KEYWORDS: Digital watermarking, Singular value decomposition, Medical imaging, Image processing, Lung, COVID 19, X-ray imaging, Optical information security
This work presents a watermarking algorithm applied to medical images by using the Steered Hermite Transform (SHT), the Singular Value Decomposition (SVD), and the Jigsaw transform (JS). The principal objective is to protect the patient’s information using imperceptible watermarking and preserve its diagnosis. Thus, the watermark imperceptibility is achieved using the high-order Steered Hermite coefficients, whereas the SVD decomposition and the JS ensure the watermark against attacks. We use the medicine symbol Caduceus as a watermark. The metrics employed to evaluate the algorithm’s performance are the Peak Signal-to-Noise Ratio (PSNR), the Mean Structural Similarity Index (MSSIM), and the Normalized Cross-Correlation (NCC). The evaluation metrics over the watermarked image show that it does not suffer quantitative and qualitative changes, and the extracted watermark was recovered successfully with high PSNR values. In addition, several watermark extraction tests were performed against geometric and common processing attacks. These tests show that the proposed algorithm is robust under critical conditions of attacks, for example, against nonlinear smoothing (median filter), high noise addition (Gaussian and Salt & Pepper noise), high compression rates (JPEG compression), rotation between 0 to 180 degree, and translations up to 100 pixels.
Nowadays eye diseases that are not treated in a timely manner can lead to blindness in the patient. Diabetic retinopathy and retinopathy of prematurity are a couple of conditions considered to be the main causes of blindness in both adults and children. The technique used to date to verify the status of the retina is a qualitative analysis by an ophthalmological expert of fundus images. However, this is entirely based on the experience acquired by the physician and being able to detect changes in the vascular structure of the retina is a great challenge which can be addressed through technology. This paper presents a novel method to carry out the numerical modeling of the major temporal arcade using orthogonal polynomials of Legendre, Chebyshev and Laguerre through a genetic algorithm that helps to determine the coefficients of the linear combination of each one. A set of twenty fundus images already outlined by an expert was used, which were processed by the algorithm, generating an adjustment curve on the set of pixels of the Major Temporal Arcade. The results obtained were compared with three existing methodologies in the literature by using two metrics, emerging the Legendre polynomials as the most suitable for modeling, as a consequence of the low values obtained in the metrics compared to the other methods.
KEYWORDS: Cryptography, Image encryption, Medical imaging, Information visualization, Visualization, RGB color model, Image processing, Statistical analysis, Medical diagnostics
In this work, we propose a novel medical image encryption algorithm. It is based on the Jigsaw transform, Langton’s ant, cyclic permutation, and a novelty way to add deterministic noise. The robustness of our algorithm has been proven through several testing, such as statistical analysis (histograms and correlation distributions), visual testing, entropy testing and key space assessment, showing in each one a high-security level.
This paper presents a new method for coronary artery segmentation in X-ray angiograms based on deep learning and a patch-based training. The blood vessel segmentation is performed using the U-Net convolutional neural network, which has been trained using patches extracted from the original angiograms instead of using complete images. The publicly available database of coronary angiograms DCA1 containing 130 angiograms with their respective ground-truth has been used to generate the training patterns and subsequently to evaluate and compare the segmentation performance of the proposed method. The hyper-parameter configuration used for training the U-Net parameters has been selected from 90 possible combinations according to five binary classification metrics. Each combination involving the selection of a patch size, weight assigned to the blood vessel class, and learning rate used by the optimization method, has been used in order to train the U-Net parameters with patterns extracted from a set of 100 images. The segmentation performance of the proposed method is compared with five specialized blood vessel segmentation methods from the state of the art using a test set of 30 images, achieving the highest accuracy (0.977) and Dice similarity coefficient (0.779). Moreover, the experimental results have also shown that the proposed method is suitable to be integrated into a computer-aided system to support decision making in medical practice.
This paper presents a novel method for the automatic design of convolutional gray-level templates for detecting coronary arteries in X-ray angiograms. The proposed method uses the metaheuristic of iterated local search (ILS) to address the high-dimensional problem (O(256n)) involved in the design of convolutional templates. This automatically generated template is convolved in the spatial domain at different orientations to form a directional filter bank in order to detect coronary arteries at different angular resolutions. The vessel detection results are compared with those obtained by four state-of-the-art vessel enhancement methods in terms of the area (Az) under the receiver operating characteristic (ROC) curve. The proposed method achieved the highest detection results with Az = 0.9405 using a training set of 50 angiograms. Moreover, the convolutional gray-level template obtained from the training step, it was directly evaluated with an independent test set of 50 X-ray angiograms obtaining an Az = 0.9565, which is the highest performance according to the comparative analysis. In addition to the experimental results, the use of metaheuristics for designing convolutional gray-level templates obtains suitable results to be considered in systems that perform computer-aided diagnosis, and it also represents an encouraging area for future research.
This paper presents a novel method for the automatic design of binary descriptors for the detection of coronary arteries in X-ray angiograms. The method is divided into two different steps for detection and segmentation. In the step of automatic vessel detection, the metaheuristic of iterated local search (ILS) is used for the design of optimal binary descriptors for detecting vessel-like structures by using the top-hat transform in the spatial image domain. The detection results are compared with those obtained by five state-of-the-art vessel enhancement methods. The proposed method obtained the highest detection results in terms of the area (Az ) under the ROC curve (Az = 0.9635) using a training set of 50 angiograms, and Az = 0.9544 with an independent test set of 50 X-ray images. In the segmentation step, the inter-class variance thresholding method was applied to classify vessel and nonvessel pixels from the top-hat filter response obtained from the binary descriptor. According to the experimental results, the vessel detection by using an automatically generated binary descriptor can be highly suitable for computer-aided diagnosis.
This paper presents an algorithm to improve images with hazing effects. Usually, the dehazing methods based on the dark channel prior make use of two different stages to compute the transmission map of the input image. The stages are the transmission map estimation and a transmission map refinement. However, the main disadvantage of these strategies is the trade-off between accurate restoration and computational time. The proposed method uses a multilayer perceptron to compute the transmission map directly from the minimum channel and a contrast stretching technique to improve the dynamic range of the restored image. The multilayer perceptron is trained in terms of mean squared error using a training set of 80 images. To evaluate the restoration quality, the metrics of peak signal-to-noise ratio (PSNR) and the structural similarity (SSIM) index are used. The experimental results have proven that the proposed method achieves superior performance in terms of restoration quality (PSNR = 18.77, SSIM index = 0.8454) compared with nine state-of-the-art dehazing methods. In addition, based on the average computational time achieved by the proposed method (0.52 s using a test set of 46 images), it can be highly suitable for real-time applications.
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