Force-adjustable parallel-occlusion grasper.

BACKGROUND: During laparoscopic surgery, the operating surgeon grasps sections of the gastrointestinal tract (GIT), including delicate structures, with long (270 mm) 5 mm diameter graspers. These grasping instruments increase the risk of iatrogenic damage due to crushing of the grasped tissue. This risk is increased significantly by diseases such as bacterial peritonitis and inflammatory bowel disease and reduced but not abolished by using parallel-closing laparoscopic instruments. This study describes the design and laboratory testing of fully developed and tested smart graspers capable of reducing the grasping force used for inflamed tissues and hollow viscera. MATERIALS AND METHODS: In an ISO 13485-certified mechanical laboratory and CAD machine workshop, the authors have designed, developed, and evaluated a smart gasper capable of exerting a preselected uniform grasping force on the gastrointestinal tract and other structures/ tissues, through a mechanism incorporated in the handle of the instrument. This enables the control and graded reduction of the grasping force by the incorporation of a compression spring. The authors named the new instrument the force-adjustable parallel-occlusion grasper (FA-POG) because, in addition to applying a uniform force on the grasped bowel/tissue, it also enables the surgeon to select the force before grasping, depending on its physical condition, and pathological state. RESULTS: FA-POG differs from traditional pinch-occlusion grasper in two respects: it exerts a uniform force on the grasped tissue/bowel and enables the operating surgeon to select and apply a predetermined uniform grasping force, ranging from 1 to 5 N, depending on the pathological condition of the bowel/structure. The ISO 13485-certified and fully developed prototype has been subjected to various grasping in-vitro tests using freshly harvested porcine small-bowel segments obtained from a local abattoir, using Instron tensiometry. CONCLUSIONS: The authors designed and α/ß tested a parallel-occlusion gasper that enables the operating surgeon to select the force before grasping. This grasper design consists of end-effectors jaws with a 4-bar linkage mechanism for wide, uniform parallel-occlusion force, surpassing traditional scissor-type laparoscopic graspers. It incorporates a force-level controller knob, based on a spring-loaded mechanism, enabling surgeon-preselected grip force to prevent excessive grasping. The authors validated the design experimentally using porcine small-bowel segments, optimizing teeth for maximum grip friction to minimize slippage.

Hydro-jet propelled colonoscopy: proof of concept in a phantom colon.

BACKGROUND: Colonoscopy is a widely used and effective procedure, but it often causes patient discomfort and its execution requires considerable skill and training. We demonstrate an alternative approach to colonoscope propulsion with the potential to minimise patient discomfort by reducing the forces exerted on the colonic wall and mesentery, and to reduce the level of skill required for execution. METHODS: A prototype colonoscopic device is described, consisting of a tethered capsule that is propelled and manoeuvred through a water-filled colon (hydro-colonoscopy) by an array of water jets. As an initial proof of concept, experiments were performed to assess the ability of the device to navigate through a simplified PVA cryogel human colon phantom arranged in various anatomical configurations. RESULTS: The prototype was capable of successfully navigating through three out of four colon configurations: a simple layout, alpha loop and reverse alpha loop. It was unable to negotiate the fourth configuration involving an "N loop", but this was attributed to problems with the colon phantom. In the successful test replicates, mean complete insertion (i.e. caecal intubation) time was 4.7 min. Measured pressures, temperatures and forces exerted on the colon appeared to be within a physiologically acceptable range. The results demonstrate the viability of propelling a colonoscope through a colon phantom using hydro-jets. CONCLUSIONS: Results indicate that this approach has the potential to enable rapid and safe caecal intubation. This suggests that further development towards clinical translation is worthwhile.

Bicomponent Conformal Electrode for Radiofrequency Sequential Ablation and Circumferential Separation of Large Tumors in Solid Organs: Development and In Vitro Evaluation.

OBJECTIVE: Complete destruction of large tumors by radiofrequency ablation (RFA) with surrounding tumor-free margin is difficult because of incomplete or nonuniform heating due to both heat-sink effect of circulating blood and limitations of existing RF electrode design. A new RF electrode is described to overcome this limitation. METHODS: A bicomponent conformal (BCC) RFA probe providing sectorial sequential ablation followed by circumferential cutting is designed and evaluated. Three-dimensional finite-element analysis model was developed with temperature feedback-controlled simulation of RFA for electrode design and optimization. The prototype bipolar BCC probe with three embedded thermocouples was constructed and evaluated in tissue-mimicking phantoms. RESULTS: Maximum tissue temperature was kept <100 ºC with power applied <15 W. A 10-min ablation time was used for each sequence and after four sequential RFA, a large ablation zone of 55 cm3 was achieved. Our experiment confirmed that lesions exceeding 3.7 cm could be ablated and separated from the surrounded tissue. CONCLUSION: The new BCC probe is, thus, capable of controlled ablation followed by circumferential separation of the lesions, when required. SIGNIFICANCE: The results of these experiments provide the proof of concept validation that the BCC probe has the potential to ablate by sequential heating tumors in solid organs >3.5 cm then separate them by electrosurgical cutting from the surrounding normal parenchyma. The combined RF ablation and physical separation could completely destroy the cancer cells at the ablation site, thus, avoid any local recurrence of cancer. It requires further in vivo validation studies in large animals.

A hydraulically driven colonoscope.

