast-enhanced magnetic resonance angiography (MRA) was performed in a 1.0-T high-field open magnetic resonance imaging (MRI) system which generates a vertical magnetic field. Three acquisition levels were defined (abdominal and pelvic level, arterial segments above the knee and segments below the knee) and a total of 1782 vessel diameter measurements were taken on a total of 11 patients with suspected peripheral arterial occlusive disease (PAOD) (8 men, 3 women; average age 66 years). In each patient, 162 vessel segments (81 each with TRANCE and DSA) were defined and measured. Pearson correlation coefficients were calculated. RESULTS At the abdominal/pelvic level, all mean values measured with DSA exceeded the mean values obtained with TRANCE. Above the knee, mean vessel diameters were measured smaller in DSA in six, equal in three, and larger in two vessel segments. Below the knee, all measured averages, except for the tibiofibular tract (TFT) measurements, were larger in TRANCE. In total, two small (≤0.3), two moderate (>0.3), 11 good (>0.5), 10 high (>0.7) and 13 very high (>0.8) correlations were obtained. CONCLUSIONS Non-contrast-enhanced imaging of the lower limb arteries using a TRANCE-sequence in a 1.0 T open MRI system is feasible with the protocol presented; however, TRANCE tends to underestimate larger vessels and overestimate smaller vessels compared to DSA.

A UK medical devices regulator’s perspective on registries

Abstract: Registries are powerful tools to support manufacturers in the fulfilment of their obligations to perform post-market surveillance and post-market clinical follow-up of implantable medical devices. They are also a valuable resource for regulators in support of regulatory action as well as in providing information around the safety of new and innovative technologies. Registries can provide valuable information on the relative performance of both generic types and manufacturer's individual products and they complement other sources of information about device performance such as post-market clinical studies and adverse incident reporting. This paper describes the experience of the UK medical device regulator - the Medicines and Healthcare Products Regulatory Agency (MHRA) - of working with registries to monitor the safety and performance of medical devices. Based upon this experience, the authors identify a number of attributes for a registry which they consider to be key if the registry is to contribute effectively to the work of regulators on patient safety monitoring and medical device regulation.

Uncoupling of cardiac and respiratory rhythm in atrial fibrillation.

Abstract: Rearranged origin of heart rhythm in patients with atrial fibrillation (AF) influences the regulation of the heart and consequently the respiratory rhythm, and the bidirectional interaction of these rhythms not documented. Hence, we examined coupling of the RR interval and the respiration (Resp) signal by coherence, Granger causality and the cross-sample entropy method of time series analysis in patients with AF and a healthy control group. In healthy subjects, the influence of respiration on cardiac rhythm was found as increased coherence at the breathing frequency (BF) range, significantly stronger interaction and synchrony from Resp to RR than from RR to Resp. On the contrary, in patients with AF, coherence at BF diminished, there were no causal interactions between signals in both directions, which resulted in equally great asynchrony between them. In AF, the absence of full functionality of the sinoatrial node, as an integrator of neural cardiac control, resulted in diminished vagal modulation of heart periods and consequently impaired bidirectional cardio-respiratory interaction.

Differential osteogenicity of multiple donor-derived human mesenchymal stem cells and osteoblasts in monolayer, scaffold-based 3D culture and in vivo

Abstract: We set out to compare the osteogenicity of human mesenchymal stem (hMSCs) and osteoblasts (hOBs). Upon osteogenic induction in monolayer, hMSCs showed superior matrix mineralization expressing characteristic bone-related genes. For scaffold cultures, both cell types presented spindle-shaped, osteoblast-like morphologies forming a dense, interconnected network of high viability. On the scaffolds, hOBs proliferated faster. A general upregulation of parathyroid hormone-related protein (PTHrP), osteoprotegrin (OPG), receptor activator of NF-κB ligand (RANKL), sclerostin (SOST), and dentin matrix protein 1 (DMP1) was observed for both cell types. Simultaneously, PTHrP, RANKL and DMP-1 expression decreased under osteogenic stimulation, while OPG and SOST increased significantly. Following transplantation into NOD/SCID mice, μCT and histology showed increased bone deposition with hOBs. The bone was vascularized, and amounts further increased for both cell types after recombinant human bone morphogenic protein 7 (rhBMP-7) addition also stimulating osteoclastogenesis. Complete bone organogenesis was evidenced by the presence of osteocytes and hematopoietic precursors. Our study results support the asking to develop 3D cellular models closely mimicking the functions of living tissues suitable for in vivo translation.

