联合图像专家组2000图像压缩方法的核医学应用研究

为研究联合图像专家组2000(Jo in t Photograph ic Expert G roup 2000,JPEG 2000)图像压缩方法在核医学中的应用,将无病变和有病变核医学静态图像用JPEG 2000软件压缩。对无损压缩图像,测量其压缩比。对有损压缩图像,由医生阅片,根据其结论作接收器操作特性(R ece iver operating characteristic,ROC)分析,获得各种图像压缩比的ROC曲线下的面积(A rea under curve,AUC),以其大小评价图像诊断质量;并将原始图像组AUC与各有损压缩图像组的AUC作配对t检验。实验发现,无损压缩的图像压缩比为(1.34±0.05)∶1。而有损压缩比越大,AUC越小。原始图像与压缩图像比较,压缩比为10∶1时没有显著性差异,压缩比更大时则有显著性差异。实验结果表明,无损压缩方法压缩比低,实用意义不大。有损压缩比不大于10∶1时,核医学静态图像的诊断质量得以保留。对核医学中的其它图像形式,可根据的图像性质,特别是固有统计噪声的大小,适当增减压缩比。     

基于存储服务的JPEG2000医学DICOM图像压缩的研究

由于医学图像所包含的数据量巨大,不利于存储和在现有网络上有效地传输,本研究使用VC++实现基于联合图像专家组2000(Joint Photographic Experts Group2000,JPEG2000)图像压缩算法对医学图像进行处理,根据医学数字图像通讯(Digital Imaging and Communicationin Medicine,DICOM)标准中存储服务的规则实现医学图像的存储服务。研究结果表明,使用JPEG2000压缩算法处理后的医学图像,不仅能大大节约存储空间,而且能降低传输时所需要的带宽。因此,JPEG2000压缩算法在DICOM推广及远程医疗的发展中具有积极意义。     

基于离散小波变换的JPEG 2000标准对肺部CT图像的无损压缩

探索基于小波变换对肺部CT图像进行无损雎缩的新方法.采用基于离散小波变换方法的JPEG2000标准对3019张肺部CT图像进行无损压缩,并针对压缩后图像效果进行统计分析.结果表明,该方法不但可以达到12.0的高压缩比,而且具有较高的图像尤损压缩质量,为临床CT医学影像的储存与诊断,提供了有益的技术与方法.     

JPEG2000压缩算法及其在医学图像DICOM格式中的实现

本文描述了在医学图像DICOM格式中实现JPEG2000压缩算法的编程思路和方法.提供了部分VC++代码,对关键函数进行了较详细的注解,并对两种图像压缩格式进行了比较,给出了一个详细的实验结果.     

一种客观定量的图像配准评价方法

算法评价是图像配准算法设计中不可缺少的一个环节。本文提出了一种基于配准函数曲线形状定量描述的客观评价方法。方法以曲线的半峰高与半峰宽之比度量配准算法的收敛速度和配准精度,以曲率变化率度量配准算法的鲁棒性,从而有效克服了传统评价方法的不可度量性和主观性;评价简单易行。通过与传统评价方法的比较,实验验证了本章所提出评价方法的有效性和优越性。     

基于超声图像分析的肝癌射频治疗效果定量评价

医学超声图像对于肝癌射频治疗后的评估具有重要作用。作为一种＂姑息性＂疗法,射频治疗不能保证肿瘤生长部位经治疗后没有癌细胞残留。为了使医生能够准确地评估肝癌射频治疗后的效果,需要建立一种定量评价体系。采用Gabor变换提取图像纹理特征,计算各阶段图像的特征距离,并采用特征距离的立方对图像矩阵的2范数加权,从而构造出肝癌射频治疗后复查的定量评价体系。该定量评价体系与病理检查结果相一致,对于辅助医生更加准确地评估出肝癌射频治疗后的效果具有潜在的应用价值。     