BACKGROUND: Conventional colonoscopy requires a high degree of operator skill and is often painful for the patient. We present a preliminary feasibility study of an alternative approach where a self-propelled colonoscope is hydraulically driven through the colon. METHODS: A hydraulic colonoscope which could be controlled manually or automatically was developed and assessed in a test bed modelled on the anatomy of the human colon. A conventional colonoscope was used by an experienced colonoscopist in the same test bed for comparison. Pressures and forces on the colon were measured during the test. RESULTS: The hydraulic colonoscope was able to successfully advance through the test bed in a comparable time to the conventional colonoscope. The hydraulic colonoscope reduces measured loads on artificial mesenteries, but increases intraluminal pressure compared to the colonoscope. Both manual and automatically controlled modes were able to successfully advance the hydraulic colonoscope through the colon. However, the automatic controller mode required lower pressures than manual control, but took longer to reach the caecum. CONCLUSIONS: The hydraulic colonoscope appears to be a viable device for further development as forces and pressures observed during use are comparable to those used in current clinical practice.

Current state of micro-robots/devices as substitutes for screening colonoscopy: assessment based on technology readiness levels.

BACKGROUND: Previous reports have described several candidates, which have the potential to replace colonoscopy, but to date, there is still no device capable of fully replacing flexible colonoscopy in the management of colonic disorders and for mass adult population screening for asymptomatic colorectal cancer. MATERIALS AND METHODS: NASA developed the TRL methodology to describe and define the stages of development before use and marketing of any device. The definitions of the TRLS used in the present review are those formulated by "The US Department of Defense Technology Readiness Assessment Guidance" but adapted to micro-robots for colonoscopy. All the devices included are reported in scientific literature. They were identified by a systematic search in Web of Science, PubMed and IEEE Xplore amongst other sources. Devices that clearly lack the potential for full replacement of flexible colonoscopy were excluded. ASSESSMENT OF THE CURRENT SITUATION: The technological salient features of all the devices included for assessment are described briefly, with particular focus on device propulsion. The devices are classified according to the TRL criteria based on the reported information. An analysis is next undertaken of the characteristics and salient features of the devices included in the review: wireless/tethered devices, data storage-transmission and navigation, additional functionality, residual technology challenges and clinical and socio-economical needs. CONCLUSIONS: Few devices currently possess the required functionality and performance to replace the conventional colonoscopy. The requirements, including functionalities which favour the development of a micro-robot platform to replace colonoscopy, are highlighted.

Image-based 3D modeling and validation of radiofrequency interstitial tumor ablation using a tissue-mimicking breast phantom.

PURPOSE: Minimally invasive treatment of solid cancers, especially in the breast and liver, remains clinically challenging, despite a variety of treatment modalities, including radiofrequency ablation (RFA), microwave ablation or high-intensity focused ultrasound. Each treatment modality has advantages and disadvantages, but all are limited by placement of a probe or US beam in the target tissue for tumor ablation and monitoring. The placement is difficult when the tumor is surrounded by large blood vessels or organs. Patient-specific image-based 3D modeling for thermal ablation simulation was developed to optimize treatment protocols that improve treatment efficacy. METHODS: A tissue-mimicking breast gel phantom was used to develop an image-based 3D computer-aided design (CAD) model for the evaluation of a planned RF ablation. First, the tissue-mimicking gel was cast in a breast mold to create a 3D breast phantom, which contained a simulated solid tumor. Second, the phantom was imaged in a medical MRI scanner using a standard breast imaging MR sequence. Third, the MR images were converted into a 3D CAD model using commercial software (ScanIP, Simpleware), which was input into another commercial package (COMSOL Multiphysics) for RFA simulation and treatment planning using a finite element method (FEM). For validation of the model, the breast phantom was experimentally ablated using a commercial (RITA) RFA electrode and a bipolar needle with an electrosurgical generator (DRE ASG-300). The RFA results obtained by pre-treatment simulation were compared with actual experimental ablation. RESULTS: A 3D CAD model, created from MR images of the complex breast phantom, was successfully integrated with an RFA electrode to perform FEM ablation simulation. The ablation volumes achieved both in the FEM simulation and the experimental test were equivalent, indicating that patient-specific models can be implemented for pre-treatment planning of solid tumor ablation. CONCLUSION: A tissue-mimicking breast gel phantom and its MR images were used to perform FEM 3D modeling and validation by experimental thermal ablation of the tumor. Similar patient-specific models can be created from preoperative images and used to perform finite element analysis to plan radiofrequency ablation. Clinically, the method can be implemented for pre-treatment planning to predict the effect of an individual's tissue environment on the ablation process, and this may improve the therapeutic efficacy.

Determination of metformin in human plasma using hydrophilic interaction liquid chromatography-tandem mass spectrometry.

A sensitive, simple and rapid assay based on hydrophilic interaction liquid chromatography (HILIC) with tandem mass spectrometry was developed and validated for the quantitative analysis of metformin in human plasma using protein precipitation. Plasma samples were prepared using a protein precipitation solution containing acetonitrile, 0.5% formic acid and the internal standard, metformin-D(6). The analytes were separated on a GL Sciences Inertsil HILIC column using an isocratic mobile phase consisting of water/acetonitrile (30:70, v/v) and 0.1% formic acid. Metformin and internal standard were recorded using multiple reaction monitoring in positive ion electrospray mode with transitions of m/z 130-71 and m/z 136-77, respectively. No endogenous components in plasma were found to interfere with metformin measurements. The lower limit of quantification (LLOQ) was 0.5 ng/mL (0.1 pg on-column). The linear range was 0.5-500 ng/mL with an average correlation coefficient of 0.999 using weighted (1/x(2)) linear least-squares regression. Dilutional linearity was evaluated up to 5000-fold dilution and the results indicate no influence on the accuracy of analysis. The absolute extraction recovery was 81% for metformin. Intra-day and inter-day precision (CV, %) ranged from 0.73% to 7.18%, and accuracy within +/-10.98% from nominal. The analyte was found to be stable for at least 38 days at -20 and -80 degrees C, 24 h at room temperature, and stable for four freeze-thaw cycles. The processed extracts were stable for 88 h at 4 degrees C.