A sensorised surgical glove to improve training and detection of obstetric anal sphincter injury: A preclinical study on a pig model.

OBJECTIVE: To create a sensorised surgical glove that can accurately identify obstetric anal sphincter injury to facilitate timely repair, reduce complications and aid training. DESIGN: Proof-of-concept. SETTING: Laboratory. SAMPLE: Pig models. METHODS: Flexible triboelectric pressure/force sensors were mounted onto the fingertips of a routine surgical glove. The sensors produce a current when rubbed on materials of different characteristics which can be analysed. A per rectum examination was performed on the intact sphincter of pig cadavers, analogous to routine examination for obstetric anal sphincter injuries postpartum. An anal sphincter defect was created by cutting through the vaginal mucosa and into the external anal sphincter using a scalpel. The sphincter was then re-examined. Data and signals were interpreted. MAIN OUTCOME MEASURES: Sensitivity and specificity of the glove in detecting anal sphincter injury. RESULTS: In all, 200 examinations were performed. The sensors detected anal sphincter injuries in a pig model with sensitivities between 98% and 100% and a specificity of 100%. The current produced when examining an intact sphincter and sphincter with a defect was significantly different (p < 0.001). CONCLUSION: In this preliminary study, the sensorised glove accurately detected anal sphincter injury in a pig model. Future plans include its clinical translation, starting with an in-human study on postpartum women, to determine whether it can accurately detect different types of obstetric anal sphincter injury in vivo.

All-optical ultrasound catheter for rapid B-mode oesophageal imaging.

All-optical ultrasound (OpUS) is an imaging paradigm that uses light to both generate and receive ultrasound, and has progressed from benchtop to in vivo studies in recent years, demonstrating promise for minimally invasive surgical applications. In this work, we present a rapid pullback imaging catheter for side-viewing B-mode ultrasound imaging within the upper gastrointestinal tract. The device comprised an ultrasound transmitter configured to generate ultrasound laterally from the catheter and a plano-concave microresonator for ultrasound reception. This imaging probe was capable of generating ultrasound pressures in excess of 1 MPa with corresponding -6 dB bandwidths > 20 MHz. This enabled imaging resolutions as low as 45 µm and 120 µm in the axial and lateral extent respectively, with a corresponding signal-to-noise ratio (SNR) of 42 dB. To demonstrate the potential of the device for clinical imaging, an ex vivo swine oesophagus was imaged using the working channel of a mock endoscope for device delivery. The full thickness of the oesophagus was resolved and several tissue layers were present in the resulting ultrasound images. This work demonstrates the promise for OpUS to provide rapid diagnostics and guidance alongside conventional endoscopy.

Miniaturised dual-modality all-optical ultrasound probe for laser interstitial thermal therapy (LITT) monitoring.

All-optical ultrasound (OpUS) has emerged as an imaging paradigm well-suited to minimally invasive imaging due to its ability to provide high resolution imaging from miniaturised fibre optic devices. Here, we report a fibre optic device capable of concurrent laser interstitial thermal therapy (LITT) and real-time in situ all-optical ultrasound imaging for lesion monitoring. The device comprised three optical fibres: one each for ultrasound transmission, reception and thermal therapy light delivery. This device had a total lateral dimension of <1 mm and was integrated into a medical needle. Simultaneous LITT and monitoring were performed on ex vivo lamb kidney with lesion depth tracked using M-mode OpUS imaging. Using one set of laser energy parameters for LITT (5 W, 60 s), the lesion depth varied from 3.3 mm to 8.3 mm. In all cases, the full lesion depth could be visualised and measured with the OpUS images and there was a good statistical agreement with stereomicroscope images acquired after ablation (t=1.36, p=0.18). This work demonstrates the feasibility and potential of OpUS to guide LITT in tumour resection.

Fiber-optic hydrophone for detection of high-intensity ultrasound waves.

