肝动脉栓塞术前、后肝脏血流动力学的实验研究

目的采用CT灌注成像及多普勒血流计测定肝脏血流量,研究肝动脉栓塞术对肝脏血流动力学的影响。材料与方法10头猪麻醉后,行肝左动脉栓塞术。于肝左动脉栓塞术前及术后,采用CT灌注成像测定肝右叶肝动脉灌注量（HAP）、门静脉灌注量（PVP）、总肝血流量（THBF）、肝动脉灌注指数（HPI）,采用多普勒血流计分别测定肝门静脉、肝固有动脉、肝左动脉及肝右动脉血流量,并进行对比分析。结果肝左动脉栓塞术前和术后肝脏右叶HAP、PVP、THBF及HPI分别为0．3376ml·min^-1·ml^-1和0．4023ml·min^-1·ml^-1、0．9237ml·min^-1·ml^-1和0．8263ml·min^-1·ml^-1、1．2613ml·min^-1·ml^-1和1．2286ml·min^-1·ml^-1、26．80％和32．74％;肝左动脉栓塞术前和术后肝门静脉、肝固有动脉、肝左动脉、肝右动脉血流量分别为793．04ml／min和987．6ml／min、316．59ml／min和188．90ml／min、164．10ml／min和10．13ml／min、158．83ml／min和186．64ml／min。与肝左动脉栓塞术前相比,栓塞术后肝右动脉血流量及灌注量增加,肝门静脉的血流灌注量减少;术后肝固有动脉血流量明显减少;肝门静脉血流量明显增加,具有统计学意义;随着肝动脉栓塞面积增加,门静脉血流灌注量逐渐增加。结论CT灌注成像可准确地定量测量肝脏血流量;肝动脉栓塞术后,通过肝动脉缓冲效应,门静脉血流量增加,维持全肝血流量基本平衡。     

运用CT动态灌注成像技术测定肝脏血流量的临床研究

目的 探讨CT灌注成像的测定方法和技术原理,以及肝硬化程度与肝脏血流量动态变化关系。资料与方法 肝硬化患者27例,其中Child A级12例,Child B级10例,CMld C级5例。对照组为无肝脏疾病者18例。选取同时含有肝脏、脾、主动脉和门静脉的层面进行CT动态增强扫描,绘制感兴趣区时间-密度曲线(TDC),计算肝脏血流量各参数。结果 (1)肝硬化患者的肝动脉灌注量(HAP)、门静脉灌注量(PVP)和总肝血流量(THBF)均较正常组降低,平均通过时间(MTT)较正常组延长。(2)肝硬化程度不同时,部分肝血流灌注参数存在显著性差异。(3)脾灌注量和门静脉灌注量呈正相关。结论 (1)肝脏CT灌注成像可定量测定肝血流量参数。(2)肝硬化时肝脏血流灌注的变化与疾病的严重程度相关。     

64层螺旋CT肝血管成像临床应用

目的 探讨64排螺旋CT肝脏血管造影在临床中的应用价值.方法 对228例患者行肝区3期血管成像扫描.重建方法为最大密度投影法(MIP)、容积再现技术(VR).结果 在228例病例中,正常肝动脉168例,肝总动脉(CHA)来源异常10例,肝左动脉(LHA)来源异常18例,肝右动脉(RHA)来源异常8例,原发性肝癌显示肿瘤供血血管18例,正常门静脉143例,门静脉变异11例,肝内门静脉栓塞28例,肝外门静脉主干栓塞38例,门静脉显影淡28 例,未显影2例,受压移位8例;正常肝静脉(HV)128例,肝静脉变异23例,右下副肝静脉2 例,肝静脉显影淡36例,未显影18例,受压移位5例.结论 64排螺旋CT肝脏3期血管成像是了解肝脏动脉及门、肝静脉系统正常、变异及病变情况的无创、安全、方便的检查方法.     

