Machine-Learning-Based Multi-Modal Force Estimation for Steerable Ablation Catheters.

Catheter-based cardiac ablation is a minimally invasive procedure for treating atrial fibrillation (AF). Electrophysiologists perform the procedure under image guidance during which the contact force between the heart tissue and the catheter tip determines the quality of lesions created. This paper describes a novel multi-modal contact force estimator based on Convolutional Neural Networks (CNNs) and Recurrent Neural Networks (RNNs). The estimator takes the shape and optical flow of the deflectable distal section as two modalities since frames and motion between frames complement each other to capture the long context in the video frames of the catheter. The angle between the tissue and the catheter tip is considered a complement of the extracted shape. The data acquisition platform measures the two-degrees-of-freedom contact force and video data as the catheter motion is constrained in the imaging plane. The images are captured via a camera that simulates single-view fluoroscopy for experimental purposes. In this sensor-free procedure, the features of the images and optical flow modalities are extracted through transfer learning. Long Short-Term Memory Networks (LSTMs) with a memory fusion network (MFN) are implemented to consider time dependency and hysteresis due to friction. The architecture integrates spatial and temporal networks. Late fusion with the concatenation of LSTMs, transformer decoders, and Gated Recurrent Units (GRUs) are implemented to verify the feasibility of the proposed network-based approach and its superiority over single-modality networks. The resulting mean absolute error, which accounted for only 2.84% of the total magnitude, was obtained by collecting data under more realistic circumstances in contrast to previous research studies. The decrease in error is considerably better than that achieved by individual modalities and late fusion with concatenation. These results emphasize the practicality and relevance of utilizing a multimodal network in real-world scenarios.

Toward construct validity for a novel sensorized instrument-based minimally invasive surgery simulation system.

Minimally invasive surgical training is complicated due to the constraints imposed by the surgical environment. Sensorized laparoscopic instruments capable of sensing force in five degrees of freedom and position in six degrees of freedom were evaluated. Novice and expert laparoscopists performed the complex minimally invasive surgical task of suturing using the novel instruments. Their force and position profiles were compared. The novel minimally invasive surgical instrument proved to be construct valid and capable of detecting differences between novices and experts in a laparoscopic suturing task with respect to force and position. Further evaluation is mandated for a better understanding of the ability to predict performance based on force and position as well as the potential for new metrics in minimally invasive surgical education.

Acinetobacter infections: a retrospective study to determine inhospital mortality rate and clinical factors associated with mortality.

A retrospective case series of acinetobacter infections at a tertiary hospital in Nairobi was conducted to determine the mortality rate and factors associated with mortality. Over an eight-year period, 80 clinically significant infections were identified. The majority of infections were ventilator-associated pneumonia (40%) and bloodstream infections (30%). Eighty-six percent of the isolates were multi-drug resistant. The mortality rate in the study cohort was 45%. Twelve patients grew Acinetobacter spp. within 48 h of hospitalization, and three of these patients had no prior healthcare contact. The mean Sequential Organ Failure Assessment score was associated with mortality from acinetobacter infections.

Electromagnetic navigation improves minimally invasive robot-assisted lung brachytherapy.

OBJECTIVE: Recent advances in minimally invasive thoracic surgery have renewed an interest in the role of interstitial brachytherapy for lung cancer. Our previous work has demonstrated that a minimally invasive robot-assisted (MIRA) lung brachytherapy system produced results that were equal to or better than those obtained with standard video-assisted thoracic surgery (VATS) and comparable to results with open surgery. The purpose of this project was to evaluate the performance of an integrated system for MIRA lung brachytherapy that incorporated modified electromagnetic navigation and ultrasound image guidance with robotic assistance. METHODS: The experimental test-bed consisted of a VATS box, ZEUS and AESOP surgical robotic arms, a seed injector, an ultrasound machine, video monitors, a computer, and an endoscope. Our previous custom-designed electromagnetic navigational software and the robotic controller were modified and incorporated into the MIRA III system to become the next-generation MIRA IV. Inactive brachytherapy seeds were injected as close as possible to a small metal ball target embedded in an opaque agar cube. The completion time, the number of attempts, and the accuracy of seed deployment were compared for manual placement, standard VATS, MIRA III, and the new MIRA IV system. RESULTS: The MIRA IV system significantly reduced the median procedure time by 61% (104 s to 41 s), tissue trauma by 75% (4 attempts to 1 attempt), and mean seed placement error by 64% (2.5 mm to 0.9 mm) when compared to a standard VATS. MIRA IV also reduced the mean procedure time by 48% (85 s to 44 s) and the seed placement error by 68% (2.8 mm to 0.9 mm) compared to the MIRA III system. CONCLUSIONS: A modified integrated system for performing minimally invasive robot-assisted lung brachytherapy was developed that incorporated electromagnetic navigation and an improved robotic controller. The MIRA IV system performed significantly better than standard VATS and better than MIRA III.