Bottlenecks and needs in human-human and human-machine interaction - a view from and into the neurosurgical OR.

Abstract: The number and complexity of user interfaces in the OR has been considerably increasing during the last years. Moreover, increasing cost and time pressure force surgeons and surgical nurses to perform different tasks in parallel. We analyzed the workflow of 25 neurosurgical procedures with a workflow analysis tool in order to analyze the present situation in the neurosurgical OR and to identify potential use-oriented risks and to develop first proposals for respective countermeasures. Application of the navigation system, the CUSA ultrasonic aspirator, and the PACS-PC was associated with errors and resulting potential risks. A number of different disruptive factors have been identified, the most prominent of those being intraoperative duty phone calls, longer absence of the circulating nurses or slipped off foot switches. Furthermore, the identified problems may lead to risks for patient, and also for staff by use errors, associated with an inappropriate cognitive workload of the surgeon or nurses. Organizational and technical countermeasures are necessary: to enhance communication, team trainings could be helpful, and the setup of a mailbox could reduce the number of intraoperative duty phone calls. Technical deficiencies have to be reduced, e.g. with more user-oriented design of devices, such as foot switches, or standard design for user interfaces. For further risk reduction in the case of use deficiencies, we propose the implementation of device interoperability and the use of a sterile integrated user interface in a networked OR.

Reliability analysis of the heart autonomic control parameters during hemodialysis sessions.

Abstract: The study of heart autonomic control (HAC) in patients with chronic kidney disease (CKD) undergoing dialysis treatment has been carried out, however, there are no studies reporting the reliability of measurements of HAC parameters involving the mentioned samples and conditions. The reliability of many HAC parameters was evaluated from patients with CKD during two sessions of hemodialysis. The successive R-R intervals were recorded during two sessions of hemodialysis from 14 CKD patients that were undergoing dialysis for at least 6 months and with no history of recurrent hypotensive events. HAC parameters were obtained with time and frequency domain analysis, as well as with nonlinear methods. The reliability was measured with the intraclass correlation coefficient (ICC). The results showed excellent reliability (ICC=0.90-0.98) for most heart rate variability (HRV) parameters, especially the parameters obtained in the time domain [square root of the mean squared differences between successive R-R intervals (RMSSD), percentage of adjacent R-R intervals that differ by more than 50 ms (pNN50), mean of the 5-min standard deviations of R-R intervals (SDNNi), and triangular index] and with non-linear methods [standard deviation of the instantaneous variability beat-to-beat (SD1), standard deviation in long-term continuous R-R intervals (SD2), detrended fluctuation analysis (DFA) α1 and α2, approximate and sample entropies, and correlation dimension (D2): ICC=0.86-0.96]. Among the parameters obtained in the frequency domain (normalized magnitude from the spectrum of low-frequency components (LFnu), normalized magnitude from the spectrum of high-frequency components (HFnu), and LF/HF ratio), the LF/HF ratio showed better reliability (ICC=0.96 vs. ICC=0.70). Measurements of HAC parameters have excellent test-retest reliability for the studied samples and conditions.

A review of beat-to-beat vectorcardiographic (VCG) parameters for analyzing repolarization variability in ECG signals.

