A Biomechanics-Aware Robot-Assisted Steerable Drilling Framework for Minimally Invasive Spinal Fixation Procedures.

In this paper, we propose a novel biomechanics-aware robot-assisted steerable drilling framework with the goal of addressing common complications of spinal fixation procedures occurring due to the rigidity of drilling instruments and implants. This framework is composed of two main unique modules to design a robotic system including (i) a Patient-Specific Biomechanics-aware Trajectory Selection Module used to analyze the stress and strain distribution along an implanted pedicle screw in a generic drilling trajectory (linear and/or curved) and obtain an optimal trajectory; and (ii) a complementary semi-autonomous robotic drilling module that consists of a novel Concentric Tube Steerable Drilling Robot (CT-SDR) integrated with a seven degree-of-freedom robotic manipulator. This semi-autonomous robot-assisted steerable drilling system follows a multi-step drilling procedure to accurately and reliably execute the optimal hybrid drilling trajectory (HDT) obtained by the Trajectory Selection Module. Performance of the proposed framework has been thoroughly analyzed on simulated bone materials by drilling various trajectories obtained from the finite element-based Selection Module using Quantitative Computed Tomography (QCT) scans of a real patient's vertebra.

A Novel Dual Layer Cascade Reliability Framework for an Informed and Intuitive Clinician-AI Interaction In Diagnosis of Colorectal Cancer Polyps.

We present a novel Cascade Reliability Framework (CRF) that integrates two independent cascade layers of reliability (i.e., variational temperature scaling and conformal prediction) with a pre-trained Machine Learning (ML) model in order to provide clinicians with a more reliable and tunable tool for early-stage diagnosis of Colorectal Cancer (CRC) polyps. The conformal prediction layer generates predictive sets that are guaranteed to contain the true polyp type with an adjustable error rate tuned by clinicians, while the confidence calibration generates meaningful confidence estimates for each predicted label. These two layers provide additional information and an error-tuning-ability for clinicians to assist them in making informed and intuitive decisions considering the outputs of the pre-trained ML model. Utilizing a novel vision-based tactile sensor and unique 3D-printed CRC polyp phantoms, we evaluated the trustworthiness of the proposed architecture and particularly dual outputs of four different types of CRF models, integrated with two different pre-trained ML models (i.e., ResNet18 and Dilated Residual Network) to highlight the model-agnostic feature of the architecture. To thoroughly assess the performance of the proposed approach, we used reliability diagrams and metrics such as accuracy, coverage, and average set size, while also addressing inter-class performance. Results demonstrate that the calibrated CRF models are well capable of handling non-ideal inputs with noise and blur. Moreover, using the conformal prediction with a user-defined error rate and various experiments, we show how clinicians can intuitively interact with a pre-trained ML model to make informed decisions and minimize the risk of CRC polyps misdiagnoses.

Design and Development of a Novel Soft and Inflatable Tactile Sensing Balloon for Early Diagnosis of Colorectal Cancer Polyps.

In this paper, with the goal of addressing the high early-detection miss rate of colorectal cancer (CRC) polyps during a colonoscopy procedure, we propose the design and fabrication of a unique inflatable vision-based tactile sensing balloon (VTSB). The proposed soft VTSB can readily be integrated with the existing colonoscopes and provide a radiation-free, safe, and high-resolution textural mapping and morphology characterization of CRC polyps. The performance of the proposed VTSB has been thoroughly characterized and evaluated on four different types of additively manufactured CRC polyp phantoms with three different stiffness levels. Additionally, we integrated the VTSB with a colonoscope and successfully performed a simulated colonoscopic procedure inside a tube with a few CRC polyp phantoms attached to its internal surface.

Impaired robotic surgical visualization: archaic issues in a modern operating room.

While robotic-assisted surgery (RAS) has been revolutionizing surgical procedures, it has various areas needing improvement, specifically in the visualization sector. Suboptimal vision due to lens occlusions has been a topic of concern in laparoscopic surgery but has not received much attention in robotic surgery. This study is one of the first to explore and quantify the degree of disruption encountered due to poor robotic visualization at a major academic center. In case observations across 28 RAS procedures in various specialties, any lens occlusions or "debris" events that appeared on the monitor displays and clinicians' reactions, the cause, and the location across the monitor for these events were recorded. Data were then assessed for any trends using analysis as described below. From around 44.33 h of RAS observation time, 163 debris events were recorded. 52.53% of case observation time was spent under a compromised visual field. In a subset of 15 cases, about 2.24% of the average observation time was spent cleaning the lens. Additionally, cautery was found to be the primary cause of lens occlusions and little variation was found within the spread of the debris across the monitor display. This study illustrates that in 6 (21.43%) of the cases, 90% of the observation time was spent under compromised visualization while only 2 (7.14%) of the cases had no debris or cleaning events. Additionally, we observed that cleaning the lens can be troublesome during the procedure, interrupting the operating room flow.

