心电相空间映射定量分析的一种新方法——棋盘映射

目的鉴于传统的标量坐标延时相空间重构方法存在运算复杂、耗时大、稳定性差等缺点,本文提出了相空间定量分析的一种新方法——"棋盘"映射(tessellated map,TM)。方法首先以逐拍心电波形为列矢量构造二维矩阵X,再通过KL变换得到X的主分量,然后由X的最大特征向量重构X。基于重构误差,从X中筛选出高SNR的正常心拍,得到二维矩阵Y。由模值归一化的Y及其衍生差分阵Z,得到"棋盘格"映射图。通过空白区域的比例、点密度、棋盘映射"位图"3个指标对TM进行定量评估。结果实验结果表明,TM能够对精神应激和非应激进行区分,能够判断心律失常,能够用于身份识别。结论TM能够有效地从ECG中提取信息,值得深入研究。     

一种基于二维图像的心电显示与处理的方法

目的 将心电矩阵进行图像化表达,从而展现"心拍群"波形的整体形态.方法 以逐拍心电波形为列矢量构造二维矩阵X;X通过平移与比例变换成为适于进行图像显示的矩阵Z;对矩阵Z进行图像化显示与处理.结果 可视化心电矩阵能够直观反映"心拍群"的波形形态,如ST区域矩阵有助于检测心肌缺血.结论 图像化心电矩阵同时具备整体性与直观性...     

四种剂量探测器对放疗加速器常用剂量率的响应特性分析

目的 探讨4种剂量探测器对放疗加速器常用剂量率的响应特性。方法 在100~600 cGy/min的剂量率范围内,分别测量PTW的0.6 cm³电离室、0.015 cm³电离室以及Matrixx Evolution 二维电离室矩阵和MapCHECK 二维半导体矩阵在同一测量条件和剂量下的剂量率响应;测量和分析0.6 cm³电离室在不同能量和工作电压下的剂量率响应特性。结果 PTW的0.6 cm³电离室、0.015 cm³电离室以及Matrixx Evolution 二维电离室矩阵在6 MV X射线能量下都表现一定的剂量率依赖性,差异均<1%,在15 MV X射线能量下,无剂量率依赖性。MapCHECK 二维半导体矩阵在6 MV X射线和15 MV X射线能量下都显示了较强剂量率依赖性,响应差异在2%左右。结论 依据剂量率变化治疗技术的放疗加速器的剂量测量,需要对测量设备进行剂量率响应测试和分析,以保证日常刻度和剂量验证的精度。     

二维电离室矩阵探测器的光子剂量学性能测试

目的 研究二维电离室矩阵探测器的剂量学特性,初步建立对其质量控制检测方法.方法 参照IEC 60731-2011报告对电离室剂量学指标的要求,在光子束(⁶⁰Co γ射线,6、10和15 MV X射线)下,对二维矩阵探测器剂量测量重复性、稳定性、剂量率依赖性、剂量响应线性和电离室间响应一致性等剂量学指标进行测试.结果 二维矩阵探测器在不同能量射线下测量重复性<0.3%,在⁶⁰Co γ射线下测量6个月的稳定性< 0.5%;在不同能量X射线下,加速器出束10~250 cGy和⁶⁰Co γ射线下剂量响应线性< 0.5%;在剂量率为200~600 MU/min下测量值最大偏差为0.87%;不同电离室间剂量响应偏差< 1%.结论 二维电离室矩阵探测器具有良好的剂量学特性;初步建立的质量控制检测方法具有可行性,并为放疗质量控制体系的建立提供理论依据.     

