Volume 16, Issue 4

Describes an extrinsic-point-based, interactive image-guided neurosurgical system designed at Vanderbilt University, Nashville, TN, as part of a collaborative effort among the Departments of Neurological Surgery, Computer Science, and Biomedical Engineering. Multimodal image-to-image (II) and image-to-physical (IP) registration is accomplished using implantable markers. Physical space tracking is accomplished with optical triangulation. The authors investigate the theoretical accuracy of point-based registration using numerical simulations, the experimental accuracy of their system using data obtained with a phantom, and the clinical accuracy of their system using data acquired in a prospective clinical trial by 6 neurosurgeons at 4 medical centers from 158 patients undergoing craniotomies to respect cerebral lesions. The authors can determine the position of their markers with an error of approximately 0.4 mm in X-ray computed tomography (CT) and magnetic resonance (MR) images and 0.3 mm in physical space. The theoretical registration error using 4 such markers distributed around the head in a configuration that is clinically practical is approximately 0.5-0.6 mm. The mean CT-physical registration error for the: phantom experiments is 0.5 mm and for the clinical data obtained with rigid head fixation during scanning is 0.7 mm. The mean CT-MR registration error for the clinical data obtained without rigid head fixation during scanning is 1.4 mm, which is the highest mean error that the authors observed. These theoretical and experimental findings indicate that this system is an accurate navigational aid that can provide real-time feedback to the surgeon about anatomical structures encountered in the surgical field.

描述了一种基于外部点的交互式图像引导神经外科系统，由田纳西州纳什维尔的范德比尔特大学设计，是神经外科、计算机科学和生物医学工程系合作的一部分。使用植入式标记实现多模态图像到图像（II）和图像到物理（IP）配准。物理空间跟踪通过光学三角测量完成。作者通过数值模拟研究了基于点的配准的理论精度，使用体模数据验证系统的实验精度，并通过6位神经外科医生在4个医疗中心对158名接受开颅手术以切除脑部病变的患者的前瞻性临床试验数据评估了系统的临床精度。作者能够以约0.4毫米的误差在X射线计算机断层扫描（CT）和磁共振（MR）图像中确定标记位置，在物理空间中误差为0.3毫米。使用4个分布头部周围且临床实用的标记的理论配准误差约为0.5-0.6毫米。体模实验中CT-物理配准的平均误差为0.5毫米，扫描时使用刚性头部固定的临床数据平均误差为0.7毫米。扫描时未使用刚性头部固定的临床数据中CT-MR配准的平均误差为1.4毫米，这是作者观察到的最高平均误差。这些理论和实验结果表明，该系统是一种精确的导航辅助工具，可为外科医生提供手术区域中遇到的解剖结构的实时反馈。

In nuclear magnetic resonance, different spectral components often correspond to different chemical species and as such, spectral selectivity can be a valuable tool for diagnostic imaging. In the work presented here, a multishot image acquisition method based upon rosette k-space trajectories has been developed and implemented for spectrally selective magnetic resonance imaging (MRI). Parametric f...

在核磁共振中，不同的频谱分量通常对应不同的化学物种，因此频谱选择性可以成为诊断成像的有价值的工具。在本文提出的工作中，开发并实现了一种基于玫瑰线k空间轨迹的多重图像采集方法，用于频谱选择性磁共振成像（MRI）。参数f...

Methods for improving the contrast-to-noise ratio (CNR) of low-contrast lesions in medical ultrasound imaging are described. Differences in the frequency spectra and amplitude distributions of the lesion and its surroundings can be used to increase the CNR of the lesion relative to the background. Automated graylevel mapping is used in combination with a contrast-weighted form of frequency-diversi...

描述了在医学超声成像中改善低对比度病变的对比度噪声比（CNR）的方法。病变及其周围环境的频谱和幅度分布差异可用于增加病变相对于背景的CNR。自动灰度映射与对比度加权的频率分集形式结合使用...

Motion and deformation analysis of the myocardium are of utmost interest in cardiac imaging. Part of the research is devoted to the estimation of the heart function by analysis of the shape changes of the left-ventricular endocardial surface. However, most clinically used shape-based approaches are often two-dimensional (2-D) and based on the analysis of the shape at only two cardiac instants. Thr...

心肌的运动和形变分析在心脏成像中至关重要。部分研究致力于通过分析左心室内膜表面的形状变化来评估心脏功能。然而，大多数临床使用的基于形状的方法通常是二维（2-D）的，并且仅基于两个心脏瞬间的形状分析。...

The objective of this work is to investigate the issue of automatically detecting regions of interest (ROI's) in medical images. It is assumed that the regions to be detected can be roughly segmented by a threshold based on a likelihood measure of the ROI, First, an analysis of the global histogram is used to compute a preliminary threshold that is likely near the optimal one. The histogram analys...

本工作的目标是研究医学图像中自动检测感兴趣区域（ROI）的问题。假设待检测区域可以通过基于ROI似然度量的阈值进行粗略分割。首先，利用全局直方图分析计算一个可能接近最优阈值的初步阈值。直方图分析...

Volume-of-interest (VOI) extraction for radionuclide and anatomical measurements requires correct identification and delineation of the anatomical feature being studied. The authors have developed a toolset for specifying three dimensional (3-D) VOIs on a multislice positron emission tomography (PET) dataset. The software is particularly suited for specifying cerebral cortex VOIs which represent a...

用于放射性核素和解剖测量的感兴趣区域（VOI）提取需要正确识别和勾画所研究的解剖结构。作者开发了一套工具集，用于在多切片正电子发射断层扫描（PET）数据集上指定三维（3-D）VOI。该软件特别适用于指定代表...的大脑皮层VOI。

A semiautomated feature extraction algorithm is presented for the extraction and measurement of the hippocampus from volumetric magnetic resonance imaging (MRI) head scans. This algorithm makes use of elements of both deformable model and region growing techniques and allows incorporation of a priori operator knowledge of hippocampal location and shape. Experimental results indicate that the algor...

提出了一种半自动特征提取算法，用于从体积磁共振成像（MRI）头部扫描中提取和测量海马体。该算法利用了可变形模型和区域生长技术的元素，并允许融合操作者对海马位置和形状的先验知识。实验结果表明，该算法...

Recent studies show that the presence of fatty lesions in the atherosclerotic vessel wall is a risk factor for acute occlusion of blood vessels. Although fat has a high electrical resistivity, existing impedance catheter systems cannot be used for detection of these lesions because artifacts owing to impedance variations in the extravascular surroundings have a major and irretraceable effect on th...

近期研究表明，动脉粥样硬化血管壁中脂肪病变的存在是血管急性闭塞的风险因素。尽管脂肪具有高电阻率，但现有阻抗导管系统无法用于检测这些病变，因为血管外环境阻抗变化引起的伪影对测量结果有重大且不可逆的影响……

The authors investigate the effects of initial conditions in the iterative maximum-likelihood (ML) reconstruction of fan-beam transmission projection data with truncation. In an iterative ML reconstruction, the estimate of the transmission reconstructed image in the previous iteration is multiplied by some factors to obtain the current estimate. Normally, a flat initial condition (FIC) or an image...

作者研究了在截断情况下，扇形束透射投影数据的迭代最大似然（ML）重建中初始条件的影响。在迭代ML重建中，前一次迭代的透射重建图像的估计值乘以某些因子以获得当前估计值。通常，平坦初始条件（FIC）或图像...