There has not been a peripheral vascular surgical procedure subject to as exquisite scruting as c... more There has not been a peripheral vascular surgical procedure subject to as exquisite scruting as carotid endarterectomy. The last decade gave a new attitude after the analysis and conclusions of the North American Symptomatic Carotid Endarterectomy Symptomatic extracranial lesions were best managed with operative intervention rather than antiplatelet treatment alone. Now, in the first decade of the new millenium, we are embarking on yet another test of carotid endarterectmy--a comparison with percutaneous angioplasty and stenting, which is a most rigorous contest because endarterectomy must now withstand comparison with another "active treatment" rather than the more passive observational modality of antiplatelet therapy. The topic of the authors was to provide a panorama of the contemporay treatment of carotid disease at this pivotal point in the life cycle carotid endarterectomy.
ABSTRACT A new procedure is proposed for image compression as an improvement on vector quantizati... more ABSTRACT A new procedure is proposed for image compression as an improvement on vector quantization of subbands. Codewords with vertical and horizontal shape are used to vector-quantize the high-frequency subimages obtained from a multiresolution analysis scheme. The codeword shapes take into account the orientation and resolution of each subband detail to preserve edges at low bit rates. Their sizes are defined according to the correlation distances in each subband for the horizontal and vertical directions.
ABSTRACT Recently, vector quantization (VQ) has received considerable attention, and has become a... more ABSTRACT Recently, vector quantization (VQ) has received considerable attention, and has become an effective tool for image compression. It provides a high compression ratio and a simple decoding process. However, studies on the practical implementation of VQ have revealed some major difficulties such as edge integrity and codebook design efficiency. After reviewing the state-of-the-art in the field of vector quantization, we focus on iterative and non-iterative codebook generation algorithms.
ABSTRACT In Vector Quantization, the codebook generation requires a clustering scheme, where the ... more ABSTRACT In Vector Quantization, the codebook generation requires a clustering scheme, where the number of the clusters (the codebook size) is pre-defined. There are several algorithms which resolve this problem. For example, we quote the well known Linde-Buzo-Gray (LBG) algorithm, and the recent finite state algorithm. Most of them are iterative, and thus, time consuming. Our purpose is to look for a fast one, which is necessary non-iterative and represents adequately the image to be coded. After a review of existing algorithms for codebook generation, we propose a Modified Decision-Directed Clustering (MDDC) technique for codebook generation and its application in radiological image. The Convergence of the (MDDC) algorithm to a globally sub-optimal codebook in finite time is proved.
There has not been a peripheral vascular surgical procedure subject to as exquisite scruting as c... more There has not been a peripheral vascular surgical procedure subject to as exquisite scruting as carotid endarterectomy. The last decade gave a new attitude after the analysis and conclusions of the North American Symptomatic Carotid Endarterectomy Symptomatic extracranial lesions were best managed with operative intervention rather than antiplatelet treatment alone. Now, in the first decade of the new millenium, we are embarking on yet another test of carotid endarterectmy--a comparison with percutaneous angioplasty and stenting, which is a most rigorous contest because endarterectomy must now withstand comparison with another "active treatment" rather than the more passive observational modality of antiplatelet therapy. The topic of the authors was to provide a panorama of the contemporay treatment of carotid disease at this pivotal point in the life cycle carotid endarterectomy.
ABSTRACT A new procedure is proposed for image compression as an improvement on vector quantizati... more ABSTRACT A new procedure is proposed for image compression as an improvement on vector quantization of subbands. Codewords with vertical and horizontal shape are used to vector-quantize the high-frequency subimages obtained from a multiresolution analysis scheme. The codeword shapes take into account the orientation and resolution of each subband detail to preserve edges at low bit rates. Their sizes are defined according to the correlation distances in each subband for the horizontal and vertical directions.
ABSTRACT Recently, vector quantization (VQ) has received considerable attention, and has become a... more ABSTRACT Recently, vector quantization (VQ) has received considerable attention, and has become an effective tool for image compression. It provides a high compression ratio and a simple decoding process. However, studies on the practical implementation of VQ have revealed some major difficulties such as edge integrity and codebook design efficiency. After reviewing the state-of-the-art in the field of vector quantization, we focus on iterative and non-iterative codebook generation algorithms.
ABSTRACT In Vector Quantization, the codebook generation requires a clustering scheme, where the ... more ABSTRACT In Vector Quantization, the codebook generation requires a clustering scheme, where the number of the clusters (the codebook size) is pre-defined. There are several algorithms which resolve this problem. For example, we quote the well known Linde-Buzo-Gray (LBG) algorithm, and the recent finite state algorithm. Most of them are iterative, and thus, time consuming. Our purpose is to look for a fast one, which is necessary non-iterative and represents adequately the image to be coded. After a review of existing algorithms for codebook generation, we propose a Modified Decision-Directed Clustering (MDDC) technique for codebook generation and its application in radiological image. The Convergence of the (MDDC) algorithm to a globally sub-optimal codebook in finite time is proved.
Uploads
Papers by N. Akrout