Publications by authors named "Benjamin Walter"

85 Publications

Evaluation of improved bi-manual endoscopic resection using a customizable 3D-printed manipulator system designed for use with standard endoscopes: a feasibility study using a porcine ex-vivo model.

Endosc Int Open 2021 Jun 27;9(6):E881-E887. Epub 2021 May 27.

Medical Clinic and Policlinic II, University Hospital Würzburg, Würzburg, Germany.

A major drawback of endoscopic en-bloc resection technique is its inability to perform bimanual tasks. Although endoscopic platforms that enable bimanual tasks are commercially available, they are neither approved for various locations nor adaptable to specific patients and indications. Based on evolution of an adaptive 3D-printable platform concept, system variants with different characteristic properties were evaluated for ESD scenarios, ex-vivo in two locations in the stomach and colorectum. In total 28 ESDs were performed (7 antrum, 7 corpus in inversion, 7 cecum, 7 rectum) in a porcine ex-vivo setup. ESD was feasible in 21 cases. Investigated manipulator variants are differently well suited for performing ESD within the varying interventions scenarios. Dual-arm manipulators allowed autonomous ESD, while single-arm flexible manipulators could be used more universally due to their compact design, especially for lesions difficult to access. Pediatric scopes were too frail to guide the overtube-manipulators in extremely angled positions. Working in the rectum was impaired using long-sized manipulator arms. The presented endoscopic platform based on 3D-printable and customizable manipulator structures might be a promising approach for future improvement of ESD procedure. With regard to localization, especially flexible manipulators attached to standard endoscopes appear to be most promising for further application of specific and individualised manipulator systems.
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http://dx.doi.org/10.1055/a-1395-7089DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8159599PMC
June 2021

Directional Stimulation in Parkinson's Disease and Essential Tremor: The Cleveland Clinic Experience.

Neuromodulation 2021 Mar 18. Epub 2021 Mar 18.

Center For Neurological Restoration, Cleveland Clinic, Cleveland, OH, USA.

Objective: To assess use of directional stimulation in Parkinson's disease and essential tremor patients programmed in routine clinical care.

Materials And Methods: Patients with Parkinson's disease or essential tremor implanted at Cleveland Clinic with a directional deep brain stimulation (DBS) system from November 2017 to October 2019 were included in this retrospective case series. Omnidirectional was compared against directional stimulation using therapeutic current strength, therapeutic window percentage, and total electrical energy delivered as outcome variables.

Results: Fifty-seven Parkinson's disease patients (36 males) were implanted in the subthalamic nucleus (105 leads) and 33 essential tremor patients (19 males) were implanted in the ventral intermediate nucleus of the thalamus (52 leads). Seventy-four percent of patients with subthalamic stimulation (65% of leads) and 79% of patients with thalamic stimulation (79% of leads) were programmed with directional stimulation for their stable settings. Forty-six percent of subthalamic leads and 69% of thalamic leads were programmed on single segment activation. There was no correlation between the length of microelectrode trajectory through the STN and use of directional stimulation.

Conclusions: Directional programming was more common than omnidirectional programming. Substantial gains in therapeutic current strength, therapeutic window, and total electrical energy were found in subthalamic and thalamic leads programmed on directional stimulation.
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http://dx.doi.org/10.1111/ner.13374DOI Listing
March 2021

Assessment of transfer of morphological characteristics of Anomalous Aortic Origin of a Coronary Artery from imaging to patient specific 3D Printed models: A feasibility study.

Comput Methods Programs Biomed 2021 Apr 21;201:105947. Epub 2021 Jan 21.

Department of Radiology, Nationwide Children's Hospital, The Ohio State University College of Medicine, 700 Children's Dr, E4A Columbus, Columbus, OH 43205, USA; Department of Pediatrics, Section of Pediatric Cardiology, Texas Children's Hospital, Baylor College of Medicine, Houston, TX, USA. Electronic address:

Background And Objective: This study aims to determine the accuracy of patient specific 3D printed models in capturing pathological anatomical characteristics derived from CT angiography (CTA) in children with anomalous aortic origin of a coronary artery (AAOCA).

Methods & Materials: Following institutional regulatory approval, a standardized protocol for CTA of AAOCA was utilized for imaging. Blood volume of the aorta and coronaries were segmented from the DICOM images. A total of 10 models from 8 AAOCA patients were created, including 2 post-operative models. Mechanical properties of Agilus30 a flexible photopolymer coated with a thin layer of parylene, polyurethane (PU) and silicone and native aortic tissue from a postmortem specimen were compared. AAOCA models with wall thicknesses of 2mm aorta and 1.5mm coronaries were 3D printed in Agilus30 and coated with PU. CT of the printed models was performed, and 3D virtual models were generated. Transfer of anatomical characteristics and geometric accuracy were compared between the patient model virtual models.

Results: Dynamic modulus of Agilus30 at 2mm thickness was found to be close to native aortic tissue. Structured reporting of anatomical characteristics by imaging experts showed good concordance between patient and model CTA Comparative patient and virtual model measurements showed Pearson's correlation (r) of 0.9959 for aorta (n=70) and 0.9538 for coronaries (n=60) linear, and 0.9949 for aorta (n=30) and 0.9538 for coronaries (n=30) cross-sectional, dimensions. Surface contour map mean difference was 0.08 ± 0.29mm.

Conclusions: Geometrically accurate AAOCA models preserving morphological characteristics, essential for risk stratification and decision-making, can be 3D printed from a patient's CTA.
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http://dx.doi.org/10.1016/j.cmpb.2021.105947DOI Listing
April 2021

The Neural Representation of Force across Grasp Types in Motor Cortex of Humans with Tetraplegia.

eNeuro 2021 Jan-Feb;8(1). Epub 2021 Feb 19.

Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106

Intracortical brain-computer interfaces (iBCIs) have the potential to restore hand grasping and object interaction to individuals with tetraplegia. Optimal grasping and object interaction require simultaneous production of both force and grasp outputs. However, since overlapping neural populations are modulated by both parameters, grasp type could affect how well forces are decoded from motor cortex in a closed-loop force iBCI. Therefore, this work quantified the neural representation and offline decoding performance of discrete hand grasps and force levels in two human participants with tetraplegia. Participants attempted to produce three discrete forces (light, medium, hard) using up to five hand grasp configurations. A two-way Welch ANOVA was implemented on multiunit neural features to assess their modulation to and Demixed principal component analysis (dPCA) was used to assess for population-level tuning to force and grasp and to predict these parameters from neural activity. Three major findings emerged from this work: (1) force information was neurally represented and could be decoded across multiple hand grasps (and, in one participant, across attempted elbow extension as well); (2) grasp type affected force representation within multiunit neural features and offline force classification accuracy; and (3) grasp was classified more accurately and had greater population-level representation than force. These findings suggest that force and grasp have both independent and interacting representations within cortex, and that incorporating force control into real-time iBCI systems is feasible across multiple hand grasps if the decoder also accounts for grasp type.
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http://dx.doi.org/10.1523/ENEURO.0231-20.2020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7920535PMC
June 2021

Flow Dynamics in Anomalous Aortic Origin of a Coronary Artery in Children: Importance of the Intramural Segment.

Semin Thorac Cardiovasc Surg 2020 Nov 23. Epub 2020 Nov 23.

Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia.. Electronic address:

This study aims to assess the differences in pressure, fractional flow reserve (FFR) and coronary flow (with increasing pressure) of the proximal coronary artery in patients with anomalous aortic origin of a coronary artery with a confirmed ischemic event, without ischemic events, and before and after unroofing surgery, and compare to a patient with normal coronary arteries. Patient-specific flow models were 3D printed for 3 subjects with anomalous right coronary arteries with intramural course, 2 of them had documented ischemia, and compared with a patient with normal coronaries. The models were placed in the aortic position of a pulse duplicator and precise measurements to quantify FFR and coronary flow rate were performed from the aortic to the mediastinal segment of the anomalous right coronary artery. In an ischemic model, a gradual FFR drop (emulating that of pressure) was shown from the ostium location (∼1.0) to the distal intramural course (0.48). In nonischemic and normal patient models, FFR for all locations did not drop below 0.9. In a second ischemic model prior to repair, a drop to 0.44 was encountered at the intramural and mediastinal intersection, improving to 0.86 postrepair. There is a difference in instantaneous coronary flow rate with increasing aortic pressure in the ischemic models (slope 0.2846), compared to the postrepair and normal models (slope >0.53). These observations on patient models support a biomechanical basis for ischemia and potentially sudden cardiac death in aortic origin of a coronary artery, with a drop in pressure and FFR in the intramural segment, and a decrease in coronary flow rate with increasing aortic pressure, with both improving after corrective surgery.
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http://dx.doi.org/10.1053/j.semtcvs.2020.11.027DOI Listing
November 2020

Colon diverticulosis is not a risk factor for the detection of adenomatous polyps - results of a prospective study.

Z Gastroenterol 2021 Feb 4;59(2):135-142. Epub 2020 Nov 4.

Klinik für Innere Medizin II, Klinikum rechts der Isar der Technischen Universität München, Munich, Germany.

Background And Aims:  Colon diverticula (CD) and adenomatous polyps are frequently found during colonoscopy. Data from the literature contains inconsistent information about whether patients with CD have a higher risk for colon adenomas. A positive correlation might influence the current guidelines for screening colonoscopies. The aim of this study was to examine whether presence of CD is associated with endoscopic adenoma detection.

Materials And Methods:  This was a prospective study at 2 centers in Germany. Patients with an indication for colonoscopy were included. The number and localization of diverticula were recorded. Detected polyps were resected, and histopathological results were captured. Logistic regression models were fitted to the data to evaluate the association between CD and adenoma detection.

Results:  A total of 938 colonoscopies was included. CD occurred in 49.1 % of the colonoscopies. The polyp and adenoma detection rates (PDR, ADR) were 50.3 % and 32.3 %. In 37.5 % of the patients with diverticula, at least 1 adenoma was detected, whereas this was the case in 27.3 % in the absence of diverticula. The presence of diverticula was positively correlated with the detection of adenomas in univariate analysis (p = 0.001), but no significant association could be found in multivariable analysis (p = 0.775). Increasing age (p < 0.001), male sex (p = 0.005), and longer withdrawal time (p < 0.001) were significant predictors for adenoma detection in the multivariable analysis. Similar results were also observed for both the distal and the proximal colon.

Discussion:  Diverticula and adenomas are frequently found during colonoscopies. However, diverticula disease was not significantly associated with adenoma detection after adjustment for relevant prognostic factors. Older age, male sex, and duration of withdrawal time are predictors for the detection of adenomatous polyps.
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http://dx.doi.org/10.1055/a-1246-3295DOI Listing
February 2021

Validation of the Mobile Application Rating Scale (MARS).

PLoS One 2020 2;15(11):e0241480. Epub 2020 Nov 2.

Department of Clinical Psychology and Psychotherapy, Institute of Psychology and Education, University Ulm, Ulm, Germany.

Background: Mobile health apps (MHA) have the potential to improve health care. The commercial MHA market is rapidly growing, but the content and quality of available MHA are unknown. Instruments for the assessment of the quality and content of MHA are highly needed. The Mobile Application Rating Scale (MARS) is one of the most widely used tools to evaluate the quality of MHA. Only few validation studies investigated its metric quality. No study has evaluated the construct validity and concurrent validity.

Objective: This study evaluates the construct validity, concurrent validity, reliability, and objectivity, of the MARS.

Methods: Data was pooled from 15 international app quality reviews to evaluate the metric properties of the MARS. The MARS measures app quality across four dimensions: engagement, functionality, aesthetics and information quality. Construct validity was evaluated by assessing related competing confirmatory models by confirmatory factor analysis (CFA). Non-centrality (RMSEA), incremental (CFI, TLI) and residual (SRMR) fit indices were used to evaluate the goodness of fit. As a measure of concurrent validity, the correlations to another quality assessment tool (ENLIGHT) were investigated. Reliability was determined using Omega. Objectivity was assessed by intra-class correlation.

Results: In total, MARS ratings from 1,299 MHA covering 15 different health domains were included. Confirmatory factor analysis confirmed a bifactor model with a general factor and a factor for each dimension (RMSEA = 0.074, TLI = 0.922, CFI = 0.940, SRMR = 0.059). Reliability was good to excellent (Omega 0.79 to 0.93). Objectivity was high (ICC = 0.82). MARS correlated with ENLIGHT (ps<.05).

