Kai Matthes

Harvard Medical School, Boston, Massachusetts, United States

Are you Kai Matthes?

Claim your profile

Publications (67)193.37 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Introduction and study aim A virtual translumenal endoscopic surgical trainer (VTEST™) is being developed to accelerate the development of natural orifice translumenal endoscopic surgery (NOTES) procedures and devices in a safe and risk-free environment. For a rapidly developing field such as NOTES, a needs analysis must be conducted regularly to discover emerging research trends and areas of potential high impact for a virtual simulator. This paper presents a survey-based study which follows a similar study conducted by this group in 2011 (Sankaranarayanan et al. in Surg Endosc 27:1607-1616, 2013). Methods A 32-point questionnaire was distributed at the 2012 Natural Orifice Surgery Consortium for Assessment and Research annual meeting. These data were subsequently augmented by an identical online survey, targeted at the members of the American Society for Gastrointestinal Endoscopy and the Society of American Gastrointestinal and Endoscopic Surgeons, and analyzed. Results Twenty-eight NOTES experts participated in the 2012 study. Cholecystectomy (CE) procedure remained the most commonly performed NOTES technique, with 18 positive responses (64 %). In contrast to 2011, the popularity of the NOTES appendectomy (AE) was significantly lower, with only 2 (7 %) instances (CE vs. AE, p p = 0.013). Strong preference toward hybrid rather than pure NOTES techniques (82 vs. 11 %, p Conclusion Based on the results of this study, a decision was made to focus exclusively on the transvaginal hybrid NOTES cholecystectomy procedure, including both rigid and flexible scope techniques. The importance of developing a virtual NOTES simulator was reaffirmed, with POEM identified as a promising candidate for future simulator development.
    Surgical Endoscopy 04/2015; DOI:10.1007/s00464-015-4182-1 · 3.31 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Safe transgastric natural orifice transluminal endoscopic surgery (NOTES) procedures require a reliable closure of the gastrotomy. Recently a novel peritoneal access method via a submucosal tunnel has been described with encouraging preliminary results. The aim is to compare a submucosal tunnel access plus over-the-scope clip (OTSC) system for closure with two other closure modalities. This is a prospective ex vivo study conducted on 42 porcine stomach models equally randomized into three groups in an academic medical center. The procedures performed in each group included: (1) Tunnel (6 cm) + endoclips; (2) Knife + balloon dilation access + OTSC; and (3) Tunnel + OTSC. A pressurized air-leak test was performed to evaluate the strength of the closure. Stomach volumes, procedure times, number of clips, and incision sizes were also registered. The mean air-leak pressure was statistically higher in Group 3 than in Groups 1 and 2-95.2 ± 19.3 mmHg versus 72.5 ± 35.2 and 79.0 ± 24.5 mmHg (P < 0.05). The gastrotomy creation times for Groups 1, 2, and 3 were 28.0 ± 10.1, 4.3 ± 1.4, and 20.1 ± 10.6 minutes, respectively, with significantly lower time in Group 2 (P < 0.001). The closure times were 16.1 ± 6.1, 6.5 ± 1.2, and 5.3 ± 3.0 minutes, respectively, and significantly longer in the endoclip group (P < 0.001). There were no differences in the volumes and the incision sizes among the three groups. The combination of a submucosal tunnel access and OTSC offers a stronger closure than the other methods studied.
    02/2015; 03(01):E90-E90. DOI:10.1055/s-0035-1547013
  • [Show abstract] [Hide abstract]
    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; 77(5). DOI:10.1007/s00464-014-3948-1 · 3.31 Impact Factor
  • [Show abstract] [Hide abstract]
    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; 62(3). DOI:10.1109/TBME.2014.2369956 · 2.23 Impact Factor
  • Gastrointestinal Endoscopy 05/2014; 79(5):AB270-AB271. DOI:10.1016/j.gie.2014.05.220 · 4.90 Impact Factor
  • Source
  • [Show abstract] [Hide abstract]
    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.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Natural orifice transluminal endoscopic surgery (NOTES) gastrojejunal anastomosis (GJA) is a less invasive surgery for bariatric procedures and gastric outlet obstruction. The aim of this study was to evaluate the feasibility, efficacy, and safety of a pure NOTES gastrojejunal bypass using an in vivo porcine model. A prospective study was performed on nine swine. A double-channel scope was used. The intervention steps were: (i) gastric incision; (ii) peritoneal access; (iii) jejunal loop selection and mobilization into the stomach; (iv) stoma creation within the gastric wall and incision; (v) anastomosis suture and pylorus closure using a T-tag prototype. The animals were assessed clinically for 3 weeks including the weight gain. The patency of the GJA was assessed at necropsy and a histological analysis was performed. We successfully performed all the procedures with a mean (standard deviation [SD]) operative time of 108 (26) minutes. We used a mean of 5.55 (1.30) stitches. There were no intraprocedural adverse events. Five animals survived up till euthanasia at 3 weeks (65 %). These showed a significant difference in weight curves of a loss of 3.2 kg compared with gain of 5.2 kg in a control group. Four pigs died from anastomotic dehiscence complicated by peritonitis. Gastrojejunal bypass with a pure NOTES approach is feasible. This procedure is effective, resulting in a patent anastomosis and a significant weight loss. However, the anastomotic dehiscence is a major concern because of its mortality rate, and further studies including improvement of the suturing device and the technique are needed.
  • [Show abstract] [Hide abstract]
    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.
    06/2013; 5(6):275-80. DOI:10.4253/wjge.v5.i6.275
  • [Show abstract] [Hide abstract]
    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; 78(5). DOI:10.1016/j.gie.2013.04.193 · 4.90 Impact Factor
  • Source
    Gastrointestinal Endoscopy 05/2013; 77(5):AB526. DOI:10.1016/j.gie.2013.03.881 · 4.90 Impact Factor
  • Source
    Gastrointestinal Endoscopy 05/2013; 77(5):AB195-AB196. DOI:10.1016/j.gie.2013.03.461 · 4.90 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
  • [Show abstract] [Hide abstract]
    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). DOI:10.1007/s00464-012-2637-1 · 3.31 Impact Factor
  • [Show abstract] [Hide abstract]
    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). DOI:10.1007/s00464-012-2402-5 · 3.31 Impact Factor
  • Gastrointestinal Endoscopy 04/2012; 75(4):AB106. DOI:10.1016/j.gie.2012.03.185 · 4.90 Impact Factor
  • [Show abstract] [Hide abstract]
    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. DOI:10.1016/j.gie.2011.11.003 · 4.90 Impact Factor

Publication Stats

660 Citations
193.37 Total Impact Points


  • 2007–2014
    • Harvard Medical School
      • Department of Surgery
      Boston, Massachusetts, United States
    • Beth Israel Deaconess Medical Center
      • Division of Gastroenterology
      Boston, Massachusetts, United States
  • 2013
    • Rensselaer Polytechnic Institute
      • Center for Modeling, Simulation, and Imaging in Medicine
      Troy, NY, United States
  • 2005–2013
    • Harvard University
      Cambridge, Massachusetts, United States
    • Friedrich-Alexander Universität Erlangen-Nürnberg
      Erlangen, Bavaria, Germany
  • 2008–2010
    • Massachusetts General Hospital
      • Department of Radiology
      Boston, Massachusetts, United States
  • 2006–2007
    • University of Massachusetts Boston
      Boston, Massachusetts, United States
    • CUNY Graduate Center
      New York, New York, United States