Technical Report on Semiautomatic Segmentation Using the Adobe Photoshop

The purpose of this research is to enable users to semiautomatically segment the anatomical structures in magnetic resonance images (MRIs), computerized tomographs (CTs), and other medical images on a personal computer. The segmented images are used for making 3D images, which are helpful to medical education and research. To achieve this purpose, the following trials were performed. The entire body of a volunteer was scanned to make 557 MRIs. On Adobe Photoshop, contours of 19 anatomical structures in the MRIs were semiautomatically drawn using MAGNETIC LASSO TOOL and manually corrected using either LASSO TOOL or DIRECT SELECTION TOOL to make 557 segmented images. In a similar manner, 13 anatomical structures in 8,590 anatomical images were segmented. Proper segmentation was verified by making 3D images from the segmented images. Semiautomatic segmentation using Adobe Photoshop is expected to be widely used for segmentation of anatomical structures in various medical images. The authors obtained consent for this research from concerned parties (a female subject and relatives of the deceased subject) after a full explanation about the nature of this procedure. In addition, we followed the cadaver management laws of South Korea.     

Enabling Real-Time Volume Rendering of Functional Magnetic Resonance Imaging on an iOS Device

Powerful non-invasive imaging technologies like computed tomography (CT), ultrasound, and magnetic resonance imaging (MRI) are used daily by medical professionals to diagnose and treat patients. While 2D slice viewers have long been the standard, many tools allowing 3D representations of digital medical data are now available. The newest imaging advancement, functional MRI (fMRI) technology, has changed medical imaging from viewing static to dynamic physiology (4D) over time, particularly to study brain activity. Add this to the rapid adoption of mobile devices for everyday work and the need to visualize fMRI data on tablets or smartphones arises. However, there are few mobile tools available to visualize 3D MRI data, let alone 4D fMRI data. Building volume rendering tools on mobile devices to visualize 3D and 4D medical data is challenging given the limited computational power of the devices. This paper describes research that explored the feasibility of performing real-time 3D and 4D volume raycasting on a tablet device. The prototype application was tested on a 9.7” iPad Pro using two different fMRI datasets of brain activity. The results show that mobile raycasting is able to achieve between 20 and 40 frames per second for traditional 3D datasets, depending on the sampling interval, and up to 9 frames per second for 4D data. While the prototype application did not always achieve true real-time interaction, these results clearly demonstrated that visualizing 3D and 4D digital medical data is feasible with a properly constructed software framework.     

基于片段融合的医学图像光线投影体绘制技术

光线投影算法是医学图像三维可视化中常用的体绘制技术,算法原理简单,具有较高的成像质量,但绘制速度较慢。我们改进算法,利用投射光线与平面簇求交,快速确定融合片段,减少插值计算量,采用基于片段的融合绘制技术,加快融合速度,并且利用包围盒技术减少对无效平面的求交,提高了光线投影的效率。实验结果表明,改进后的算法既能保证绘制质量,又能显著减少计算量,提高体绘制的速度。     

基于片段融合的医学图像光线投影体绘制技术

光线投影算法是医学图像三维可视化中常用的体绘制技术,算法原理简单,具有较高的成像质量,但绘制速度较慢.我们改进算法,利用投射光线与平面簇求交,快速确定融合片段,减少插值计算量,采用基于片段的融合绘制技术,加快融合速度,并且利用包围盒技术减少对无效平面的求交,提高了光线投影的效率.实验结果表明,改进后的算法既能保证绘制质量,又能显著减少计算量,提高体绘制的速度.     

Volume and Shape in Feature Space on Adaptive FCM in MRI Segmentation

Intensity non-uniformity (bias field) correction, contextual constraints over spatial intensity distribution and non-spherical cluster’s shape in the feature space are incorporated into the fuzzy c-means (FCM) for segmentation of three-dimensional multi-spectral MR images. The bias field is modeled by a linear combination of smooth polynomial basis functions for fast computation in the clustering iterations. Regularization terms for the neighborhood continuity of either intensity or membership are added into the FCM cost functions. Since the feature space is not isotropic, distance measures, other than the Euclidean distance, are used to account for the shape and volumetric effects of clusters in the feature space. The performance of segmentation is improved by combining the adaptive FCM scheme with the criteria used in Gustafson-Kessel (G-K) and Gath-Geva (G-G) algorithms through the inclusion of the cluster scatter measure. The performance of this integrated approach is quantitatively evaluated on normal MR brain images using the similarity measures. The improvement in the quality of segmentation obtained with our method is also demonstrated by comparing our results with those produced by FSL (FMRIB Software Library), a software package that is commonly used for tissue classification.     

