消除右胸电阻抗容积波中呼吸干扰的方法

目的：消除右胸电阻抗容积波中呼吸的干扰。方法：首先讨论了对传统抗呼吸干扰的相干平均法改进，同时提出了估计拟合呼吸波和时域切比雪夫正交多项式消除呼吸干扰的方法。结果：３种处理方法结果表明，估计似合呼吸方法在实时性和保持逐拍信息性方面要优于其他两种。结论：解决了实时监护的难点。     

多路独立人体阻抗测量和信号分析

目的：测量多路阻抗信号，使用分解多路阻抗信号信源分析阻抗信号。方法：本文提出的阻抗测量系统采用独立电流源设计，可以同时采集多路阻抗信号。使用基于锁相环的相敏相干检测技术，可以直接得到阻抗信号的幅度变化。利用奇异值分解方法分解胸部阻抗信号，得到产生阻抗变化的源信号－心、肺阻抗信号。然后把经过频谱甄别的源信号重新投影在测量电极位置上。结果：对系统实测得到的阻抗信号成功地进行了分解和投影处理，取得了较好的结果。结论:多路阻抗系统能够提供单导测量系统无法提供的信息。在阻抗信号分析具有良好应用价值。     

动态环境血氧饱和度监测的运动干扰分离自适应对消方法

目的为解决动态环境中脉搏血氧饱和度监测容易受到运动干扰的问题,提出一种新的运动干扰分离自适应对消方法。方法在对动态环境光电容积脉搏波信号干扰分析的基础上,首先通过计算信号包络提取出红光和红外光光电容积脉搏波信号的交流分量,并分离出与干扰相关的信号,然后将其作为参考信号进行自适应滤波,去除运动干扰。结果采用本文提出的方法可有效抑制运动干扰对血氧饱和度结果的影响。结论本方法充分利用了光电容积脉搏波信号包含的信息,具有结果准确、稳定,运算量小的特点,可应用于动态环境血氧饱和度的监测。     

功能性消化不良胃动力信息检测与评价

目的 研究功能性消化不良患者胃动力系统的电过程和机械过程.方法 根据临床标准筛选15例功能性消化不良患者,从体表提取生物阻抗胃动力信号和胃电信号,并利用小波变换将阻抗胃动力信号从呼吸和血流等生物阻抗信号中分离出来.通过能谱和频谱分析方法,以及主能量和支配频率等将信号进行分类.结果 接受药物治疗1周后,15例FD患者主述其症状还没有明显缓解或者消除,但此时提取的胃电参数与治疗前相比大都有显著性改变,而来源于阻抗信号的胃动力参数没有显著性变化.结论 阻抗胃动力参数反映胃的运动过程和效果,与同步胃电的结合将为FD和胃动力功能研究提供一种新的无创检测和评价方法.     

背心式呼吸感应体积描记系统设计

目的 为解决呼吸感应体积描记技术存在的高信噪比与低系统功耗之间的固有矛盾,并消除胸、腹信号耦合干扰,研发一种新型的呼吸感应体积描记技术,并以可穿戴技术的设计理念,设计出可穿戴式呼吸感应体积描记系统。方法 采用脉冲式分时激励的方案,在极短的时间内以极高的功率来依次轮流激励各传感线圈;设计了新型的传感线圈结构,将其嵌入背心中,实现了可穿戴式呼吸感应体积描记系统设计。结果获得了高信噪比（高激励功率）、低系统功耗的设计效果,消除了胸、腹信号之间的耦合干扰;背心式的系统设计,外形美观,使用方便,可用于长期动态测量使用。结论 该系统性能优良,达到了设计要求,经过标定能够实现通气量无创测量,用于睡眠医学研究能够有效发现睡眠呼吸暂停事件并鉴别类型。     

军事飞行人员心理咨询的阻抗来源及应对方法

目的：探讨飞行人员心理咨询中阻抗的来源，总结阻抗的应对技巧。方法：采用描述性分析的方法，对235例飞行人员心理咨询中产生阻抗的原因进行分析，并对阻抗的应对方法进行了分析、归纳和总结。结果：飞行人员心理咨询中的阻抗主要来自于对医生的戒备、对咨询目的理解的偏差和无真正的求治动机，运用共情、移情和开放式提问等技巧可有效地消除阻抗。结论：有效地应对和消除心理阻抗，是决定飞行人员心理咨询和治疗取得成功的关键因素之一，也是衡量临床航空心理治疗水平的重要标志。     