Conclusion: The metric evaluation of the MARS demonstrated its suitability for the quality assessment. As such, the MARS could be used to make the quality of MHA transparent to health care stakeholders and patients. Future studies could extend the present findings by investigating the re-test reliability and predictive validity of the MARS.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0241480PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7605637PMC
December 2020

Evaluation of an Objective Measurement Tool for Stress Level Reduction by Individually Chosen Music During Colonoscopy-Results From the Study "ColoRelaxTone".

Front Med (Lausanne) 2020 15;7:525. Epub 2020 Sep 15.

Klinik für Innere Medizin I, Universitätsklinik Ulm, Ulm, Germany.

Colonoscopy as standard procedure in endoscopy is often perceived as uncomfortable for patients. Patient's anxiety is therefore a significant issue, which often lead to avoidance of participation of relevant examinations as CRC-screening. Non-pharmacological anxiety management interventions such as music might contribute to relaxation in the phase prior and during endoscopy. Although music's anxiolytic effects have been reported previously, no objective measurement of stress level reduction has been reported yet. Focus of this study was to evaluate the objective measurement of the state of relaxation in patients undergoing colonoscopy. Prospective study ( = 196) performed at one endoscopic high-volume center. Standard colonoscopy was performed in control group. Interventional group received additionally self-chosen music over earphones. Facial Electromyography (fEMG) activity was obtained. Clinician Satisfaction with Sedation Instrument (CSSI) and Patients Satisfaction with Sedation Instrument (PSSI) was answered by colonoscopists and patients, respectively. Overall satisfaction with music accompanied colonoscopy was obtained if applicable. Mean difference measured by fEMG via musculus zygomaticus major indicated a significantly lower stress level in the music group [7.700(±5.560) μV vs. 4.820(±3.330) μV; = 0.001]. Clinician satisfaction was significantly higher with patients listening to music [82.69(±15.04) vs. 87.3(±15.02) pts.; = 0.001]. Patient's satisfaction was higher but did not differ significantly. We conclude that self-chosen music contributes objectively to a reduced stress level for patients and therefore subjectively perceived satisfaction for endoscopists. Therefore, music should be considered as a non-pharmacological treatment method of distress reduction especially in the beginning of endoscopic procedures.
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http://dx.doi.org/10.3389/fmed.2020.00525DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7522161PMC
September 2020

Extreme events for fractional Brownian motion with drift: Theory and numerical validation.

Phys Rev E 2020 Aug;102(2-1):022102

Laboratoire de Physique de l'Ecole Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité, 24 rue Lhomond, 75005 Paris, France.

We study the first-passage time, the distribution of the maximum, and the absorption probability of fractional Brownian motion of Hurst parameter H with both a linear and a nonlinear drift. The latter appears naturally when applying nonlinear variable transformations. Via a perturbative expansion in ɛ=H-1/2, we give the first-order corrections to the classical result for Brownian motion analytically. Using a recently introduced adaptive-bisection algorithm, which is much more efficient than the standard Davies-Harte algorithm, we test our predictions for the first-passage time on grids of effective sizes up to N_{eff}=2^{28}≈2.7×10^{8} points. The agreement between theory and simulations is excellent, and by far exceeds in precision what can be obtained by scaling alone.
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http://dx.doi.org/10.1103/PhysRevE.102.022102DOI Listing
August 2020

Risk of appendicitis after endoscopic full-thickness resection of lesions involving the appendiceal orifice: a retrospective analysis.

Endoscopy 2021 Apr 7;53(4):424-428. Epub 2020 Sep 7.

Klinikum Ludwigsburg, Klinik für Innere Medizin, Gastroenterologie, Hämato-Onkologie, Pneumologie, Diabetologie und Infektiologie, Ludwigsburg, Germany.

Background:  Conventional endoscopic resection of lesions affecting the appendiceal orifice is difficult. Endoscopic full-thickness resection (EFTR) is a novel technique in interventional endoscopy. As EFTR near the appendiceal orifice is associated with a subtotal appendectomy, it remains unclear whether the risk of developing appendicitis is increased. We conducted a retrospective analysis of lesions involving the appendiceal orifice treated by EFTR.

Methods:  This was a multicenter retrospective analysis of patients (n = 50) treated with EFTR for lesions involving the appendiceal orifice between 2014 and 2019. The objective was to evaluate the occurrence of appendicitis.

Results:  Acute appendicitis occurred in seven patients (14 %) during follow-up. Conservative treatment was sufficient in four cases, and three patients underwent appendectomy.

Conclusions:  EFTR of lesions involving the appendiceal orifice may be associated with an imminent risk of developing appendicitis and a consecutive need for appendectomy. Patients should be informed about this specific risk prior to resection. It is unclear why some patients develop appendicitis while the majority remains asymptomatic.
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http://dx.doi.org/10.1055/a-1227-4555DOI Listing
April 2021

Efficacy and Safety of Endoscopic Full-Thickness Resection in the Colorectum: Results From the German Colonic FTRD Registry.

Am J Gastroenterol 2020 12;115(12):1998-2006

Department of Medicine II, Medical Center, University of Freiburg, Freiburg, Germany.

Introduction: Endoscopic full-thickness resection (EFTR) is a powerful option for resection of colorectal lesions not amenable to conventional endoscopic resection. The full-thickness resection device (FTRD) allows clip-assisted EFTR with a single-step technique. We report on results of a large nationwide FTRD registry.

Methods: The "German colonic FTRD registry" was created to further assess efficacy and safety of the FTRD System after approval in Europe. Data were analyzed retrospectively.

Results: Sixty-five centers contributed 1,178 colorectal FTRD procedures. Indications for EFTR were difficult adenomas (67.1%), early carcinomas (18.4%), subepithelial tumors (6.8%), and diagnostic EFTR (1.3%). Mean lesion size was 15 × 15 mm and most lesions were pretreated endoscopically (54.1%). Technical success was 88.2% and R0 resection was achieved in 80.0%. R0 resection was significantly higher for subepithelial tumor compared with that for other lesions. No difference in R0 resection was found for smaller vs larger lesions or for colonic vs rectal procedures. Adverse events occurred in 12.1% (3.1% major events and 2.0% required surgical treatment). Endoscopic follow-up was available in 58.0% and showed residual/recurrent lesions in 13.5%, which could be managed endoscopically in most cases (77.2%).