In Vivo Measurement of Real-Time Aortic Segmental Volume Using the Conductance Catheter

The goal of this investigation was to determine if the conductance catheter technique for chamber volume measurement could be applied in vivo to determine real-time phasic aortic segmental volume. A four-electrode conductance catheter was used to measure time-varying resistance of the descending thoracic aorta in open-chest, anesthetized dogs. Resistance was converted to segmental volume and the slope correction factor () and parallel conductance volume (V _P ) were determined. The results showed excellent linear correlation between conductance and sonomicrometric segmental volume. The correction factors and V _P were found to be empirically related to average vessel diameter. The relatively high values for the slope correction factor (=4.59±0.17 SEM) were found to be primarily related to low-resistivity shunt paths probably originating in the periadventitial aortic wall and to a lesser extent to changes in flow-induced increases in blood resistivity, hematocrit, catheter position, and other adjacent tissue resistivity. The results demonstrate that correction factors empirically derived from measurements of mean aortic diameter could be used to determine absolute real-time phasic segmental volume, cross-sectional area, or diameter. The conductance technique may possess the same potential for determining aortic mechanical properties which has already been demonstrated for determining ventricular mechanical properties.     

Ultrasound Prostate Segmentation Using Adaptive Selection Principal Curve and Smooth Mathematical Model

Journal of Digital Imaging - Accurate prostate segmentation in ultrasound images is crucial for the clinical diagnosis of prostate cancer and for performing image-guided prostate surgery. However,...     

Accuracy of a Mitral Valve Segmentation Method Using J-Splines for Real-Time 3D Echocardiography Data

Patient-specific models of the heart’s mitral valve (MV) exhibit potential for surgical planning. While advances in 3D echocardiography (3DE) have provided adequate resolution to extract MV leaflet geometry, no study has quantitatively assessed the accuracy of their modeled leaflets vs. a ground-truth standard for temporal frames beyond systolic closure or for differing valvular dysfunctions. The accuracy of a 3DE-based segmentation methodology based on J-splines was assessed for porcine MVs with known 4D leaflet coordinates within a pulsatile simulator during closure, peak closure, and opening for a control, prolapsed, and billowing MV model. For all time points, the mean distance error between the segmented models and ground-truth data were 0.40 ± 0.32 mm, 0.52 ± 0.51 mm, and 0.74 ± 0.69 mm for the control, flail, and billowing models. For all models and temporal frames, 95% of the distance errors were below 1.64 mm. When applied to a patient data set, segmentation was able to confirm a regurgitant orifice and post-operative improvements in coaptation. This study provides an experimental platform for assessing the accuracy of an MV segmentation methodology at phases beyond systolic closure and for differing MV dysfunctions. Results demonstrate the accuracy of a MV segmentation methodology for the development of future surgical planning tools.     

Improvement of Partial Volume Segmentation for Brain Tissue on Diffusion Tensor Images Using Multiple-Tensor Estimation

To improve evaluations of cortical and subcortical diffusivity in neurological diseases, it is necessary to improve the accuracy of brain diffusion tensor imaging (DTI) data segmentation. The conventional partial volume segmentation method fails to classify voxels with multiple white matter (WM) fiber orientations such as fiber-crossing regions. Our purpose was to improve the performance of segmentation by taking into account the partial volume effects due to both multiple tissue types and multiple WM fiber orientations. We quantitatively evaluated the overall performance of the proposed method using digital DTI phantom data. Moreover, we applied our method to human DTI data, and compared our results with those of a conventional method. In the phantom experiments, the conventional method and proposed method yielded almost the same root mean square error (RMSE) for gray matter (GM) and cerebrospinal fluid (CSF), while the RMSE in the proposed method was smaller than that in the conventional method for WM. The volume overlap measures between our segmentation results and the ground truth of the digital phantom were more than 0.8 in all three tissue types, and were greater than those in the conventional method. In visual comparisons for human data, the WM/GM/CSF regions obtained using our method were in better agreement with the corresponding regions depicted in the structural image than those obtained using the conventional method. The results of the digital phantom experiment and human data demonstrated that our method improved accuracy in the segmentation of brain tissue data on DTI compared to the conventional method.     

A Semi-automated Approach to Improve the Efficiency of Medical Imaging Segmentation for Haptic Rendering

The Sensimmer platform represents our ongoing research on simultaneous haptics and graphics rendering of 3D models. For simulation of medical and surgical procedures using Sensimmer, 3D models must be obtained from medical imaging data, such as magnetic resonance imaging (MRI) or computed tomography (CT). Image segmentation techniques are used to determine the anatomies of interest from the images. 3D models are obtained from segmentation and their triangle reduction is required for graphics and haptics rendering. This paper focuses on creating 3D models by automating the segmentation of CT images based on the pixel contrast for integrating the interface between Sensimmer and medical imaging devices, using the volumetric approach, Hough transform method, and manual centering method. Hence, automating the process has reduced the segmentation time by 56.35% while maintaining the same accuracy of the output at ±2 voxels.     