A Concentric Tube Steerable Drilling Robot for Minimally Invasive Spinal Fixation of Osteoporotic Vertebrae.

Spinal fixation with rigid pedicle screws have shown to be an effective treatment for many patients. However, this surgical option has been proved to be insufficient and will eventually fail for patients experiencing osteoporosis. This failure is mainly attributed to the lack of dexterity in the existing rigid drilling instruments and the complex anatomy of vertebrae, forcing surgeons to implant rigid pedicle screws within the osteoporotic regions of anatomy. To address this problem, in this article, we present the design, fabrication, and evaluation of a unique flexible yet structurally strong concentric tube steerable drilling robot (CT-SDR). The CT-SDR is capable of drilling smooth and accurate curved trajectories through hard tissues without experiencing buckling and failure; thus enabling the use of novel flexible pedicle screws for the next generation of spinal fixation procedures. Particularly, by decoupling the control of bending and insertion degrees of freedom (DoF) of the CT-SDR, we present a robotic system that (i) is intuitive to steer as it does not require an on-the-fly control algorithm for the bending DoF, and (ii) is able to address the contradictory requirements of structural stiffness and dexterity of a flexible robot interacting with the hard tissue. The robust and repeatable performance of the proposed CT-SDR have been experimentally evaluated by conducting various drilling procedures on simulated bone materials and animal bone samples. Experimental results indicate drilling times as low as 35 seconds for curved trajectories with 41 mm length and remarkable steering accuracy with a maximum 2% deviation error.

A Reliable and Sensitive Framework for Simultaneous Type and Stage Detection of Colorectal Cancer Polyps.

With the goal of enhancing the early diagnosis of colorectal cancer (CRC) polyps and reducing the risk of mortality in cancer patients, in this article, we present a unique diagnosis framework including a Vision-based Surface Tactile Sensor (VS-TS) and complementary Artificial Intelligence algorithms. Leveraging the morphological characteristics (i.e., shape and texture) and stiffness features of the CRC polyps, the proposed framework is able to reliably and sensitively identify their type and stage. To thoroughly characterize and identify the required VS-TS sensitivity for reliable identification of polyps, we first fabricated three different VS-TSs and qualitatively evaluated their performances on 48 different types of polyp phantoms fabricated based on four different types of realistic CRC polyps and three different materials. Next, to quantitatively compare the performance and sensitivity of the fabricated VS-TSs, we used Support Vector Machine (SVM) algorithm and employed various statistical metrics (i.e., accuracy, reliability, and sensitivity). Next, using the most sensitive VS-TS, we classified the type of tumors using the SVM algorithm and applied the t-Distributed Stochastic Neighbor Embedding algorithm to successfully identify the stiffness of classified polyp phantoms solely based on the output images of the VS-TS sensor. Results demonstrated that an SVM algorithm applied on the image outputs of a VS-TS with a Shore hardness of 00-40 scale is able to classify all types of polyps with > 90% accuracy, sensitivity, and reliability. We also repeated experiments on samples of ex-vivo lamb tripe tissues and successfully verified the high sensitivity and reliability of the proposed framework (i.e., > 94%).

Influence of Antagonistic Tensions on Distributed Friction Forces of Multisegment Tendon-Driven Continuum Manipulators With Irregular Geometry.

In this paper, we thoroughly analyze the effect of single-tendon and antagonistic tendons actuation on tension loss of multi-segment tendon-driven continuum manipulators (TD-CMs) with irregular geometry. To this end, we propose a generic analytical modeling approach and iterative algorithm that can solve the unknown correlation between distributed friction force, tendons' tension transmission loss, and planar deformation behavior of TD-CMs during tendons' pulling and releasing phases. The proposed generic model solely relies on known input tendons' tensions and does not require a priori knowledge of the manipulator's shape and/or other experimental conditions. To investigate the influence of actuation type on tension loss and deformation behavior of TD-CMs, we fabricated two different TD-CMs and performed various simulation and experimental studies with single-tendon and antagonistic tensions actuations. The obtained results indicate the importance of considering the effect of distributed friction force and actuation type on tension(s) loss of multi-segment TD-CMs. Moreover, it clearly demonstrates the efficacy and accuracy of the proposed model in providing insights and understanding of tension transmission process in various types of actuations in multi-segment TD-CMs with irregular geometry.

