结合硬斑块特征的心血管内超声图像中-外膜边缘检测

针对心血管内超声(IVUS)图像中-外膜(media-adventitia)边缘检测中,硬斑块和声影等造成中-外膜边缘难以准确检测的问题,提出一种结合硬斑块特征的中-外膜边缘检测方法。首先,采用k均值聚类分割IVUS图像,根据图像中不同类型斑块的成像特点检测硬斑块位置;然后,计算IVUS图像方向梯度,结合斑块位置和图像灰度,获得代价矩阵;最后,利用启发式图搜索方法,实现IVUS图像的中-外膜边缘检测。对临床图像的实验结果表明,本方法能克服图像中声影和斑块干扰等问题,使检测正确率达到95.57%,提高了IVUS图像中-外膜边缘检测的准确性。     

腹部出血的近红外光场分布模型仿真

目的针对腹部闭合性损伤和腹部出血诊断的困难,近红外光谱技术是一种无创伤、无污染的腹部出血检测的新方法。方法采用Monte Carlo方法仿真近红外光场分布模型。首先,建立了腹部多层组织的生物学模型。然后,为探究腹腔体液和血液对光子的吸收情况,对正常腹部和腹部出血时的光强信号进行了仿真模拟。通过探究光源和探测器间距不同时的光强分布来确定腹部出血位置。同时,为确定出血量对检测信号的影响和近红外光在腹部的检测深度,还对出血体积和检测深度的规律进行探究。结果在模拟腹腔体液和血液对光子吸收时,二者对光子的吸收有较大区别。出血位置的仿真结果表明,当出血位置在光源和探测器连线的中心位置靠光源侧时检测深度最深。近红外光在腹部的检测深度为48 mm。在一定范围内,光强信号与出血体积成反比。结论近红外光谱技术可以实现对浅层腹部出血进行检测,并且具有较好的灵敏度。     

基于相关检测的多通道近红外光组织光学测量系统

研制了一套基于相关检测技术的三波长多通道近红外光信号采集系统.采用相敏检波模块CD505R有效提高信噪比.Delphi开发的上位机程序通过串口方式与单片机通信.使用光纤传递光源及探测信号,使系统具有更大的灵活性,适用于多种组织光学特性测量方式.模型实验的结果证明该系统准确可靠,前臂阻断实验表明系统对不同深度组织血氧状况具有较好的测量能力.     

CT血管成像指导下急诊手术治疗脑动静脉畸形并脑内血肿

目的研究CT血管成像(CTA)对脑动静脉畸形(AVM)并脑内血肿在急诊术前诊断和手术评估中的价值,以及急诊手术方法的选择及疗效。方法选择2012年2月至2015年12月解放军第一七一医院收治的经CT和CTA检查确诊为AVM并脑内血肿的患者32例,其中男性22例,女性10例;年龄14~57岁,平均年龄33.1岁。发病至住院时间1~36 h。根据CTA进行术前评估,对其中28例急诊行畸形血管切除术加脑内血肿清除术,4例行血肿清除术。术后行数字减影血管造影(DSA)或磁共振血管造影(MRA)检查。随访3~12个月,对患者神经功能按日常生活能力(ADL)量表进行评价。结果 28例急诊行畸形血管切除术者均存活,术后DSA或MRA检查,脑AVM血管团均消失。4例仅行血肿清除术者,1例术后6 h死亡(畸形血管团位于基底节区,术前双侧脑疝),另外3例后期行介入或放射治疗。31例随访3~12个月,ADLⅠ级13例,Ⅱ级8例,Ⅲ级7例,Ⅳ级3例。结论手术是脑AVM并急性脑内血肿的首选治疗方法 ,CTA检查对脑AVM并急性脑内血肿的诊断及急诊手术评估有重要的价值,能作为判断手术方式的依据,指导手术过程,提高手术的安全性。     

梅毒特异性抗体的两种血清学检测方法比较

本文比较梅毒螺旋体明胶颗粒凝集试验法(TPPA)与酶联免疫吸附试验法(TP - EL ISA)两种方法的敏感性和特异性,评价两种方法在梅毒检测中的应用效果及临床意义.结论 发现明胶颗粒凝集试验法(TPPA)检测及酶联免疫吸附试验法(TP - EL ISA)两种检测方法都可以准确地检测梅毒螺旋体抗体,可根据具体情况选择需要的检测方法.     

