脑出血血肿周围局部脑血流的检测

影像学技术是研究脑血流的主要手段,文章综述了各种神经影像学技术对脑出血血肿周围半暗带的定义以及脑出血血肿周围局部脑血流的研究现状。     

A New Approach to Electromagnetic Blood Flow Determination by Means of Catheter in an External Magnetic Field

Maximal reduction in transverse catheter dimension has been achieved for the purpose of creating an intravascular electromagnetic flow sensor capable of percutaneous introduction into the vascular system. The electrodes are mounted on a flexible frame which collapses as it passes through a small branch blood vessel and expands to span the diameter of the main vascular trunk when entering it. Unlike the catheter flow sensors developed previously, which are velometers, i.e., sensors of fluid velocity, the present one is capable of measuring the volume rate of flow in branch blood vessels as well as in the major sections of the vascular tree. The magnetic field is provided by a large air core electromagnet placed externally to the animal or patient. A special circuit utilizing two electrodes and three leads permits reduction of the unwanted quadrature signal to zero. A standard sine wave electromagnetic flow meter channel designed for use with conventional electromagnetic flow transducers is adequate for flow measurements as well as for power supply to the large magnet. Illustrations of the performance of the apparatus in vitro and in vivo are presented.     

The Measurement of Hemodialysis Access Blood Flow by a Conductivity Step Method

Background and objectives: Measurement of blood flow rate (Qa) is used to monitor dialysis access, AV fistulas, and grafts. Indicator dilution measurements of the recirculation (R) induced by reversal of hemodialysis blood lines are commonly used. This plus the dialysis circuit flow (Qb) allows calculation of Qa. R also changes the conductivity, which can be measured by a conductivity cell in the spent dialysate. The change in conductivity caused by line reversal should vary with Qa. A methodology for Qa measurement utilizing this conductivity step is proposed. This study compares conductivity step methodology against the reference method of ultrasound dilution (Qa-Trans).Design, setting, participants, & measurements: This was an open diagnostic test study in a single academic hospital setting involving 15 hemodialysis-dependent patients. Each was studied over four hemodialysis treatments. During each treatment, two pairs of Qa measurements (conductivity step and Trans) were made. Pre- and postdialysis sodium levels were also measured.Results: Average Qa-conductivity step was 1040 ml/min. Average Qa-Trans was 1030 ml/min. The difference was NS. The data pairs showed mean difference of 1.3 ± 17% (SD). The SD indicates a relatively large variation between data pairs. There was significant linear correlation between the Qa-conductivity step and Qa-Trans results (r = 0.91, P < 0.001). Serum sodium rose slightly but significantly over dialysis (P < 0.001).Conclusions: Qa measurement by conductivity step may be an acceptable alternative to ultrasound dilution methodology. Care must be taken to prevent salt loading when the conductivity step is used.The measurement of hemodialysis blood access flow rate (Qa, ml/min) in arteriovenous (AV) fistulas and grafts is common. Reduced or falling levels of Qa indicate access dysfunction and predict thrombosis (1). Most Qa measurements use indicator dilution techniques to measure the amount of recirculation induced by reversal of blood lines. This plus the dialysis circuit flow rate (Qb, ml/min) allows for the calculation of Qa (1). One methodology for Qa measurement involves ultrasound velocity measurements of flowing blood and their dilution by saline using the Transonics hemodialysis monitor (Transonics, Inc., Ithaca, NY). Details of this and other technologies are given elsewhere (2). Because access recirculation is inversely related to Qa (3) and because it will lead to a decreased dialyzer urea clearance, we hypothesized that needle reversal can measure Qa by observing the effect on dialysate urea concentrations. This hypothesis was proven and the results have been published (4). Mercadal et al. (5) and Gotch et al. (6) have shown that the change in effective ionic dialysance (EID) values induced by line reversal can be used to measure Qa. As pointed out in our Discussion (4), Fresenius Medical Care (www.fmc-ag.com) had incorporated propriety software into their dialysis machine (2008K) to measure Qa utilizing EID. At that time, there was no published work regarding the accuracy and validity of this methodology beyond the original theory validation (5). Subsequently, Lacson et al. (7) of Fresenius Medical Care and Whittier et al. (8) have separately published validation data for EID incorporated into the Fresenius 2008K machine using ultrasound velocity measurements as the “gold standard” comparator. Their results showed good agreement between the methodologies. The EID-based measurements rely on two separate determinations of ionic dialysance obtained many minutes apart. Knowing the effect of line reversal on dialysate urea concentrations, we examined the possibility to directly measure Qa from the conductivity change induced by the reversal of lines (conductivity step method).     