Abstract: Elevated ventricular repolarization lability is believed to be linked to the risk of ventricular tachycardia/ventricular fibrillation. However, ventricular repolarization is a complex electrical phenomenon, and abnormalities in ventricular repolarization are not completely understood. To evaluate repolarization lability, vectorcardiography (VCG) is an alternative approach where the electrocardiographic (ECG) signal can be considered as possessing both magnitude and direction. Recent research has shown that VCG is advantageous over ECG signal analysis for identification of repolarization abnormality. One of the key reasons is that the VCG approach does not rely on exact identification of the T-wave offset, which improves the reproducibility of the VCG technique. However, beat-to-beat variability in VCG is an emerging area for the investigation of repolarization abnormality though not yet fully realized. Therefore, the purpose of this review is to explore the techniques, findings, and efficacy of beat-to-beat VCG parameters for analyzing repolarization lability, which may have potential utility for further study.

Entropy at the right atrium as a predictor of atrial fibrillation recurrence outcome after pulmonary vein ablation.

Abstract: Atrial fibrillation (AF) recurrence rates after successful ablation procedures are still high and difficult to predict. This work studies the capability of entropy measured from intracardiac recordings as an indicator for recurrence outcome. Intra-atrial recordings from 31 AF patients were registered previously to an ablation procedure. Four electrodes were located at the right atrium (RA) and four more at the left atrium (LA). Sample entropy measurements were applied to these signals, in order to characterize different non-linear AF dynamics at the RA and LA independently. In a 3 months follow-up, 19 of them remained in sinus rhythm, whereas the other 12 turned back to AF. Entropy values can be associated to a proarrhythmic indicator as they were higher in patients with AF recurrence (1.11±0.15 vs. 0.91±0.13), in persistent patients (1.03±0.19 vs. 0.96±0.15), and at the LA with respect to the RA (1.03±0.23 vs. 0.89±0.15 for paroxysmal AF patients). Furthermore, entropy values at the RA arose as a more reliable predictor for recurrence outcome than at the LA. Results suggest that high entropy values, especially at the RA, are associated with high risk of AF recurrence. These findings show the potential of the proposed method to predict recurrences post-ablation, providing additional insights to the understanding of arrhythmia.

Differences in mean arterial pressure of young and elderly people measured by oscilometry during inflation and deflation of the arm cuff.

Abstract: Systemic arterial blood pressure (BP) is one of the most important parameters of the cardiovascular system. An oscillometric NIBP monitor was specifically designed to measure oscillometric pulsations and mean arterial pressure (MAP) during inflation and deflation of the cuff. Nineteen healthy young (age 23.1±1.7 years; mean±SD) and 35 elderly (83.9±7.9 years; mean±SD) subjects were studied. Differential analysis of MAP during inflation and deflation show mean |ΔMAP|=2.9±2.6 mm Hg in the young group (mean±SD) and |ΔMAP|=6.3±5.2 mm Hg for seniors (mean±SD). There was a significant difference (p<0.05) in means of |ΔMAP| measured during cuff inflation and cuff deflation between both groups. In about 50% of elderly subjects |ΔMAP| was higher than 5 mm Hg. Potential clinical relevance of the method needs to be further evaluated.

3D automatic liver segmentation using feature-constrained Mahalanobis distance in CT images.

Abstract: Automatic 3D liver segmentation is a fundamental step in the liver disease diagnosis and surgery planning. This paper presents a novel fully automatic algorithm for 3D liver segmentation in clinical 3D computed tomography (CT) images. Based on image features, we propose a new Mahalanobis distance cost function using an active shape model (ASM). We call our method MD-ASM. Unlike the standard active shape model (ST-ASM), the proposed method introduces a new feature-constrained Mahalanobis distance cost function to measure the distance between the generated shape during the iterative step and the mean shape model. The proposed Mahalanobis distance function is learned from a public database of liver segmentation challenge (MICCAI-SLiver07). As a refinement step, we propose the use of a 3D graph-cut segmentation. Foreground and background labels are automatically selected using texture features of the learned Mahalanobis distance. Quantitatively, the proposed method is evaluated using two clinical 3D CT scan databases (MICCAI-SLiver07 and MIDAS). The evaluation of the MICCAI-SLiver07 database is obtained by the challenge organizers using five different metric scores. The experimental results demonstrate the availability of the proposed method by achieving an accurate liver segmentation compared to the state-of-the-art methods.