螺旋CT门静脉成像在肝脏疾病诊断中的应用

目的　探讨螺旋CT门静脉成像 (SCTP)在肝脏疾病诊断中的应用价值。方法　 81例疑有肝脏疾病的患者进行了SCTP检查 ,观察了肝脏疾病的SCTP表现及肝外门静脉侧枝循环情况 ;在重建横断面图像上 ,测量门静脉及脾静脉主干短径。结果　SCTP能精确定位并诊断肝脏病变 ,能清晰显示肝内外门静脉系统 ;肝硬化病人门静脉及脾静脉主干明显增粗 (Ρ <0 .0 5 )。结论　SCTP具有无创、直观、简单易行 ,对肝脏疾病诊断有较高的临床应用价值。     

肝脏灌注成像的CT扫描方法及应用价值

目的:探讨单层CT动态增强扫描测定肝硬化肝脏血流量的扫描方法及其应用价值。方法:15例经临床、实验室及B超检查诊断为肝硬化的患者,其中ChildB级患者10例,ChildC级患者5例。对照组为13例无肝脏疾病的患者。所有患者均选取同时含有肝脏、脾脏、主动脉和门静脉的层面进行单层CT动态增强扫描,绘制感兴趣区时间密度曲线,计算各血流灌注参数。结果:单层CT动态增强扫描测量肝组织的肝动脉灌注量(HAP)、门静脉灌注量(PVP)、总肝血流量(THBF)和肝动脉灌注指数(HPI)。正常组的HAP、PVP、THBF和HPI分别为(0.28±0.10)ml/min·ml、(1.18±0.40)ml/min·ml、(1.46±0.44)ml/min·ml和(19.73±5.81)%;肝硬化组的HAP、PVP、THBF和HPI分别为(0.23±0.11)ml/min·ml、(0.61±0.25)ml/min·ml、(0.84±0.32)ml/min·ml和(27.16±12.75)%。结论:肝脏单层CT灌注成像,可定量测定各项肝脏血流灌注参数,对肝硬化患者的量化诊断有一定的参考价值。     

闪烁显像评价肝血流动力学的方法及意义

重点介绍利用99mTc-胶体和99mTcθ₄-显像测定总肝血流量、门静脉和肝动脉相对血流量及门静脉血液绕过肝脏的分流分数的方法,并阐述其临床意义。     

CT灌注成像对肝硬化血流动力学的临床研究

目的　采用单层CT动态成像测定肝脏血流量 ,研究肝硬化程度与肝脏血流量动态变化的关系。方法　对 2 7例肝硬化患者及 13例对照者选取同时含有肝脏、脾脏、主动脉和门静脉的层面进行单层CT动态增强扫描 ,绘制感兴趣区时间 密度曲线 ,计算肝脏血流量各参数。结果　正常组肝动脉灌注量为 (0 2 82 3± 0 0 96 9)ml·min-1·ml-1,门静脉灌注量为 (1 1788± 0 4 0 0 4 )ml·min-1·ml-1,总肝血流量为 (1 4 5 6 3± 0 4 4 39)ml·min-1·ml-1,肝动脉灌注指数为 (19 73± 5 81) %。肝硬化程度不同时 ,肝动脉灌注量、门静脉灌注量、肝脏总血流量及肝动脉灌注指数变化间差异存在显著性意义。ChildA、B级患者肝动脉灌注量 [(0 16 85± 0 10 6 8)ml·min-1·ml-1,(0 192 1± 0 0 986 )ml·min-1·ml-1]降低 ,而ChildC级患者肝动脉灌注量 [(0 30 72± 0 114 5 )ml·min-1·ml-1]比ChildA、B级患者增加 ,肝动脉灌注指数 [(37 4 8± 16 6 5 ) % ]也增加。ChildB、C级患者门静脉灌注量 [(0 6 331± 0 2 0 70 )ml·min-1·ml-1,(0 5 70 2± 0 35 6 2 )ml·min-1·ml-1]及总肝血流量 [(0 82 5 2± 0 2 95 2 )ml·min-1·ml-1,(0 8774± 0 4 118)ml·min-1·ml-1]下降。结论　肝脏CT灌注成像可定量测     

