Kai Matthes

Rensselaer Polytechnic Institute, Troy, NY, United States

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Publications (62)175.49 Total impact

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    ABSTRACT: Peroral endoscopic pyloromyotomy is a novel technique that has recently been described in the literature. There is little data to guide the length of myotomy created. The aim of study was to evaluate the proper incision length of the muscular layer during peroral endoscopic pyloromyotomy using a submucosal tunnel technique. The study was designed as a prospective ex vivo study. Fresh ex vivo porcine stomachs from animals weighing 80-100 kg and porcine stomachs from animals weighing 15-25 kg were used for pyloromyotomy. Four different myotomy lengths (1, 2, 3, and 4) were compared in the large animal series and three different myotomy lengths (1, 2, and 3) were compared in the small series. A total of 23 cases of the submucosal tunnel technique were performed by two endoscopists using 12 large stomachs and 11 small stomachs. The mean overall procedure time (±SD) of pyloromyotomy was 65.7 (±14.3) min. In the large stomach series, the mean pyloric diameter (±SD) and change from baseline (as percentage) following a 1, 2, 3, and 4 pyloromyotomy were 13.3 ± 9.5 mm (7.1 %), 20.7 ± 11.7 mm (10.6 %), 31.1 ± 15.0 mm (15.2 %), and 33.0 ± 15.0 mm (16.0 %), respectively. In the small stomach series, the changes of mean pyloric diameter following a 1, 2, and 3 cm pyloromyotomy were 12.2 ± 5.6 mm (7.5 %), 23.1 ± 7.6 mm (13.1 %), and 28.0 ± 10.4 mm (15.5 %), respectively. A 3 cm pyloromyotomy for a large animal series and 2 cm for the small animal series appeared to be most appropriate for enlargement of the pylorus.
    Surgical Endoscopy 11/2014; · 3.31 Impact Factor
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    ABSTRACT: We have developed an instrumented endoscope grip handle equipped with a 6-axis load cell and measured forces and torques during a simulated transgastric NOTES appendectomy procedure performed in an EASIE-R© ex vivo simulator. The data were collected from 10 participating surgeons of varying degrees of expertise which was analyzed to compute a set of 6 force and torque parameters for each coordinate axis for each of the nine tasks of the appendectomy procedure. The mean push/pull force was found to be 3.64 N (σ=3.54 N) in the push direction and the mean torque was 3.3 N-mm (σ=38.6 N-mm) in the counter-clockwise direction about the push/pull axis. Most interestingly, the force and torque data about the non-dominant x and z axes showed a statistically significant difference (p<0.05) between the expert and novice groups for five of the nine tasks. This data may be useful in developing surgical platforms especially new haptic devices and simulation systems for emerging natural orifice procedures.
    IEEE transactions on bio-medical engineering 11/2014; · 2.15 Impact Factor
  • Gastrointestinal Endoscopy 05/2014; 79(5):AB270-AB271. · 4.90 Impact Factor
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  • Haptics Symposium (HAPTICS), 2014 IEEE. 01/2014;
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    ABSTRACT: Natural Orifice Translumenal Endoscopic Surgery is an emerging procedure that requires training and adoption to be successful. Currently no objective performance metrics exist for evaluating skills for NOTES. In this work, we have improved upon our previous study on objective performance metrics using kinematic measures by introducing two new measures, the flex and the roll and recruiting more subjects to increase the statistical power. The measures were evaluated in a transgastric NOTES appendectomy procedure performed with ex-vivo organs using the EASIE-R<sup>TM</sup> trainer box. Four motion tracking sensors attached to an endoscope were used to measure the scope position and orientation to compute the kinematic measures. Results from our study showed that completion time, economy of motion, jerk and roll of the scope are valid kinematic measures to differentiate between expert and novice NOTES surgeons.
    Studies in health technology and informatics 01/2014; 196:339-45.