脑淀粉样血管病脑出血患者血清抗Aβ抗体检测及临床治疗

目的探讨脑淀粉样血管病(CAA)脑出血患者血清自身抗Aβ抗体水平及亲和力的情况和临床治疗效果。方法选择2007年9月-2011年9月在本院住院的CAA脑出血患者和正常老年对照组各20例,通过间接ELISA法检测各组血清抗Aβ抗体水平及亲和力;分别采用方体定向钻颅置软管血肿排空术、开颅血肿清除术和保守治疗CAA脑出血患者26例。结果 CAA脑出血组血清抗Aβ抗体水平及亲和力均低于正常;26例患者经不同方案治疗后,14例患者痊愈,10例遗留不同程度偏瘫失语,2例死亡。结论自身抗Aβ抗体异常可能在CAA脑出血发病机制中发挥重要作用;CAA脑出血患者应根据病情选择合适的治疗方案,三种治疗方案各有其相对的适应证。     

癫痫病灶检测技术的研究进展

癫痫病灶检测技术已成为治疗难治性癫痫的一种重要手段,病灶的准确检测是保证手术安全、取得良好疗效的关键。本文综述了癫痫病灶检测技术的新进展,包括脑电图(electroencephalogram,EEG)、常规磁共振(magnetic resonance imaging,MRI)、功能性磁共振(functional magnetic resonance imaging,f-MRI)、同步脑电联合功能磁共振成像(electroencephalogram-functional magnetic resonance imaging,EEG-f MRI)、磁共振波谱分析(magnetic resonance spectroscopy,MRS)、脑磁图(magnetoencephalogram,MEG)、磁源性影像(magnetic source imaging,MSI)、单光子发射计算机断层扫描(single photon emission computed tomography,SPECT)、正电子发射断层扫描-计算机断层成像(positron emission tomography-computed tomography,PET-CT)以及偶极子定位(dipole localization method,DLM)等检测方法,并分析了每种方法的优缺点及发展方向。     

采用广义似然比检测的肌肉收缩起始时刻判断算法

肌电假肢利用残肢残存肌肉的肌电信号实行对假肢的控制。对于低信噪比的残肢表面肌电,本研究采用广义似然比检测方法判断肌肉收缩起始时刻,其中判别阈值与肌电信号信噪比有关。针对不同信噪比的模拟肌电信号,采用离线仿真方法得到肌肉收缩起始时刻检测误差最小的判别阈值,得到信噪比-经验阈值拟合曲线,确定信噪比与阈值的对应关系;根据肌电信噪比由阈值拟合曲线得到判别阈值,采用似然比检测算法在线分析肌肉收缩的起始时刻。与传统算法比较,对于模拟肌电信号,本算法误差均值和标准差分别减小35%和43%;对于真实肌电信号,误差均值和标准差分别减少29%和23%。可见在小信噪比条件下广义似然比检测算法判断肌肉收缩起始时刻较传统算法更为准确。     