Fiber-optic hydrophones (FOHs) are widely used to detect high-intensity focused ultrasound (HIFU) fields. The most common type consists of an uncoated single-mode fiber with a perpendicularly cleaved end face. The main disadvantage of these hydrophones is their low signal-to-noise ratio (SNR). To increase the SNR, signal averaging is performed, but the associated increased acquisition times hinder ultrasound field scans. In this study, with a view to increasing SNR while withstanding HIFU pressures, the bare FOH paradigm is extended to include a partially reflective coating on the fiber end face. Here, a numerical model based on the general transfer-matrix method was implemented. Based on the simulation results, a single-layer, 172 nm TiO2-coated FOH was fabricated. The frequency range of the hydrophone was verified from 1 to 30 MHz. The SNR of the acoustic measurement with the coated sensor was 21 dB higher than that of the uncoated one. The coated sensor successfully withstood a peak positive pressure of 35 MPa for 6000 pulses.

Flexible triboelectric nanogenerators using transparent copper nanowire electrodes: energy harvesting, sensing human activities and material recognition.

Triboelectric nanogenerators (TENGs) have emerged as a promising green technology to efficiently harvest otherwise wasted mechanical energy from the environment and human activities. However, cost-effective and reliably performing TENGs require rational integration of triboelectric materials, spacers, and electrodes. The present work reports for the first time the use of oxydation-resistant pure copper nanowires (CuNWs) as an electrode to develop a flexible, and inexpensive TENG through a potentially scalable approach involving vacuum filtration and lactic acid treatment. A ∼6 cm2 device yields a remarkable open circuit voltage (Voc) of 200 V and power density of 10.67 W m-2 under human finger tapping. The device is robust, flexible and noncytotoxic as assessed by stretching/bending maneuvers, corrosion tests, continuous operation for 8000 cycles, and biocompatibility tests using human fibroblast cells. The device can power 115 light emitting diodes (LEDs) and a digital calculator; sense bending and motion from the human hand; and transmit Morse code signals. The robustness, flexibility, transparency, and non-cytotoxicity of the device render it particularly promising for a wide range of energy harvesting and advanced healthcare applications, such as sensorised smart gloves for tactile sensing, material identification and safer surgical intervention.

A Triboelectric Nanocomposite for Sterile Sensing, Energy Harvesting, and Haptic Diagnostics in Interventional Procedures from Surgical Gloves.

Advanced interfacial engineering has the potential to enable the successful realization of three features that are particularly important for a variety of healthcare applications: wettability control, antimicrobial activity to reduce infection risks, and sensing of physiological parameters. Here, a sprayable multifunctional triboelectric coating is exploited as a nontoxic, ultrathin tactile sensor that can be integrated directly on the fingertips of surgical gloves. The coating is based on a polymer blend mixed with zinc oxide (ZnO) nanoparticles, which enables antifouling and antibacterial properties. Additionally, the nanocomposite is superhydrophobic (self-cleaning) and is not cytotoxic. The coating is also triboelectric and can be applied directly onto surgical gloves with printed electrodes. The sensorized gloves so obtained enable mechanical energy harvesting, force sensing, and detection of materials stiffness changes directly from fingertip, which may complement proprioceptive feedback for clinicians. Just as importantly, the sensors also work with a second glove on top offering better reassurance regarding sterility in interventional procedures. As a case study of clinical use for stiffness detection, the sensors demonstrate successful detection of pig anal sphincter injury ex vivo. This may lead to improving the accuracy of diagnosing obstetric anal sphincter injury, resulting in prompt repair, fewer complications, and improved quality of life.

A Sensorised Surgical Glove to Analyze Forces During Neurosurgery.