Impact of Generic Tendon Routing on Tension Loss of Tendon-Driven Continuum Manipulators with Planar Deformation.

We present a novel physically-intuitive mathematical formulation to investigate the effects of a fully-constrained generic tendon routing (GTR) on the correlation between tension loss and deformation behavior of a variable-curvature tendon-driven continuum manipulator (TD-CM). The proposed model can account for distributed friction forces/moments along a GTR path that have been typically ignored in the previous approaches (e.g., the well-known frictionless Cosserat rod model). For the first time, the internal distributed forces on a GTR are expressed using three physically-intuitive generic functions. Solely relying on the known actuation input(s), the proposed mathematical formulation can also solve the entangled and unknown correlation between GTR, internal distributed forces, tension loss and deformation behavior of TD-CMs. To evaluate the performance of the proposed approach, we performed various simulation studies using eight different GTR paths. Additionally, we fabricated two different types of TD-CMs with different GTRs to experimentally evaluate the efficacy and performance of the proposed mathematical framework. The results demonstrate the proposed model can successfully and accurately (i.e., about <10% error) capture the trends of substantial tension loss (e.g., about <50%) on fully constrained GTRs, which reveals the importance of considering tension loss in modeling these TD-CMs.

Advances in microfabrication technologies in tissue engineering and regenerative medicine.

BACKGROUND: Tissue engineering provides various strategies to fabricate an appropriate microenvironment to support the repair and regeneration of lost or damaged tissues. In this matter, several technologies have been implemented to construct close-to-native three-dimensional structures at numerous physiological scales, which are essential to confer the functional characteristics of living tissues. METHODS: In this article, we review a variety of microfabrication technologies that are currently utilized for several tissue engineering applications, such as soft lithography, microneedles, templated and self-assembly of microstructures, microfluidics, fiber spinning, and bioprinting. RESULTS: These technologies have considerably helped us to precisely manipulate cells or cellular constructs for the fabrication of biomimetic tissues and organs. Although currently available tissues still lack some crucial functionalities, including vascular networks, innervation, and lymphatic system, microfabrication strategies are being proposed to overcome these issues. Moreover, the microfabrication techniques that have progressed to the preclinical stage are also discussed. CONCLUSIONS: This article aims to highlight the advantages and drawbacks of each technique and areas of further research for a more comprehensive and evolving understanding of microfabrication techniques in terms of tissue engineering and regenerative medicine applications.

Coaxial 3D bioprinting of tri-polymer scaffolds to improve the osteogenic and vasculogenic potential of cells in co-culture models.

The crosstalk between osteoblasts and endothelial cells is critical for bone vascularization and regeneration. Here, we used a coaxial 3D bioprinting method to directly print an osteon-like structure by depositing angiogenic and osteogenic bioinks from the core and shell regions of the coaxial nozzle, respectively. The bioinks were made up of gelatin, gelatin methacryloyl (GelMA), alginate, and hydroxyapatite (HAp) nanoparticles and were loaded with human umbilical vascular endothelial cells (HUVECs) and osteoblasts (MC3T3) in the core and shell regions, respectively. Conventional monoaxial 3D bioprinting was used as a control method, where the hydrogels, HAp nanoparticles, MC3T3 cells, and HUVECs were all mixed in one bioink and printed from the core nozzle. As a result, the bioprinted scaffolds were composed of cell-laden fibers with either a core-shell or homogenous structure, providing a non-contact (indirect) or contact (direct) co-culture of MC3T3 cells and HUVECs, respectively. Both structures supported the 3D culture of HUVECs and osteoblasts over a long period. The scaffolds also supported the expression of osteogenic and angiogenic factors. However, the gene expression was significantly higher for the core-shell structure than the homogeneous structure due to the well-defined distribution of osteoblasts and endothelial cells and the formation of vessel-like structures in the co-culture system. Our results indicated that the coaxial bioprinting technique, with the ability to create a non-contact co-culture of cells, can provide a more efficient bioprinting strategy for printing highly vascularized and bioactive bone structures.