采用小波描述子实现表面渲染数据的渐进传输

为了实现医学可视化的网络应用,提出一种基于小波描述子的表面渲染数据渐进传输方法.首先针对用于表面重建的序列平面轮廓为周期序列的特点,提出数字轮廓小波描述子的概念.基于小波描述子进行渐进传输的基本思想是,在发送端将轮廓采用小波描述子表示,然后对这些小波描述子系数序列渐进发送.在接收端,利用陆续收到的描述子系数序列重构轮廓,进行表面重建与渲染,重建精度和渲染效果随着不断收到‘细节'部分数据而得到改善并最终达到发送端的效果.该方法可以在数据无损传输的情况下,降低对传输网络带宽的要求,文中实验研究表明了方法的可行性.     

基于边缘流和距离图Snake模型分割淋巴结超声图像

提出一种基于边缘流的距离图Snake模型的图像分割方法，用于淋巴结超声图像的分割。首先由给定的4个标记点获得Snake模型的初始轮廓，然后综合图像灰度和纹理特征构造边缘流，由边缘流演化所得边缘图来构造距离图，通过定义基于距离图的势能函数，作为Snake模型的外部势能，来引导模型形变，实现对淋巴结超声图像的半自动分割。     

Computational Modeling and Real-Time Control of Patient-Specific Laser Treatment of Cancer

An adaptive feedback control system is presented which employs a computational model of bioheat transfer in living tissue to guide, in real-time, laser treatments of prostate cancer monitored by magnetic resonance thermal imaging. The system is built on what can be referred to as cyberinfrastructure—a complex structure of high-speed network, large-scale parallel computing devices, laser optics, imaging, visualizations, inverse-analysis algorithms, mesh generation, and control systems that guide laser therapy to optimally control the ablation of cancerous tissue. The computational system has been successfully tested on in vivo, canine prostate. Over the course of an 18 min laser-induced thermal therapy performed at M.D. Anderson Cancer Center (MDACC) in Houston, Texas, the computational models were calibrated to intra-operative real-time thermal imaging treatment data and the calibrated models controlled the bioheat transfer to within 5 °C of the predetermined treatment plan. The computational arena is in Austin, Texas and managed at the Institute for Computational Engineering and Sciences (ICES). The system is designed to control the bioheat transfer remotely while simultaneously providing real-time remote visualization of the on-going treatment. Post-operative histology of the canine prostate reveal that the damage region was within the targeted 1.2 cm diameter treatment objective.

用红外图像实时跟踪和监测眼睛的方法

眼睑和眼球状态是判断司机是否出现瞌睡和困倦的主要指标，其核心是实时地跟踪和检测眼睑的活动状态和眼球的注视位置，从而辨识出困倦程度，以便报警或提醒司机。当前较为理想的非接触式的检测途径是用摄像技术获取眼部的动态图像，并利用实时图像处理技术，跟踪和分析眼睑状态和眼球的注视位置，目前市场上尚无很成功的产品。本研究旨在探索利用摄像技术实时动态地提取眼睑和眼球状态的新方法。在850mn的红外线照射下，利用瞳孔和虹膜对红外光吸收率的显著差别，引导图像处理区域改变，实现司机在一定范围内活动时跟踪眼睛，测量眼睑和跟球状态的分析技术。该方法为检测司机在驾驶中是否困倦提供了关键的技术，对驾驶员实际录像测量显示该方法是有效的。对汽车司机进行了3次共7．5h的实际驾车测验，跟踪准确率在97．5％，判断测量准确度为97％。     

Volume Ordering for Analysis and Modeling of Vascular Systems

Morphological characteristics of vascular systems are commonly presented in terms of Strahler order because the logarithms of quantities such as vessel diameter and length are often linearly related to Strahler order. However, the ability to interpret Strahler order geometrically or physiologically is compromised because the precision of the order number is limited to integer values. This limitation is overcome by the volume ordering scheme, in which volume order number is defined as the logarithm of the estimated perfused tissue volume for each vascular segment. While Strahler and volume order numbers are equivalent for completely symmetrical branching trees, they deviate in the presence of asymmetries. The physiology-based definition of volume ordering offers benefits in the analysis of vascular design, fractal characterization of vascular systems, and blood flow modeling. These benefits are illustrated based on arterial kidney data that show a linear relationship of logarithmic vessel diameter and conductance as a function of both Strahler order and volume order with differing proportionality constants, which are expected to depend on the branching characteristics of the particular organ investigated.     