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    ABSTRACT: To evaluate the efficacy of circumferential endoscopic mucosal resection (EMR) with a tissue-anchoring device in comparison to forceps precut EMR and conventional endoscopic submucosal dissection (ESD). The study was designed as a prospective, randomized, ex vivo study. Fresh ex vivo specimens were harvested from adult white Yorkshire pigs weighing 30-50 kg. Seventy-five standardized, artificial lesions measuring 3 cm × 3 cm were created by methylene blue tattoo at the greater curvature in fresh ex vivo stomachs using the EASIE-R simulator platform (Endosim LLC, Berlin, MA, United States). The three advanced endoscopists performed the three resection techniques such as circumferential EMR using the tissue-anchoring device (TA-EMR), forceps precut EMR (FP-EMR), and endoscopic submucosal dissection. The endoscopists and the type of cutting methods were determined randomly by grouped randomized selection. The resection bed was grossly inspected to determine whether the lesion was resected "en-bloc" (defined as no remaining mucosal tattoo remaining on specimen). The resection bed was also probed for evidence of perforation. The procedural time of circumferential resection, submucosal dissection, and injection frequency were recorded by an independent observer. All 75 created lesions were successfully resected by three advanced endoscopists using the three techniques. The mean ± SD size of resected specimens (long axis) were 39.5 ± 5.6 mm, 36.5 ± 7.3 mm, and 44.6 ± 5.6 mm for TA-EMR, FP-EMR, and ESD respectively. The overall mean dissection time of both the TA-EMR and FP-EMR was significant shorter than ESD (TA-EMR: 5.1 ± 3.3 min, FP-EMR: 3.5 ± 2.0 min vs ESD: 15.8 ± 9.5 min, P < 0.001, P < 0.001). The overall mean total procedure time of both the tissue-anchoring and forceps circumferential EMR was significantly shorter than ESD (TA-EMR: 17.5 ± 6.0 min, FP-EMR: 16.6 ± 6.6 min vs ESD: 28.6 ± 13.9 min, P < 0.001, P < 0.001). The en-bloc resection rate of ESD was 100% (25/25) and the en-bloc resection rate of the TA-EMR (84.0%, 21/25) was higher than for the FP-EMR (60.0%, 15/25), yet not statistically significant (P = 0.18). The perforation rate of each technique was 8.0% (2/25). TA-EMR appears to be quicker than ESD, and there was a trend towards improved en bloc resection rate with the TA-EMR when compared to the FP-EMR.
    World journal of gastrointestinal endoscopy. 06/2013; 5(6):275-80.
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    ABSTRACT: BACKGROUND: A prototype endoscope was designed to improve visualization and dissection of tissue with the use of 2 working channels with different deflections. OBJECTIVE: To evaluate the efficacy and operability of a prototype endoscope in comparison with a conventional double-channel endoscope for rectal endoscopic submucosal dissection (ESD). DESIGN: Randomized, prospective, controlled, ex vivo study. SETTING: Academic medical center. METHODS: A total of 80 standardized artificial lesions measuring 3 × 3 cm were created approximately 5 cm from the anal verge in fresh ex vivo porcine colorectal specimens. Two endoscopists each completed 20 cases with the prototype endoscope and 20 cases with the conventional endoscope. MAIN OUTCOME MEASUREMENTS: An independent observer recorded procedure time, specimen size, en bloc resection, and perforation rate. RESULTS: For the ESD novice, the mean submucosal dissection time (10.5 ± 3.8 vs 14.9 ± 7.3 minutes; P = .024) and total procedure time (18.1 ± 5.2 vs 23.6 ± 8.2 minutes; P = .015) were significantly shorter in the prototype group in comparison with the conventional group. For the ESD expert, there was no significant difference between the mean circumferential resection, submucosal dissection, and total procedure time (prototype group 14.2 ± 6.0 minutes, conventional group 14.2 ± 8.8 minutes; P = .992). The overall perforation and en bloc resection rates were not significantly different between groups. LIMITATIONS: Ex vivo study. CONCLUSION: In this ex vivo prospective comparison study, there was a technical advantage for the ESD novice with the prototype endoscope that resulted in a shorter procedure time, which was not observed for cases performed by the ESD expert.
    Gastrointestinal endoscopy 06/2013; · 4.90 Impact Factor
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    ABSTRACT: Natural orifice translumenal endoscopic surgery is an emerging procedure. High fidelity virtual reality-based simulators allow development of new surgical procedures and tools and train medical personnel without risk to human patients. As part of a project funded by the National Institutes of Health, we are developing a Virtual Transluminal Endoscopic Surgery Trainer (VTEST<sup>TM</sup>) for this purpose. In this work, objective performance measures derived from motion tracking sensors attached to an endoscope was tested for the transgastric NOTES appendectomy procedure performed with ex-vivo pig organs using the EASIE-R<sup>TM</sup> trainer box. Results from our study shows that both completion time and economy of motion parameters were able to differentiate between expert and novice NOTES surgeons with p value of 0.039 and 0.02 respectively. Jerk computed on sensor 2 data also showed significant results (p = 0.02). We plan to incorporate these objective performance measures in VTEST<sup>TM</sup>.