Multiphysical Analytical Modeling and Design of A Magnetically Steerable Robotic Catheter for Treatment of Peripheral Artery Disease.

This article presents a unique multiphysical analytical modeling framework and solution algorithm to provide an effective tool for design of magnetically steerable robotic catheters (MSRCs) experiencing external interaction loads. Particularly, in this study, we are interested in design and fabrication of a MSRC with flexural patterns for treatment of peripheral artery disease (PAD). Aside from the parameters involved in the magnetic actuation system and the external interaction loads acting on the MSRC, the considered flexural patterns have a critical role on the deformation behavior and steerability of the proposed MSRC. Therefore, to optimally design such MSRC, we utilized the proposed multiphysical modeling approach and thoroughly evaluated the influence of involved parameters on the performance of the MSRC via two simulations studies. We also conducted experimental studies in a free bending condition and in the presence of different external interaction loads on two custom-designed MSRCs to thoroughly evaluate the efficacy of the proposed multiphysical model and solution algorithm. Our analysis demonstrates the accuracy of the proposed approach and necessity of utilizing such models to optimally design a MSRC before fabrication procedure.

Stochastic Force-based Insertion Depth and Tip Position Estimations of Flexible FBG-Equipped Instruments in Robotic Retinal Surgery.

Vitreoretinal surgery is among the most delicate surgical tasks during which surgeon hand tremor may severely attenuate surgeon performance. Robotic assistance has been demonstrated to be beneficial in diminishing hand tremor. Among the requirements for reliable assistance from the robot is to provide precise measurements of system states e.g. sclera forces, tool tip position and tool insertion depth. Providing this and other sensing information using existing technology would contribute towards development and implementation of autonomous robot-assisted tasks in retinal surgery such as laser ablation, guided suture placement/assisted needle vessel cannulation, among other applications. In the present work, we use a state-estimating Kalman filtering (KF) to improve the tool tip position and insertion depth estimates, which used to be purely obtained by robot forward kinematics (FWK) and direct sensor measurements, respectively. To improve tool tip localization, in addition to robot FWK, we also use sclera force measurements along with beam theory to account for tool deflection. For insertion depth, the robot FWK is combined with sensor measurements for the cases where sensor measurements are not reliable enough. The improved tool tip position and insertion depth measurements are validated using a stereo camera system through preliminary experiments and a case study. The results indicate that the tool tip position and insertion depth measurements are significantly improved by 77% and 94% after applying KF, respectively.

A Surgical Robotic System for Treatment of Pelvic Osteolysis Using an FBG-Equipped Continuum Manipulator and Flexible Instruments.

This paper presents the development and experimental evaluation of a redundant robotic system for the less-invasive treatment of osteolysis (bone degradation) behind the acetabular implant during total hip replacement revision surgery. The system comprises a rigid-link positioning robot and a Continuum Dexterous Manipulator (CDM) equipped with highly flexible debriding tools and a Fiber Bragg Grating (FBG)-based sensor. The robot and the continuum manipulator are controlled concurrently via an optimization-based framework using the Tip Position Estimation (TPE) from the FBG sensor as feedback. Performance of the system is evaluated on a setup that consists of an acetabular cup and saw-bone phantom simulating the bone behind the cup. Experiments consist of performing the surgical procedure on the simulated phantom setup. CDM TPE using FBGs, target location placement, cutting performance, and the concurrent control algorithm capability in achieving the desired tasks are evaluated. Mean and standard deviation of the CDM TPE from the FBG sensor and the robotic system are 0.50 mm, and 0.18 mm, respectively. Using the developed surgical system, accurate positioning and successful cutting of desired straight-line and curvilinear paths on saw-bone phantoms behind the cup with different densities are demonstrated. Compared to the conventional rigid tools, the workspace reach behind the acetabular cup is 2.47 times greater when using the developed robotic system.

Analytical Design of a Pneumatic Elastomer Robot with Deterministically Adjusted Stiffness.

This paper presents a novel Pneumatic Elastomer Robot (PER), called Deterministically Adjusted Stiffness-Pneumatic Elasotmer Robot (DAS-PER), that can concurrently display preprogrammed elongation and bending behaviors. Our design methodology integrates a comprehensive analytical modeling and additive manufacturing-based fabrication to (i) address current ad-hoc and arduous PERs' fabrication limitations, and (ii) enable deterministic stiffness and deformation behavior tuning based on the desired application. To thoroughly evaluate the efficacy of the presented modeling and fabrication approaches, based on the developed model, we first designed and fabricated two DAS-PERs with different bending and elongation stiffnesses. Next, we performed experimental studies to thoroughly evaluate and compare the expected and obtained deformation behaviors. Results demonstrated the efficacy of the fabrication procedure and model fidelity for successful tunability of DAS-PERs solely based on adjusting two internal structure diameter parameters.