健康成年人膈肌呼吸运动的动态MRI初步研究

目的探讨动态呼吸MR成像对研究膈肌运动的可行性。方法运用单次激发快速自旋回波(SSTSE)序列,对35例健康志愿者(男21例,女14例)进行MR动态扫描,并在1~2个深慢呼吸周期内采集图像。利用电影回放的方法获得膈肌运动的最高点和最低点,进而测量膈肌的运动幅度。比较左右侧膈肌的呼吸动度,与肺功能结果进行比较,利用时间距离曲线描述膈肌的运动特点。结果左、右侧膈肌动度的平均值为12.81 mm和9.11 mm。膈肌的动度与肺功能指标FVC、FEV1以及FEV1/FVC、MVV和SVC之间具有明显的相关性。结论左右侧膈肌动度之间的差异有统计学意义,动态呼吸运动成像能够很好的评价膈肌运动,具有潜在的临床应用价值。     

基于AD5933的多通道生物电阻抗测量仪的设计与实现

目的研究适于微重力条件下在轨应用的生物电阻抗测量方法。方法以STM32为控制中枢,以阻抗转换芯片AD5933为测量核心,进行多通道、多频生物电阻抗测量方法的研究设计,并进行通道一致性、有效性、人体试验验证。结果对64通道进行扫频测量,以第一通道为参考,多次测量相对误差可控制在2‰以内;与CHI604e生化分析仪(精度优于2‰)进行对比,测量相对误差在6‰以内;在显著度P=0.01的情况,本测量仪测量值与CHI604e测量值一致性高达0.997;对测试者的左上肢电阻RLA和右上肢电阻RRA进行30次多频测量,在P=0.01的情况,相邻两次的测量结果的相关系数高达0.994,任意两次测量结果不低于0.992。结论研制出一种支持多通道、多频的自动化测量设备。经测量分析验证,重复性和一致性较好,精度可以达到6‰。     

基于小型电极的新型阻抗血流图测量系统的研究

目的 研制基于小型一体化生物电阻抗电极的用于多部位阻抗血流图检测的仪器,用于检测手腕、颈、脑等多部位阻抗血流图和评价运动负荷状态下组织中阻抗血流图的变化。方法 采用高共模抑制比的差动放大器和相关检测原理对小型电极提取的微弱信号进行处理,设计相应的电路,提高信噪比,实现阻抗血流小型传感器微弱信号的检测。结果 经过实验验证,该仪器能够提取手腕、颈、脑等部位的阻抗血流信号,应用相干检测技术得到了很高的信噪比,测量方便,可以进行连续监测。结论 该仪器能够检测人体不同部位阻抗血流信号的搏动分量和非搏动性的直流分量,更好地评价局部血液循环状况,并且有望对运动负荷状态下的阻抗血流动力学参数作出评价。     

脂肪乳对光学法血小板计数影响研究

目的分析脂肪乳对光学法血小板计数的影响。方法采集患者新鲜血标本,分别采用Sysmex XT-4000i型血细胞分析仪光学法和阻抗法、手工草酸铵法、外周血片估算法进行血小板计数,分析4种方法血小板计数的差异。结果患者在输注脂肪乳后,光学法检测低值血小板计数的结果偏高,其他3种方法结果基本一致;输注脂肪乳7 h后,干扰因素消除,4种方法血小板计数结果基本一致。结论光学法血小板计数对于低值血小板标本检测存在局限性,实验室应建立完善显微镜复检规则,及时发现并纠正各种干扰因素对血小板计数的影响。     

Effectiveness of deep breath-hold SPECT in torso area: examination concerning improvement of resolution

Because SPECT images are acquired under normal respiration, the respiratory motion induces artifacts and decreases resolution. In this study we developed a novel method of acquiring SPECT data during deep inhalation breath-hold (BrST) and assessed its efficacy in reducing motion artifacts and improving resolution. Reproducibility studies found that variations in SPECT image homogeneity were reduced using the BrST method to within a clinically non-problematic range. An experiment using a custom-built respiration phantom showed almost complete elimination of motion artifacts and significant improvement in resolution using the BrST method. Clinical assessment confirmed a significant reduction in motion artifacts along with the improvement in resolution. The BrST method enabled visualization of lesions that previously had been impossible to detect by standard acquisition under normal respiration. The BrST method is expected to both significantly reduce motion artifacts and improve resolution.     

