1,663 research outputs found
3D Quasi-Static Ultrasound Elastography With Plane Wave In Vivo
In biological tissue, an increase in elasticity is often a marker of
abnormalities. Techniques such as quasi-static ultrasound elastography have
been developed to assess the strain distribution in soft tissues in two
dimensions using a quasi-static compression. However, as abnormalities can
exhibit very heterogeneous shapes, a three dimensional approach would be
necessary to accurately measure their volume and remove operator dependency.
Acquisition of volumes at high rates is also critical to performing real-time
imaging with a simple freehand compression. In this study, we developed for the
first time a 3D quasi-static ultrasound elastography method with plane waves
that estimates axial strain distribution in vivo in entire volumes at high
volume rate. Acquisitions were performed with a 2D matrix array probe of 2.5MHz
frequency and 256 elements. Plane waves were emitted at a volume rate of 100
volumes/s during a continuous motorized and freehand compression. 3D B-mode
volumes and 3D cumulative axial strain volumes were successfully estimated in
inclusion phantoms and in ex vivo canine liver before and after a high
intensity focused ultrasound ablation. We also demonstrated the in vivo
feasibility of the method using freehand compression on the calf muscle of a
human volunteer and were able to retrieve 3D axial strain volume at a high
volume rate depicting the differences in stiffness of the two muscles which
compose the calf muscle. 3D ultrasound quasi-static elastography with plane
waves could become an important technique for the imaging of the elasticity in
human bodies in three dimensions using simple freehand scanning
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
EchoFusion: Tracking and Reconstruction of Objects in 4D Freehand Ultrasound Imaging without External Trackers
Ultrasound (US) is the most widely used fetal imaging technique. However, US
images have limited capture range, and suffer from view dependent artefacts
such as acoustic shadows. Compounding of overlapping 3D US acquisitions into a
high-resolution volume can extend the field of view and remove image artefacts,
which is useful for retrospective analysis including population based studies.
However, such volume reconstructions require information about relative
transformations between probe positions from which the individual volumes were
acquired. In prenatal US scans, the fetus can move independently from the
mother, making external trackers such as electromagnetic or optical tracking
unable to track the motion between probe position and the moving fetus. We
provide a novel methodology for image-based tracking and volume reconstruction
by combining recent advances in deep learning and simultaneous localisation and
mapping (SLAM). Tracking semantics are established through the use of a
Residual 3D U-Net and the output is fed to the SLAM algorithm. As a proof of
concept, experiments are conducted on US volumes taken from a whole body fetal
phantom, and from the heads of real fetuses. For the fetal head segmentation,
we also introduce a novel weak annotation approach to minimise the required
manual effort for ground truth annotation. We evaluate our method
qualitatively, and quantitatively with respect to tissue discrimination
accuracy and tracking robustness.Comment: MICCAI Workshop on Perinatal, Preterm and Paediatric Image analysis
(PIPPI), 201
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