二维电离室矩阵在鼻咽癌调强适形放射治疗相对剂量验证中的应用

目的 利用二维电离室矩阵(matrixx)对鼻咽癌调强适形放射治疗(IMRT)计划进行相对剂量验证。方法 将30例鼻咽癌患者的IMRT计划移植到matrixx验证模型,生成验证计划。对二维电离室矩阵按验证计划进行实际机架角度下照射,将测得的平面剂量分布与验证计划中相同平面剂量分布分别输入到ominiPro-IMRT软件,依次进行验证计划与实测剖面图分析、验证计划与实测等剂量曲线分析,并用gamma分析量化。gamma值[γ(rm)]≤1的通过点,大于90%时表示患者IMRT计划通过。结果 30例患者的IMRT计划有27例患者计划通过点大于90%;有3例患者通过点分别为85.89%、86.56%、80.53%,经修正IMRT计划后,亦获得通过。结论 二维电离室矩阵可以作为IMRT计划平面剂量分布验证的工具,且使用简捷、方便。应用matrixx进行IMRT计划相对剂量验证的方法,可保证IMRT计划实施的准确性。     

脑功能成像对早期视区感知调节的研究

目的：对视网膜映射皮层区V1及V2的视觉调节作用进行初步探讨.方法：利用fMRI方法,对7例健康志愿者采用旋转及扩展棋盘格的视觉刺激进行视网膜皮层映射成像来确定早期视区的位置及大小;然后应用组块设计通过两个不同空间距离的楔形棋盘块进行视觉刺激,将V1及V2皮层区的激活采用ANOVA方法分析比较其变化及意义,以判定不同视区视觉内容的调节方式.结果：上视野对应的V2v区域激活变化显著（P=0.047）,并且两个小楔形棋盘块在视野中及映射在皮层表面位置为空间最短距离时激活反应最强烈,激活强度随其中一个楔形棋盘块距离增加而衰减.在V2d区域,有显著调节趋势（P=0.054）,在两个楔形棋盘块于同一视野而皮层投影最长距离时反应最弱.初级视皮层V1区域没有发现明显的变化趋势（P=0.073）.结论：视觉内容调节在早期视区主要发生在V2区域,V1区域没有调节功能.如果视觉刺激分别位于左右不同视野内时,V2区域也不发生调节作用.     

氦氧暴露对潜水员空间记忆与心理旋转能力的影响

目的研究0～2.50 MPa氦氧暴露对潜水员空间记忆广度、二维和三维心理旋转的影响。方法采用模拟棋盘的方法对潜水员的空间记忆进行评价,并进一步通过二维与三维心理旋转测验的方法评价其空间认知能力。结果 0～2.50 MPa高气压环境会直接损害潜水员的空间认知能力,主要表现为降低潜水员空间记忆能力,二维和三维心理旋转正确率下降。结论潜水员空间认知能力受损可能与高气压对大脑整体的抑制有关,并非对某个中枢的选择性损害。     

一种高能X射线任意形状野剂量计算模型的建立方法

目的探讨建立一种可用于模拟计算任意形状和强度的高能X射线外照射射束分布的快速剂量计算模型.方法基于蒙特卡罗方法建立的源模型包含一个由方形网格元素组成的光子注量矩阵,通过对源模型进行重构,以反映物理射束经过加速器射束成形部件后所引起的形状改变.结果比较规则野和不规则野的计算和测量结果,规则野误差小于2%,不规则野在10%等剂量线误差稍大.结论这一模型能够较为精确的模拟计算任意形状和强度的外照射放射治疗射束分布.     

免疫学方法分离哺乳动物精子的现状和将来

人们已经发明和改进了多种分离X、Y精子的方法,但尚无一种被广泛接受。我们对于Y精子能够、而X精子不能够在其质膜上表达一种雄性特异抗原的问题重新进行了探讨。用血清学检测的高效价雄性特异抗血清所作的免疫组织化学研究表明,这种雄性特异抗原存在于大约50％的精子上,并且定位在顶体后端和尾部中段。其他研究工作者在牛精子上获得了类似结果。这些资料重新提出了这个问题,即精子表面雄性特异抗原是否是Y染色体特异的单倍体基因表达的结果。如果是这样,那么免疫学方法分离X、Y精子可借助于此雄性特异抗原而实现。     