Discussion: To date, this is the largest study of colorectal EFTR using the FTRD System. The study demonstrated favorable efficacy and safety for "difficult-to-resect" colorectal lesions and confirms results of previous studies in a large "real-world" setting. Further studies are needed to compare EFTR with other advanced resection techniques and evaluate long-term outcome.
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http://dx.doi.org/10.14309/ajg.0000000000000795DOI Listing
December 2020

Proposal for an integrated silicon-photonics terahertz gas detector using photoacoustics.

Opt Express 2020 Jul;28(15):22424-22442

A design and multiphysical model is presented for an on-chip gas sensor that transduces terahertz gas absorption through sound generation into a mechanical motion that can be read out externally. The signal is triply enhanced by designing a structure that functions simultaneously as an optical, an acoustical and a mechanical resonator. The structure is made in high-resistivity silicon and can be fabricated using CMOS and MEMS fabrication technologies. The sensor is a purely passive element, so an external THz source and read-out are required. The chip has a footprint of 3 mm. A detection limit of 234 ppb of methanol for a source power of 1 mW and an integration time of 1 ms is predicted.
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http://dx.doi.org/10.1364/OE.397272DOI Listing
July 2020

Sampling first-passage times of fractional Brownian motion using adaptive bisections.

Phys Rev E 2020 Apr;101(4-1):043312

Laboratoire de Physique de l'École Normale Supérieure, ENS, Université PSL, Centre National de la Recherche Scientifique, Sorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité, 24 rue Lhomond, 75005 Paris, France.

We present an algorithm to efficiently sample first-passage times for fractional Brownian motion. To increase the resolution, an initial coarse lattice is successively refined close to the target, by adding exactly sampled midpoints, where the probability that they reach the target is non-negligible. Compared to a path of N equally spaced points, the algorithm achieves the same numerical accuracy N_{eff}, while sampling only a small fraction of all points. Though this induces a statistical error, the latter is bounded for each bridge, allowing us to bound the total error rate by a number of our choice, say P_{error}^{tot}=10^{-6}. This leads to significant improvements in both memory and speed. For H=0.33 and N_{eff}=2^{32}, we need 5000 times less CPU time and 10000 times less memory than the classical Davies-Harte algorithm. The gain grows for H=0.25 and N_{eff}=2^{42} to 3×10^{5} for CPU and 10^{6} for memory. We estimate our algorithmic complexity as C^{ABSec}(N_{eff})=O[(lnN_{eff})^{3}], to be compared to Davies-Harte, which has complexity C^{DH}(N)=O(NlnN). Decreasing P_{error}^{tot} results in a small increase in complexity, proportional to ln(1/P_{error}^{tot}). Our current implementation is limited to the values of N_{eff} given above, due to a loss of floating-point precision. Our algorithm can be adapted to other extreme events and arbitrary Gaussian processes. It enables one to numerically validate theoretical predictions that were hitherto inaccessible.
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http://dx.doi.org/10.1103/PhysRevE.101.043312DOI Listing
April 2020

Smartphone Application to Reinforce Education Increases High-Quality Preparation for Colorectal Cancer Screening Colonoscopies in a Randomized Trial.

Clin Gastroenterol Hepatol 2021 02 30;19(2):331-338.e5. Epub 2020 Mar 30.

Medizinische Klinik und Poliklinik II, Universitätsklinikum Würzburg, Würzburg, Germany.

Background & Aims: Sufficient bowel preparation is crucial for successful screening and surveillance colonoscopy. However, rates of inadequate preparation are still high. We investigated the effects of reinforced patient education using a smartphone application software (APP) for colonoscopy preparation in participants in a CRC screening program.

Methods: We performed a prospective, endoscopist-blinded study of 500 patients undergoing split-dose bowel preparation for CRC screening or surveillance colonoscopies at multiple centers in Germany, from November 2017 through January 2019. Participants (n = 500) were given oral and written instructions during their initial appointment and then randomly assigned (1:1) to groups that received reinforced education starting 3 days before the colonoscopy (APP group) or no further education (controls). The primary outcome was quality of bowel preparation according to the Boston bowel preparation scale. Secondary outcomes included polyp and adenoma detection rates, compliance with low-fiber diet, split-dose laxative intake, perceived discomfort from the preparation procedure.

Results: The mean Boston bowel preparation scale score was significantly higher in the APP-group (7.6 ± 0.1) than in the control group (6.7 ± 0.1) (P < .0001). The percentage of patients with insufficient bowel preparation was significantly lower in the APP group (8%) than in the control group (17%) (P = .0023). The adenoma detection rate was significantly higher in the APP group (35% vs 27% in controls) (P = .0324). Use of the APP was accompanied by a lower level of non-compliance with correct laxative intake (P =.0080) and diet instructions (P = .0089). The APP group reported a lower level of discomfort during preparation (P < .0001).

Conclusions: In a randomized trial, reinforcing patient education with a smartphone application optimized bowel preparation in the 3 days before colonoscopy, increasing bowel cleanliness, adenoma detection, and compliance in patients undergoing CRC screening or surveillance. ClinicalTrials.gov no: NCT03290157.
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http://dx.doi.org/10.1016/j.cgh.2020.03.051DOI Listing
February 2021

Predictors of second-sided deep brain stimulation for Parkinson's disease.

J Neurosurg 2020 Feb 14:1-7. Epub 2020 Feb 14.

3Center for Neurological Restoration, and.

Objective: Parkinson's disease (PD) is a progressive neurological movement disorder that is commonly treated with deep brain stimulation (DBS) surgery in advanced stages. The purpose of this study was to investigate factors that affect time to placement of a second-sided DBS lead for PD when a unilateral lead is initially placed for asymmetrical presentation. The decision whether to initially perform unilateral or bilateral DBS is largely based on physician and/or patient preference.

Methods: This study was a retrospective cohort analysis of patients with PD undergoing initial unilateral DBS for asymmetrical disease between January 1999 and December 2017 at the authors' institution. Patients treated with DBS for essential tremor or other conditions were excluded. Variables collected included demographics at surgery, time since diagnosis, Unified Parkinson's Disease Rating Scale motor scores (UPDRS-III), patient-reported quality-of-life outcomes, side of operation, DBS target, intraoperative complications, and date of follow-up. Paired t-tests were used to assess mean changes in UPDRS-III. Cox proportional hazards analysis and the Kaplan-Meier method were used to determine factors associated with time to second lead insertion over 5 years.