BACKGROUND: Measuring intraoperative forces in real time can provide feedback mechanisms to improve patient safety and surgical training. Previous force monitoring has been achieved through the development of specialized and adapted instruments or use designs that are incompatible with neurosurgical workflow. OBJECTIVE: To design a universal sensorised surgical glove to detect intraoperative forces, applicable to any surgical procedure, and any surgical instrument in either hand. METHODS: We created a sensorised surgical glove that was calibrated across 0 to 10 N. A laboratory experiment demonstrated that the sensorised glove was able to determine instrument-tissue forces. Six expert and 6 novice neurosurgeons completed a validated grape dissection task 20 times consecutively wearing the sensorised glove. The primary outcome was median and maximum force (N). RESULTS: The sensorised glove was able to determine instrument-tissue forces reliably. The average force applied by experts (2.14 N) was significantly lower than the average force exerted by novices (7.15 N) ( P = .002). The maximum force applied by experts (6.32 N) was also significantly lower than the maximum force exerted by novices (9.80 N) ( P = .004). The sensorised surgical glove's introduction to operative workflow was feasible and did not impede on task performance. CONCLUSION: We demonstrate a novel and scalable technique to detect forces during neurosurgery. Force analysis can provide real-time data to optimize intraoperative tissue forces, reduce the risk of tissue injury, and provide objective metrics for training and assessment.

Bend-insensitive fiber optic ultrasonic tracking probe for cardiovascular interventions.

BACKGROUND: Transesophageal echocardiography (TEE) is widely used to guide medical device placement in minimally invasive cardiovascular procedures. However, visualization of the device tip with TEE can be challenging. Ultrasonic tracking, enabled by an integrated fiber optic ultrasound sensor (FOUS) that receives transmissions from the TEE probe, is very well suited to improving device localization in this context. The problem addressed in this study is that tight deflections of devices such as a steerable guide catheter can result in bending of the FOUS beyond its specifications and a corresponding loss of ultrasound sensitivity. PURPOSE: A bend-insensitive FOUS was developed, and its utility with ultrasonic tracking of a steerable tip during TEE-based image guidance was demonstrated. METHODS: Fiberoptic ultrasound sensors were fabricated using both standard and bend insensitive single mode fibers and subjected to static bending at the distal end. The interference transfer function and ultrasound sensitivities were compared for both types of FOUS. The bend-insensitive FOUS was integrated within a steerable guide catheter, which served as an exemplar device; the signal-to-noise ratio (SNR) of tracking signals from the catheter tip with a straight and a fully deflected distal end were measured in a cardiac ultrasound phantom for over 100 frames. RESULTS: With tight bending at the distal end (bend radius < 10 mm), the standard FOUS experienced a complete loss of US sensitivity due to high attenuation in the fiber, whereas the bend-insensitive FOUS had largely unchanged performance, with a SNR of 47.7 for straight fiber and a SNR of 36.8 at a bend radius of 3.0 mm. When integrated into the steerable guide catheter, the mean SNRs of the ultrasonic tracking signals recorded with the catheter in a cardiac phantom were similar for straight and fully deflected distal ends: 195 and 163. CONCLUSION: The FOUS fabricated from bend-insensitive fiber overcomes the bend restrictions associated with the FOUS fabricated from standard single mode fiber, thereby enabling its use in ultrasonic tracking in a wide range of cardiovascular devices.

Enhancement of instrumented ultrasonic tracking images using deep learning.

PURPOSE: Instrumented ultrasonic tracking provides needle localisation during ultrasound-guided minimally invasive percutaneous procedures. Here, a post-processing framework based on a convolutional neural network (CNN) is proposed to improve the spatial resolution of ultrasonic tracking images. METHODS: The custom ultrasonic tracking system comprised a needle with an integrated fibre-optic ultrasound (US) transmitter and a clinical US probe for receiving those transmissions and for acquiring B-mode US images. For post-processing of tracking images reconstructed from the received fibre-optic US transmissions, a recently-developed framework based on ResNet architecture, trained with a purely synthetic dataset, was employed. A preliminary evaluation of this framework was performed with data acquired from needle insertions in the heart of a fetal sheep in vivo. The axial and lateral spatial resolution of the tracking images were used as performance metrics of the trained network. RESULTS: Application of the CNN yielded improvements in the spatial resolution of the tracking images. In three needle insertions, in which the tip depth ranged from 23.9 to 38.4 mm, the lateral resolution improved from 2.11 to 1.58 mm, and the axial resolution improved from 1.29 to 0.46 mm. CONCLUSION: The results provide strong indications of the potential of CNNs to improve the spatial resolution of ultrasonic tracking images and thereby to increase the accuracy of needle tip localisation. These improvements could have broad applicability and impact across multiple clinical fields, which could lead to improvements in procedural efficiency and reductions in risk of complications.

