共查询到18条相似文献,搜索用时 359 毫秒
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目前,基于离散余弦变换的JPEG图像载体隐写已经可以达到较高的隐蔽性及鲁棒性,但隐写容量与传统的空域隐写相比仍有较大差距。在已有算法的基础上,提出了一种基于扩展DCT块变换的改进算法,一定程度上提升了隐藏容量,并使其在隐蔽性和展示性方面优于既有算法。该算法在最终量化前加入了扩展分块变换隐藏,避开了直接将密信隐藏于JPEG的量化后DCT系数中。在维持结果图片符合标准的同时,增强了隐写的隐蔽性和复杂性,实现了对原有算法的综合与改进。仿真实验结果显示出了该算法在隐写容量及隐秘性上相对于原有算法的提升。 相似文献
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在图像和视频编码的过程中,基于块的离散余弦变换DCT被广泛应用于JPEG、MPEG以及H.26x等压缩标准中。当压缩图像的比特率较低时会产生明显的方块化效应,影响人的主观视觉感受。许多文献提出了去除块效应的方法,但是如何评价这些方法的有效性,需要有一定的评价标准来衡量。针对这一情况,提出了一种新的评价去除块效应有效性的方法(BBSR)。该方法通过计算各种编码方法后图像的块效应度和模糊度来计算编码方法对图像的去块效应的改善结果和影响,实验结果表明该方法的评价结果与人的主观感觉一致。 相似文献
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目的 用JPEG2000算法对传统X光胶片进行数字化处理及有效压缩,并对有损压缩造成的图像信息缺失对临床诊断影响程度进行质量评价.方法 选取80幅保存较好的传统X光胶片,通过专用胶片扫描仪对其进行数字化转换,用JPEG2000压缩软件对数字化图像分别进行无损压缩与有损压缩处理,采用主观图像质量测量方法对压缩图像进行质量评估.结果 统计结果表明标准有损压缩与无损压缩的图像质量无明显差异,高压缩比有损压缩(20:1)与无损压缩存在图像质量差异,但不影响诊断.结论 对传统X光胶片的数字化处理可以进行适度的有损压缩(低于20:1). 相似文献
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目前,在基于Web的医学图像传输显示领域中,存在多种技术,如ACTIVE—XHTML、Flash、HTML5等。不同技术在不同的网络环境下表现出不同的特点。对两种基于Web的医学影像传输显示系统进行了设计和评估,第一种是瘦客户端系统,其工作原理是基于HTML的瘦客户端与具有WADO接口的PACSweb服务器进行数据交换,传输的影像格式为JPEG或PNG;第二种是胖客户端系统,工作原理是富客户端,如ActiveX控件、HTML5或FLASHRIA程序与具有WADO接口的PACSweb服务器进行数据交换,传输的影像格式为非压缩DICOM,压缩格式的DICOM~JPIP码流。经测试,在不同网络环境下,两种系统各有优缺点。 相似文献
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The role of compression is vital in telemedicine for the storage and transmission of medical images. This work is based on Contextual Vector Quantization (CVQ) compression algorithm with codebook optimization by Simulated Annealing (SA) for the compression of CT images. The region of interest (foreground) and background are separated initially by region growing algorithm. The region of interest is encoded with low compression ratio and high bit rate; the background region is encoded with high compression ratio and low bit rate. The codebook generated from foreground and background is merged, optimized by simulated annealing algorithm. The performance of CVQ-SA algorithm was validated in terms of metrics like Peak to Signal Noise Ratio (PSNR), Mean Square Error (MSE) and Compression Ratio (CR), the result was superior when compared with classical VQ, CVQ, JPEG lossless and JPEG lossy algorithms. The algorithms are developed in Matlab 2010a and tested on real-time abdomen CT datasets. The quality of reconstructed image was also validated by metrics like Structural Content (SC), Normalized Absolute Error (NAE), Normalized Cross Correlation (NCC) and statistical analysis was performed by Mann Whitney U Test. The outcome of this work will be an aid in the field of telemedicine for the transfer of medical images. 相似文献
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The idea for softcopy viewing of medical image outside the radiology reading room spread among the scientists in various fields for several years. An image could be read on workstation of all types, from desktop across movable to handheld.
Benefits are numerous and continue to grow as physicians use them discovering new usage cases. Proposed solutions vary with PACS architecture invasion level, communication and storage image formats, and utilization. We employ JPEG2000
standard because of its high (lossy/lossless) compression ratio with minimal spatial distortion, retrieval-oriented storage,
and streaming. It is embedded in PACS as the DICOM Private Data Element containing JPIP parameter string, so-called DICOM2000.
