2,301 research outputs found
Autonomous Tissue Scanning under Free-Form Motion for Intraoperative Tissue Characterisation
In Minimally Invasive Surgery (MIS), tissue scanning with imaging probes is
required for subsurface visualisation to characterise the state of the tissue.
However, scanning of large tissue surfaces in the presence of deformation is a
challenging task for the surgeon. Recently, robot-assisted local tissue
scanning has been investigated for motion stabilisation of imaging probes to
facilitate the capturing of good quality images and reduce the surgeon's
cognitive load. Nonetheless, these approaches require the tissue surface to be
static or deform with periodic motion. To eliminate these assumptions, we
propose a visual servoing framework for autonomous tissue scanning, able to
deal with free-form tissue deformation. The 3D structure of the surgical scene
is recovered and a feature-based method is proposed to estimate the motion of
the tissue in real-time. A desired scanning trajectory is manually defined on a
reference frame and continuously updated using projective geometry to follow
the tissue motion and control the movement of the robotic arm. The advantage of
the proposed method is that it does not require the learning of the tissue
motion prior to scanning and can deal with free-form deformation. We deployed
this framework on the da Vinci surgical robot using the da Vinci Research Kit
(dVRK) for Ultrasound tissue scanning. Since the framework does not rely on
information from the Ultrasound data, it can be easily extended to other
probe-based imaging modalities.Comment: 7 pages, 5 figures, ICRA 202
A Survey on 3D Ultrasound Reconstruction Techniques
This book chapter aims to discuss the 3D ultrasound reconstruction and visualization. First, the various types of 3D ultrasound system are reviewed, such as mechanical, 2D array, position tracking-based freehand, and untracked-based freehand. Second, the 3D ultrasound reconstruction technique or pipeline used by the current existing system, which includes the data acquisition, data preprocessing, reconstruction method and 3D visualization, is discussed. The reconstruction method and 3D visualization will be emphasized. The reconstruction method includes the pixel-based method, volume-based method, and function-based method, accompanied with their benefits and drawbacks. In the 3D visualization, methods such as multiplanar reformatting, volume rendering, and surface rendering are presented. Lastly, its application in the medical field is reviewed as well
AiAReSeg: Catheter Detection and Segmentation in Interventional Ultrasound using Transformers
To date, endovascular surgeries are performed using the golden standard of
Fluoroscopy, which uses ionising radiation to visualise catheters and
vasculature. Prolonged Fluoroscopic exposure is harmful for the patient and the
clinician, and may lead to severe post-operative sequlae such as the
development of cancer. Meanwhile, the use of interventional Ultrasound has
gained popularity, due to its well-known benefits of small spatial footprint,
fast data acquisition, and higher tissue contrast images. However, ultrasound
images are hard to interpret, and it is difficult to localise vessels,
catheters, and guidewires within them. This work proposes a solution using an
adaptation of a state-of-the-art machine learning transformer architecture to
detect and segment catheters in axial interventional Ultrasound image
sequences. The network architecture was inspired by the Attention in Attention
mechanism, temporal tracking networks, and introduced a novel 3D segmentation
head that performs 3D deconvolution across time. In order to facilitate
training of such deep learning networks, we introduce a new data synthesis
pipeline that used physics-based catheter insertion simulations, along with a
convolutional ray-casting ultrasound simulator to produce synthetic ultrasound
images of endovascular interventions. The proposed method is validated on a
hold-out validation dataset, thus demonstrated robustness to ultrasound noise
and a wide range of scanning angles. It was also tested on data collected from
silicon-based aorta phantoms, thus demonstrated its potential for translation
from sim-to-real. This work represents a significant step towards safer and
more efficient endovascular surgery using interventional ultrasound.Comment: This work has been submitted to the IEEE for possible publicatio
A coarse-to-fine approach to prostate boundary segmentation in ultrasound images
BACKGROUND: In this paper a novel method for prostate segmentation in transrectal ultrasound images is presented. METHODS: A segmentation procedure consisting of four main stages is proposed. In the first stage, a locally adaptive contrast enhancement method is used to generate a well-contrasted image. In the second stage, this enhanced image is thresholded to extract an area containing the prostate (or large portions of it). Morphological operators are then applied to obtain a point inside of this area. Afterwards, a Kalman estimator is employed to distinguish the boundary from irrelevant parts (usually caused by shadow) and generate a coarsely segmented version of the prostate. In the third stage, dilation and erosion operators are applied to extract outer and inner boundaries from the coarsely estimated version. Consequently, fuzzy membership functions describing regional and gray-level information are employed to selectively enhance the contrast within the prostate region. In the last stage, the prostate boundary is extracted using strong edges obtained from selectively enhanced image and information from the vicinity of the coarse estimation. RESULTS: A total average similarity of 98.76%(± 0.68) with gold standards was achieved. CONCLUSION: The proposed approach represents a robust and accurate approach to prostate segmentation
Correlation of micro and nano–scale defects with WVTR for aluminium oxide barrier coatings for flexible photovoltaic modules
This paper seeks to establish a correlation between surface topographical defects and water vapour transmission rate (WVTR) measured under laboratory conditions for aluminium–oxide (Al2O3) barrier film employed in flexible photovoltaic (PV) modules. Defects in the barrier layers of PV modules causing high WVTR are not well characterised and understood. A WVTR of ~10−1 g/m2/day is sufficient for the most packaging applications, but ≤10−6 g/m2/day is required for the encapsulation of long–life flexible PV modules (Carcia et al., 2010a, 2010b). In this study, surface metrology techniques along with scanning electron microscopy (SEM) were used for a quantitative characterisation of the barrier film defects. The investigation have provided clear evidence for the correlation of surface defect density and the transmission of water vapour through the barrier coating layer. The outcomes would appear to suggest that small numbers of large defects are the dominant factor in determining WVTR for these barrier layers
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