Low-Field Actuating Magnetic Elastomer Membranes Characterized using Fibre-Optic Interferometry.

Smart robotic devices remotely powered by magnetic field have emerged as versatile tools for wide biomedical applications. Soft magnetic elastomer (ME) composite membranes with high flexibility and responsiveness are frequently incorporated to enable local actuation for wireless sensing or cargo delivery. However, the fabrication of thin ME membranes with good control in geometry and uniformity remains challenging, as well as the optimization of their actuating performances under low fields (milli-Tesla). In this work, the development of ME membranes comprising of low-cost magnetic powder and highly soft elastomer through a simple template-assisted doctor blading approach, is reported. The fabricated ME membranes are controllable in size (up to centimetre-scale), thickness (tens of microns) and high particle loading (up to 70 wt.%). Conflicting trade-off effects of particle concentration upon magnetic responsiveness and mechanical stiffness are investigated and found to be balanced off as it exceeds 60 wt.%. A highly sensitive fibre-optic interferometric sensing system and a customized fibre-ferrule-membrane probe are first proposed to enable dynamic actuation and real-time displacement characterization. Free-standing ME membranes are magnetically excited under low field down to 2 mT, and optically monitored with nanometer accuracy. The fast and consistent responses of ME membranes showcase their promising biomedical applications in nanoscale actuation and sensing.

Intraoperative Needle Tip Tracking with an Integrated Fibre-Optic Ultrasound Sensor.

Ultrasound is an essential tool for guidance of many minimally-invasive surgical and interventional procedures, where accurate placement of the interventional device is critical to avoid adverse events. Needle insertion procedures for anaesthesia, fetal medicine and tumour biopsy are commonly ultrasound-guided, and misplacement of the needle may lead to complications such as nerve damage, organ injury or pregnancy loss. Clear visibility of the needle tip is therefore critical, but visibility is often precluded by tissue heterogeneities or specular reflections from the needle shaft. This paper presents the in vitro and ex vivo accuracy of a new, real-time, ultrasound needle tip tracking system for guidance of fetal interventions. A fibre-optic, Fabry-Pérot interferometer hydrophone is integrated into an intraoperative needle and used to localise the needle tip within a handheld ultrasound field. While previous, related work has been based on research ultrasound systems with bespoke transmission sequences, the new system-developed under the ISO 13485 Medical Devices quality standard-operates as an adjunct to a commercial ultrasound imaging system and therefore provides the image quality expected in the clinic, superimposing a cross-hair onto the ultrasound image at the needle tip position. Tracking accuracy was determined by translating the needle tip to 356 known positions in the ultrasound field of view in a tank of water, and by comparison to manual labelling of the the position of the needle in B-mode US images during an insertion into an ex vivo phantom. In water, the mean distance between tracked and true positions was 0.7 ± 0.4 mm with a mean repeatability of 0.3 ± 0.2 mm. In the tissue phantom, the mean distance between tracked and labelled positions was 1.1 ± 0.7 mm. Tracking performance was found to be independent of needle angle. The study demonstrates the performance and clinical compatibility of ultrasound needle tracking, an essential step towards a first-in-human study.

Enhanced Photoacoustic Visualisation of Clinical Needles by Combining Interstitial and Extracorporeal Illumination of Elastomeric Nanocomposite Coatings.

