353,846 research outputs found
Using neural networks to describe tracer correlations
Neural networks are ideally suited to describe the spatial and temporal dependence of tracer-tracer correlations. The neural network performs well even in regions where the correlations are less compact and normally a family of correlation curves would be required. For example, the CH<sub>4</sub>-N<sub>2</sub>O correlation can be well described using a neural network trained with the latitude, pressure, time of year, and methane volume mixing ratio (v.m.r.). In this study a neural network using Quickprop learning and one hidden layer with eight nodes was able to reproduce the CH<sub>4</sub>-N<sub>2</sub>O correlation with a correlation coefficient between simulated and training values of 0.9995. Such an accurate representation of tracer-tracer correlations allows more use to be made of long-term datasets to constrain chemical models. Such as the dataset from the Halogen Occultation Experiment (HALOE) which has continuously observed CH<sub>4 </sub> (but not N<sub>2</sub>O) from 1991 till the present. The neural network Fortran code used is available for download
A Fixed-Point Model for Pancreas Segmentation in Abdominal CT Scans
Deep neural networks have been widely adopted for automatic organ
segmentation from abdominal CT scans. However, the segmentation accuracy of
some small organs (e.g., the pancreas) is sometimes below satisfaction,
arguably because deep networks are easily disrupted by the complex and variable
background regions which occupies a large fraction of the input volume. In this
paper, we formulate this problem into a fixed-point model which uses a
predicted segmentation mask to shrink the input region. This is motivated by
the fact that a smaller input region often leads to more accurate segmentation.
In the training process, we use the ground-truth annotation to generate
accurate input regions and optimize network weights. On the testing stage, we
fix the network parameters and update the segmentation results in an iterative
manner. We evaluate our approach on the NIH pancreas segmentation dataset, and
outperform the state-of-the-art by more than 4%, measured by the average
Dice-S{\o}rensen Coefficient (DSC). In addition, we report 62.43% DSC in the
worst case, which guarantees the reliability of our approach in clinical
applications.Comment: Accepted to MICCAI 2017 (8 pages, 3 figures
Multi-Planar Deep Segmentation Networks for Cardiac Substructures from MRI and CT
Non-invasive detection of cardiovascular disorders from radiology scans
requires quantitative image analysis of the heart and its substructures. There
are well-established measurements that radiologists use for diseases assessment
such as ejection fraction, volume of four chambers, and myocardium mass. These
measurements are derived as outcomes of precise segmentation of the heart and
its substructures. The aim of this paper is to provide such measurements
through an accurate image segmentation algorithm that automatically delineates
seven substructures of the heart from MRI and/or CT scans. Our proposed method
is based on multi-planar deep convolutional neural networks (CNN) with an
adaptive fusion strategy where we automatically utilize complementary
information from different planes of the 3D scans for improved delineations.
For CT and MRI, we have separately designed three CNNs (the same architectural
configuration) for three planes, and have trained the networks from scratch for
voxel-wise labeling for the following cardiac structures: myocardium of left
ventricle (Myo), left atrium (LA), left ventricle (LV), right atrium (RA),
right ventricle (RV), ascending aorta (Ao), and main pulmonary artery (PA). We
have evaluated the proposed method with 4-fold-cross validation on the
multi-modality whole heart segmentation challenge (MM-WHS 2017) dataset. The
precision and dice index of 0.93 and 0.90, and 0.87 and 0.85 were achieved for
CT and MR images, respectively. While a CT volume was segmented about 50
seconds, an MRI scan was segmented around 17 seconds with the GPUs/CUDA
implementation.Comment: The paper is accepted to STACOM 201
Prognosis of prostate gland morphology study using artificial neural network
The research goal is to optimize the management of patients with serum PSA level falling in the range of 4-10 ng/ ml by designing and educating of an artificial neural network, which may be used to predict prostate gland morphology basing on clinical, laboratory and imaging data. Material and methods. Data of 254 patients, who were admitted to the oncological Department of S. R. Mirotvortsev Clinical hospital for transrectal prostate biopsy, was collected to construct several artificial neural networks with different architecture. External validation was performed on 27 patients, who had prostate biopsy in January-February 2014. Results. One-layer network, consisting of 11 input, 9 hidden and 3 output neurons, was determined to be the most successful: in 92.6% cases it was correct in predicting prostate cancer or its absence. Input factors were evaluated according to their relative importance, from more important to less important: prostate volume, serum PSA, patient's age, prostate consistency, PSA velocity, prostate symmetry, previous negative biopsy, free serum PSA, intake of 5-alpha-reductase inhibitors. Conclusion. Artificial neural networks may be used to predict morphological findings in prostate biopsy. High PSA density and firm prostate consistency should cause suspicion of prostate cancer
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