Gastric antral vascular ectasia (GAVE) is one of the uncommon causes of upper gastrointestinal bleeding. Major treatment of GAVE includes pharmacotherapy, endoscopy, and surgery. The efficacy and safety of pharmacotherapy have not been sufficiently confirmed; and surgery is just considered when conservative treatment is ineffective. By comparison, endoscopy is a common treatment option for GAVE. This paper reviews the currently used endoscopic approaches for GAVE, mainly including argon plasma coagulation (APC), radiofrequency ablation (RFA), and endoscopic band ligation (EBL). It also summarizes their efficacy and procedure-related adverse events. The endoscopic success rate of APC is 40–100%; however, APC needs several treatment sessions, with a high recurrence rate of 10–78.9%. The endoscopic success rates of RFA and EBL are 90–100% and 77.8–100%, respectively; and their recurrence rates are 21.4–33.3% and 8.3–48.1%, respectively. Hyperplastic gastric polyps and sepsis are major adverse events of APC and RFA; and Mallory–Weiss syndrome is occasionally observed after APC. Adverse events of EBL are rare and mild, such as nausea, vomiting, esophageal or abdominal pain, and hyperplastic polyps. APC is often considered as the first-line choice of endoscopic treatment for GAVE. RFA and EBL have been increasingly used as alternatives in patients with refractory GAVE. A high recurrence of GAVE after endoscopic treatment should be fully recognized and cautiously managed by follow-up endoscopy. In future, a head-to-head comparison of different endoscopic approaches for GAVE is warranted.
Recently, great concerns have been raised regarding the issue of medical image protection due to the increasing demand for telemedicine services, especially the teleradiology service. To meet this challenge, a novel chaos-based approach is suggested in this paper. To address the security and efficiency problems encountered by many existing permutation-diffusion type image ciphers, the new scheme utilizes a single 3D chaotic system, Chen's chaotic system, for both permutation and diffusion. In the permutation stage, we introduce a novel shuffling mechanism, which shuffles each pixel in the plain image by swapping it with another pixel chosen by two of the three state variables of Chen's chaotic system. The remaining variable is used for quantification of pseudorandom keystream for diffusion. Moreover, the selection of state variables is controlled by plain pixel, which enhances the security against known/chosen-plaintext attack. Thorough experimental tests are carried out and the results indicate that the proposed scheme provides an effective and efficient way for real-time secure medical image transmission over public networks.
This paper presents a new chaos-based image cipher using a plaintext-related permutation. The cat map and Lorenz system are employed to shuffle the positions of image pixels and generate the diffusion keystream, respectively. The control parameters of the cat map, i.e. the permutation key, are determined by the Murmur2 hash value of the original image. Owing to the avalanche property of hash functions, completely different shuffled images will be produced even if there is a tiny difference between the original ones, and it helps accelerate the diffusion process. Experimental results indicate that the proposed scheme requires only one and two cipher cycles to achieve an acceptable and a satisfactory diffusion properties, respectively, whereas two and three cipher cycles are needed by typical schemes to achieve the same properties. Thorough security analysis is carried out, and the results demonstrate the satisfactory security of the proposed scheme.
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