    Studies in health technology and informatics 01/2013; 184:78-84.
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    ABSTRACT: INTRODUCTION AND STUDY AIM: Natural orifice translumenal endoscopic surgery (NOTES) is an emerging surgical technique that requires a cautious adoption approach to ensure patient safety. High-fidelity virtual-reality-based simulators allow development of new surgical procedures and tools and train medical personnel without risk to human patients. As part of a project funded by the National Institutes of Health, we are developing the virtual transluminal endoscopic surgery trainer (VTEST™) for this purpose. The objective of this study is to conduct a structured needs analysis to identify the design parameters for such a virtual-reality-based simulator for NOTES. METHODS: A 30-point questionnaire was distributed at the 2011 National Orifice Surgery Consortium for Assessment and Research meeting to obtain responses from experts. Ordinal logistic regression and the Wilcoxon rank-sum test were used for analysis. RESULTS: A total of 22 NOTES experts participated in the study. Cholecystectomy (CE, 68 %) followed by appendectomy (AE, 63 %) (CE vs AE, p = 0.0521) was selected as the first choice for simulation. Flexible (FL, 47 %) and hybrid (HY, 47 %) approaches were equally favorable compared with rigid (RI, 6 %) with p < 0.001 for both FL versus RI and HY versus RI. The transvaginal approach was preferred 3 to 1 to the transgastric. Most participants preferred two-channel (2C) scopes (65 %) compared with single (1C) or three (3C) or more channels with p < 0.001 for both 2C versus 1C and 2C versus 3C. The importance of force feedback and the utility of a virtual NOTES simulator in training and testing new tools for NOTES were rated very high by the participants. CONCLUSION: Our study reinforces the importance of developing a virtual NOTES simulator and clearly presents expert preferences. The results of this analysis will direct our initial development of the VTEST™ platform.
    Surgical Endoscopy 12/2012; 27(5). · 3.31 Impact Factor
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    ABSTRACT: INTRODUCTION: Endoscopic submucosal dissection (ESD) has become a standard therapy for early gastric neoplasia, particularly in Asian countries. From a safety and efficacy standpoint, simulation training may empower the endoscopist to be able to learn the basic tenets of ESD in a safe, controlled and supervised setting before attempting first in humans. METHODS AND PROCEDURES : This study was designed as a prospective ex vivo study. Ex vivo porcine organs were utilized in the EASIE-R endoscopic simulator. A total of 150 artificial lesions, each 2 × 2 cm in size, were created in fresh ex vivo porcine stomachs at six different anatomical sites (fundus anterior and posterior, body anterior and posterior, antrum anterior and posterior). Three examiners (2 beginners, 1 expert) participated in this study. All parameters (procedure time, specimen size, en-bloc resection status, perforation) were recorded by an independent observer for each procedure. RESULTS: All 150 lesions were successfully resected using the ESD technique by the three endoscopists. After 30 ESD cases, the two novices performed ESD with a 100 % en-bloc resection rate and without perforation. For the procedures performed by the novices, the total procedure time and perforation rate in the last 30 cases were significantly lower than during the first 30 cases (p < 0.05). CONCLUSIONS: Our study suggests that performing 30 ESD resections in an ex vivo simulator leads to a significant improvement in safety and efficiency of performing the ESD technique.