Methods and mechanisms for contact feedback in a robot-assisted minimally invasive environment.

Providing a surgeon with information regarding contacts made between instruments and tissue during robot-assisted interventions can improve task efficiency and reliability. In this report, different methods for feedback of such information to the surgeon are discussed. It is hypothesized that various methods of contact feedback have the potential to enhance performance in a robot-assisted minimally invasive environment. To verify the hypothesis, novel mechanisms needed for incorporating contact feedback were designed, including a surgeon-robot interface with full force feedback capabilities and a surgical end-effector with full force sensing capabilities, that are suitable for minimally invasive applications. These two mechanisms were used to form a robotic "master-slave" test bed for studying the effect of contact feedback on the system and user performance. Using the master-slave system, experiments for surgical tasks involving soft tissue palpation were conducted. The performance of the master-slave system was validated in terms of criteria that assess the accurate transmission of task-related information to the surgeon, which is critical in the context of soft tissue surgical applications. Moreover, using a set of experiments involving human subjects, the performance of several users in carrying out the task was compared among different methods of contact feedback.

Haptic interaction and visualization of elastic deformation.

In this paper, we represent a new method to model real-time local and global deformations on a variety of three-dimensional sculptured surfaces governed by physical principles. The deformable objects are highly elastic with linear behavior in the range of typical haptic forces. A deformation model is developed for incompressible material based on a mapping technique and the superposition principle. The law of energy conservation is used to calculate real-time force reflection. Using the divergence theorem, force reflection is calculated for volumetric deformations.

Serum metabolic and minerals profile in norgestomet primed postpartum anestrous surti buffaloes.

AIM: The study was undertaken to find out the serum metabolic and minerals profile in postpartum anestrous surti buffaloes treated with norgestomet ear implants alone and in combination with pregnant mare serum gonadotropin (PMSG). MATERIALS AND METHODS: The study was conducted on 18 postpartum anestrous Surti buffaloes divided into three groups of six animals each at random to conduct the experiment. The buffaloes in Group-I and Group-II were implanted with Crestar ear implant for 9 days together with 2 ml injection of Crestar solution given i/m on the day of the implant insertion. In Group-II, additionally 500 IU PMSG was given i/m on the day of implant removal, whereas the buffaloes in Group-III served as anestrous control group and received 5 ml Normal Saline i/m on day 0 and 9 as a placebo treatment. RESULTS: The overall serum total protein values did not differ significantly (p > 0.05) between time (days) intervals in any of the groups. The mean serum total cholesterol levels at 10(th) day and on the day of estrus were found significantly lower (p < 0.05) in the control group as compared to treatment Groups I and II. However, there was no significant difference (p > 0.05) at 10(th) day and on the day of estrus between treatment groups (T1 and T2). The overall mean serum cobalt, zinc, iron, and manganese values did not differ significantly (p > 0.05) between different time intervals among any of the groups, except copper which was significantly lower (p < 0.05) at 10(th) day in control group as compared to treatment groups. CONCLUSION: Microelements cannot be synthesized in the body. Hence, it is concluded that the mineral mixture should be supplied daily in the animals ration to suffice the requirement of the trace elements. The mean serum metabolic and micro-minerals profiles in treatment and control groups revealed that overall mean serum total protein, cholesterol, copper, and zinc levels were apparently higher in treatment groups whereas, mean serum cobalt, iron, and manganese concentration had no consistent trend between treatment and control groups of Surti buffaloes.

Characterization of gentamicin pharmacokinetics in patients hemodialyzed with high-flux polysulfone membranes.

To characterize the pharmacokinetics of gentamicin during and after hemodialysis (using polysulfone Fresenius F-80 membranes (Fresenius USA, Inc, Walnut Creek, CA), surface area 1.6 m(2)), eight patients with end-stage renal disease undergoing chronic hemodialysis receiving the drug for therapeutic indications were enrolled. Intradialytic gentamicin half-life, clearance, and amount of gentamicin recovered during a hemodialysis session were also determined. Serum gentamicin concentrations were analyzed using fluorescence polarization immunoassay. The amount of gentamicin recovered was 64.3 +/- 14.4 mg, whereas the intradialytic gentamicin half-life was 2.24 +/- 0.83 hours, with a clearance of 116 +/- 9 mL/min. Gentamicin concentrations rebounded by 27.86% +/- 16.4% at 1. 5 +/- 0.52 hours after the end of the hemodialysis session. The decrease in gentamicin concentrations comparing maximum rebound to prehemodialysis concentrations was 53.54% +/- 9.97%. A variable yet substantial amount of gentamicin is removed during hemodialysis using F-80 membranes; hence, supplemental doses are necessary to avoid potential treatment failures. The supplemental doses of gentamicin calculated based on gentamicin concentrations obtained immediately postdialysis could be overestimated if the postdialysis rebound concentrations are not considered. A dosing regimen is suggested using the pharmacokinetic parameters defined by the present study and population estimate of volume of distribution.