应用放射治疗模拟机对二次复形真空袋体位固定精度的验证研究

目的:探讨半软状态二次复形真空袋体位固定误差,为立体定向放射治疗中能否使用其提供依据。方法:抽取无漏气真空袋120例为对照组,抽取半软状态二次抽真空复形真空袋45例为实验组,应用模拟定位机对照射前、后测量灯光野与照射野X、Y、Z方向的移动情况进行比较,并进行统计学处理。结果:无漏气真空袋体位固定患者的X、Y、Z坐标的偏差率为5.83%,而半软状态二次复形真空袋体位固定患者X、Y、Z坐标的偏差率为35.65%,二者比较差异有显著性意义(P<0.01),故提示不能使用二次复形真空袋作为立体定向放射治疗的体位固定。结论:本研究结果表明在X-刀治疗中,使用真空袋体位偏差率及偏差幅度低,具有较好的体位固定效果,能保证良好的体位重复性。半软状态二次复形真空袋则有较大偏差率及偏差幅度,不宜在立体定向放射治疗中继续应用,应当重新制作真空袋进行CT定位。     

The effect of position of patient on the passage of metrizamide (Amipaque), meglumine iocarmate (Dimer X) and ioserinate (Myelografin) into the blood after lumbar myelography

Lumbar myelography was carried out with the contrast media Amipaque, Dimer X and Myelografin in 10 patients each. Five of the patients treated with each contrast medium were kept in a sitting position after the examination, the others lay flat. Blood levels and excretion were measured up to 24 h. The results are interpreted as follows: 1. After lumbar injection of the contrast media there is a short phase of distribution in the subarachnoid space (lag time) and they then are transferred into the blood with a half-life of 3.9 +/- 2.4 h. The transport from the CSF is almost completed approximately after 24 h. The velocity of transport varies greatly between the individual patients. Watersoluble contrast media presumably flow passively with the CSF through the arachnoid villi into the venous blood. 2. The horizontal position of the patient reduces the lag time until the beginning of the actual transfer of the contrast medium. 3. The transfer of Dimer X begins somewhat later compared with Amipaque and Myelografin.     

Method for determining pilot stress through analysis of voice communication.

Factors inherent in aircraft communication systems hinder customary approaches to voice analysis in the determination of the degree of stress experienced by a pilot during an inflight emergency. By means of a sound spectrogram, the mean vibration space of a voice can be analyzed if the space between the vertical deflections of the vowel sounds is calculated in micrometers. The vibration space shift rate (VSSR) is calculated by comparing the widest vibration space of the voice during the normal phase of the same flight (standard vibration space: SVS) with that encountered during the emergency situation (EVS) by the following formula: VSSR = ((SUS-EVS)/SUS) X 100%. The number of measuring points in each case differs in regard to the length of communication during the emergency. The VSSR can be divided into three phases - normal, urgent, and emergency - each with three grades of 0.5 S.D. apiece.     

Turboprop+: Enhanced turboprop diffusion‐weighted imaging with a new phase correction

Faster periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) diffusion‐weighted imaging acquisitions, such as Turboprop and X‐prop, remain subject to phase errors inherent to a gradient echo readout, which ultimately limits the applied turbo factor (number of gradient echoes between each pair of radiofrequency refocusing pulses) and, thus, scan time reductions. This study introduces a new phase correction to Turboprop, called Turboprop+. This technique employs calibration blades, which generate 2‐D phase error maps and are rotated in accordance with the data blades, to correct phase errors arising from off‐resonance and system imperfections. The results demonstrate that with a small increase in scan time for collecting calibration blades, Turboprop+ had a superior immunity to the off‐resonance‐related artifacts when compared to standard Turboprop and recently proposed X‐prop with the high turbo factor (turbo factor = 7). Thus, low specific absorption rate and short scan time can be achieved in Turboprop+ using a high turbo factor, whereas off‐resonance related artifacts are minimized. Magn Reson Med 70:497–503, 2013. © 2012 Wiley Periodicals, Inc.     