Results: The final cohort included 105 patients who underwent initial unilateral DBS for asymmetrical PD; 59% of patients had a second-sided lead placed within 5 years with a median time of 34 months. Factors found to be significantly associated with early second-sided DBS included patient age 65 years or younger, globus pallidus internus (GPi) target, and greater off-medication reduction in UPDRS-III score following initial surgery. Older age was also found to be associated with a smaller preoperative UPDRS-III levodopa responsiveness score and with a smaller preoperative to postoperative medication-off UPDRS-III change.

Conclusions: Younger patients, those undergoing GPi-targeted unilateral DBS, and patients who responded better to the initial DBS were more likely to undergo early second-sided lead placement. Therefore, these patients, and patients who are more responsive to medication preoperatively (as a proxy for DBS responsiveness), may benefit from consideration of initial bilateral DBS.
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http://dx.doi.org/10.3171/2019.12.JNS19638DOI Listing
February 2020

Neural Representation of Observed, Imagined, and Attempted Grasping Force in Motor Cortex of Individuals with Chronic Tetraplegia.

Sci Rep 2020 01 29;10(1):1429. Epub 2020 Jan 29.

Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, 44016, USA.

Hybrid kinetic and kinematic intracortical brain-computer interfaces (iBCIs) have the potential to restore functional grasping and object interaction capabilities in individuals with tetraplegia. This requires an understanding of how kinetic information is represented in neural activity, and how this representation is affected by non-motor parameters such as volitional state (VoS), namely, whether one observes, imagines, or attempts an action. To this end, this work investigates how motor cortical neural activity changes when three human participants with tetraplegia observe, imagine, and attempt to produce three discrete hand grasping forces with the dominant hand. We show that force representation follows the same VoS-related trends as previously shown for directional arm movements; namely, that attempted force production recruits more neural activity compared to observed or imagined force production. Additionally, VoS-modulated neural activity to a greater extent than grasping force. Neural representation of forces was lower than expected, possibly due to compromised somatosensory pathways in individuals with tetraplegia, which have been shown to influence motor cortical activity. Nevertheless, attempted forces (but not always observed or imagined forces) could be decoded significantly above chance, thereby potentially providing relevant information towards the development of a hybrid kinetic and kinematic iBCI.
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http://dx.doi.org/10.1038/s41598-020-58097-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6989675PMC
January 2020

Optomechanical resonating probe for very high frequency sensing of atomic forces.

Nanoscale 2020 Feb 24;12(5):2939-2945. Epub 2020 Jan 24.

Matériaux et Phénomènes Quantiques, Université de Paris, CNRS UMR 7162, Paris, France.

Atomic force spectroscopy and microscopy are invaluable tools to characterize nanostructures and biological systems. State-of-the-art experiments use resonant driving of mechanical probes, whose frequency reaches MHz in the fastest commercial instruments where cantilevers are driven at nanometer amplitude. Stiffer probes oscillating at tens of picometers provide a better access to short-range interactions, yielding images of molecular bonds, but they are little amenable to high-speed operation. Next-generation investigations demand combining very high frequency (>100 MHz) with deep sub-nanometer oscillation amplitude, in order to access faster (below microsecond) phenomena with molecular resolution. Here we introduce a resonating optomechanical atomic force probe operated fully optically at a frequency of 117 MHz, two decades above cantilevers, with a Brownian motion amplitude four orders below. Based on Silicon-On-Insulator technology, the very high frequency probe demonstrates single-pixel sensing of contact and non-contact interactions with sub-picometer amplitude, breaking open current limitations for faster and finer force spectroscopy.
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http://dx.doi.org/10.1039/c9nr09690fDOI Listing
February 2020

The "Twist-Needle" - a new concept for endoscopic ultrasound-guided fine needle-biopsy.

Endosc Int Open 2019 Dec 25;7(12):E1658-E1662. Epub 2019 Nov 25.

Interventional and Experimental Endoscopy (InExEn), Internal Medicine II, University Hospital Wuerzburg, Wuerzburg, Germany.

 Endoscopic ultrasound-guided fine-needle biopsy (EUS-FNB) represents a standard method for tissue acquisition of lesions adjacent to the gastrointestinal wall. Needles of 19 gauge acquire more tissue than needles with a smaller diameter, but are often unable to penetrate solid, rigid masses. In this study we evaluated a novel prototype that links forward movement of the needle to rotation of the needle tip. Two needle-models that generate either a regular axial movement or a combination of axial movement with rotation of the needle tip were compared ex vivo for measurement of pressure needed to penetrate artificial tissue. Furthermore, a standard 19-gauge EUS-FNB needle was compared to a modified model ("Twist Needle") in an ex vivo model to measure the amount of tissue obtained.  Pressure measurements using the rotating needle revealed that significantly less pressure is needed for penetration compared to the regular axial movement (mean ± SEM; 3.7 ± 0.3 N vs. 5.5 ± 0.3 N). Using the modified 19-gauge "Twist Needle" did not diminish tissue acquisition measured by surface amount compared to a standard needle (37 ± 5 mm² vs. 35 ± 6 mm²). The method of rotation of an EUS-FNB needle tip upon forward movement requires less pressure for penetration but does not diminish tissue acquisition. Hence, the concept of our "Twist Needle" may potentially reduce some of the current limitations of standard EUS-FNB.
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http://dx.doi.org/10.1055/a-0998-3997DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6877432PMC
December 2019

Volume explored by a branching random walk on general graphs.

Sci Rep 2019 10 30;9(1):15590. Epub 2019 Oct 30.

Department of Mathematics, Imperial College London, London, SW7 2AZ, UK.

Branching processes are used to model diverse social and physical scenarios, from extinction of family names to nuclear fission. However, for a better description of natural phenomena, such as viral epidemics in cellular tissues, animal populations and social networks, a spatial embedding-the branching random walk (BRW)-is required. Despite its wide range of applications, the properties of the volume explored by the BRW so far remained elusive, with exact results limited to one dimension. Here we present analytical results, supported by numerical simulations, on the scaling of the volume explored by a BRW in the critical regime, the onset of epidemics, in general environments. Our results characterise the spreading dynamics on regular lattices and general graphs, such as fractals, random trees and scale-free networks, revealing the direct relation between the graphs' dimensionality and the rate of propagation of the viral process. Furthermore, we use the BRW to determine the spectral properties of real social and metabolic networks, where we observe that a lack of information of the network structure can lead to differences in the observed behaviour of the spreading process. Our results provide observables of broad interest for the characterisation of real world lattices, tissues, and networks.
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http://dx.doi.org/10.1038/s41598-019-51225-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6821755PMC
October 2019

The BougieCap - a new method for endoscopic treatment of complex benign esophageal stenosis: results from a multicenter study.