    Surgical Endoscopy 07/2012; 27(1). · 3.31 Impact Factor
  • Gastrointestinal Endoscopy 04/2012; 75(4):AB106. · 4.90 Impact Factor
  • Natural Orifice Translumenal Endoscopic Surgery (NOTES). 01/2012;
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    ABSTRACT: Recently, endoscopic clip application devices have undergone redesign and improvements to optimize their clinical use and effectiveness. Initially designed for the treatment of bleeding nonvariceal lesions, these devices are also increasingly used for the closure of perforations, fistulas, and anastomotic leaks. Several clinical studies, both randomized and nonrandomized, have used endoscopic hemoclips for hemostasis. However, no comparative studies have yet been reported in the literature comparing the latest endoscopic clip devices for usability and effectiveness for hemostasis of acute upper GI hemorrhage. We aimed to compare the usability and efficacy of 3 different types of endoscopic clip application devices in an established experimental setting by using a porcine ex-vivo simulator of upper GI hemorrhage. Randomized, controlled, ex-vivo study. Academic medical center. Spurting vessels were created within ex-vivo porcine stomachs as published in prior studies. The vessels were attached to a pressure transducer to record the pressure of the circulating blood replacement. Before the initiation of bleeding, each vessel was randomized to 1 of 3 endoscopic clipping devices: 2 different commonly used hemoclips deployed through the working channel and 1 novel clip deployed via an over-the-scope applications device. Two investigators treated 45 bleeding sites (15 bleeding sites for each device at various randomized locations in the stomach: fundus, body, and antrum). Usability was measured via the endpoints of procedure time and quantity of clips required to achieve hemostasis. Efficacy was measured via the endpoint of pressure increase (Δp) from baseline to after treatment. All of the 45 hemostasis treatments were carried out successfully. The mean procedure times were significantly different among the hemoclips, with the clip deployed in an over-the-scope fashion requiring significantly less time to attain hemostasis compared with the other 2 clips. For number of clips needed to attain hemostasis, the clip deployed in an over-the-scope fashion was significantly superior to the others. There were also significant differences among the changes in pressure (Δp ± SD) among the different hemoclips tested. Ex-vivo study. In this prospective, randomized ex-vivo study, we observed significant differences in the usability (time to achieve hemostasis and number of clips required) and the efficacy (change in pressure achieved by the hemoclips) among the 3 clips. The clip applied in the over-the-scope fashion was superior to the other 2 tested clips with regard to time to achieve hemostasis and number of clips required.
    Gastrointestinal endoscopy 01/2012; 75(1):3-10. · 4.90 Impact Factor
  • Natural Orifice Translumenal Endoscopic Surgery: Textbook and Video Atlas. 01/2012;
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    ABSTRACT: Training simulators have been used for decades with success; however, a standardized educational strategy for diagnostic EGD is still lacking. Development of a training strategy for diagnostic upper endoscopy. Prospective, randomized trial. A total of 28 medical and surgical residents without endoscopic experience were enrolled. Basic skills evaluations were performed following a structured program involving theoretical lectures and a hands-on course in diagnostic EGD. Subsequently, stratified randomization to clinical plus simulator training (group 1, n = 10), clinical training only (group 2, n = 9), or simulator training only (group 3, n = 9) was performed. Ten sessions of simulator training were conducted for groups 1 and 3 during the 4-month program. Group 2 underwent standard training in endoscopy without supplemental simulator training. The final evaluation was performed on the simulator and by observation of 3 clinical cases. Skills and procedural times were recorded by blinded and unblinded evaluators. Time to reach the duodenum, pylorus, or esophagus. All trainees demonstrated a significant reduction in procedure time during a simple manual skills test (P < .05) and significantly better skills scores (P = .006, P = .042 and P = .017) in the simulator independent of the training strategy. Group 1 showed shorter times to intubate the esophagus (61 ± 26 seconds vs 85 ± 30 seconds and 95 ± 36 seconds) and the pylorus (183 ± 65 seconds vs 207 ± 61 seconds and 247 ± 66 seconds) during the clinical evaluation. Blinded assessment of EGD skills showed significantly better results for group 1 compared with group 3. Blinded and unblinded evaluations were not statistically different. Small sample size. Structured simulator training supplementing clinical training in upper endoscopy appears to be superior to clinical training alone. Simulator training alone does not seem to be sufficient to improve endoscopic skills.