Contrast‐enhanced whole‐heart coronary magnetic resonance angiography at 3 T with radial EPI

Whole‐heart coronary magnetic resonance angiography is a promising method for detecting coronary artery disease. However, the imaging time is relatively long (typically 10–15 min). The goal of this study was to implement a radial echo planar imaging sequence for contrast‐enhanced whole‐heart coronary magnetic resonance angiography, with the aim of combining the scan efficiency of echo planar imaging with the motion insensitivity of radial k‐space sampling. A self‐calibrating phase correction technique was used to correct for off‐resonance effects, trajectory measurement was used to correct for k‐space trajectory errors, and variable density sampling was used in the partition direction to reduce streaking artifacts. Seven healthy volunteers and two patients were scanned with the proposed radial echo planar imaging sequence, and the images were compared with a traditional gradient echo and X‐ray angiography techniques, respectively. Whole‐heart images with the radial EPI technique were acquired with a resolution of 1.0 × 1.0 × 2.0 mm³ in a scan time of 5 min. In healthy volunteers, the average image quality scores and visualized vessel lengths of the RCA and LAD were similar for the radial EPI and gradient echo techniques (P value > 0.05 for all). Anecdotal patient studies showed excellent agreement of the radial EPI technique with X‐ray angiography. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

A multiple regression analysis for predicting local control of esophageal carcinoma treated by intracavitary irradiation

A multiple regression analysis for predicting local control of esophageal carcinoma treated by intracavitary irradiation is reported. In phase I, the value of predicting local control (VPLC) was determined by five parameters: VPLC = 1.38950 - 0.01571 X (age) + 0.04517 X (tumor length) + 0.62167 X (stenosis) + 0.94811 X (deep ulcer) - 0.02969 X (Total dose of intracavitary irradiation). From correlations between VPLC and the local control observed in 19 phase I patients, it was determined that a VPLC value of 0.5 or more predicted local failure and a VPLC of less than 0.5 signified successful local control. In phase II, prediction of local failure or local control was made for another 24 patients by calculating VPLC, and 22 of the 24 cases (91.7%) were correctly predicted. These results indicate that VPLC is a useful index for predicting of local control after intracavitary irradiation in cases with esophageal carcinoma.     

T2-weighted thin-section imaging with the multislab three-dimensional RARE technique.

A novel three-dimensional (3D) RARE (rapid acquisition with relaxation enhancement) sequence was implemented on a clinical imager. In this technique, multiple slabs are excited in the same way as in the multisection spin-echo sequence, and each slab is further phase encoded into eight sections along the section-slab direction. With a 16-echo RARE sequence, 128 excitations cover the 256 X 256 X 8 3D k space. With a TR of 2,500 msec, 10 slabs can be excited sequentially at each TR, yielding 80 sections in 5 minutes. Slabs were overlapped to give contiguous sections after discarding of the aliased sections at slab edges. This relatively fast sequence makes contiguous thin-section T2-weighted imaging possible, an impractical achievement with the much longer spin-echo method. Compared with 3D Fourier transform gradient-echo imaging, the sensitivity of 3D RARE sequences to magnetic susceptibility is reduced. The clinical potential of T2-weighted 3D imaging is illustrated with high-resolution brain, spine, and temporomandibular joint images.     

Gated blood pool SPECT improves reproducibility of right and left ventricular Fourier phase analysis in radionuclide angiography

OBJECTIVES: The ventricular phase angle, a parametric method applied to Fourier phase analysis (FPA) in radionuclide ventriculography, allows the quantitative analysis of ventricular contractile synchrony. However, FPA reproducibility using gated blood pool SPECT (GBPS) has not been fully evaluated. The present study evaluates whether by using GBPS, the reproducibility of FPA could be improved over that in planar radionuclide angiography (PRNA). METHODS: Forty-three subjects underwent both GBPS and PRNA, of which 10 subjects were normal controls, 25 had dilated cardiomyopathy, and 8 had various heart diseases. Interventricular contractile synchrony was measured as the absolute difference in RV and LV mean ventricular phase angle as delta(phi) (RV - LV). Intraventricular contractile synchrony was measured as the standard deviation of the mean phase angle for the RV and LV blood pools (RVSD(phi), LVSD(phi)). Two nuclear physicians processed the same phase images of GBPS to evaluate the interobserver reproducibility of the phase angles using data from the 43 study participants. Phase images acquired from PRNA were processed in the same manner. RESULTS: Excellent reproducibility of delta(phi) (RV - LV) was obtained with both GBPS (Y = -3.10 + 0.89 x X; r = 0.901) and PRNA (Y = -4.51 + 0.81 x X; r = 0.834). In regard to RVSD(phi) reproducibility was not adequate with PRNA (Y = 18.56 + 0.35 x X; r = 0.424), while it was acceptable with GBPS (Y = 5.22 + 0.85 x X; r = 0.864). LVSD(phi) reproducibility was superior using both GBPS (Y = 4.15 + 0.97 x X; r = 0.965) and PRNA (Y = -0.55 + 0.98 x X; r = 0.910). CONCLUSION: Our results demonstrate FPA obtained using GBPS to be highly reproducible for evaluating delta(phi) (RV - LV), RVSD(phi) and LVSD(phi), in comparison with the PRNA method. We thus consider GBPS appropriate for evaluating ventricular contractile synchrony.     