Endoscopy 2019 09 23;51(9):866-870. Epub 2019 Jul 23.

InExEn, Klinik für Innere Medizin I, Universitätsklinikum Ulm, Ulm, Germany.

Background: A major limitation of current treatment strategies for nonmalignant upper gastrointestinal stenoses is the lack of either optical or haptic feedback during dilation. Wire guidance and fluoroscopy is often necessary to control the position.

Methods: A novel device for endoscopic dilation, the BougieCap (Ovesco Endoscopy AG, Tübingen, Germany) was evaluated in a prospective multicenter trial. Primary outcome was successful dilation of stenosis and secondary outcome was alteration in dysphagia symptoms in short-term follow-up.  RESULTS:  50 patients with benign esophageal strictures were included. Endoscopic bougienage was successful in 96 %. Bougienage failed in two cases because of high resistance. Symptoms of dysphagia decreased significantly after bougienage (59.0 points at Day 0 vs. 28.6 points at Day 14;  < 0.001). Adverse events were loss of BougieCap into the stomach in two cases; no severe adverse events were reported.

Conclusions: Endoscopic treatment of benign stenoses using the BougieCap enabled direct visual control of the bougienage procedure. This might help to adapt treatment more precisely to the stricture. Symptoms of dysphagia were improved in short-term follow-up. Additional wire guidance may be used for selected cases (e. g. narrow lumen, pediatric scope).
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http://dx.doi.org/10.1055/a-0959-1535DOI Listing
September 2019

Mast Cell/Proteinase Activated Receptor 2 (PAR2) Mediated Interactions in the Pathogenesis of Discogenic Back Pain.

Front Cell Neurosci 2019 5;13:294. Epub 2019 Jul 5.

College of Engineering, The Ohio State University, Columbus, OH, United States.

Mast cells (MCs) are present in the painful degenerate human intervertebral disc (IVD) and are associated with disease pathogenesis. MCs release granules containing enzymatic and inflammatory factors in response to stimulants or allergens. The serine protease, tryptase, is unique to MCs and its activation of the G-protein coupled receptor, Protease Activated Receptor 2 (PAR2), induces inflammation and degradation in osteoarthritic cartilage. Our previously published work has demonstrated increased levels of MC marker tryptase in IVD samples from discogenic back pain patients compared to healthy control IVD samples including expression of chemotactic agents that may facilitate MC migration into the IVD. To further elucidate MCs' role in the IVD and mechanisms underlying its effects, we investigated whether (1) human IVD cells can promote MC migration, (2) MC tryptase can mediate up-regulation of inflammatory/catabolic process in human IVD cells and tissue, and (3) the potential of PAR2 antagonist to function as a therapeutic drug in human and bovine pilot models of disease. MC migration was quantitatively assessed using conditioned media from primary human IVD cells and MC migration examined through Matrigel. Exposure to soluble IVD factors significantly enhanced MC migration, suggesting IVD cells can recruit MCs. We also demonstrated significant upregulation of MC chemokine SCF and angiogenic factor VEGFA gene expression in human IVD cells in response to recombinant human tryptase, suggesting tryptase can enhance recruitment of MCs and promotion of angiogenesis into the usually avascular IVD. Furthermore, tryptase can degrade proteoglycans in IVD tissue as demonstrated by significant increases in glycosaminoglycans released into surrounding media. This can create a catabolic microenvironment compromising structural integrity and facilitating vascular migration usually inhibited by the anti-angiogenic IVD matrix. Finally, as a "proof of concept" study, we examined the therapeutic potential of PAR2 antagonist (PAR2A) on human IVD cells and bovine organ culture IVD model. While preliminary data shows promise and points toward structural restoration of the bovine IVD including down-regulation of VEGFA, effects of PAR2 antagonist on human IVD cells differ between gender and donors suggesting that further validation is required with larger cohorts of human specimens.
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http://dx.doi.org/10.3389/fncel.2019.00294DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6625229PMC
July 2019

Tremor in chronic inflammatory demyelinating polyneuropathy: Proof of unifying network model for dystonia.

Prog Brain Res 2019 2;249:285-294. Epub 2019 May 2.

Department of Neurology, University Hospitals Cleveland Medical Center and Case Western Reserve University, Cleveland, OH, United States; Daroff-DellOsso Ocular Motility Laboratory and Neurology Service, Louis Stokes Cleveland VA Medical Center, Cleveland, OH, United States; National VA PD Consortium Center, Louis Stokes Cleveland VA Medical Center, Cleveland, OH, United States. Electronic address:

Traditional hypotheses for the pathogenesis of dystonia, the third most common movement disorder, have focused primarily on the basal ganglia. Contemporary theories have emphasized the role of the cerebellum. The modulation of peripheral proprioception also affects dystonia. We proposed a unifying network model for dystonia where the cerebellum, basal ganglia, and peripheral proprioception are connected in a circuit that forms the neural integrator network, ensuring steady position. We suggested that impairment anywhere along this circuit leads to common phenomenology-slow drifts followed by corrective movements, resembling dystonic tremor. We tested this concept in a patient with chronic inflammatory demyelinating polyneuropathy with resulting abnormal proprioception. Quantitative assessment of tremor in this patient revealed drifts in limb position followed by corrective movements and superimposed sinusoidal oscillations-consistent with neural integrator dysfunction. This unique case of chronic inflammatory demyelinating polyneuropathy describes the role of proprioception on the unifying network model for dystonia.
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http://dx.doi.org/10.1016/bs.pbr.2019.03.032DOI Listing
May 2020

Nonviral Transfection With Brachyury Reprograms Human Intervertebral Disc Cells to a Pro-Anabolic Anti-Catabolic/Inflammatory Phenotype: A Proof of Concept Study.

J Orthop Res 2019 11 29;37(11):2389-2400. Epub 2019 Jul 29.

Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio.

Intervertebral disc (IVD) degeneration is a major contributor to chronic low back pain and is characterized by decreases in cellularity and proteoglycan synthesis, upregulation of matrix degradation, and increases in pro-inflammatory factors with neurovascular invasion. Current treatments fail to target the underlying pathology or promote tissue repair and approaches such as viral transfection raise safety concerns due to mutagenesis and unwarranted immune responses. To avoid such concerns, nonviral transfection is a viable method of gene delivery into the host cell while bypassing the caveats of viral delivery. Brachyury is expressed in the developing notochord and is associated with an immature healthy nucleus pulposus (NP). We hypothesize that Brachyury can reprogram degenerate NP cells to a healthy pro-anabolic phenotype with increased proteoglycan content and decreased expression of catabolic, inflammatory, and neurovascular markers. NP cells obtained from human autopsy and surgical tissues were transfected with plasmids encoding for Brachyury or an empty vector control via bulk electroporation. Post transfection, cells were seeded in three-dimensional agarose constructs cultured over 4 weeks and analyzed for viability, gene expression, and proteoglycan. Results demonstrated successful transfection of both autopsy and surgical NP cells. We observed long-term Brachyury expression, significant increased expression of NP phenotypic markers FOXF1, KRT19, and chondrogenic marker SOX9 with decreases in inflammatory cytokines IL1-β/IL6, NGF, and MMPs and significant increases in glycosaminoglycan accumulation. These results highlight nonviral transfection with developmental transcription factors, such as Brachyury, as a promising method to reprogram degenerate human disc cells toward a healthy NP phenotype. Clinical significance: This project proposes a novel translational approach for the treatment of intervertebral disc degeneration via direct reprogramming of diseased human patient-derived IVD cells to a healthy phenotype. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2389-2400, 2019.
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http://dx.doi.org/10.1002/jor.24408DOI Listing
November 2019

Principled BCI Decoder Design and Parameter Selection Using a Feedback Control Model.

Sci Rep 2019 06 20;9(1):8881. Epub 2019 Jun 20.

Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA.

Decoders optimized offline to reconstruct intended movements from neural recordings sometimes fail to achieve optimal performance online when they are used in closed-loop as part of an intracortical brain-computer interface (iBCI). This is because typical decoder calibration routines do not model the emergent interactions between the decoder, the user, and the task parameters (e.g. target size). Here, we investigated the feasibility of simulating online performance to better guide decoder parameter selection and design. Three participants in the BrainGate2 pilot clinical trial controlled a computer cursor using a linear velocity decoder under different gain (speed scaling) and temporal smoothing parameters and acquired targets with different radii and distances. We show that a user-specific iBCI feedback control model can predict how performance changes under these different decoder and task parameters in held-out data. We also used the model to optimize a nonlinear speed scaling function for the decoder. When used online with two participants, it increased the dynamic range of decoded speeds and decreased the time taken to acquire targets (compared to an optimized standard decoder). These results suggest that it is feasible to simulate iBCI performance accurately enough to be useful for quantitative decoder optimization and design.
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http://dx.doi.org/10.1038/s41598-019-44166-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6586941PMC
June 2019

Endoscopic full-thickness resection of gastric subepithelial tumors with the gFTRD-system: a prospective pilot study (RESET trial).

Surg Endosc 2020 02 11;34(2):853-860. Epub 2019 Jun 11.

Department of Gastroenterology, Klinikum Ludwigsburg, Posilipostraße 4, 71640, Ludwigsburg, Germany.

Background: Gastric subepithelial tumors (SET) are rare and usually benign. However, up to 13% are malignant. Histology after conventional biopsy often is inconclusive. Surveillance endoscopies are the consequence in the majority of gastric SET cases. For SET arising from deeper layers endoscopic resection (ER) with the standard techniques is difficult and associated with the risk of perforation. The RESET trial further evaluates feasibility, efficacy and safety of clip-assisted endoscopic full-thickness resection (EFTR) for gastric SET using the novel gastric full-thickness-resection device (gFTRD).

Materials And Methods: The RESET trial was initiated in March 2017 (NCT03096236) and designed as prospective observational multicenter pilot trial. Gastric SET up to 15 mm were included. Primary endpoint was technical success (complete enbloc resection). Secondary endpoints were R0 resection, full-thickness resection, adverse events and recurrency at 3-months follow-up. For resection we used the gFTRD (Ovesco Endoscopy, Tübingen, Germany).

Results: 29 patients underwent gastric EFTR. Histology prior EFTR after conventional biopsy could define histological tumor type in only 31.2%. Primary endpoint was reached in 89.7%. Histology of the full-thickness-resection specimen could define histological tumor type in 100%. 76% of all SET could be resected histologically complete (R0) and a full-thickness-resection specimen could be obtained in 65.5%. In 31% periprocedural minor bleeding was observed and managed endoscopically. Follow-up was available in 79.3% (OTSC detachment in 78.3%, OTSC in position in 21.7%). No signs of residual or recurrent tumors were observed after 3 months.

Conclusion: EFTR of gastric SET with gFTRD is feasible and safe. EFTR allows a definite histological diagnosis (including sufficient risk stratification in case of GIST or NET) in contrast to conventional biopsy. R0-resection is possible in most cases and might obviate the need for further surveillance endoscopies for selected patients.
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http://dx.doi.org/10.1007/s00464-019-06839-2DOI Listing
February 2020

Improved endoscopic resection of large flat lesions and early cancers using an external additional working channel (AWC): a case series.

Endosc Int Open 2019 Feb 8;7(2):E298-E301. Epub 2019 Feb 8.

Clinic for Internal Medicine I, Department of Gastroenterology, InExEn, University Hospital Ulm, Ulm, Germany.

En-bloc resection of large, flat lesions or early stages of cancer is challenging. No bimanual tasks are possible using standard endoscopes. Dual-channel endoscopes are not available everywhere and have a small distance between the channels. A new external additional working channel (AWC) (Ovesco, Tuebingen, Germany) was designed and developed potentially enabling bimanual tasks. Fixed to the tip of a standard gastroscope or pediatric colonoscope, a second endoscopic tool can be inserted through the AWC and used for tissue retraction during endoscopic resection. In the upper and lower gastrointestinal tract, endoscopic mucosal resection (EMR) with a modified grasp-and-snare technique and endoscopic submucosal dissection (ESD) were performed successfully using the AWC in eight patients. Complications were acute arterial bleeding post-EMR in two cases treated by endoscopic clipping. We conclude that a newly developed external additional working channel (AWC) enables endoscopic resection of large lesions in the upper and lower gastrointestinal tract. Potential benefits are its suitability for EMR and ESD, no need for a dual-channel endoscope and an adjustable distance of working channels.
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http://dx.doi.org/10.1055/a-0824-6912DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6368484PMC
February 2019

Thirty-eight-negative kinase 1 mediates trauma-induced intestinal injury and multi-organ failure.