Ultrasound (US) image guidance is widely used for minimally invasive procedures, but the invasive medical devices (such as metallic needles), especially their tips, can be poorly visualised in US images, leading to significant complications. Photoacoustic (PA) imaging is promising for visualising invasive devices and peripheral tissue targets. Light-emitting diodes (LEDs) acting as PA excitation sources facilitate the clinical translation of PA imaging, but the image quality is degraded due to the low pulse energy leading to insufficient contrast with needles at deep locations. In this paper, photoacoustic visualisation of clinical needles was enhanced by elastomeric nanocomposite coatings with superficial and interstitial illumination. Candle soot nanoparticle-polydimethylsiloxane (CSNP-PDMS) composites with high optical absorption and large thermal expansion coefficients were applied onto the needle exterior and the end-face of an optical fibre placed in the needle lumen. The excitation light was delivered at the surface by LED arrays and through the embedded optical fibre by a pulsed diode laser to improve the visibility of the needle tip. The performance was validated using an ex-vivo tissue model. An LED-based PA/US imaging system was used for imaging the needle out-of-plane and in-plane insertions over approach angles of 20 deg to 55 deg. The CSNP-PDMS composite conferred substantial visual enhancements on both the needle shaft and the tip, with an average of 1.7- and 1.6-fold improvements in signal-to-noise ratios (SNRs), respectively. With the extended light field involving extracorporeal and interstitial illumination and the highly absorbing coatings, enhanced visualisation of the needle shaft and needle tip was achieved with PA imaging, which could be helpful in current US-guided minimally invasive surgeries.

High-resolution sub-millimetre diameter side-viewing all-optical ultrasound transducer based on a single dual-clad optical fibre.

All-optical ultrasound (OpUS), where ultrasound is both generated and received using light, has emerged as a modality well-suited to highly miniaturised applications. In this work we present a proof-of-concept OpUS transducer built onto a single optical fibre with a highly miniaturised lateral dimension (<0.8 mm). A key innovation was to use a dual-clad optical fibre (DCF) to provide multimode light for ultrasound generation and single mode light for ultrasound reception. The transducer comprised a proximal section of DCF spliced to a short section of single mode fibre (SMF). Multimode light was outcoupled at the splice joint and guided within a square capillary to provide excitation for ultrasound generation. Whilst single mode light was guided to the distal tip of the SMF to a plano-concave microresonator for ultrasound reception. The device was capable of generating ultrasound with pressures >0.4 MPa and a corresponding bandwidth >27 MHz. Concurrent ultrasound generation and reception from the transducer enabled imaging via motorised pull-back allowing image acquisition times of 4 s for an aperture of 20 mm. Image resolution was as low as ~50 µm and 190 µm in the axial and lateral extents, respectively, without the need for image reconstruction. Porcine aorta was imaged ex vivo demonstrating detailed ultrasound images. The unprecedented level of miniaturisation along with the high image quality produced by this device represents a radical new paradigm for minimally invasive imaging.

PDMS composites with photostable NIR dyes for multi-modal ultrasound imaging.

Abstract: All-optical ultrasound (OpUS) imaging has emerged as an imaging paradigm well-suited for minimally invasive surgical procedures. With this modality, ultrasound is generated when pulsed or modulated light is absorbed within a coating material. By engineering wavelength-selective coatings, complementary imaging and therapeutic modalities can be integrated with OpUS. Here, we present a wavelength-selective composite material comprising a near-infrared absorbing dye and polydimethylsiloxane. The optical absorption for this material peaked in the vicinity of 1064 nm, with up to 91% of incident light being absorbed, whilst maintaining lower optical absorption at other wavelengths. This material was used to generate ultrasound, demonstrating ultrasound pressures > 1  MPa, consistent with those used for imaging applications. Crucially, long exposure photostability and device performance were found to be stable over a one hour period (peak pressure variation < 10 %), longer than required for standard clinical imaging applications.

Improving needle visibility in LED-based photoacoustic imaging using deep learning with semi-synthetic datasets.