System Identification of Human Cerebral Blood Flow Regulatory Mechanisms

Regulation of cerebral blood flow (CBF) is important to protect the brain against ischemia or excessive capillary pressure and hyperperfusion. In addition to the myogenic and metabolic mechanisms of pressure autoregulation, which tend to maintain CBF relatively constant with changes in arterial blood pressure (ABP), several other variables, like CO₂, intracranial pressure, metabolic demand, sympathetic activity, cerebrovascular resistance, and endothelial metabolites are also involved in the dynamic control of CBF. Increasingly, system identification techniques are being used to shed light on the physiology of CBF regulation and to provide clinical tools for diagnosis, monitoring, and prognosis of patients with cerebrovascular conditions. In the frequency domain, the transfer function between ABP and CBF for normal subjects, is characterized by a reduced coherence, below 0.1 Hz, a positive phase response, below 0.2 Hz, and an amplitude frequency response that tends to rise continuously with frequency. One or more of these functions have been shown to be altered in patients with prematurity, carotid artery disease, severe head injury, and subarachnoid hemorrhage. Time-domain approaches are becoming more popular, involving autoregressive moving average structures (ARMA), cross-correlation analysis, or linear system models, such as the second-order differential equation used to calculate the dynamic autoregulation index (ARI), which has been adopted in many clinical studies. Nonlinear methods, based on the Wiener–Volterra approach have also been proposed, including new implementations based on dedicated neural networks. One trend in this area is the use of multivariate time-domain models to include other variables, such as CO₂, in addition to ABP. However, the inclusion of other key variables, such as intracranial pressure, metabolic demand, and sympathetic activity, will depend on refinements of noninvasive measurement techniques to quantify their input load. Open access databases, containing representative recording from patients with different conditions, would be important to standardize the validation of system identification techniques by different research groups. The use of hybrid models, incorporating elements of mathematical modeling of well-known physiological phenomena, might also be a worthwhile approach in the future.     

Evaluation of Endoscopic Laser Doppler Flowmetry for Measurement of Human Gastric Blood Flow: Methodologic Aspects

Endoscopic measurement of gastric blood perfusion by laser Doppler flowmetry (LDF) has been evaluated in 28 patients and 15 healthy volunteers. During the recordings it was necessary to keep the probe in light contact with the mucosa to obtain stable curves and to avoid artificial Doppler signals caused by relative movements between the gastric wall and the probe. Gastric distention by air insufflation did not influence the recorded flow level significantly when air insufflation was moderate. The intravenous injection of 0.6 mg atropine did not cause any significant alteration in recorded blood flow, and this drug may be used as premedication before endoscopic blood flow measurements. Recordings with both 4-and 12-kHz bandwidth of the LDF instrument showed a relative constant relationship for different flow levels, the flow values measured with 12 kHz being about twice the corresponding values measured with 4 kHz. With 12-kHz bandwidth more of the disturbance signal is recorded, which makes analysis of endoscopic recorded flow curves difficult and inaccurate. It is therefore recommended to use 4-kHz bandwidth during endoscopic measurements in conscious humans. Blood flow measurements from both sides of the gastric wall were consistently of the same order of magnitude (r = 0.91), and the endoscopically recorded output signal increased in three of five patients when a reflecting mirror was placed at the serosal side. The results indicate that endoscopic LDF usually represents blood perfusion in all layers of the gastric wall.     

Comparison of Neutron Activated and Radiolabeled Microsphere Methods for Measurement of Transmural Myocardial Blood Flow in Dogs

Background: The ‘gold standard’ radioactive microsphere (RM) technique for measurement of organ blood flow under various experimental conditions is inaccessible to many researchers due to increasing environmental concerns regarding safety and disposal of low-level radioactive waste materials. A new method using neutron activated microspheres (NAM) has recently been described.Methods: We compared regional myocardial blood flows using the new formulation STERIspheres™ (NAM; 15.0 ± 0.1 [SD] μ m; density 1.5 gr/mL) with RM (15.0 ± 0.1 [SD] μ m; density 1.5 gr/mL) under different experimental conditions during acute ischemia-reperfusion injury in dogs. Random paired combinations of four different RM and NAM were co-injected into the left atrium during autoregulation, coronary occlusion and flow-mediated hyperemia (reperfusion) in the same animal. The left ventricle was divided into non-ischemic and ischemic regions and further subdivided into endocardial, mid-myocardial and epicardial portions. After gamma-counting, blood and myocardial tissue samples (n = 180) were dried and then shipped to a core facility for neutron activation and analysis. NAM-RM blood flow data were directly compared by ANOVA and regression analysis; Bland and Altman analysis was also performed to assess mean differences in blood flow with NAM-RM.Results: A direct relation for blood flow between NAM-RM was observed; the slope of the relation (1.17 RM ± 0.04 [SEE]) was different from unity but the intercept (0.06 ± 0.06 [SEE]) was not different from the origin. Intermethod mean differences were minimal between NAM-RM in the low to normal range of blood flow and were increased at the higher blood flow levels the latter being of minor physiological consequence. A direct relation for endo/epicardial blood flow ratios between NAM-RM was also observed; the slope of the relation (0.98 RM ± 0.04 [SEE]) and the intercept (0.03 ± 0.06 [SEE]) were not different from unity or the origin, respectively.Conclusions: Results show that in addition to limiting production of radioactive waste materials, NAM accurately measure myocardial blood flow, endocardial/epicardial and ischemic/non-ischemic blood flow distributions over a wide range.Abbreviated abstract We compared myocardial blood flows using paired combinations of neutron activated (NAM) and the ‘gold standard’ radiolabeled microspheres (RM) co-injected during autoregulation, coronary occlusion and flow-mediated hyperemia in an in situ canine ischemia-reperfusion preparation. A direct relation for blood flow and endo/epicardial blood flow ratios between NAM-RM was observed; intermethod mean differences between NAM-RM were minimal in the low to normal blood flow range but increased at higher blood flow levels. These results indicate that NAM accurately measure myocardial blood flow and its transmural distribution in addition to limiting unnecessary production of radioactive laboratory waste products.     