    Gastrointestinal endoscopy 12/2011; 75(2):254-60. · 4.90 Impact Factor
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    ABSTRACT: A novel, over-the-scope clip (OTSC) system may be suitable for closure of various GI perforations. The strength and maximum diameter of closure for a single OTSC, however, are unknown. To determine the maximum closure capacity (diameter) and pressure threshold for a single OTSC. Prospective ex-vivo study. Academic medical center. Full-thickness, standardized defects of 5 mm, 10 mm, 15 mm, 20 mm, and 25 mm were created in porcine stomachs. Similarly, full-thickness defects of 10 mm, 20 mm, 25 mm, 30 mm, and 35 mm were created in porcine colons. A single OTSC was endoscopically deployed 5 times for each full-thickness defect size in an ex-vivo endoscopic simulator. Each closure site was tested under water with compressed air for burst pressure. We achieved successful closure in all stomach defects ranging from 5 to 20 mm by using 12-mm OTSCs with short teeth and colon defects ranging from 10 to 30 mm with 14-mm OTSCs with short teeth. Mean (± standard deviation [SD]) burst pressures for the gastric closure sites were 74.9 ± 17.5 mm Hg for 15-mm defects, 49.3 ± 21.6 mm Hg for 20-mm defects, and 15.2 ± 4.1 mm Hg for 25-mm defects. Mean (± SD) burst pressures for the colon closure sites were 117.9 ± 40.1 mm Hg for 20-mm defects, 57.4 ± 4.2 mm Hg for 30-mm defects, and 10.9 ± 7.6 mm Hg for 35-mm defects. Ex-vivo study, does not reflect difficult locations. Full-thickness tissue defects ranging from 5 to 20 mm in the stomach and from 10 to 30 mm in the colon can be closed adequately with a single OTSC in an ex-vivo experimental setting. Tissue defects larger than 20 mm in the stomach and 30 mm in the colon may require more than one OTSC or supplemental endoclips to achieve adequate closure. Endoscopic inspection of the closure site does not assure adequate closure of larger perforations.
    Gastrointestinal endoscopy 12/2011; 74(6):1369-75. · 4.90 Impact Factor
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    ABSTRACT: A 30 year old woman who was 8 weeks postpartum with a history of cholelithiasis and gallstone pancreatitis, and who was status-post endoscopic retrograde cholangiopancreatography (ERCP) with sphincterotomy, was treated with a single-incision laparoscopic (SIL) cholecystectomy. A transversus abdominis plane block (TAP) was performed after induction of anesthesia. The patient required no intraoperative or postoperative opioids.
    Journal of clinical anesthesia 11/2011; 24(1):65-7. · 1.32 Impact Factor
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    ABSTRACT: Clip application has been proven to be effective for endoscopic hemostasis. There are limited bench data on the efficacy of the over-the-scope clip (OTSC) for the treatment of spurting GI hemorrhage. We evaluated the hemodynamic efficacy of the OTSC in an established bleeding model. To evaluate the hemodynamic efficacy of the OTSC in an established bleeding model. Prospective experimental trial with historical comparison. We tested the OTSC prospectively in a validated bleeding model by using the compact Erlangen Active Simulator for Interventional Endoscopy equipped with an upper GI organ package. The artificial blood circulation system of the simulator was connected to an arterial pressure transducer. Two investigators with different endoscopic experience (4000 and 10,000 endoscopies performed) participated. Each investigator treated 16 bleeding sites in the simulator with the OTSC by using only suction (n = 8) and a novel retraction device to grasp tissue (n = 8). Systemic pressures were recorded 1 minute before, during, and 1 minute after clip application to objectify the effects of clipping on the vessel diameter. Mean and maximum reduction in vessel diameter. The application of the OTSC on the bleeding vessel led to a significant increase in systemic pressure (P < .001) and decreased vessel diameter (P < .001) independent of the endoscopic experience of the investigator. There was no difference in the decrease in vessel diameter based on the application technique (suction vs suction plus grasping). A historical comparison with our former trials demonstrated that the OTSC decreased the vessel diameter significantly more than other traditional endoclips. Small sample size. We could demonstrate the efficacy of the OTSC with increased hemodynamic efficiency compared with other endoscopic clip devices tested previously.
    Gastrointestinal endoscopy 11/2011; 75(1):152-9. · 4.90 Impact Factor

Publication Stats

579 Citations
175.49 Total Impact Points


  • 2013
    • Rensselaer Polytechnic Institute
      • Center for Modeling, Simulation, and Imaging in Medicine
      Troy, NY, United States
  • 2007–2013
    • Beth Israel Deaconess Medical Center
      • • Division of Gastroenterology
      • • Department of Medicine
      Boston, MA, United States
  • 2006–2012
    • Harvard Medical School
      • Department of Surgery
      Boston, Massachusetts, United States
  • 2011
    • Boston Children's Hospital
      Boston, Massachusetts, United States
  • 2007–2010
    • Massachusetts General Hospital
      • • Department of Radiology
      • • Department of Pathology
      Boston, Massachusetts, United States
  • 2005
    • Friedrich-Alexander Universität Erlangen-Nürnberg
      Erlangen, Bavaria, Germany