The DICOM2000 message is transparent for standard DICOM devices at the slightest level of invasion. Thanks to sophisticated
JPEG2000 streaming, medical image becomes suitable for any resolution and quality display and (wireless) networks. The solution
is validated on the ACR/NEMA standard test set of PACS images. 相似文献
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目的 探讨多层螺旋CT(MSCT)重组技术对先天性血管环伴气管狭窄的诊断价值.方法 收集温州医学院附属第二医院2004年10月至2010年4月经手术证实的先天性血管环伴气道狭窄患儿9例,均行心脏大血管薄层CT增强扫描,所得数据传至工作站进行多平面重组(MPR)、容积再现技术(VRT)及VR透明化重组,以手术结果为标准,与超声心动图(UCG)对比分析其影像学特点.结果 9例中,肺动脉吊带4例,右位主动脉弓伴左迷走锁骨下动脉3例,双主动脉弓1例,无名动脉压迫综合征1例,其中5例伴有其他心内外畸形(法洛四联症2例,右室双出口伴动脉导管未闭及室间隔缺损1例,室间隔缺损1例,双上腔静脉1例),1例法洛四联症主动脉周围见多发迂曲侧支动脉,上述畸形VRT及MPR均多角度直观显示;VR透明化技术可立体显示气管及支气管受压情况,其中主气管受压6例,主气管及左主支气管受压2例,主气管及右主支气管受压1例;UCG均检出上述心内畸形,1例肺动脉吊带误诊为动脉导管未闭,余8例血管环、气管及支气管狭窄改变均漏诊.结论 MSCT重组技术是一种无创、快速检查方法,可多方位清晰显示先天性血管环及气管受压狭窄程度,有利于临床减少误诊并及时治疗.Abstract: Objective To evaluate the diagnostic value of multi-slice CT (MSCT) reconstructions for congenital vascular rings together with tracheal stenosis. Methods 9 cases of children with congenital vascular ring and tracheal stenosis confirmed by surgery were collected in the study, all cases had undergone thin slice CT contrast enhancement, the MSCT data were transmitted to the workstation for multiplanar reconstruction( MPR), volume rendering technique(VRT) and VR transparency resconstruction. With the surgical results as the gold standard, the imaging characteristics of echocardiography (UCG) and MSCT were comparatively analyzed. Results In 9 cases, there were 4 cases of pulmonary artery sling, 3 cases of right aortic arch combination with left aberrant subclavian artery, 1 case of double aortic arch, Ⅰ case of innominate artery compression syndrome. In this group, 5 cases were accompanied with other cardiac malformations (tetralogy of Fallot in 2 cases, double outlet right ventricle with patent ductus arteriosus and ventricular septal defect in 1 case, ventricular septal defect in 1 case, double superior vena cava in 1 case),1 case of tetralogy of Fallot demonstrated many tortuous collateral arteries around aorta. All malformations were well displayed by VRT, MPR. VR transparency resconstruction can stereoscopically display trachea and bronchial compression condition, the main trachea was compressed in 6 cases, the main trachea and left main bronchus was compressed in 2 cases, the main trachea and left main bronchus was compressed in 1 cases,UCG detected all intracardiac malformations, 1 case of pulmonary artery sling was misdiagnosed as patent ductus arteriosus, 8 cases of vascular rings, tracheal and bronchial stenosis were missed. Conclusion MSCT reconstruction technology is a noninvasive, rapid diagnostic method, it can clearly show the congenital vascular rings abnormalities and the degree of tracheal stenosis, it has important significance for clinic treatment. 相似文献
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目的:探讨螺旋CT三维重建(Three-DimensionalReconstruction,3D)技术在胸腰椎爆裂骨折中的诊断及临床应用价值。方法:使用GEHispeed螺旋CT扫描机对87例脊椎损伤患者进行扫描,其中,男63例,女24例;年龄21岁~58岁,平均年龄36岁。全部数据输入SunSpace20工作站进行三维重建,并与X线平片、二维CT(2DCT)检查结果对照分析,所有图像由两位有经验的影像科医师采用双肓法进行评估。结果:将X线平片、2DCT、3DCT图像资料结合起来进行综合评估所得结果与X线平片合并2DCT图像评估相比较,在显示椎管内骨折片的数量方面,两者差异有显著性(χ2=4.086,P<0.05)。多平面重建(Multi-PlanarReconstruction,MPR)能清晰地显示椎管内脊髓受压迫情况。结论:3D技术在胸腰椎爆裂骨折的诊断中具有重要价值,有助于临床医师选择手术方式,减少手术创伤和并发症。 相似文献
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目的探讨螺旋CT三维重建(3D)技术在胸腰椎爆裂骨折中的诊断及临床应用价值。方法使用GEHispeed螺旋CT扫描机对75例脊柱损伤患者进行扫描,其中男53例,女22例;年龄20~55岁,平均34岁。全部数据输入SunSpace20工作站进行三维重建,并与X线平片、二维CT(2DCT)检查结果对照分析,所有图像由两位有经验的影像科医师采用双肓法进行评估。结果将X线平片、2DCT、3DCT图像资料结合起来进行综合评估所得结果与X线平片合并2DCT图像评估相比较,在显示椎管内骨折片的数量方面,两者差异有统计学意义(Χ^2=5.164,P〈0.01)。多平面重建(MPR)能清晰地显示椎管内脊髓受压迫情况。结论3D技术在胸腰椎爆裂骨折的诊断中具有重要价值,有助于临床医师选择手术方式,减少手术创伤和并发症。 相似文献