296 research outputs found
Automatic Segmentation and Disease Classification Using Cardiac Cine MR Images
Segmentation of the heart in cardiac cine MR is clinically used to quantify
cardiac function. We propose a fully automatic method for segmentation and
disease classification using cardiac cine MR images. A convolutional neural
network (CNN) was designed to simultaneously segment the left ventricle (LV),
right ventricle (RV) and myocardium in end-diastole (ED) and end-systole (ES)
images. Features derived from the obtained segmentations were used in a Random
Forest classifier to label patients as suffering from dilated cardiomyopathy,
hypertrophic cardiomyopathy, heart failure following myocardial infarction,
right ventricular abnormality, or no cardiac disease. The method was developed
and evaluated using a balanced dataset containing images of 100 patients, which
was provided in the MICCAI 2017 automated cardiac diagnosis challenge (ACDC).
The segmentation and classification pipeline were evaluated in a four-fold
stratified cross-validation. Average Dice scores between reference and
automatically obtained segmentations were 0.94, 0.88 and 0.87 for the LV, RV
and myocardium. The classifier assigned 91% of patients to the correct disease
category. Segmentation and disease classification took 5 s per patient. The
results of our study suggest that image-based diagnosis using cine MR cardiac
scans can be performed automatically with high accuracy.Comment: Accepted in STACOM Automated Cardiac Diagnosis Challenge 201
Coronary Artery Centerline Extraction in Cardiac CT Angiography Using a CNN-Based Orientation Classifier
Coronary artery centerline extraction in cardiac CT angiography (CCTA) images
is a prerequisite for evaluation of stenoses and atherosclerotic plaque. We
propose an algorithm that extracts coronary artery centerlines in CCTA using a
convolutional neural network (CNN).
A 3D dilated CNN is trained to predict the most likely direction and radius
of an artery at any given point in a CCTA image based on a local image patch.
Starting from a single seed point placed manually or automatically anywhere in
a coronary artery, a tracker follows the vessel centerline in two directions
using the predictions of the CNN. Tracking is terminated when no direction can
be identified with high certainty.
The CNN was trained using 32 manually annotated centerlines in a training set
consisting of 8 CCTA images provided in the MICCAI 2008 Coronary Artery
Tracking Challenge (CAT08). Evaluation using 24 test images of the CAT08
challenge showed that extracted centerlines had an average overlap of 93.7%
with 96 manually annotated reference centerlines. Extracted centerline points
were highly accurate, with an average distance of 0.21 mm to reference
centerline points. In a second test set consisting of 50 CCTA scans, 5,448
markers in the coronary arteries were used as seed points to extract single
centerlines. This showed strong correspondence between extracted centerlines
and manually placed markers. In a third test set containing 36 CCTA scans,
fully automatic seeding and centerline extraction led to extraction of on
average 92% of clinically relevant coronary artery segments.
The proposed method is able to accurately and efficiently determine the
direction and radius of coronary arteries. The method can be trained with
limited training data, and once trained allows fast automatic or interactive
extraction of coronary artery trees from CCTA images.Comment: Accepted in Medical Image Analysi
Programmable two-photon quantum interference in channels in opaque scattering media
We investigate two-photon quantum interference in an opaque scattering medium
that intrinsically supports transmission channels. By adaptive spatial
phase-modulation of the incident wavefronts, the photons are directed at
targeted speckle spots or output channels. From experimentally available
coupled channels, we select two channels and enhance their transmission, to
realize the equivalent of a fully programmable beam splitter. By
sending pairs of single photons from a parametric down-conversion source
through the opaque scattering medium, we observe two-photon quantum
interference. The programmed beam splitter need not fulfill energy conservation
over the two selected output channels and hence could be non-unitary.