兔肝脏纤维化模型CT灌注成像参数变化实验研究

目的 研究CT灌注成像参数在兔肝脏纤维化模型中变化情况.材料与方法 新西兰大白兔4只为对照组,兔肝脏纤维化模型13只,对其进行CT灌注成像扫描,以肝脏病理组织学评分分级和纤维化分期为标准,研究分析CT灌注参数变化.采用单向方差分析方法 ,P＜0.05为差异有统计学意义.结果 与正常对照组相比较,全部CT灌注成像参数在肝脏纤维化分期方面差异均有统计学意义(P＜0.05);血流量(BF)、血容量(BV)、肝动脉灌注指数(HAI)、肝动脉灌注量(BFA)测量结果 在病理评分分级方面差异有统计学意义(P＜0.05);平均通过时间(MTT)、毛细血管通透性表面积乘积(PS)和门静脉灌注量(BFP)在病理评分分级方面差异无统计学意义(P＞0.05).结论 在肝脏纤维化时BF、BV、HAI和BFA值明显低于正常对照组,且随着肝脏病理变化的进展和纤维化分期的增加BF、BV、和BFP值下降越加明显.形成这一变化的病理基础为Disse间隙内大量胶原纤维沉积、窦状间隙变小、伴有肝细胞肿胀、炎性浸润、肝细胞再生和假小叶形成等,使得肝内血管阻力升高,导致肝脏血流量减少.     

多层螺旋CT门静脉成像及其在肝脏解剖分段中的应用

目前,肝脏外科学发展迅速,肝段、亚肝段甚至楔形切除已成为可能,因此临床迫切需要对肝脏病变进行术前准确定位.门静脉系统是肝脏分叶分段的重要标志,CT门静脉成像(CTP)有助于肝脏病变的准确定位.近年来,多层螺旋CT已开始广泛应用于临床,其扫描及成像速度均较单层螺旋CT大大提高,且三维重建时间缩短,图像质量明显提高.在一次屏气状态下,用较薄的层厚即可完成整个肝脏的容积扫描,因此,选择门静脉增强最佳时期进行全肝扫描并应用后处理技术进行三维重建,有助于肝脏的精确分段.多层螺旋CT门静脉成像可无创性地提供有助于制定手术计划的门静脉及肝脏病变的图像.     

肝脏CT灌注成像技术及其在肝硬化中的初步应用

目的　采用单层CT动态成像测定肝脏血流量 ,探讨CT灌注成像测定肝血流量的技术原理。资料与方法　 15例经临床及实验室、B超检查诊断为肝硬化患者 ,其中ChildB级者 10例 ,ChildC级者 5例。对照组为 13例无肝脏疾病者。所有患者均选取同时含有肝脏、脾脏、主动脉和门静脉的层面进行单层CT动态增强扫描 ,绘制感兴趣区时间 密度曲线计算肝脏血流量各参数。结果　正常组肝动脉灌注量 (HAP)为 0 .2 82 3± 0 .0 96 9ml·min-1·ml-1,门静脉灌注量 (PVP)为 (1.1788± 0 .4 0 0 4 )ml·min-1·ml-1,总肝血流量 (THBF)为 (1.4 5 6 3± 0 .4 4 39)ml·min-1·ml-1,肝动脉灌注指数 (HPI)为 (19.73± 5 .81) %。肝硬化时PVP为 (0 .6 12 1± 0 .2 5 4 4 )ml·min-1·ml-1,较正常组降低 ;THBF也减低 ,为 (0 .84 2 6± 0 .32 4 2 )ml·min-1·ml-1。肝硬化患者的HPI较正常组略有升高 ,为 (2 7.16±12 .75 ) % ,但无统计学差异 (P =0 .0 6 5 )。结论　肝脏CT灌注成像可定量测定肝脏血流量参数     

