A method for going from 2D laparoscope to 3D acquisition of surface landmarks by a novel computer vision approach.

PURPOSE: This paper presents a method to use the Smart Trocars-our new surgical instrument recognition system-or any accurate localization system of surgical instrument for acquiring intraoperative surface data. Complex laparoscopic surgeries need a proper guidance system which requires registering the preoperative data from a CT or MRI scan to the intraoperative patient state. The Smart Trocar can be used to localize the instruments when it comes to contact with the soft tissue surface. METHOD: Two successive views through the laparoscope at different angles with the 3D localization of a fixed tool at one single location using the Smart Trocars can point out visible features during the surgery and acquire their location in 3D to provide a depth map in the region of interest. In other words, our method transforms a standard laparoscope system into a system with three-dimensional registration capability. RESULT: This method was initially tested on a simulation for uncertainty assessment and then on a rigid model for verification with an accuracy within 2 mm distance. In addition, an in vivo experiment on pig model was also conducted to investigate how the method might be used during a physiologic respiratory cycle. CONCLUSION: This method can be applied in a large number of surgical applications as a guidance system on its own or in conjunction with other navigation techniques. Our work encourages further testing with realistic surgical applications in the near future.

The SmartOR: a distributed sensor network to improve operating room efficiency.

BACKGROUND: Despite the significant expense of OR time, best practice achieves only 70% efficiency. Compounding this problem is a lack of real-time data. Most current OR utilization programs require manual data entry. Automated systems require installation and maintenance of expensive tracking hardware throughout the institution. This study developed an inexpensive, automated OR utilization system and analyzed data from multiple operating rooms. STUDY DESIGN: OR activity was deconstructed into four room states. A sensor network was then developed to automatically capture these states using only three sensors, a local wireless network, and a data capture computer. Two systems were then installed into two ORs, recordings captured 24/7. The SmartOR recorded the following events: any room activity, patient entry/exit time, anesthesia time, laparoscopy time, room turnover time, and time of preoperative patient identification by the surgeon. RESULTS: From November 2014 to December 2015, data on 1003 cases were collected. The mean turnover time was 36 min, and 38% of cases met the institutional goal of ≤30 min. Data analysis also identified outlier cases (>1 SD from mean) in the domains of time from patient entry into the OR to intubation (11% of cases) and time from extubation to patient exiting the OR (11% of cases). Time from surgeon identification of patient to scheduled procedure start time was 11 min (institution bylaws require 20 min before scheduled start time), yet OR teams required 22 min on average to bring a patient into the room after surgeon identification. CONCLUSION: The SmartOR automatically and reliably captures data on OR room state and, in real time, identifies outlier cases that may be examined closer to improve efficiency. As no manual entry is required, the data are indisputable and allow OR teams to maintain a patient-centric focus.

Image-guided simulation of tissue deformation using a mechanical model on a surgical application.

This paper presents a method for localizing the position of a liver and a tumor within the tissue during a minimally invasive liver operation. From pre-operative CT scans, the liver volume and its internal structures are segmented using image-processing techniques. Based on these segmentations, a three-dimensional mechanical model is built to compute the liver volume and internal structure displacement under boundary conditions such as external forces from the surgical instrument. This can help the surgeon understand the motion of internal structures when manipulating the liver. To validate our method, an experiment on a porcine liver explant was performed to assess the difference between actual tissue motion and the mechanical model.

A robust and non-obtrusive automatic event tracking system for operating room management to improve patient care.

BACKGROUND: Optimization of OR management is a complex problem as each OR has different procedures throughout the day inevitably resulting in scheduling delays, variations in time durations and overall suboptimal performance. There exists a need for a system that automatically tracks procedural progress in real time in the OR. This would allow for efficient monitoring of operating room states and target sources of inefficiency and points of improvement. STUDY DESIGN: We placed three wireless sensors (floor-mounted pressure sensor, ventilator-mounted bellows motion sensor and ambient light detector, and a general room motion detector) in two ORs at our institution and tracked cases 24 h a day for over 4 months. RESULTS: We collected data on 238 total cases (107 laparoscopic cases). A total of 176 turnover times were also captured, and we found that the average turnover time between cases was 35 min while the institutional goal was 30 min. Deeper examination showed that 38 % of laparoscopic cases had some aspect of suboptimal activity with the time between extubation and patient exiting the OR being the biggest contributor (16 %). CONCLUSION: Our automated system allows for robust, wireless real-time OR monitoring as well as data collection and retrospective data analyses. We plan to continue expanding our system and to project the data in real time for all OR personnel to see. At the same time, we plan on adding key pieces of technology such as RFID and other radio-frequency systems to track patients and physicians to further increase efficiency and patient safety.

Endoscopic suture fixation of self-expanding metallic stents with and without submucosal injection.