葡聚糖结合蛋白的原核表达及检测深部真菌感染的应用

目的 验证葡聚糖特异性的结合蛋白用于检测深部真菌感染(IFI)患者血清中(1,3)-β-D-葡聚糖的应用价值。方法 通过构建美洲鲎葡聚糖结合蛋白(GBP)252位氨基酸至668位氨基酸活性区域表达质粒——pET30a-GBP252-668,表达并纯化获得GBP252-668重组蛋白。随后通过棋盘法构建双GBP252-668夹心法,并以此检测IFI患者血清中(1,3)-β-D-葡聚糖。同时与G试验(G-Test)进行检测性能的比对。结果 成功纯化获得分子质量约为46 ku的GBP252-668重组蛋白,并确定最佳包被浓度和检测浓度分别为8和16 g/L,以此构建了GBP252-668夹心法。对48名深部真菌感染患者和48名健康人血清进行检测,根据受试者工作特征曲线(ROC)可得其灵敏度为91.67%,特异度为89.58%。其灵敏度与G-Test相当,特异性高于同批次G-Test(79.17%)。结论 本研究构建的双GBP夹心法是一种极具潜力检测侵袭性真菌的方法,其灵敏度与G-Test相当,特异性高于同批次G-Test。     

脑脊液β2-m、SF检测在小儿化脓性脑炎与病毒性脑炎中的鉴别诊断价值

目的 :通过对脑脊液 β2 -微球蛋白 (β2 -m)、铁蛋白 (SF)含量检测 ,快速鉴别诊断小儿化脓性脑炎(化脓脑 )与病毒性脑炎 (病毒脑 )。方法 :选择用药前 4 2例化脓脑患儿 (化脓脑组 ) ,4 4例病毒脑患儿 (病毒脑组 ) ,2 2例对照组小儿脑脊液 ,用放射免疫分析 (RIA)测其β2 -m、化学发光法 (CLIA)测其SF含量。结果 :脑脊液 β2 -m及SF含量化脓脑组、病毒脑组均显著高于对照组 (P <0 0 0 1) ,化脓脑组均显著高于病毒脑组 (P <0 0 0 1)。结论 :脑脊液 β2 -m、SF任何一项或两项同时检测 ,均对小儿化脓脑与病毒脑具有快速鉴别诊断价值 ,从而为临床尽早用药提供实验室依据。     

Improved sensitivity to cerebral hemodynamics during brain activation with a time-gated optical system: analytical model and experimental validation

Time domain (TD) diffuse optical measurement systems are being applied to neuroimaging, where they can detect hemodynamics changes associated with cerebral activity. We show that TD systems can provide better depth sensitivity than the more traditional continuous wave (CW) systems by gating late photons, which carry information about deep layers of the brain, and rejecting early light, which is sensitive to the superficial physiological signal clutter. We use an analytical model to estimate the contrast due to an activated region of the brain, the instrumental noise of the systems, and the background signal resulting from superficial physiological signal clutter. We study the contrast-to-noise ratio and the contrast-to-background ratio as a function of the activation depth and of the source-detector separation. We then present experimental results obtained with a time-gated instrument on the motor cortex during finger-tapping exercises. Both the model and the experimental results show a similar contrast-to-noise ratio for CW and TD, but that estimation of the contrast is experimentally limited by background fluctuations and that a better contrast-to-background ratio is obtained in the TD case. Finally, we use the time-gated measurements to resolve in depth the brain activation during the motor stimulus.     

Modeling scintillator-photodiodes as detectors for megavoltage CT

The use of cadmium tungstate (CdWO4) and cesium iodide [CsI(Tl)] scintillation detectors is studied in megavoltage computed tomography (MVCT). A model describing the signal acquired from a scintillation detector has been developed which contains two steps: (1) the calculation of the energy deposited in the crystal due to MeV photons using the EGSnrc Monte Carlo code; and (2) the transport of the optical photons generated in the crystal voxels to photodiodes using the optical Monte Carlo code DETECT2000. The measured detector signals in single CdWO4 and CsI(Tl) scintillation crystals of base 0.275 x 0.8 cm2 and heights 0.4, 1, 1.2, 1.6 and 2 cm were, generally, in good agreement with the signals calculated with the model. A prototype detector array which contains 8 CdWO4 crystals, each 0.275 x 0.8 x 1 cm3, in contact with a 16-element array of photodiodes was built. The measured attenuation of a Cobalt-60 beam as a function of solid water thickness behaves linearly. The frequency dependent modulation transfer function [MTF(f)], noise power spectrum [NPS(f)], and detective quantum efficiency [DQE(f)] were measured for 1.25 MeV photons (in a Cobalt-60 beam). For 6 MV photons, only the MTF(f) was measured from a linear accelerator, where large pulse-to-pulse fluctuations in the output of the linear accelerator did not allow the measurement of the NPS(f). A two-step Monte Carlo simulation was used to model the detector's MTF(f), NPS(f) and DQE(f). The DQE(0) of the detector array was found to be 26% and 19% for 1.25 MeV and 6 MV photons, respectively. For 1.25 MeV photons, the maximum discrepancies between the measured and modeled MTF(f), relative NPS(f) and the DQE(f) were found to be 1.5%, 1.2%, and 1.9%, respectively. For the 6 MV beam, the maximum discrepancy between the modeled and the measured MTF(f) was found to be 2.5%. The modeling is sufficiently accurate for designing appropriate detectors for MVCT.     