J Clin Invest 2018 11 15;128(11):5056-5072. Epub 2018 Oct 15.

Institute of Anesthesiological Pathophysiology and Process Engineering, Ulm University, Ulm, Germany.

Dysregulated intestinal epithelial apoptosis initiates gut injury, alters the intestinal barrier, and can facilitate bacterial translocation leading to a systemic inflammatory response syndrome (SIRS) and/or multi-organ dysfunction syndrome (MODS). A variety of gastrointestinal disorders, including inflammatory bowel disease, have been linked to intestinal apoptosis. Similarly, intestinal hyperpermeability and gut failure occur in critically ill patients, putting the gut at the center of SIRS pathology. Regulation of apoptosis and immune-modulatory functions have been ascribed to Thirty-eight-negative kinase 1 (TNK1), whose activity is regulated merely by expression. We investigated the effect of TNK1 on intestinal integrity and its role in MODS. TNK1 expression induced crypt-specific apoptosis, leading to bacterial translocation, subsequent septic shock, and early death. Mechanistically, TNK1 expression in vivo resulted in STAT3 phosphorylation, nuclear translocation of p65, and release of IL-6 and TNF-α. A TNF-α neutralizing antibody partially blocked development of intestinal damage. Conversely, gut-specific deletion of TNK1 protected the intestinal mucosa from experimental colitis and prevented cytokine release in the gut. Finally, TNK1 was found to be deregulated in the gut in murine and porcine trauma models and human inflammatory bowel disease. Thus, TNK1 might be a target during MODS to prevent damage in several organs, notably the gut.
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http://dx.doi.org/10.1172/JCI97912DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6205400PMC
November 2018

Virtual reality in GI endoscopy: intuitive zoom for improving diagnostics and training.

Gut 2019 06 18;68(6):957-959. Epub 2018 Sep 18.

Interventional and Experimental Endoscopy (InExEn), Department of Internal Medicine I, Ulm University, Ulm, Germany.

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http://dx.doi.org/10.1136/gutjnl-2018-317058DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6580767PMC
June 2019

Improving the quality and acceptance of colonoscopy preparation by reinforced patient education with short message service: results from a randomized, multicenter study (PERICLES-II).

Gastrointest Endosc 2019 03 21;89(3):506-513.e4. Epub 2018 Aug 21.

Medizinische Klinik II, RoMed Klinikum Rosenheim, Rosenheim, Germany.

Background And Aims: Sufficient bowel preparation is crucial for successful screening and surveillance colonoscopy. However, the rates of inadequate preparation are still high. We investigated the effects of reinforcing patient education and guidance by using the short message service (SMS).

Methods: In this prospective, endoscopist-blinded, multicenter study, standard instructions pertaining to split-dose preparation were provided in a verbal and written format to all patients during the initial appointment. Patients were randomly assigned (1:1) to a group that received reinforced education starting 4 days before the colonoscopy (SMS group) or to the control group which did not receive further education. The primary outcome was the percentage of insufficient preparation results (Boston Bowel Preparation Scale [BBPS] score <6). The secondary outcomes included quality of bowel preparation according to the BBPS, polyp and adenoma detection rates, and patients' perceived discomfort in the preparation procedure.

Results: The percentage of patients with insufficient bowel preparation was significantly lower in the SMS group (9%) than in the control group (19%) (P = .0013). The mean BBPS score was significantly higher in the SMS group (7.4 ± 0.1) than in the control group (6.5 ± 0.1) (P < .0001). Each colon segment had significantly higher BBPS scores in the SMS group. The adenoma detection rate and number of detected adenomas in the right segment of the colon were higher in the SMS group. SMS messages were accompanied by a lower level of discomfort during preparation (numeric rating scale) (5.2 SMS vs 5.8 controls) (P = .0042).

Conclusions: Reinforced patient education by using SMS messages during the 4 days before colonoscopy increased bowel cleanliness, adenoma detection in the right segment of the colon, and reduced discomfort. (Clinical trial registration number: NCT02272036.).
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http://dx.doi.org/10.1016/j.gie.2018.08.014DOI Listing
March 2019

A Comparison of Intention Estimation Methods for Decoder Calibration in Intracortical Brain-Computer Interfaces.

IEEE Trans Biomed Eng 2018 09 14;65(9):2066-2078. Epub 2017 Dec 14.

Objective: Recent reports indicate that making better assumptions about the user's intended movement can improve the accuracy of decoder calibration for intracortical brain-computer interfaces. Several methods now exist for estimating user intent, including an optimal feedback control model, a piecewise-linear feedback control model, ReFIT, and other heuristics. Which of these methods yields the best decoding performance?

Methods: Using data from the BrainGate2 pilot clinical trial, we measured how a steady-state velocity Kalman filter decoder was affected by the choice of intention estimation method. We examined three separate components of the Kalman filter: dimensionality reduction, temporal smoothing, and output gain (speed scaling).

Results: The decoder's dimensionality reduction properties were largely unaffected by the intention estimation method. Decoded velocity vectors differed by <5% in terms of angular error and speed vs. target distance curves across methods. In contrast, the smoothing and gain properties of the decoder were greatly affected (> 50% difference in average values). Since the optimal gain and smoothing properties are task-specific (e.g. lower gains are better for smaller targets but worse for larger targets), no one method was better for all tasks.

Conclusion: Our results show that, when gain and smoothing differences are accounted for, current intention estimation methods yield nearly equivalent decoders and that simple models of user intent, such as a position error vector (target position minus cursor position), perform comparably to more elaborate models. Our results also highlight that simple differences in gain and smoothing properties have a large effect on online performance and can confound decoder comparisons.
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http://dx.doi.org/10.1109/TBME.2017.2783358DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6043406PMC
September 2018