BACKGROUND: Self-expanding metallic stents (SEMS) are useful for treating leaks after bariatric procedures but stent migration (12 to 40 %) remains a problem. Suture fixation has been used to minimize migration but has attendant risks of transmural penetration. We hypothesized that submucosal injection would decrease the risk of full thickness suture penetration while still providing greater pullout forces than endoscopic clipping. METHODS: Porcine explant models and 155 mm SEMS were used with a force meter to measure the pullout forces required to dislodge the stent. Stents were first deployed without fixation and this pullout force acted as a control. The explants were then randomized to receive fixation with clips, endoscopic suturing with submucosal elevation, or endoscopic suturing without submucosal elevation. The pullout force was again measured and the ratio of the experimental to control pullout forces was used as a measure of the efficacy of the fixation. RESULTS: Endoscopic suture fixation after submucosal injection resulted in statistically significant increased pullout force compared to clip fixation (n = 5; mean force ratio 462 %; 95 % confidence interval [CI] 281-643 %; p < 0.01). Endoscopic suturing fixation without submucosal injection also resulted in statistically significant increased pullout force (n = 5; mean force ratio 765 %; 95 % CI 258-632 %; p < 0.01). Fixation with clips did not result in significantly increased pullout force compared to no fixation (n = 5; mean force ratio 108 %; 95 % CI 56-159 %; p < 0.01). Submucosal injection also eliminated full thickness suture penetration (0/10 submucosal injection; 7/10 no injection). CONCLUSIONS: Endoscopic suture fixation of SEMS resulted in a statistically significant increase in pullout force necessary to displace the stents. Submucosal injection prior to suture fixation preserves the increased pullout force while minimizing the risk of transmural penetration with the potential for less risk of injury to mediastinal structures.

Neural precursor cell lines promote neurite branching.

Schwann cells and primary progenitor cells improve regeneration across peripheral nerve defects. This study examined the impact of immortalized neural precursor cells on regeneration of rat nerve defects. Across 10-mm gaps, neuromas formed without neural cables with C17.2- or RN33B-transplanted cells, but neural cables formed across 5-mm gaps seeded with RN33B cells. In vitro, dorsal root ganglia neurites elongated across Schwann and RN33B cells; RN33B cells induced neurite branching with shorter total outgrowth. Neural cable formation in vivo was likely determined by the balance of guidance and branch-inducing factors secreted by Schwann and transplanted precursor cells.

Degradation behavior of poly(glycerol sebacate).

Poly(glycerol sebacate) (PGS), a promising scaffold material for soft tissue engineering applications, is a soft, tough elastomer with excellent biocompatibility. However, the rapid in vivo degradation rate of PGS limits its use as a scaffold material. To determine the impact of crosslink density on degradation rate, a family of PGS materials was synthesized by incrementally increasing the curing time from 42 to 144 h, at 120 degrees C and 10 mTorr vacuum. As expected, PGS became a stiffer, tougher, and stronger elastomer with increasing curing time. PGS disks were subcutaneously implanted into rats and periodically harvested; only mild tissue responses were observed and the biocompatibility remained excellent. Regardless of crosslink density, surface erosion degradation was observed. The sample dimensions linearly decreased with implantation time, and the mass loss rates were constant after 1-week implantation. As surface erosion degradation frequently correlates with enzymatic digestion, parallel in vitro digestion studies were conducted in lipase solutions which hydrolyze ester bonds. Enzymatic digestion played a significant role in degrading PGS, and the mass loss rates were not a function of curing time. Alternative chemistry approaches will be required to decrease the enzymatic hydrolysis rate of the ester bonds in PGS polymers.

Comparison of hydrogels in the in vivo formation of tissue-engineered bone using mesenchymal stem cells and beta-tricalcium phosphate.

Availability of grafts and morbidity at the donor site limit autologous transplantation in patients requiring bone reconstruction. A tissue-engineering approach can overcome these limitations by producing bone-like tissue of custom shape and size from isolated cells. Several hydrogels facilitate osteogenesis on porous scaffolds; however, the relative suitability of various hydrogels has not been rigorously assessed. Fibrin glue, alginate, and collagen I hydrogels were mixed with swine bone marrow-derived differentiated mesenchymal stem cells (MSCs), applied to 3-dimensionally printed porous beta-tricalcium phosphate (beta-TCP) scaffolds and implanted subcutaneously in nude mice. Although noninvasive assessment of osteogenesis in 3 dimensions is desirable for monitoring new bone formation in vivo, correlations with traditional histological and mechanical testing need to be established. High-resolution volumetric computed tomography (VCT) scanning, histological examination, biomechanical compression testing, and osteonectin (ON) expression were performed on excised scaffolds after 1, 2, 4, and 6 weeks of subcutaneous implantation in mice. Statistical correlation analyses were performed between radiological density, stiffness, and ON expression. Use of collagen I as a hydrogel carrier produced superior bone formation at 6 weeks, as demonstrated using VCT scanning with densities similar to native bone and the highest compression values. Continued contribution of the seeded MSCs was demonstrated using swine-specific messenger ribonucleic acid probes. Radiological density values correlated closely with the results of histological and biomechanical testing and ON expression. High-resolution VCT is a promising method for monitoring osteogenesis.