图像域迭代重建算法对腹部CT平扫图像质量和辐射剂量的影响

目的:探讨图像域迭代重建算法对腹部CT平扫图像质量及辐射剂量的影响。 方法:以辽阳市中心医院2017年1月~2018年4月行腹部CT平扫的150例患者为研究对象,依据就诊先后顺序随机将其分为观察组与对照组,各75例。均行自动毫安控制技术扫描,管电压均为130 kV。观察组预设图像质量参考毫安秒150 mAs,行图像域迭代重建算法重建;对照组预设图像质量参考毫安秒250 mAs,行滤波反投影重组。通过CT值、图像噪声SD、图像信噪比、对比噪声比评价两组图像客观质量,并行图像质量主观评价,记录两组CT剂量容积指数。 结果:观察组肝脏、脾脏的图像噪声SD均显著低于对照组,图像信噪比均显著高于对照组,差异有统计学意义（P<0.05）;CT值、对比噪声比、主观整体质量评分两组比较差异均无统计学意义（P>0.05）;观察组CT剂量容积指数为（10.02±2.85） mGy,显著低于对照组的（15.68±4.36） mGy,差异有统计学意义（P<0.05）。 结论:图像域迭代重建算法不仅能保证腹部CT平扫图像质量,而且能有效减少辐射剂量。     

一种基于水平集的脊柱MRI图像分割算法的研究

水平集方法应用于图象分割的曲线或曲面进化问题,是一种稳定有效的数值计算方法.本文基于水平集方法提出了一种新的医学图像解剖轮廓分割算法,定义了一种用于终止进化的速度函数,构造了一种基于领域的进化方式.并对脊柱MRI图象进行了分割实验.得到了令人鼓舞的结果.表明了该种算法的可行性和有效性.     

人胎儿房室结的细胞分类--图像分析定量研究

目的　探讨胎儿房室结内的细胞类型和大小。　方法　石蜡切片 ,H E染色 ,光镜观察胎儿心脏房室结的细胞形态、类型 ;采用HIPAS 10 0 0图像分析仪对其进行定量分析。　结果　胎儿房室结的细胞主要为亮细胞、暗细胞和移行细胞。亮细胞和暗细胞为纺锤形或椭圆形 ,少数多边形 ;移行细胞细短柱形。亮细胞和移行细胞的细胞核明显大于暗细胞。　结论　胎儿房室结的起搏细胞包括亮细胞和暗细胞 ,它们可能是一种细胞的不同功能状态     

滤波器组合对医学图像融合效果的影响

滤波器的不同组合影响医学图像融合性能,恰当地进行滤波器组合是医学图像融合技术的前提。本文通过优化滤波器组合对无下采样Contourlet变换(nonsubsampled contourlet transform,NSCT)医学图像融合影响进行深入讨论,比较了不同滤波器组合后的融合结果。结果显示滤波器组合对融合性能有较大影响,lax滤波器组合图像融合效果各项指标分别优于db3滤波器组合。实验结果证明,使用合适的滤波器组合,即使在融合准则很简单、分解层数较少的情况下,同样可以获得很好的融合结果,从而大大减少融合算法的复杂度。     

JPEG2000 Still Image Coding Quality

This work demonstrates the image qualities between two popular JPEG2000 programs. Two medical image compression algorithms are both coded using JPEG2000, but they are different regarding the interface, convenience, speed of computation, and their characteristic options influenced by the encoder, quantization, tiling, etc. The differences in image quality and compression ratio are also affected by the modality and compression algorithm implementation. Do they provide the same quality? The qualities of compressed medical images from two image compression programs named Apollo and JJ2000 were evaluated extensively using objective metrics. These algorithms were applied to three medical image modalities at various compression ratios ranging from 10:1 to 100:1. Following that, the quality of the reconstructed images was evaluated using five objective metrics. The Spearman rank correlation coefficients were measured under every metric in the two programs. We found that JJ2000 and Apollo exhibited indistinguishable image quality for all images evaluated using the above five metrics (r > 0.98, p < 0.001). It can be concluded that the image quality of the JJ2000 and Apollo algorithms is statistically equivalent for medical image compression.     