3-dimensional adaptive raw-data filter: evaluation in low dose chest multidetector-row computed tomography

OBJECTIVES: To evaluate a 3-dimensional adaptive raw-data filter in reducing streak artifacts in low dose chest computed tomographic (CT) images. METHODS: Fourteen adult patients who underwent low dose chest CT examination (parameters: 25 or 50 mAs, 120 kV) on 64-detector CTscanner were included in this study. We prepared 2 sets of contiguous 5-mm thick images by reconstruction with and without 3-dimensional adaptive raw-data filter (filter-processed and unprocessed images). Streak artifacts and visualization of peripheral vessels in both filter-processed and unprocessed images were evaluated using a 5-point scale. Upper, middle, and lower thorax were evaluated separately. RESULTS: The difference in artifact severity was statistically significant in upper and lower thorax (P = 0.002 and 0.03, respectively), whereas it was not significant in middle thorax (P = 0.13). The difference in the visibility of peripheral pulmonary vessels was not statistically significant in all anatomical regions. CONCLUSIONS: The 3-dimensional adaptive raw-data filter reduced streak artifacts in low dose chest CT in upper and lower thorax.     

Kalman filtering for real-time navigator processing

Navigator echoes are used in high-resolution cardiac MRI for tracking physiological motion to suppress motion artifacts. Alternatives to the conventional diaphragm navigator such as the cardiac fat navigator and the k-space center signal (self-navigator) were developed to monitor heart motion directly. These navigator data can be noisy or may contain undesirable frequency components. Real-time filtering of navigator data without delay, as opposed to the previously used retrospective frequency band filtering, is required for effective prospective navigator gating. One of the commonly used real-time filtering techniques is the Kalman filter, which adaptively estimates motion and suppresses measurement noise by using Bayesian statistics and a motion model. The Kalman filter is investigated in this work to filter noise and distinguish cardiac and respiratory components in navigator data. Preliminary imaging data demonstrate the feasibility of real-time Kalman filtering for prospective respiratory self-gating in CINE cardiac MRI.     

Adaptive noise cancellation to suppress electrocardiography artifacts during real-time interventional MRI

Purpose:

To develop a system for artifact suppression in electrocardiogram (ECG) recordings obtained during interventional real‐time magnetic resonance imaging (MRI).

Materials and Methods:

We characterized ECG artifacts due to radiofrequency pulses and gradient switching during MRI in terms of frequency content. A combination of analog filters and digital least mean squares adaptive filters were used to filter the ECG during in vivo experiments and the results were compared with those obtained with simple low‐pass filtering. The system performance was evaluated in terms of artifact suppression and ability to identify arrhythmias during real‐time MRI.

Results:

Analog filters were able to suppress artifacts from high‐frequency radiofrequency pulses and gradient switching. The remaining pulse artifacts caused by intermittent preparation sequences or spoiler gradients required adaptive filtering because their bandwidth overlapped with that of the ECG. Using analog and adaptive filtering, a mean improvement of 38 dB (n = 11, peak QRS signal to pulse artifact noise) was achieved. This filtering system was successful in removing pulse artifacts that obscured arrhythmias such as premature ventricular complexes and complete atrioventricular block.

Conclusion:

We have developed an online ECG monitoring system employing digital adaptive filters that enables the identification of cardiac arrhythmias during real‐time MRI‐guided interventions. J. Magn. Reson. Imaging 2011;33:1184–1193. © 2011 Wiley‐Liss, Inc.     

Retrospective adaptive motion correction for navigator-gated 3D coronary MR angiography

Retrospective adaptive motion correction (AMC) was developed for reducing effects of residual respiration in real-time navigator-gated three-dimensional (3D) coronary magnetic resonance (MR) angiography. In both motion phantom and in vivo experiments, AMC improved image sharpness of coronary arteries. This navigator-based technique combining adaptive correction and real-time gating is potentially an efficient and effective motion reduction method for 3D coronary MR angiography.     

Automated monitoring of diaphragm end-expiratory position for real-time navigator echo MR coronary angiography

Real-time navigator echo (NE)-gated magnetic resonance coronary angiography (MRCA) during free respiration is now possible. However, the mean diaphragm end-expiratory position (DEEP) drifts over time, and this results in a reduction in scanning efficiency and increased artifacts due to the acquisition of data during periods of high diaphragm velocity. To address these problems, a diaphragm monitoring program that follows the mean DEEP over time has been developed. Fifteen subjects with ischemic heart disease underwent continuous NE monitoring of their diaphragm for 30 minutes. Using these diaphragm traces, theoretical MRCA scans were performed. Several diaphragm monitoring algorithms were developed and compared with the simplest case (a stationary 5 mm NE acceptance window placed around the mean DEEP, as measured by NE monitoring at the outset of the scan). An overall scan efficiency was calculated, and the number of completed scans where the mean DEEP lay within the NE acceptance window was recorded. Of the six algorithms considered, the most effective one monitored the mean DEEP and prospectively placed the upper limit of the NE acceptance window on this position for the subsequent acquisition. Using this algorithm in comparison with the simplest stationary scenario, both scan efficiency (47.9% vs. 38.5%, P = 0.01) and the number of completed scans where the mean DEEP lay within the NE acceptance window (71.2 vs. 30.3, P < 0.001) were improved. The implementation of such a monitoring algorithm, in combination with adaptive motion correction techniques, should improve overall scan efficiency while maintaining the end-expiratory position at the top end of the NE acceptance window, to reduce image artifacts.     