Consequently, we have the freedom to tune the quantum interference from
bunching (Hong-Ou-Mandel-like) to antibunching. Our results establish opaque
scattering media as a platform for high-dimensional quantum interference that
is notably relevant for boson sampling and physical-key-based authentication
Deep learning analysis of the myocardium in coronary CT angiography for identification of patients with functionally significant coronary artery stenosis
In patients with coronary artery stenoses of intermediate severity, the
functional significance needs to be determined. Fractional flow reserve (FFR)
measurement, performed during invasive coronary angiography (ICA), is most
often used in clinical practice. To reduce the number of ICA procedures, we
present a method for automatic identification of patients with functionally
significant coronary artery stenoses, employing deep learning analysis of the
left ventricle (LV) myocardium in rest coronary CT angiography (CCTA). The
study includes consecutively acquired CCTA scans of 166 patients with FFR
measurements. To identify patients with a functionally significant coronary
artery stenosis, analysis is performed in several stages. First, the LV
myocardium is segmented using a multiscale convolutional neural network (CNN).
To characterize the segmented LV myocardium, it is subsequently encoded using
unsupervised convolutional autoencoder (CAE). Thereafter, patients are
classified according to the presence of functionally significant stenosis using
an SVM classifier based on the extracted and clustered encodings. Quantitative
evaluation of LV myocardium segmentation in 20 images resulted in an average
Dice coefficient of 0.91 and an average mean absolute distance between the
segmented and reference LV boundaries of 0.7 mm. Classification of patients was
evaluated in the remaining 126 CCTA scans in 50 10-fold cross-validation
experiments and resulted in an area under the receiver operating characteristic
curve of 0.74 +- 0.02. At sensitivity levels 0.60, 0.70 and 0.80, the
corresponding specificity was 0.77, 0.71 and 0.59, respectively. The results
demonstrate that automatic analysis of the LV myocardium in a single CCTA scan
acquired at rest, without assessment of the anatomy of the coronary arteries,
can be used to identify patients with functionally significant coronary artery
stenosis.Comment: This paper was submitted in April 2017 and accepted in November 2017
for publication in Medical Image Analysis. Please cite as: Zreik et al.,
Medical Image Analysis, 2018, vol. 44, pp. 72-8
Depth-Supervised NeRF for Multi-View RGB-D Operating Room Images
Neural Radiance Fields (NeRF) is a powerful novel technology for the
reconstruction of 3D scenes from a set of images captured by static cameras.
Renders of these reconstructions could play a role in virtual presence in the
operating room (OR), e.g. for training purposes. In contrast to existing
systems for virtual presence, NeRF can provide real instead of simulated
surgeries. This work shows how NeRF can be used for view synthesis in the OR. A
depth-supervised NeRF (DS-NeRF) is trained with three or five synchronised
cameras that capture the surgical field in knee replacement surgery videos from
the 4D-OR dataset. The algorithm is trained and evaluated for images in five
distinct phases before and during the surgery. With qualitative analysis, we
inspect views synthesised by a virtual camera that moves in 180 degrees around
the surgical field. Additionally, we quantitatively inspect view synthesis from
an unseen camera position in terms of PSNR, SSIM and LPIPS for the colour
channels and in terms of MAE and error percentage for the estimated depth.
DS-NeRF generates geometrically consistent views, also from interpolated camera
positions. Views are generated from an unseen camera pose with an average PSNR
of 17.8 and a depth estimation error of 2.10%. However, due to artefacts and
missing of fine details, the synthesised views do not look photo-realistic. Our
results show the potential of NeRF for view synthesis in the OR. Recent
developments, such as NeRF for video synthesis and training speedups, require
further exploration to reveal its full potential.Comment: 12 pages, 4 figures, submitted to the 14th International Conference
on Information Processing in Computer-Assisted Intervention
Polymers grafted to porous membranes
We study a single flexible chain molecule grafted to a membrane which has
pores of size slightly larger than the monomer size. On both sides of the
membrane there is the same solvent. When this solvent is good, i.e. when the
polymer is described by a self avoiding walk, it can fairly easily penetrate
the membrane, so that the average number of membrane crossings tends, for chain
length , to a positive constant. The average numbers of monomers on
either side of the membrane diverges in this limit, although their ratio
becomes infinite. For a poor solvent, in contrast, the entire polymer is
located, for large , on one side of the membrane. For good and for theta
solvents (ideal polymers) we find scaling laws, whose exponents can in the
latter case be easily understood from the behaviour of random walks.Comment: 4 pages, 6 figure
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