Signal-to-noise ratio and spatial resolution in x-ray electronic imagers: is the MTF a relevant parameter?

In most imaging detectors, the modulation transfer function (MTF) is regarded as a good parameter to describe spatial resolution. This is undoubtedly valid for visual observation. However, the detectability of a detail is essentially a matter of signal-to-noise ratio, which is not accounted for by the MTF. In x-ray imaging, signal-to-noise ratio in the image is generally limited by incident photons statistics, often larger than readout noises. Therefore, the MTF of the detector applies to both signal and noise, and does not impair the image content. Contrast can easily be restored by image processing without altering the signal-to-noise ratio. However, a number of effects may alter very differently noise and signal: (i) If the MTF significantly extends beyond half the sampling frequency, the aliasing introduced by spatial sampling can severely enhance the noise and cancel the benefit of the good signal transfer. This is illustrated by synthetic images which simulate the response of imagers with different MTFs to the same test pattern in the presence of quantum noise. (ii) Parallax and blurring by the x-ray spot size or motion are shown to degrade the transfer properties of signal, but do not affect the quantum noise; they must be treated separately. Contrary to the x-ray converter MTF, parallax directly impacts the detective quantum efficiency (DQE). Finally, it is shown that only the detective quantum efficiency can reliably describe the spatial resolution of an x-ray imaging detector in the presence of noise, parallax and blurring.     

Improvement of the optical imaging technique for intact rat brain using a plano-concave lens

Use of a plano-concave lens improved the quality of optical signals from the rat cerebral cortex by improving the focus. When detecting neural activity from a curved surface of an in vivo brain by optical techniques, it is not possible to adjust the focus equally over the entire detecting area in the two-dimensional plane, since the active window of the optical detector is usually flat, while the intact brain surface is spherical. It has been known that the size of the optical signal is reduced as the distance of the real image to the active window of the detector increases; therefore, the level of the signal-to-noise ratio obtained from the unfocused area often becomes insufficient for quantitative physiological analyses. By placing a plano-concave lens on the cerebral cortex, we succeeded in obtaining a two-dimensional image that has no unfocused area over an entire image recorded by the detector.     

Direct conversion detectors: the effect of incomplete charge collection on detective quantum efficiency

Direct conversion detectors offer the potential for very high resolution and high quantum efficiency for x-ray imaging, however, variations in signal can arise due to incomplete charge collection. A charge transport model was developed to describe the signal and noise resulting from incomplete charge collection. This signal to noise ratio (SNR) reduction was incorporated into the cascaded systems model for a simple x-ray detector. A new excess noise factor, A(c) (termed the collection noise factor) is introduced to describe the reduction in detective quantum efficiency (DQE). The DQE is proportional to the product of the quantum efficiency and the collection noise factor. If the trapping cross sections for electrons and holes are very different, and if the detector is biased improperly, the collection noise factor can drop to as low as 50%. In addition, the signal loss due to incomplete charge collection will reduce the DQE in the presence of added noise. Because of this, the DQE generally does not continue to improve with greater detector thickness. The collection noise factor and DQE are predicted for CdZnTe, PbI2, and Se. The optimization of detector thickness should be based not only on quantum efficiency but also on the charge collection statistics, which are influenced by bias field and polarity.     