A Perceptual Evaluation of JPEG 2000 Image Compression for Digital Mammography: Contrast-Detail Characteristics

In this investigation the effect of JPEG 2000 compression on the contrast-detail (CD) characteristics of digital mammography images was studied using an alternative forced choice (AFC) technique. Images of a contrast-detail phantom, acquired using a clinical full-field digital mammography system, were compressed using a commercially available software product (JPEG 2000). Data compression was achieved at ratios of 1:1, 10:1, 20:1, and 30:1 and the images were reviewed by seven observers on a high-resolution display. Psychophysical detection characteristics were first computed by fitting perception data using a maximum-likelihood technique from which CD curves were derived at 50%, 62.5%, and 75% threshold levels. Statistical analysis indicated no significant difference in the perception of mean disk thickness up to 20:1 compression except for disk diameter of 1 mm. All other compression combinations exhibited significant degradation in CD characteristics.Certain aspects of this research were presented as a poster at the SCAR 2003 conference in Boston, MA, and was awarded the second place in the poster awards category by the SCAR committee.     

Computed Tomography Image Compressibility and Limitations of Compression Ratio-Based Guidelines

Finding optimal compression levels for diagnostic imaging is not an easy task. Significant compressibility variations exist between modalities, but little is known about compressibility variations within modalities. Moreover, compressibility is affected by acquisition parameters. In this study, we evaluate the compressibility of thousands of computed tomography (CT) slices acquired with different slice thicknesses, exposures, reconstruction filters, slice collimations, and pitches. We demonstrate that exposure, slice thickness, and reconstruction filters have a significant impact on image compressibility due to an increased high frequency content and a lower acquisition signal-to-noise ratio. We also show that compression ratio is not a good fidelity measure. Therefore, guidelines based on compression ratio should ideally be replaced with other compression measures better correlated with image fidelity. Value-of-interest (VOI) transformations also affect the perception of quality. We have studied the effect of value-of-interest transformation and found significant masking of artifacts when window is widened.     

Mammographic Image Denoising and Enhancement Using the Anscombe Transformation, Adaptive Wiener Filtering, and the Modulation Transfer Function

A new restoration methodology is proposed to enhance mammographic images through the improvement of contrast features and the simultaneous suppression of noise. Denoising is performed in the first step using the Anscombe transformation to convert the signal-dependent quantum noise into an approximately signal-independent Gaussian additive noise. In the Anscombe domain, noise is filtered through an adaptive Wiener filter, whose parameters are obtained by considering local image statistics. In the second step, a filter based on the modulation transfer function of the imaging system in the whole radiation field is applied for image enhancement. This methodology can be used as a preprocessing module for computer-aided detection (CAD) systems to improve the performance of breast cancer screening. A preliminary assessment of the restoration algorithm was performed using synthetic images with different levels of quantum noise. Afterward, we evaluated the effect of the preprocessing on the performance of a previously developed CAD system for clustered microcalcification detection in mammographic images. The results from the synthetic images showed an increase of up to 11.5 dB (p = 0.002) in the peak signal-to-noise ratio. Moreover, the mean structural similarity index increased up to 8.3 % (p < 0.001). Regarding CAD performance, the results suggested that the preprocessing increased the detectability of microcalcifications in mammographic images without increasing the false-positive rates. Receiver operating characteristic analysis revealed an average increase of 14.1 % (p = 0.01) in overall CAD performance when restored image sets were used.     

测量距离和角度与喉动态镜图像关系的实验研究

探讨喉动态镜成像大小与被检测对象间距离及角度的关系及其密切程度。使用基于虚拟仪器的喉动态观测系统,测量大小固定的物体,取不同距离、不同角度时所呈现图像的面积与长度。结果：当被测物体大小固定时,测量距离对被测物体所呈现的喉镜图像的面积和长度有显著影响,而测量角度对被测物体所呈现的喉镜图像的面积和长度无显著影响。     

组织B型超声图像灰度与其温度相关性研究

本文研究了生物组织B型超声图像灰度与其温度的相关性.以新鲜的离体猪肝为研究对象,采集离体猪肝在不同温度(28℃～45℃)下的B超图,再利用图像处理技术提取不同温度下的B超图像灰度值,从而确定猪肝组织B超图像灰度与其温度的相关性.实验结果表明:猪肝B超图像中AOI(area ofinterest)的平均灰度与温度存在明显的相关性,当猪肝温度发生变化时,其B超图像灰度也发生变化.利用生物组织B超图像灰度的温度相关性可无创检测癌微波热疗中的组织温度.     