Bringing physiology into PET of the liver

Several physiologic features make interpretation of PET studies of liver physiology an exciting challenge. As with other organs, hepatic tracer kinetics using PET is quantified by dynamic recording of the liver after the administration of a radioactive tracer, with measurements of time-activity curves in the blood supply. However, the liver receives blood from both the portal vein and the hepatic artery, with the peak of the portal vein time-activity curve being delayed and dispersed compared with that of the hepatic artery. The use of a flow-weighted dual-input time-activity curve is of importance for the estimation of hepatic blood perfusion through initial dynamic PET recording. The portal vein is inaccessible in humans, and methods of estimating the dual-input time-activity curve without portal vein measurements are being developed. Such methods are used to estimate regional hepatic blood perfusion, for example, by means of the initial part of a dynamic (18)F-FDG PET/CT recording. Later, steady-state hepatic metabolism can be assessed using only the arterial input, provided that neither the tracer nor its metabolites are irreversibly trapped in the prehepatic splanchnic area within the acquisition period. This is used in studies of regulation of hepatic metabolism of, for example, (18)F-FDG and (11)C-palmitate.     

Dynamic CT scanning of the normal canine liver: interpretation of time density curves resulting from an intravenous bolus injection of contrast material

Seven adult male mongrel dogs were monitored by electromagnetic flow probes and string occluders around the hepatic artery and portal vein. Then, time density curves of the liver, aorta and portal vein were recorded using dynamic CT scanning following the bolus injection of contrast material into a peripheral vein (n = 7) and a mesenteric vein branch (n = 5). Information on total hepatic blood flow could not be obtained from the mesenteric vein injection. The hepatic time density curve could, however, be broken into its two components, hepatic arterial and portal venous flow contribution, by selective ligation of the hepatic artery or portal vein. It could be demonstrated that the arterial component of liver enhancement reached its peak at the end of the aortic wash-out of contrast material. Thus, the hepatic time-density curve could be broken in its two components by superimposing the aortic time density curve onto the hepatic curve. An attempt was made to estimate relative portal venous blood flow by using the slopes or the peaks of both components of the hepatic curve. Using the slopes of the hepatic curve resulted in a consistent underestimation of portal venous blood flow, whereas the peaks gave an estimate of portal venous flow with an accuracy within +/- 8%.     

Improved diagnosis of hepatic perfusion disorders: value of hepatic arterial phase imaging during helical CT.

The liver has a unique dual blood supply, which makes helical computed tomography (CT) a highly suitable technique for hepatic imaging. Helical CT allows single breath-hold scanning without motion artifacts. Because of rapid image acquisition, two-phase (hepatic arterial phase and portal venous phase) evaluation of the hepatic parenchyma is possible, improving tumor detection and tumor characterization in a single CT study. The arterial and portal venous supplies to the liver are not independent systems. There are several communications between the vessels, including transsinusoidal, transvasal, and transplexal routes. When vascular compromise occurs, there are often changes in the volume of blood flow in individual vessels and even in the direction of blood flow. These perfusion disorders can be detected with helical CT and are generally seen as an area of high attenuation on hepatic arterial phase images that returns to normal on portal venous phase images; this finding reflects increased arterial blood flow and arterioportal shunting in most cases. Familiarity with the helical CT appearances of these perfusion disorders will result in more accurate diagnosis. By recognizing these perfusion disorders, false-positive diagnosis (hypervascular tumors) or overestimation of the size of liver tumors (eg, hepatocellular carcinoma) can be avoided.     

Liver kinetics of glucose analogs measured in pigs by PET: importance of dual-input blood sampling.