Biophotons, microtubules and CNS, is our brain a "holographic computer"?

Several experiments show that there is a cell to cell communication by light in different cell types. This article describes theoretical mechanisms and subcellular structures that could be involved in this phenomenon. Special consideration is given to the nervous system, since it would have excellent conditions for such mechanisms. Neurons are large colourless cells with wide arborisations, have an active metabolism generating photons, contain little pigment, and have a prominent cytoskeleton consisting of hollow microtubules. As brain and spinal cord are protected from environmental light by bone and connective tissue, the signal to noise ratio should be high for photons as signal. Fluorescent and absorbing substances should interfere with such a communication system. Of all biogenic amines nature has chosen the ones with the strongest fluorescence as neurotransmitters for mood reactions: serotonin, dopamine and norepinephrine. If these mechanisms are of relevance our brain would have to be looked upon as a "holographic computer".     

Detection efficiency of a high-pressure gas scintillation proportional chamber

The detection efficiency of a high-pressure, gas scintillation proportional chamber (GSPC), designed for medical imaging in the 30-150 keV energy range, has been investigated through measurement and Monte Carlo simulation. Measurements were conducted on a GSPC containing 4 atm of pure xenon separated from a hexagonal array of seven ultraviolet-sensitive photomultiplier tubes by 1.27-cm-thick fused-silica windows. Experimental measurements of the photopeak efficiency, fluorescence escape efficiency, and the energy collection efficiency were obtained. Results were also obtained for different photon energies and different values of temporal resolution. The measurements were compared with the results obtained from a Monte Carlo simulation designed specifically for investigating the imaging of low-energy photons (below 150 keV) with a gas-filled detector. The simulation was used to estimate photopeak efficiency, fluorescence escape efficiency, photopeak-to-fluorescence escape peak ratio, quantum interaction efficiency, energy collection efficiency, and local energy collection efficiency. The photopeak efficiency of the GSPC relative to that of a 3-in. (7.62-cm)-thick sodium iodide crystal was measured to be 0.284 +/- 0.001 at 60 keV and 0.057 +/- 0.001 at 140 keV. Of the 60-keV photons incident upon the detector, 70% +/- 4% interacted in the detector, with 28% +/- 1% being in the photopeak, as estimated both by experimentation and through the simulation. The maximum energy collection efficiency was found to be 65% at 60 keV, with 46% being deposited within 0.2 cm of the initial photon interaction. The information gained from this study is being used to design an optimized detector for use in specialized nuclear medicine studies.     

A Mathematical Model for Detection of Back-Scattered Radiation during Diagnostic Scanning with a Narrow X-Ray Beam

A mathematical model for detection of foreign impurities in the inspected object with the use of a narrow scanning X-ray beam is suggested. A generalized expression for signal/noise ratio for the diagnostic system with a detector of the back-scattered radiation was derived.     

Computer simulation of image intensifier-based computed tomography detector: vascular application

This present study reports the results of a computer simulation whose aim was to predict the low-contrast imaging performance of which a conventional x-ray image intensifier with charge coupled device (CCD) camera would be capable if incorporated into a computed tomography (CT) volume imager. A vascular imaging task was modeled in our simulation. The effects of detector noise, x-ray exposure levels, analog-to-digital conversion (ADC) precision and residual levels of detected x-ray scatter were considered. The results of this simulation indicate that the low-contrast imaging performance of an image intensifier-based CT system was most limited by the CCD detector readout noise. Given this limitation the detection of greater than about 100,000 detected photons/pixel/projection gave marginal improvement in low-contrast resolution. At these exposures 12 bit ADC precision resulted in little additional image noise. The effects of detecting scattered x rays are twofold; decreasing the signal-to-noise ratio associated with our modeled artery and introducing a cupping artifact. Based on the results from the simulation, it appears that an image intensifier-based CT system is a feasible concept from a noise viewpoint, if the anticipated imaging task is intravenous angiography.