Neural network based tracking control of a flexible macro-micro manipulator system.

In this paper, we address the problem of stable tracking control of a flexible macro-micro manipulator (M(3)) system. A two-layer neural network is utilized to approximate the nonlinear robot dynamic behavior of the M(3) system, and the controllers for the macro and micro arms are developed without any need for prior knowledge of the dynamic model of the controlled M(3) system. A learning algorithm for the neural network using Lyapunov stability theory is derived. It is shown that both the tracking error and the weight-tuning error are uniformly ultimately bounded under this new control scheme. Simulation results are presented and compared to those obtained using a PD controller.

Identification of a two-link flexible manipulator using adaptive time delay neural networks.

This paper deals with identification of a two-link flexible manipulator belonging to a class of multi-input, multi-output (MIMO) nonlinear systems, by using adaptive time delay neural networks (ATDNNs). Two neuro-dynamic identifiers are proposed. The capabilities of the proposed structures for representing the nonlinear input-output map of the flexible manipulator are shown analytically. Selection criteria for specifying the fixed structural parameters as well as the adaptation laws for updating the adjustable parameters of the networks are provided. During identification, the two-link flexible manipulator is under nonlinear control and the input-output data sets are generated for different desired trajectories. Simulation results reveal that the proposed neuro-dynamic structures are capable of successfully identifying a highly nonlinear system without any a priori information about the nonlinearities of the system and without any off-line training.

Live-donor liver transplantation: the USC experience.

BACKGROUND: Liver transplantation is currently the standard of care for patients with end stage liver disease. However due to the cadaveric organ shortage, live donor liver transplantation (LDLT), has been recently introduced as a potential solution. We analyzed and support our initial experience with this procedure at USC. MATERIAL AND METHODS: From September 1998 until July 2000, a total of 27 patients underwent LDLT at USC University Hospital and Los Angeles Children's Hospital. There were 12 children with the median age of 10 months (4-114) and 15 adults with the median age of 56 years (35-65). The most common indication for transplantation was biliary atresia for children and hepatitis C for adults. RESULTS: All donors did well postoperatively; the median postoperative stay was five days (5-7) for left lateral segmentectomy and seven days (4-12) for lobar donation. None of the donors required blood transfusion, re-operation or postoperative invasive procedure. However, five of them (18%) experienced minor complications. The survival rate in pediatric patients was 100% and only one graft was lost at nine months due to rejection. Two adult recipients died in the postoperative period, one from graft non-function and one from necrotizing fascitis. 37% of adult recipients experienced postoperative complications, mainly related to biliary reconstruction. Also 26% of the recipients underwent reoperation for some of these complications. CONCLUSION: LDLT is an excellent alternative to cadaveric transplantation with excellent results in the pediatric population. However, in adult patients it still carries a significant complication rate and it should be used with caution.

Spontaneous expulsion of unusual tracheobronchial foreign body.

An extremely rare case of long, thin and sharp pin in a young boy which was inhaled initially and defied removal at branchoscopy was eventually recovered in stool after a long and variable course through alimentary tract has been reported.

Melanotic neuroectodermal tumour of infancy (progonoma).

A case of Melanotic neuroectodermal tumour of infancy (melanotic progonoma, melanoameloblastoma, retinal anlarge tumour) presenting as tumour of maxilla in a female infant is reported. Clinically a teratoma was suspected but ultrasound shoved it a solid mass. At exploration, characteristic melanotic pigmentation clinched the diagnosis which was later confirmed by histopathological examination.

Integration of force reflection with tactile sensing for minimally invasive robotics-assisted tumor localization.

Tactile sensing and force reflection have been the subject of considerable research for tumor localization in soft-tissue palpation. The work presented in this paper investigates the relevance of force feedback (presented visually as well as directly) during tactile sensing (presented visually only) for tumor localization using an experimental setup close to one that could be applied for real robotics-assisted minimally invasive surgery. The setup is a teleoperated (master-slave) system facilitated with a state-of-the-art minimally invasive probe with a rigidly mounted tactile sensor at the tip and an externally mounted force sensor at the base of the probe. The objective is to capture the tactile information and measure the interaction forces between the probe and tissue during palpation and to explore how they can be integrated to improve the performance of tumor localization. To quantitatively explore the effect of force feedback on tactile sensing tumor localization, several experiments were conducted by human subjects to locate artificial tumors embedded in the ex vivo bovine livers. The results show that using tactile sensing in a force-controlled environment can realize, on average, 57 percent decrease in the maximum force and 55 percent decrease in the average force applied to tissue while increasing the tumor detection accuracy by up to 50 percent compared to the case of using tactile feedback alone. The results also show that while visual presentation of force feedback gives straightforward quantitative measures, improved performance of tactile sensing tumor localization is achieved at the expense of longer times for the user. Also, the quickness and intuitive data mapping of direct force feedback makes it more appealing to experienced users.