A multichannel bioimpedance monitor for full-body blood flow monitoring.

Abstract: The design, properties, and possible diagnostic contribution of a multichannel bioimpedance monitor (MBM) with three independent current sources are presented in this paper. The simultaneous measurement of bioimpedance at 18 locations (the main part of the body, legs, arms, and neck) provides completely new information, on the basis of which more precise haemodynamic parameters can be obtained. The application of the MBM during various haemodynamic stages, such as resting in a supine position, tilting, exercise stress, and various respiration manoeuvres, is demonstrated. Statistical analysis on a group of 34 healthy volunteers is presented for demonstration of blood flow monitoring by using the proposed method.

Development of antibiotic-loaded silk fibroin/hyaluronic acid polyelectrolyte film coated CoCrMo alloy.

Abstract: Bacteria related infections are still a major problem for the implant materials. Such infections have occurred in nearly 3% of hip and knee replacements resulting in failure of device. There are two main approaches for inhibiting the bacterial adhesion to the surface. These involve bactericidal substances and anti-adhesive coatings. In this study, the efficiency of antibiotic-loaded silk fibroin/hyaluronic acid polyelectrolyte film coated CoCrMo alloy, prepared by means of complex coacervate and layer by layer techniques, was investigated. A medical grade CoCrMo was coated with variable number of silk fibroin/hyaluronic acid up to 14 layers at room temperature. The morphological evolution during and after formation of the crystal structure on the coating layer, the resulting surface roughness, and the corresponding alterations in the coating layer thicknesses were thoroughly studied using various analytical techniques, including attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). As a result, only 10 layers of silk fibroin/hyaluronic acid complex coacervate films were found to convey the general characteristics of the mixture of silk I and II, while layer by layer coated samples exhibited the mixture of silk I and II. Moreover, regardless of the preparation method applied, the surface roughness and the coating layer thicknesses were determined to increase with the increasing number of layers. The antibacterial test results suggested that the samples loaded with antibiotic successfully induced a bactericidal resistance against Staphylococcus aureus bacteria.

Development and experimental evaluation of an alarm concept for an integrated surgical workstation.

Abstract: INTRODUCTION Alarm conditions of the technical equipment in operating rooms represent a prevalent cause for interruptions of surgeons and scrub nurses, resulting in an increase of workload and potential reduction of patient safety. In this work, an alarm concept for an integrated operating room system based on open communication standards is developed and tested. METHODS In a laboratory experiment, the reactions of surgeons were analysed, comparing the displaying of alarms on an integrated workstation and on single devices: disruptive effects of alarm handling on primary task (ratings of perceived distraction, resumption lag, deterioration of speed, accuracy, and prospective memory), efficiency and effectiveness of identification of alarms, as well as perceived workload were included. RESULTS The identification of the alarm cause is significantly more efficient and effective with the integrated alarm concept. Moreover, a slightly lower deterioration of performance of the primary task due to the interruption of alarm handling was observed. CONCLUSION Displaying alarms on an integrated workstation supports alarm handling and consequently reduces disruptive effects on the primary task. The findings show that even small changes can reduce workload in a complex work environment like the operating room, resulting in improved patient safety.

A human factors perspective on medical device alarms: problems with operating alarming devices and responding to device alarms.

Abstract: Medical devices emit alarms when a problem with the device or with the patient needs to be addressed by healthcare personnel. At present, problems with device alarms are frequently discussed in the literature, the main message being that patient safety is compromised because device alarms are not as effective and safe as they should - and could - be. There is a general consensus that alarm-related hazards result, to a considerable degree, from the interactions of human users with the device. The present paper addresses key aspects of human perception and cognition that may relate to both operating alarming devices and responding to device alarms. Recent publications suggested solutions to alarm-related hazards associated with usage errors based on assumptions on the causal relations between, for example, alarm management and human perception, cognition, and responding. However, although there is face validity in many of these assumptions, future research should provide objective empirical evidence in order to deepen our understanding of the actual causal relationships, and hence improve and expand the possibilities for taking appropriate action.