Real-time and Freehand Multimodal Imaging: Combining White Light Endoscopy with All-Optical Ultrasound

Minimally invasive surgery offers significant benefits over open surgery in terms of patient recovery, complication rates, and cost. Accurate visualisation is key for successful interventions; however, no single imaging modality offers sufficient resolution, penetration, and soft-tissue contrast to adequately monitor interventional treatment. Consequently, multimodal interventional imaging is intensively investigated. All-optical ultrasound (AOUS) imaging is an emerging modality where light is used to both generate and detect ultrasound. Using fibre-optics, highly miniaturised imaging probes can be fabricated that yield high-quality pulse-echo images and are readily integrated into minimally invasive interventional instruments. In this work, we present the integration of a miniature (diameter: 800 µm), highly directional AOUS imaging probe into a commercially available white light urethroscope, and demonstrate the first real-time, 3D multimodal imaging combining AOUS and white light endoscopy. Through the addition of an electromagnetic tracker, the position and pose of the instrument could be continuously recorded. This facilitated accurate real-time registration of the imaging modalities, as well as freehand operation of the instrument. In addition, the freehand imaging paradigm allowed for “piece-wise” scanning where the instrument was retracted and repositioned without recalibration. The presented imaging probe and system could significantly improve the quality of image guidance during interventional surgery

Ultrasound 3D reconstruction of malignant masses in robotic-assisted partial nephrectomy using the PAF rail system: a comparison study

PURPOSE: In robotic-assisted partial nephrectomy (RAPN), the use of intraoperative ultrasound (IOUS) helps to localise and outline the tumours as well as the blood vessels within the kidney. The aim of this work is to evaluate the use of the pneumatically attachable flexible (PAF) rail system for US 3D reconstruction of malignant masses in RAPN. The PAF rail system is a novel device developed and previously presented by the authors to enable track-guided US scanning. METHODS: We present a comparison study between US 3D reconstruction of masses based on: the da Vinci Surgical System kinematics, single- and stereo-camera tracking of visual markers embedded on the probe. An US-realistic kidney phantom embedding a mass is used for testing. A new design for the US probe attachment to enhance the performance of the kinematic approach is presented. A feature extraction algorithm is proposed to detect the margins of the targeted mass in US images. RESULTS: To evaluate the performance of the investigated approaches the resulting 3D reconstructions have been compared to a CT scan of the phantom. The data collected indicates that single camera reconstruction outperformed the other approaches, reconstructing with a sub-millimetre accuracy the targeted mass. CONCLUSIONS: This work demonstrates that the PAF rail system provides a reliable platform to enable accurate US 3D reconstruction of masses in RAPN procedures. The proposed system has also the potential to be employed in other surgical procedures such as hepatectomy or laparoscopic liver resection

A Continuum Robot and Control Interface for Surgical Assist in Fetoscopic Interventions

Twin-twin transfusion syndrome requires interventional treatment using a fetoscopically introduced laser to sever the shared blood supply between the fetuses. This is a delicate procedure relying on small instrumentation with limited articulation to guide the laser tip and a narrow field of view to visualize all relevant vascular connections. In this letter, we report on a mechatronic design for a comanipulated instrument that combines concentric tube actuation to a larger manipulator constrained by a remote centre of motion. A stereoscopic camera is mounted at the distal tip and used for imaging. Our mechanism provides enhanced dexterity and stability of the imaging device. We demonstrate that the imaging system can be used for computing geometry and enhancing the view at the operating site. Results using electromagnetic sensors for verification and comparison to visual odometry from the distal sensor show that our system is promising and can be developed further for multiple clinical needs in fetoscopic procedures

3D printed kidney phantoms for an LED-based photoacoustic and ultrasound imaging system