Photoacoustic imaging has shown great potential for guiding minimally invasive procedures by accurate identification of critical tissue targets and invasive medical devices (such as metallic needles). The use of light emitting diodes (LEDs) as the excitation light sources accelerates its clinical translation owing to its high affordability and portability. However, needle visibility in LED-based photoacoustic imaging is compromised primarily due to its low optical fluence. In this work, we propose a deep learning framework based on U-Net to improve the visibility of clinical metallic needles with a LED-based photoacoustic and ultrasound imaging system. To address the complexity of capturing ground truth for real data and the poor realism of purely simulated data, this framework included the generation of semi-synthetic training datasets combining both simulated data to represent features from the needles and in vivo measurements for tissue background. Evaluation of the trained neural network was performed with needle insertions into blood-vessel-mimicking phantoms, pork joint tissue ex vivo and measurements on human volunteers. This deep learning-based framework substantially improved the needle visibility in photoacoustic imaging in vivo compared to conventional reconstruction by suppressing background noise and image artefacts, achieving 5.8 and 4.5 times improvements in terms of signal-to-noise ratio and the modified Hausdorff distance, respectively. Thus, the proposed framework could be helpful for reducing complications during percutaneous needle insertions by accurate identification of clinical needles in photoacoustic imaging.

A patient-specific multi-modality abdominal aortic aneurysm imaging phantom.

PURPOSE: Multimodality imaging of the vascular system is a rapidly growing area of innovation and research, which is increasing with awareness of the dangers of ionizing radiation. Phantom models that are applicable across multiple imaging modalities facilitate testing and comparisons in pre-clinical studies of new devices. Additionally, phantom models are of benefit to surgical trainees for gaining experience with new techniques. We propose a temperature-stable, high-fidelity method for creating complex abdominal aortic aneurysm phantoms that are compatible with both radiation-based, and ultrasound-based imaging modalities, using low cost materials. METHODS: Volumetric CT data of an abdominal aortic aneurysm were acquired. Regions of interest were segmented to form a model compatible with 3D printing. The novel phantom fabrication method comprised a hybrid approach of using 3D printing of water-soluble materials to create wall-less, patient-derived vascular structures embedded within tailored tissue-mimicking materials to create realistic surrounding tissues. A non-soluble 3-D printed spine was included to provide a radiological landmark. RESULTS: The phantom was found to provide realistic appearances with intravascular ultrasound, computed tomography and transcutaneous ultrasound. Furthermore, the utility of this phantom as a training model was demonstrated during a simulated endovascular aneurysm repair procedure with image fusion. CONCLUSION: With the hybrid fabrication method demonstrated here, complex multimodality imaging patient-derived vascular phantoms can be successfully fabricated. These have potential roles in the benchtop development of emerging imaging technologies, refinement of novel minimally invasive surgical techniques and as clinical training tools.

Neural Network Kalman Filtering for 3-D Object Tracking From Linear Array Ultrasound Data.

Many interventional surgical procedures rely on medical imaging to visualize and track instruments. Such imaging methods not only need to be real time capable but also provide accurate and robust positional information. In ultrasound (US) applications, typically, only 2-D data from a linear array are available, and as such, obtaining accurate positional estimation in three dimensions is nontrivial. In this work, we first train a neural network, using realistic synthetic training data, to estimate the out-of-plane offset of an object with the associated axial aberration in the reconstructed US image. The obtained estimate is then combined with a Kalman filtering approach that utilizes positioning estimates obtained in previous time frames to improve localization robustness and reduce the impact of measurement noise. The accuracy of the proposed method is evaluated using simulations, and its practical applicability is demonstrated on experimental data obtained using a novel optical US imaging setup. Accurate and robust positional information is provided in real time. Axial and lateral coordinates for out-of-plane objects are estimated with a mean error of 0.1 mm for simulated data and a mean error of 0.2 mm for experimental data. The 3-D localization is most accurate for elevational distances larger than 1 mm, with a maximum distance of 6 mm considered for a 25-mm aperture.

Ultrasonic Needle Tracking with Dynamic Electronic Focusing.