氯丙烯中毒微循环及超微结构观察

氯丙烯中毒可引起周围微循环障碍,微血管出现痉挛→痉挛或扩张→扩张。微动脉及微静脉自律运动频率及幅度减弱,血流速度减缓,组织单位面积灌流量减少;微血管胆碱酯酶量减少。脊髓及脊神经根神经纤维微丝、微管及线粒体变性;心肌、肝细胞、肾近曲小管上皮细胞线粒体嵴减少,内质网空泡样变,部分心肌细胞断裂,肌原纤维之间间隙增大。本文讨论了氯丙烯中毒的毒性机理,认为微循环障碍是重要因素之一。     

宗教对精神疾病患者及家属影响的对照研究

目的调查精神疾病患者和家属的一般资料、宗教行为及心理健康情况,探讨宗教信念对其影响。方法对在北京回龙观医院门诊就诊的患者和陪同家属通过面谈选择符合入组条件的各56例。自制问卷调查两组人员的一般资料及宗教信仰情况,将其特征进行配对比较。两组使用症状自评量表(SCL-90)[1]自评,所得数据进行配对比较。家属组使用亲属应激量表(RSS)[2]自评。结果1家属组的RSS总分均值为17.00±5.98;2SCL-90中抑郁、焦虑和躯体化3个因子分的均值比较,家属组分别为2.27±0.08、1.91±0.14和1.21±0.11,大于患者组(0.64±0.06,1.56±0.13和0.92±0.08);3两组一般资料主要特征的比较:无配偶者中,患者有54例(96.4%),家属有50例(82.4%);无业或不上学者中,患者有51例(91.1%),家属有31例(55.4%);4宗教方面主要特征的比较:作祈祷或静修者中,患者有56例(100%),家属有40例(71.4%);认为信仰宗教能获得心理支持者中,患者有45例(80.4%),家属有48例(85.7%)。结论精神疾病患者和家属处于心理应激状态,其宗教信念和行为具有一定的心理功能作用。     

颅脑64排螺旋CTA与高场强MRA效果对比及影响因素研究

目的 探讨64排螺旋CT颅脑计算机断层血管成像（CTA）和高场强磁共振成像血管（MRA）的效果及影响图像质量的因素.方法 对1 128例脑CTA患者中的138例和1 558例脑MRA患者中的208例1周内行数字减影血管造影（DSA）检查.CTA与MRA图像分为5级,得分1～5分.颅内动脉瘤按瘤体长径分为：小型（＜5 mm）,中型（5～10 mm）,大型（10～25 mm）,巨大型（＞25 mm）;动脉狭窄按直径分：轻度（＜50%）,中度（50%～74%）,严重（75%～99%）,闭塞（100%）.结果 以DSA为标准,CTA、MRA评估小型、中型、大型、巨大型动脉瘤的灵敏度分别为：（72%、60.9%）,（83.7%、78.3%）,（92.6%、87.5%）,（100%、100%）;评估动脉狭窄轻度、中度、严重、闭塞的灵敏度分别为（50%、44.8%）,（80%、78.9%）,（88.9%、84.6%）,（100%、100%）.影响CTA的因素有成像技术、延迟时间、旋转时间/螺距、造影剂单位剂量与注射速度、血管钙化、重建技术等;影响MRA的因素有饱和带、磁化传递、TR/TE/FA、激励次数/采集矩阵、成像技术、动脉钙化等.结论 颅脑CTA检出动脉瘤和动脉狭窄的灵敏度高于MRA而低于DSA.CTA、MRA能满足临床检出动脉瘤和血管狭窄的要求.