Photoacoustic imaging is a powerful and increasingly popular technique for tissue diagnostics. Suitable tissue- equivalent phantoms are in high demand for validating photoacoustic imaging methods and for clinical training. In this work, we describe a method of directly 3D printing a photoacoustic tissue-equivalent phantom of a kidney based on Gel Wax, which is a mix of polymer and mineral oil. A kidney phantom that is compatible with photoacoustic scanning will enable clinicians to evaluate a portable LED-based photoacoustic and ultrasound imaging system as a means of locating tumors and other abnormalities. This represents a significant step towards clinical translation of the compact system. Training using realistic phantoms reduces the risks associated with clinical procedures. Complications during procedures can arise due to the specific structure of the kidney under investigation. Thus the ability to create a 3D printed phantom based on detailed anatomical images of a specific patient enables clinicians to train on a phantom with exactly the same structure as the kidney to be treated. Recently we developed a novel 3D printer based on gel wax. The device combines native gel wax with glass microspheres and titanium dioxide (TiO 2 ) particles to obtain a medium with tissue-like optical and acoustic properties. 3D models created using this printer can be given a range of values of optical absorption reduced scattering coefficients. The ability to 3D patient-specific phantoms at low cost has the potential to revolutionize the production and use of tissue-equivalent phantoms in future, and can be applied to a wide range of organs and imaging modalities

Publisher Correction: Hydro-climatic changes of wetlandscapes across the world

Assessments of ecosystem service and function losses of wetlandscapes (i.e., wetlands and their hydrological catchments) suffer from knowledge gaps regarding impacts of ongoing hydro-climatic change. This study investigates hydro-climatic changes during 1976–2015 in 25 wetlandscapes distributed across the world’s tropical, arid, temperate and cold climate zones. Results show that the wetlandscapes were subject to precipitation (P) and temperature (T) changes consistent with mean changes over the world’s land area. However, arid and cold wetlandscapes experienced higher T increases than their respective climate zone. Also, average P decreased in arid and cold wetlandscapes, contrarily to P of arid and cold climate zones, suggesting that these wetlandscapes are located in regions of elevated climate pressures. For most wetlandscapes with available runoff (R) data, the decreases were larger in R than in P, which was attributed to aggravation of climate change impacts by enhanced evapotranspiration losses, e.g. caused by land-use changes

Developing a simulator for multispectral optoacoustic tomography.

The aim of this study was the development of a simulator for Multispectral Optoacoustic Tomography (MSOT). The modelling pathway of the simulator was separated into the optical, the acoustic and the reconstruction part in generating finally a photoacoustic image. In this paper, the presented simulation geometry was based on a recently developed MSOT imaging system, but it can be easily modified to other imaging geometries. Through comparison between experimental and simulated data, a validation of the model as well as its limitations, perspectives and modifications are presented

Large area all-optical ultrasound imaging using robotic control

n this study we report the integration of an all-optical ultrasound probe and robotic manipulator. The alloptical ultrasound probe comprised two optical fibres, a MWCNT/PDMS composite coated multimode fibre for ultrasound generation, and a concave Fabry-Perot fibre optic hydrophone for ultrasound reception. The ultrasound probe generated pressures in excess of 2 MPa at 1:5 mm, with a corresponding -6 dB bandwidth of ca. 30 MHz. The probe was built into a rigid endoscope (outer diameter: 5 mm, length: 300 mm) and mounted on a robotic manipulator. Ultrasound A-lines were acquired during robot manipulation in order to reconstruct a 3D image which was displayed as a point cloud. Large area images (80 × 80 mm) of a tissue mimicking gel wax phantom where acquired and displayed in real-time. This work demonstrates the potential for integrating miniature fibre optic ultrasound devices with robotics

Robotic Control of a Multi-Modal Rigid Endoscope Combining Optical Imaging with All-Optical Ultrasound

Fetoscopy is a technically challenging surgery, due to the dynamic environment and low diameter endoscopes often resulting in a limited field of view. In this paper, we report on the design and operation of a robotic multimodal endoscope with optical ultrasound and white light stereo camera. The manufacture and control of the endoscope is presented, along with large area (80 mm x 80 mm) surface visualisations of a placenta phantom using the optical ultrasound sensor. The repeatability of the surface visualisations was found to be 0.446 ± 0.139 mm and 0.267 ± 0.017 mm for a raster and spiral scan, respectively