Semi-automatic Segmentation of Brain Tumors Using Population and Individual Information

Efficient segmentation of tumors in medical images is of great practical importance in early diagnosis and radiation plan. This paper proposes a novel semi-automatic segmentation method based on population and individual statistical information to segment brain tumors in magnetic resonance (MR) images. First, high-dimensional image features are extracted. Neighborhood components analysis is proposed to learn two optimal distance metrics, which contain population and patient-specific information, respectively. The probability of each pixel belonging to the foreground (tumor) and the background is estimated by the k-nearest neighborhood classifier under the learned optimal distance metrics. A cost function for segmentation is constructed through these probabilities and is optimized using graph cuts. Finally, some morphological operations are performed to improve the achieved segmentation results. Our dataset consists of 137 brain MR images, including 68 for training and 69 for testing. The proposed method overcomes segmentation difficulties caused by the uneven gray level distribution of the tumors and even can get satisfactory results if the tumors have fuzzy edges. Experimental results demonstrate that the proposed method is robust to brain tumor segmentation.     

The Morphology and Electrophysiology of the Cochlea of the Miniature Pig

To report the cochlear morphology and electrophysiology of Chinese experimental miniature pigs. Twenty Chinese experimental miniature pigs were used in this study. Auditory brainstem responses (ABR), cochlear endolymphatic potentials (EP), and the potassium concentrations of cochlear endolymph were recorded. Hair cell morphology was examined using electron microscopy. The capsule of cochlea of the miniature pig has three and one‐half turns which contains a 39‐mm long membranous labyrinth. The organ of Corti in the labyrinth encompasses three rows of outer hair cells and one row of inner hair cells. The stereocilia of the hair cells in the apical turn of the cochlea were significantly longer than those in the basal turn. The vestibular apparatus consists of three semicircular canals and the otolith organs. The average threshold of the ABR was 35–45 dB SPL (n = 20) from 4 to 32 kHz. There was no significant difference in the threshold or latency of the ABR between 1‐day‐old and 30‐day‐old miniature pigs. The average EP value was 77.3 ± 14 mV (n = 9) and the average potassium concentration was 147.1 ± 13 mM (n = 5) recorded from the second turn of the cochlea. These studies on the cochlear morphology and electrophysiology of the miniature pigs help to establish the Chinese experimental miniature pig as an animal model for future studies in otology and audiology. Anat Rec, 298:494–500, 2015. © 2014 Wiley Periodicals, Inc.     

利用超声射频实现肿瘤热疗实时无创测温方法

无创测温是肿瘤热疗的技术难题,超声射频测温技术是一种临床应用前景较好的无创测温方法。本文根据4种超声射频参数对超声射频测温方法进行了综述。诸多特征参数均与温度存在一定的相关性,测量方法中超声回波时移测温技术最为成熟,测温精度达到0．24℃。频移、能量、声衰减测温方法分别受不同因素的影响,定量测温尚存在一定困难。超声特征参数提取精度的提高将有效改善测温效果,多参数融合分析和凝固区定征识别也是超声无创测温技术的发展方向。     

Relationship Between the Contrast Effects of Raw Data Projection Images from Three-Dimensional Digital Subtraction Angiography and the Optimal Volume Rendering Parameters

Volume rendering (VR) is a technique commonly used for the reconstruction of three-dimensional (3D) digital subtraction angiography (DSA) images, and the rendering parameters greatly affect the characteristics of the 3D image. This study aimed to test whether the optimal VR parameters for 3D DSA could be estimated from the contrast effects in rotational two-dimensional (2D) DSA images acquired using 3D DSA. Simulated blood vessels filled with various concentrations of contrast medium were scanned, and the 3D DSA data sets were reconstructed. The syngo AX vessel analysis software that was able to analyze 3D DSA VR image was used for objective measures. Raw data projection images of the 3D DSA data sets in which the mean diameter was calculated as a true value by the software at nine different thresholds for vessel segmentation were selected. In each image set, five images of all 133 rotational 2D DSA images were selected, and the contrast-enhanced area was extracted using a region-growing algorithm. Mean values and standard deviations of each contrast-enhanced area were calculated, and as the thresholds for vessel segmentation of the software increased by 500 every time, significant differences were observed in the mean values (P < 0.01). This optimal threshold can be applied to the window settings of the VR technique. Therefore, the optimal VR parameters for 3D DSA may be determined by analyzing the contrast effects of the raw data projection images, and user-dependent over- and underestimations of 3D DSA VR images also may be prevented.     

基于场路耦合的体导电建模与分析

体导电数值模拟可用于分析体导电能量传递过程并探索各物理因素对能量传递效率的影响。本文在研究三维准静态电场的有限元求解的基础上,考虑体导电电路和电场的相互耦合关系,建立了体导电的场路耦合模型。该模型在电路层面上实现了体导电的仿真,为体导电的优化设计提供直接的理论指导。利用软件FEM3.5搭建了采用圆形柱体电极的体导电场路耦合模型,并仿真分析了电极截面积、电极间距以及各电路参数对系统整体性能的影响,为进一步优化能量传递效率奠定了基础。