345 research outputs found
Recovering Dense Tissue Multispectral Signal from in vivo RGB Images
Hyperspectral/multispectral imaging (HSI/MSI) contains rich information
clinical applications, such as 1) narrow band imaging for vascular
visualisation; 2) oxygen saturation for intraoperative perfusion monitoring and
clinical decision making [1]; 3) tissue classification and identification of
pathology [2]. The current systems which provide pixel-level HSI/MSI signal can
be generally divided into two types: spatial scanning and spectral scanning.
However, the trade-off between spatial/spectral resolution, the acquisition
time, and the hardware complexity hampers implementation in real-world
applications, especially intra-operatively. Acquiring high resolution images in
real-time is important for HSI/MSI in intra-operative imaging, to alleviate the
side effect caused by breathing, heartbeat, and other sources of motion.
Therefore, we developed an algorithm to recover a pixel-level MSI stack using
only the captured snapshot RGB images from a normal camera. We refer to this
technique as "super-spectral-resolution". The proposed method enables recovery
of pixel-level-dense MSI signals with 24 spectral bands at ~11 frames per
second (FPS) on a GPU. Multispectral data captured from porcine bowel and
sheep/rabbit uteri in vivo has been used for training, and the algorithm has
been validated using unseen in vivo animal experiments.Comment: accepted by Hamlyn Symposium 201
Minimally-invasive surgical application of multispectral and polarization resolved imaging
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Noise, transient dynamics, and the generation of realistic interspike interval variation in square-wave burster neurons
First return maps of interspike intervals for biological neurons that
generate repetitive bursts of impulses can display stereotyped structures
(neuronal signatures). Such structures have been linked to the possibility of
multicoding and multifunctionality in neural networks that produce and control
rhythmical motor patterns. In some cases, isolating the neurons from their
synaptic network revealsirregular, complex signatures that have been regarded
as evidence of intrinsic, chaotic behavior.
We show that incorporation of dynamical noise into minimal neuron models of
square-wave bursting (either conductance-based or abstract) produces signatures
akin to those observed in biological examples, without the need for fine-tuning
of parameters or ad hoc constructions for inducing chaotic activity. The form
of the stochastic term is not strongly constrained, and can approximate several
possible sources of noise, e.g. random channel gating or synaptic bombardment.
The cornerstone of this signature generation mechanism is the rich,
transient, but deterministic dynamics inherent in the square-wave
(saddle-node/homoclinic) mode of neuronal bursting. We show that noise causes
the dynamics to populate a complex transient scaffolding or skeleton in state
space, even for models that (without added noise) generate only periodic
activity (whether in bursting or tonic spiking mode).Comment: REVTeX4-1, 18 pages, 9 figure
Maximising Achievable Rates of Experimental Nonlinear Optical Fibre Transmission Systems
It is generally expected that the demand for digital data services will continue to grow, placing ever greater requirements on optical fibre networks which carry the bulk of digital data. Research to maximise achievable information rates (AIR) over fibre has led to increasing spectral efficiency, symbol rate and bandwidth use. All of these contribute to transmission impairments due to the nonlinear nature of the optical fibre. This thesis describes research performed to investigate the effects of nonlinear impair- ments on the AIRs of experimental optical fibre transmission. To maximise throughput, the entire available optical bandwidth should be filled with transmission channels. An investigation into large bandwidth transmission through the use of spectrally shaped amplified spontaneous emission noise (SS-ASE) was con- ducted. The enhanced Gaussian noise model is used to analytically describe this tech- nique, and SS-ASE was experimentally shown to provide a lower bound on the AIR. Nonlinear interference (NLI) was modelled from an inter-symbol interference (ISI) model to characterise the noise and was experimentally verified. This new understand- ing helps quantify potential gain available from nonlinearity mitigation. Multicore fibres offer an alternative route to improve AIR, and are susceptible to another noise source known as crosstalk. This inter-core crosstalk can be controlled by suitable design of the fibre, hence in the limiting case, NLI rather than crosstalk will limit AIR. Nonlinearity compensation was, for the first time, experimentally demon- strated in the presence of crosstalk in a homogeneous 7-core fibre and shown to provide an increase in AIR. The results of this thesis can be used to evaluate future transmission systems for maximising information rates. It was shown that experimentally, SS-ASE is a viable transmission tool to evaluate system performance, NLI can be characterised using an ISI model and nonlinearity mitigation is possible in MCF systems limited by crosstalk
Detecting the Sensing Area of A Laparoscopic Probe in Minimally Invasive Cancer Surgery
In surgical oncology, it is challenging for surgeons to identify lymph nodes
and completely resect cancer even with pre-operative imaging systems like PET
and CT, because of the lack of reliable intraoperative visualization tools.
Endoscopic radio-guided cancer detection and resection has recently been
evaluated whereby a novel tethered laparoscopic gamma detector is used to
localize a preoperatively injected radiotracer. This can both enhance the
endoscopic imaging and complement preoperative nuclear imaging data. However,
gamma activity visualization is challenging to present to the operator because
the probe is non-imaging and it does not visibly indicate the activity
origination on the tissue surface. Initial failed attempts used segmentation or
geometric methods, but led to the discovery that it could be resolved by
leveraging high-dimensional image features and probe position information. To
demonstrate the effectiveness of this solution, we designed and implemented a
simple regression network that successfully addressed the problem. To further
validate the proposed solution, we acquired and publicly released two datasets
captured using a custom-designed, portable stereo laparoscope system. Through
intensive experimentation, we demonstrated that our method can successfully and
effectively detect the sensing area, establishing a new performance benchmark.
Code and data are available at
https://github.com/br0202/Sensing_area_detection.gitComment: Accepted by MICCAI 202
Fluorescence lifetime imaging microscopy: in vivo application to diagnosis of oral carcinoma
A compact clinically compatible fluorescence lifetime imaging microscopy (FLIM) system was designed and built for intraoperative disease diagnosis and validated in vivo in a hamster oral carcinogenesis model. This apparatus allows for the remote image collection via a flexible imaging probe consisting of a gradient index objective lens and a fiber bundle. Tissue autofluorescence (337 nm excitation) was imaged using an intensified CCD with a gate width down to 0.2 ns. We demonstrate a significant contrast in fluorescence lifetime between tumor (1.77±0.26 ns) and normal (2.50±0.36 ns) tissues at 450 nm and an over 80% intensity decrease at 390 nm emission in tumor versus normal areas. The time-resolved images were minimally affected by tissue morphology, endogenous absorbers, and illumination. These results demonstrate the potential of FLIM as an intraoperative diagnostic technique
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