Treatment of Diuretic Resistance with a Novel Percutaneous Blood Flow Regulator: Concept and Initial Experience

Diuretic resistance in acute heart failure is a common clinical problem, and it is associated with adverse outcomes. Effective therapies are still lacking. The Doraya catheter, a temporary intravenous flow regulator placed in the inferior vena cava below the level of the renal veins, is a novel device designed to target renal and cardiac congestion, thereby improving diuretic response. A first-in-man clinical study is currently ongoing.     

A Next-Generation Guide Extension System for Percutaneous Coronary Intervention

BackgroundGuide catheter extension is an integral part of percutaneous coronary intervention (PCI). First generation guide catheter extension devices are monorail, blunt ended tubular structures with limitations. The CrossLiner™ is a next generation guide extension “system” intended to allow safe, deep, coronary intubation.MethodsThe CrossLiner was tested in a head-to-head study with the GuideLiner™ and GuideZilla™ in a porcine coronary model, with stenting. Data were collected from 8 coronary vessels from four animals, to evaluate the ability to deeply intubate the vessel with the guide extension.ResultsThe CrossLiner crossed distally and through a distal stented segment in 8/8 vessels, while the first-generation devices were stuck proximal to the stent (n=2/8) or at the stent edge (n=4/8), or passed partially into the deployed stent with difficulty (2/8) vessels (p < 0.0002 for deliverability). The average depth of guide extension delivery/ “intubation” was 12.9±3.6 cm for the CrossLiner and 5.6±1.1 cm for the first-generation guide extension (p < 0.001).ConclusionsThe CrossLiner is a next generation guide extension system that may offer advantages over first generation devices. Further clinical evaluation will be required to assess the role of this new device in PCI.     

血流速度测定对肝炎诊断及判断病情的应用价值

应用彩色多普勒超声对肝炎肝硬化１６７例患者和５９例正常人作血流动力学测定。结果示：（１）急,慢性为在发病初期的门静脉平均和血流速度均显著高于对照组,治疗后均降低,与治疗前比较有意义;肝硬化血流速度低于正常人,亦有意义;（２）急,慢性肝炎及肝硬化的脾静脉血流速度逐渐增高。     

血流储备分数在冠心病介入治疗中的应用

在冠心病的诊断和治疗中,对狭窄冠状动脉进行血运重建应遵循心肌缺血的客观证据,近年备受重视的血流储备分数能更好反应冠状动脉真实灌注状态,它对指导经皮冠状动脉介入治疗或冠状动脉搭桥术有重要价值,尤其适用于冠状动脉狭窄临界病变及特殊病变的缺血评估。     

消化道粘膜血流图像处理对胃角溃疡愈合时间的预测

目的应用消化道粘膜血流图像处理技术定量研究胃角溃疡及其周边粘膜血流,并对溃疡愈合时间进行预测.方法由计算机自动计算电子内镜图像上每一像素的血红蛋白浓度指数(HI=32lnVr/Vg,Vr红图像灰度值,Vg绿图像灰度值);根据溃疡及其周边充血粘膜的HI计算溃疡面积和充血粘膜面积(像素数),溃疡面积与充血粘膜面积比值的对数值称为溃疡愈合指数.予13例胃角溃疡患者以兰索拉唑治疗,对同一患者,利用治疗前、后两次内镜检查测得的溃疡愈合指数和检查时间预测溃疡愈合时间,并在预测的溃疡愈合时间范围内,观察其实际愈合情况.结果溃疡愈合过程中,充血粘膜面积逐渐增大,并于愈合1期达到峰值,至瘢痕期明显下降.溃疡愈合指数(y)与溃疡发生的时间过程(x,指从溃疡发生至进入瘢痕期的时间)呈直线相关关系(y=-o.15x+0.80,r=0.89,P＜0.001),溃疡愈合指数减少一半的平均时间为4.00天±1.92天;在预测的溃疡愈合时间范围内,所有溃疡均愈合.结论消化道粘膜血流图像处理技术能定量、客观地预测溃疡愈合时间,可用于临床抗溃疡药物的疗效判定.