胸部双能减影的运动伪影分析与对策探讨

目的 分析胸部双能减影的运动伪影（MA）。方法 对连续抽取的211例胸部双能减影，评价运动伪影的影像特征及图像满意度。运动伪影可分为：没有、轻、中、重4级，整体图像满意度分为：优、良、中、差4级。结果 运动伪影表现为在运动方向上被观察结构边界处出现的黑色或白色条纹影。双侧中、下肺野内带、双侧下肺野中带以及左中肺野中带、心缘旁、横膈、骨性胸廓是最容易出现运动伪影的部位。左下心缘是重度伪影最常见的部位。心脏搏动在所有病例中参与了运动伪影形成，呼吸运动和胸部移动分别在91．0％和6．2％的病例中参与了运动伪影形成。图像满意度为中等及以上者共占所有病例的80．1％。结论 运动伪影是影响胸部双能减影图像质量的重要因素，呼吸运动和心脏搏动是运动伪影的主要来源，从抑制运动伪影入手，可进一步提高胸部双能减影图像质量。     

A comparative study of electrocardiogram multi-segment reconstruction and dual source computed tomography using a computer controlled coronary phantom

Currently, there are two main methods for improving temporal resolution of coronary computed tomography (CT): electrocardiogram-gated multi-segment reconstruction (EMR) and dual source scanning using dual source CT (DSCT). We developed a motion phantom system for image quality assessment of cardiac CT to evaluate these two methods. This phantom system was designed to move an object at arbitrary speeds during a desired phase range in cyclic motion. By using this system, we obtained coronary CT mode images for motion objects like coronary arteries. We investigated the difference in motion artifacts between EMR and the DSCT using a 3-mm-diameter acrylic rod resembling the coronary artery. EMR was evaluated using 16-row multi-slice CT (16MSCT). To evaluate the image quality, we examined the degree of motion artifacts by analyzing the profiles around the rod and the displacement of a peak pixel in the rod image. In the 16MSCT, remarkable increases of artifacts and displacement were caused by the EMR. In contrast, the DSCT presented excellent images with fewer artifacts. The results showed the validity of DSCT to improve true temporal resolution.     

Retrospective coregistration of functional magnetic resonance imaging data using external monitoring.

Coregistration is essential for correcting head motion artifacts in functional magnetic resonance imaging (fMRI). Coregistration algorithms typically realign images through optimization of a similarity measure based on voxel signal intensities. However, coregistration can also be performed through external monitoring, whereby a tracking device measures head motion directly and independently of the imaging data. This paper describes development of external monitoring using fMRI-compatible infrared cameras. Three subjects participated in block-design fMRI experiments consisting of bilateral finger tapping alone and tapping combined with visuomotor tracking to produce controlled task-correlated head motion. Functional MRI time-series were coregistered using the external monitoring technique and a known image-based algorithm for comparison. Over various performance characteristics, external monitoring and image-based coregistration exhibited good agreement, in particular reducing signals correlated with millimeter task-correlated motions by 50-100%, with a 5% difference between the two techniques. These results promise future applications and refinements of external monitoring in patient populations where head motion is especially problematic. Possibilities include 3D prospective coregistration during real-time fMRI, coregistration of individual slices, and motion correction in anatomic MRI.     

Rapid autocorrection using prescan navigator echoes.

Autocorrection is an adaptive motion correction algorithm that does not require an in vivo measurement of the motion record. A novel method for ensuring convergence of this algorithm when motion is severe is presented. A limited number of navigator echoes are acquired before the imaging sequence to obtain a "snapshot" of the object. Phase differences between the navigator and image k-space data are used as an estimate of motion-induced phase shifts in the image, followed by autocorrection. In phantom data a six-fold reduction in computation time compared to autocorrection alone was realized. These results indicate that this navigator/autocorrection combination may be useful for reducing motion artifacts and computation time for MR exams when motion along the image phase encoding axis is severe.