A semi-infinite programming approach to preoperative planning of robotic cardiac surgery under geometric uncertainty.

In this paper, a computational framework for patient-specific preoperative planning of Robotics-Assisted Minimally Invasive Cardiac Surgery (RAMICS) is presented. It is expected that preoperative planning of RAMICS will improve the success rate by considering robot kinematics, patient-specific thoracic anatomy, and procedure-specific intraoperative conditions. Given the significant anatomical features localized in the preoperative computed tomography images of a patients thorax, port locations and robot orientations (with respect to the patients body coordinate frame) are determined to optimize qualities such as dexterity, reachability, tool approach angles and maneuverability. To address intraoperative geometric uncertainty, the problem is formulated as a Generalized Semi-Infinite Program (GSIP) with a convex lower-level problem to seek a plan that is less sensitive to geometric uncertainty in the neighborhood of surgical targets. It is demonstrated that with a proper formulation of the problem, the GSIP can be replaced by a tractable constrained nonlinear program that uses a multi-criteria objective function to balance between the nominal task performance and robustness to collisions and joint limit violations. Finally, performance of the proposed formulation is demonstrated by a comparison between the plans generated by the algorithm and those recommended by an experienced surgeon for several case studies.

A fast torsionally compliant kinematic model of concentric-tube robots.

Concentric-tube robots have the potential to become an important surgical tool for robot-assisted percutaneous interventions. They can provide dexterous operation in a small constrained environment. The kinematic model of a concentric-tube robot has been well developed in terms of accuracy, but the computational cost places limitations on real-time implementation. In this paper, we propose a new technique that will substantially improve the computational efficiency of evaluating the kinematics of a concentric-tube robot in the context of developing a control strategy without sacrificing the accuracy of the results. In this paper we develop a torsionally compliant kinematic model using global variables. The model is validated by comparing the results obtained by computing the kinematic model corresponding to an experimental setup of a concentric-tube robot to which a force/torque sensor has been mounted at its base with those obtained directly from the experimental setup. The results indicate that it is feasible to compute the kinematics of the concentric-tube robot fast enough to allow the position/force control loop to be implemented at a rate of 1 kHz.

Optimal transseptal puncture location for robot-assisted left atrial catheter ablation.

BACKGROUND: The preferred method of treatment for atrial fibrillation (AF) is by catheter ablation, in which a catheter is guided into the left atrium through a transseptal puncture. However, the transseptal puncture constrains the catheter, thereby limiting its manoeuvrability and increasing the difficulty in reaching various locations in the left atrium. In this paper, we address the problem of choosing the optimal transseptal puncture location for performing cardiac ablation to obtain maximum manoeuvrability of the catheter. METHODS: We have employed an optimization algorithm to maximize the global isotropy index (GII) to evaluate the optimal transseptal puncture location. As part of this algorithm, a novel kinematic model for the catheter has been developed, based on a continuum robot model. Pre-operative MR/CT images of the heart are segmented using the open source image-guided therapy software, 3D Slicer, to obtain models of the left atrium and septal wall. These models are input to the optimization algorithm to evaluate the optimal transseptal puncture location. RESULTS: The continuum robot model accurately describes the kinematics of the catheter. Simulation and experimental results for the optimal transseptal puncture location are presented in this paper. The optimization algorithm generates discrete points on the septal wall for which the dexterity of the catheter in the left atrium is maximum, corresponding to a GII of 0.4362. CONCLUSION: We have developed an optimization algorithm based on the GII to evaluate the optimal position of the transseptal puncture for left atrial cardiac ablation.

New tactile sensing system for minimally invasive surgical tumour localization.

BACKGROUND: Minimally invasive surgery (MIS) suffers from the inability to directly palpate organs for tumour localization. A tactile sensing system (TSS), consisting of a probe and a visualization interface, was developed to present an active pressure map of the contact surface to locate tumours during MIS. METHODS: The TSS performance was compared to MIS graspers to locate occult 10 mm phantom tumours in ex vivo bovine liver and ex vivo porcine lung. Performance assessment included applied pressure, localization distance and accuracy. RESULTS: The TSS realized a relative 71% reduction in maximum applied pressure and a 31% increase in detection accuracy in liver tissue (when compared to MIS graspers) and demonstrated no significant differences in performance when palpating lung tissue. CONCLUSIONS: The TSS may help surgeons to identify occult tumours during surgery by restoring some of the haptic information lost during MIS.