Intraoperative cerebral blood flow monitoring in neurosurgery: A review of contemporary technologies and emerging perspectives

Intraoperative monitoring of cerebral blood flow (CBF) has become an invaluable adjunct to vascular and oncological neurosurgery, reducing the risk of postoperative morbidity and mortality. Several technologies have been developed during the last two decades, including laser-based techniques, videomicroscopy, intraoperative MRI, indocyanine green angiography, and thermography. Although these technologies have been thoroughly studied and clinically applied outside the operative room, current practice lacks an optimal technology that perfectly fits the workflow within the neurosurgical operative room. The different available technologies have specific strengths but suffer several drawbacks, mainly including limited spatial and/or temporal resolution. An optimal CBF monitoring technology should meet particular criteria for intraoperative use: excellent spatial and temporal resolution, integration in the operative workflow, real-time quantitative monitoring, ease of use, and non-contact technique. We here review the main contemporary technologies for intraoperative CBF monitoring and their current and potential future applications in neurosurgery.     

三维斑点追踪技术预测急性心肌梗死患者近期急性心衰风险的研究

目的:分析三维斑点追踪技术预测急性心肌梗死(AMI)患者近期发生急性心衰的诊断价值。方法:选取医院诊治的155例AMI患者,均予抗血小板聚集、改善心肌供血等对症治疗,并对患者出院后进行为期3个月的随访,除3例患者失联外,将剩余152例患者纳入随访结果研究。将152例患者中出现急性心力衰竭的43例患者纳入心衰组,未出现心力衰竭的109例患者纳入无心衰组。比较两组患者的年龄、性别等一般资料,并对患者N-末端脑钠肽前体(NT-pro BNP)、超敏C反应蛋白(hs-CRP)、肌钙蛋白I(cTnI)等临床常用指标及三维斑点相关指标进行比较。结果:心衰组患者的年龄、NT-proBNP、hs-CRP、c Tn I及左室收缩末期容积指数(LVESVI)均明显高于无心衰组,差异有统计学意义(t=2.279,t=3.385,t=2.212,t=2.943,t=2.289;P<0.05),射血分数(EF)、左室整体径向应变(GRS)、整体圆周应变(GCS)、整体纵向应变(GLS)及整体面积应变(GAS)明显低于无心衰组,差异有统计学意义(t=6.606,t=2.804,t=2.945,t=7.226,t=2.687;P<0.05);而两组患者的性别、合并高血压等一般资料及肾小球滤过率(e GFR)、LVEDVI等指标间差异均无统计学意义;多因素logistic分析提示,NT-pro BNP、LVESVI是影响急性心衰的独立危险因素(OR=1.002,OR=1.118;P<0.05),EF、GLS则是其独立保护因素(OR=0.795,OR=0.452;P<0.05);受试者工作特征(ROC)曲线提示GLS预测急性心衰的ROC曲线下面积(AUC)为0.881,显著高于NT-pro BNP、LVESVI及EF(Z=2.751,Z=3.107,Z=2.895;P<0.05),其诊断的最佳截点<13.42%,此时其灵敏度为95.3%,特异度为67.9%。结论:三维斑点追踪技术可以对急性AMI患者近期发生急性心衰进行有效地预测,具有较高的灵敏性及诊断效能,可以应用于急性AMI患者心衰的早期预测。     

小波变换在消除超声成像噪声中的应用

小波分析是目前国际上公认的性能优良的信号时—频分析工具,其多分辨率分析具有良好的空间域和频率域局部化特性,因此很适合于对二维图像信号进行处理。本文针对肝脏超声成像中因相位不同的散射回波相互干涉而产生的斑点噪声,利用小波变换对其进行消噪处理。处理结果显示此方法能达到较好的消噪效果。     

Reproducibility of Echocardiograph‐Derived Multilevel Left Ventricular Apical Twist Mechanics