多层螺旋CT在小肠Crohn病中的应用研究

目的 探讨MSCT双期动态增强扫描在小肠Crohn病中的应用价值.方法 45例经综合方法 诊断,并通过临床治疗证实的小肠Crohn病患者均行MSCT双期动态增强扫描,并在ADW4.2工作站进行后处理.测量患病肠段在不同期相内的CT值,采用方差分析比较其CT值;并测量各期相内患病肠段与正常肠段的CT值筹值,以差别10 HU为界,划分病例数,将不同期相内的病例数采用卡方检验进行比较.结果病变肠段平扫平均CT值为(39.3±3.7)HU,动脉期为(74.8±13.8)HU,门静脉期为(90.2±12.3)HU,差异有统计学意义(F=258.87,P<0.01).病变肠段平扫与动脉期和门静脉期CT值两两比较,差异均有统计学意义(P<0.05).45例中,平扫CT值差值≤10 HU和>10 HU者分别为44和1例,动脉期分别为6和39例,门静脉期分别为2和43例,经X2检验,平扫与动脉期间差异有统计学意义(X2=32.49,P<0.01),平扫与门静脉期间差异有统计学意义(X2=39.22,P<0.01),动脉期与门静脉期间差异无统计学意义(X2=1.10,P>0.05).增强扫描使病灶显示更为清楚,大大提高了小肠Crohn病的检出率.结论 MSCT双期动态增强扫描可对小肠Crohn病作出初步诊断,并可对病变进行全面评价.     

Correction for geometric distortion and N/2 ghosting in EPI by phase labeling for additional coordinate encoding (PLACE).

Echo-planar imaging (EPI) is vulnerable to geometric distortion and N/2 ghosting. These artifacts can be analyzed with an intuitive k-t space tool, and here we propose a simple method for their correction. In a slightly modified additional EPI acquisition, we sample the k-t space with a shift in k(y) by adding a small area to the phase-encoding (PE) gradient. Physically, the added gradient area creates a relative phase ramp across the object and directly encodes the undistorted original y-coordinate of each voxel into a phase difference between two distorted complex images, in a method called "phase labeling for additional coordinate encoding" (PLACE). The phase information is then used to map the mismapped signals back to their original locations for geometric and intensity correction. Smoothing of expanded complex data matrix effectively reduces noise in the differential phase map and allows subpixel warping. The two acquired images can also be averaged to effectively suppress the N/2 ghost. Efficient correction for both artifacts can be achieved with three acquisitions. These acquisitions can also serve as reference scans to correct for geometric distortion and/or N/2 ghost artifacts on all images in a time series. The technique was successfully demonstrated in phantom and animal studies.     

Independent phase modulation for efficient dual-band 3D imaging.

Certain applications of MRI, such as bilateral breast imaging, require simultaneous imaging of multiple volumes. Although image data can be acquired sequentially, the SNR is often improved if both slabs are excited and imaged together, typically with phase encoding across a volume including both slabs and the space between them. The use of independent phase modulation of multiple slabs eliminates the need to encode empty space between slabs, which can result in a significant time reduction. Each slab is excited with a phase proportional to phase-encode number such that the slab positions in the acquired data are shifted to reduce empty space. With careful consideration this technique is compatible with different pulse sequences (e.g., spin-echo, gradient-echo, RF spoiling, and balanced SSFP (bSSFP)) and acceleration strategies (e.g., partial k-space and parallel imaging). This technique was demonstrated in phantoms and applied to bilateral breast imaging, where scan times were reduced by 20-30%.