SCADE: Simultaneous Sensor Calibration and Deformation Estimation of FBG-Equipped Unmodeled Continuum Manipulators.

In this article, we present a novel stochastic algorithm called simultaneous sensor calibration and deformation estimation (SCADE) to address the problem of modeling deformation behavior of a generic continuum manipulator (CM) in free and obstructed environments. In SCADE, using a novel mathematical formulation, we introduce a priori model-independent filtering algorithm to fuse the continuous and inaccurate measurements of an embedded sensor (e.g., magnetic or piezoelectric sensors) with an intermittent but accurate data of an external imaging system (e.g., optical trackers or cameras). The main motivation of this article is the crucial need of obtaining an accurate shape/position estimation of a CM utilized in a surgical intervention. In these robotic procedures, the CM is typically equipped with an embedded sensing unit (ESU) while an external imaging modality (e.g., ultrasound or a fluoroscopy machine) is also available in the surgical site. The results of two different set of prior experiments in free and obstructed environments were used to evaluate the efficacy of SCADE algorithm. The experiments were performed with a CM specifically designed for orthopaedic interventions equipped with an inaccurate Fiber Bragg Grating (FBG) ESU and overhead camera. The results demonstrated the successful performance of the SCADE algorithm in simultaneous estimation of unknown deformation behavior of the utilized unmodeled CM together with realizing the time-varying drift of the poor-calibrated FBG sensing unit. Moreover, the results showed the phenomenal out-performance of the SCADE algorithm in estimation of the CM's tip position as compared to FBG-based position estimations.

FBG-based Kalman Filtering and Control of Tool Insertion Depth For Safe Robot-assisted Vitrectomy.

Vitrectomy is that portion of retinal surgery in which the vitreous gel is removed either as a definitive treatment or to provide direct tool access to the retina. This procedure should be conducted prior to several eye surgeries in order to provide better access to the eyeball posterior. It is a relatively repeatable and straight forward procedure that lends itself to robotic assistance or potentially autonomous performance if tool contact with critical structures can be avoided. One of the detrimental incidences that can occur during the robot-assisted vitrectomy is when the robot penetrates the tool more than allowed boundaries into the eyeball toward retina. In this paper, we provide filtering and control to guide instrument insertion depth in order to avoid tool-to-retina contact. For this purpose, first the tool insertion depth measurement is improved using a Kalman filtering (KF) algorithm. This improved measurement is then used in an adaptive control strategy by which the robot reduces the tool insertion depth based on a predefined and safe trajectory for it, when safe boundaries are overstepped. The performance of the insertion depth safety control system is then compared to one in which the insertion depth is not passed through a Kalman filter prior to being fed to the control system. Our results indicate that applying KF in the adaptive control of the robot enhances procedure safety and enables the robot to always keep the tool insertion depth under the safe levels.

Radiation-free methods for navigated screw placement in slipped capital femoral epiphysis surgery.

PURPOSE: For orthopedic procedures, surgeons utilize intra-operative medical images such as fluoroscopy to plan screw placement and accurately position the guide wire with the intended trajectory. The number of fluoroscopic images needed depends on the complexity of the case and skill of the surgeon. Since more fluoroscopic images lead to more exposure and higher radiation dose for both surgeon and patient, a solution that decreases the number of fluoroscopic images would be an improvement in clinical care. METHODS: This article describes and compares three different novel navigation methods and techniques for screw placement using an attachable Inertial Measurement Unit device or a robotic arm. These methods provide projection and visualization of the surgical tool trajectory during the slipped capital femoral epiphysis procedure. RESULTS: These techniques resulted in faster and more efficient preoperative calibration and set up times compared to other intra-operative navigation systems in our phantom study. We conducted an experiment using 120 model bones to measure the accuracy of the methods. CONCLUSION: As conclusion, these approaches have the potential to improve accuracy of surgical tool navigation and decrease the number of required X-ray images without any change in the clinical workflow. The results also show 65% decrease in total error compared to the conventional manual approach.