Left ventricular (LV) twist mechanics are routinely assessed via echocardiography in clinical and research trials investigating the function of obliquely oriented myocardial fibers. However, echocardiograph‐derived measures of LV twist may be compromised by nonstandardized acquisition of the apical image. This study examined the reproducibility of echocardiograph‐derived parameters of apical twist mechanics at multiple levels of the apical myocardium. Two sets of 2D LV parasternal short‐axis images were obtained in 30 healthy subjects (24 men; 19–57 year) via echocardiography. Images were acquired immediately distal to the papillary muscles (apical image 1), immediately above the point of LV cavity obliteration at end systole (apical image 3), and midway between apical image 1 and apical image 3 (apical image 2). Repeat scans were performed within 1 hour, and twist mechanics (rotation and rotation rate) were calculated via frame‐by‐frame tracking of natural acoustic echocardiographic markers (speckle tracking). The magnitude of apical rotation increased progressively toward the apex (apical image 1: 4.2 ± 2.1°, apical image 2: 7.2 ± 3.9°, apical image 3: 11.8 ± 4.6°). apical images 1, 2, and 3 each had moderate to good correlations between repeat scans (ICC: 0.531–0.856). When apical images 1, 2, and 3 were averaged, rotation was 7.7 ± 2.7° and between‐scan correlation was excellent (ICC: 0.910). Similar results were observed for systolic and diastolic rotation rates. Averaging multiple standardized apical images, tending progressively toward the apex, generated the most reproducible rotation indices and may be optimal for the assessment of LV twist mechanics across therapeutic, interventional, and research studies; however, care should be taken given the influence of acquisition level on the magnitude of apical rotation.     

Assessment of Left Ventricular Size and Function during Cardiac Surgery. An Intraoperative Evaluation of Six Two‐Dimensional Echocardiographic Methods with Real Time Three‐Dimensional Echocardiography as a Reference

Transesophageal echocardiography is recommended to monitor left ventricular (LV) size and function in various operations. Generally, two‐dimensional (2D) methods are applied intraoperatively. The aim of this study was to compare the accuracy and feasibility of 6 commonly used 2D methods to assess LV function during surgery. LV function in 120 consecutive patients was evaluated. Real time three‐dimensional transesophageal echocardiograpy (3DTEE) served as reference. End‐diastolic and end‐systolic volumes and ejection fraction (EF) were analyzed with Simpson's method of discs (monoplane [MP] and biplane [BP]), eyeball method, Teichholz' method, and speckle tracking (ST) methods. Furthermore, fractional area change (FAC) and peak systolic pressure rise (dP/dt) were determined. Each 2D method was evaluated regarding correlation and agreement with 3DE, intra‐ and interobserver variability and the time required for evaluation. Simpson BP showed the strongest correlation and best agreement with 3DE for EF (limits of agreement 3.7 ± 11.6%) and volumes. Simpson MP showed similar agreement with 3DE compared to ST (2.8 ± 14.5% vs. 2.0 ± 15.3% and 3.8 ± 14.4% vs. 1.9 ± 15.6%, respectively). Both the eyeball method and Teichholz' method showed wide limits of agreement (?1.5 ± 18.2% and 5.2 ± 22.1%, respectively). DP/dt did not correlate with 3DE. FAC and ST FAC showed similar agreement. Application of 3DE (429 ± 108 seconds) took the longest time, and the eyeball method took the shortest time (8 ± 5 seconds) for analysis. Simpson BP is the most accurate intraoperative 2D method to evaluate LV function, followed by long‐axis MP evaluations. Short‐axis views were less accurate but may be suited for monitoring. We do not recommend using dP/dt.     

Structure–function relations of primate lower incisors: a study of the deformation of Macaca mulatta dentition using electronic speckle pattern interferometry (ESPI)

Teeth adopt a variety of different morphologies, each of which is presumably optimized for performing specific functions during feeding. It is generally agreed that the enamel cap is a crucial element in controlling the mechanical behavior of mammalian teeth under load. Incisors are particularly interesting in terms of structure–function relations, as their role in feeding is that of the ‘first bite’. However, little is known how incisor cap morphology is related to tooth deformation. In the present paper we examine the mechanical behavior of mandibular central incisors in the cercopithecine primate Macaca mulatta under loads similar to those encountered during ingestion. We map three‐dimensional displacements on the labial surface of the crown as it is compressed, using electronic speckle pattern interferometry (ESPI), an optical metrology method. In addition, micro‐computed tomography is used to obtain data regarding the morphology of the enamel cap, which in the M. mulatta lower incisors exhibits missing or very little enamel on the lingual face. The results showed that although compressed along a longitudinal axis, deformation in the incisors mostly occurred in the lingual direction and orthogonal to the direction of the applied load. Both isolated, embedded teeth and teeth in the mandible showed considerable lingual deformation. Incisor deformation in the mandible was generally greater, reflecting the additional freedom of movement enabled by the supporting structures. We show that the association with adjacent teeth in the arch is significant for the behavior of the tooth under load. Finally, loading two teeth simultaneously in the mandible showed that they work as one functional unit. We suggest that these results demonstrate the importance of enamel cap morphology in directing deformation behavior; an ability stemming from the stiffness of the enamel cap overlying the more pliable dentin.