Accurate identification of the needle tip is a key challenge with ultrasound-guided percutaneous interventions in regional anaesthesia, foetal surgery and cardiovascular medicine. In this study, we developed an ultrasonic needle tracking system in which the measured needle tip location was used to set the electronic focus of the external ultrasound imaging probe. In this system, needle tip tracking was enabled with a fibre-optic ultrasound sensor that was integrated into a needle stylet, and the A-lines recorded by the sensor were processed to generate tracking images of the needle tip. The needle tip position was estimated from the tracking images. The dependency of the tracking image on the electronic focal depth of the external ultrasound imaging probe was studied in a water bath and with needle insertions into a clinical training phantom. The variability in the estimated tracked position of the needle tip, with the needle tip at fixed depths in the imaging plane across a depth range from 0.5 to 7.5 cm, was studied. When the electronic focus was fixed, the variability of tracked position was found to increase with distance from that focus. The variability with the fixed focus was found to depend on the the relative distance between the needle tip and focal depth. It was found that with dynamic focusing, the maximum variability of tracked position was below 0.31 mm, as compared with 3.97 mm for a fixed focus.

Dual-modality fibre optic probe for simultaneous ablation and ultrasound imaging.

All-optical ultrasound (OpUS) is an emerging high resolution imaging paradigm utilising optical fibres. This allows both therapeutic and imaging modalities to be integrated into devices with dimensions small enough for minimally invasive surgical applications. Here we report a dual-modality fibre optic probe that synchronously performs laser ablation and real-time all-optical ultrasound imaging for ablation monitoring. The device comprises three optical fibres: one each for transmission and reception of ultrasound, and one for the delivery of laser light for ablation. The total device diameter is < 1 mm. Ablation monitoring was carried out on porcine liver and heart tissue ex vivo with ablation depth tracked using all-optical M-mode ultrasound imaging and lesion boundary identification using a segmentation algorithm. Ablation depths up to 2.1 mm were visualised with a good correspondence between the ultrasound depth measurements and visual inspection of the lesions using stereomicroscopy. This work demonstrates the potential for OpUS probes to guide minimally invasive ablation procedures in real time.

Preventing stillbirth from obstructed labor: A sensorized, low-cost device to train in safer operative birth.

Background: 98% of stillbirths occur in low- and middle- income countries. Obstructed labor is a common cause for both neonatal and maternal mortality, with a lack of skilled birth attendants one of the main reasons for the reduction in operative vaginal birth, especially in low- and middle- income countries. We introduce a low cost, sensorized, wearable device for digital vaginal examination to facilitate accurate assessment of fetal position and force applied to the fetal head, to aid training in safe operative vaginal birth. Methods: The device consists of flexible pressure/force sensors mounted onto the fingertips of a surgical glove. Phantoms of the neonatal head were developed to replicate sutures. An Obstetrician tested the device on the phantoms by performing a mock vaginal examination at full dilatation. Data was recorded and signals interpreted. Software was developed so that the glove can be used with a simple smartphone app. A patient and public involvement panel was consulted on the glove design and functionality. Results: The sensors achieved a 20 Newton force range and a 0.1 Newton sensitivity, leading to 100% accuracy in detecting fetal sutures, including when different degrees of molding or caput were present. They also detected sutures and force applied with a second sterile surgical glove on top. The software developed allowed a force threshold to be set, alerting the clinician when excessive force is applied. Patient and public involvement panels welcomed the device with great enthusiasm. Feedback indicated that women would accept, and prefer, clinicians to use the device if it could improve safety and reduce the number of vaginal examinations required. Conclusion: Under phantom conditions to simulate the fetal head in labor, the novel sensorized glove can accurately determine fetal sutures and provide real-time force readings, to support safer clinical training and practice in operative birth. The glove is low cost (approximately 1 USD). Software is being developed so fetal position and force readings can be displayed on a mobile phone. Although substantial steps in clinical translation are required, the glove has the potential to support efforts to reduce the number of stillbirths and maternal deaths secondary to obstructed labor in low- and -middle income countries.