Metabolic processes studied by PET are quantified traditionally using compartmental models, which relate the time course of the tracer concentration in tissue to that in arterial blood. For liver studies, the use of arterial input may, however, cause systematic errors to the estimated kinetic parameters, because of ignorance of the dual blood supply from the hepatic artery and the portal vein to the liver. METHODS: Six pigs underwent PET after [15O]carbon monoxide inhalation, 3-O-[11C]methylglucose (MG) injection, and [18F]FDG injection. For the glucose scans, PET data were acquired for 90 min. Hepatic arterial and portal venous blood samples and flows were measured during the scan. The dual-input function was calculated as the flow-weighted input. RESULTS: For both MG and FDG, the compartmental analysis using arterial input led to systematic underestimation of the rate constants for rapid blood-tissue exchange. Furthermore, the arterial input led to absurdly low estimates for the extracellular volume compared with the independently measured hepatic blood volume of 0.25 +/- 0.01 mL/mL (milliliter blood per milliliter liver tissue). In contrast, the use of a dual-input function provided parameter estimates that were in agreement with liver physiology. Using the dual-input function, the clearances into the liver cells (K1 = 1.11 +/- 0.11 mL/min/mL for MG; K1 = 1.07 +/- 0.19 mL/min/mL for FDG) were comparable with the liver blood flow (F = 1.02 +/- 0.05 mL/min/mL). As required physiologically, the extracellular volumes estimated using the dual-input function were larger than the hepatic blood volume. The linear Gjedde-Patlak analysis produced parameter estimates that were unaffected by the choice of input function, because this analysis was confined to time scales for which the arterial-input and dual-input functions were very similar. CONCLUSION: Compartmental analysis of MG and FDG kinetics using dynamic PET data requires measurements of dual-input activity concentrations. Using the dual-input function, physiologically reasonable parameter estimates of K1, k2, and Vp were obtained, whereas the use of conventional arterial sampling underestimated these parameters compared with independent measurements of hepatic flow and hepatic blood volume. In contrast, the linear Gjedde-Patlak analysis, being less informative but more robust, gave similar parameter estimates (K, V) with both input functions.     

CT arteriography of hepatic tumors]

The liver has dual blood supply from the portal vein and hepatic artery. Computed tomographic findings of hepatic neoplasms are greatly influenced by hepatic blood flow, and abnormal portal and hepatic arterial blood flow needs to be examined separately by CT arteriography (CTA) and CT during arterial portography (CTAP). Both CTA and CTAP have advantages over conventional CT in that they can provide greater contrast enhancement of hepatic tumors by injecting contrast material directly into the hepatic or superior mesenteric arteries. The methods of CTA and CTAP are described. CTA and CTAP were useful in the detection of small hepatic lesions, evaluation of changes in hepatic parenchymal blood flow, and evaluation of portal flow in hepatocellular carcinoma, which contribute to the classification of HCC. In conclusion, CTA and CTAP were indispensable in selecting a therapeutic approach.     

Difference in regional hepatic blood flow in liver segments —Non-invasive measurement of regional hepatic arterial and portal blood flow in human by positron emission tomography with H2 15O—

Organ blood flow can be quantitatively measured by positron emission tomography (PET). As the liver has dual blood supplies, arterial and portal, regional hepatic blood flow had not been measured quantitatively. However, we succeeded in simultaneously measuring both regional hepatic arterial and portal blood flow by PET in non-stressed patients. Mean regional portal hepatic blood flow in patients with normal liver and cirrhotic liver was 57.5 and 36.7 ml/minutes/100 g, respectively. Mean regional arterial blood flow was 42.5 and 30.7 ml/minutes/100 g, respectively. A significant difference between regional portal hepatic blood flows in normal and cirrhotic patients was noted. Mean regional portal hepatic blood flow in the lateral, medial, anterior, and posterior segments of the liver was 29.8, 43.4, 50.0, and 40.9 ml/minutes/100 g, respectively. Mean regional arterial blood flow in each liver segment was 37.6, 30.0, 28.2, and 31.6 mi/minutes/100 g, respectively. A significant difference between regional portal hepatic blood flows in lateral and anterior segment was noted. The p value was less than 0.025 and the 95 % confidence interval of the difference between means was from ?20.2 to ?2.7 ml/minutes/100 g by ANOVA. These results showed that regional hepatic blood flow is not the same in all the liver segments.     

Perfusion imaging of the liver: current challenges and future goals

Improved therapeutic options for hepatocellular carcinoma and metastatic disease place greater demands on diagnostic and surveillance tests for liver disease. Existing diagnostic imaging techniques provide limited evaluation of tissue characteristics beyond morphology; perfusion imaging of the liver has potential to improve this shortcoming. The ability to resolve hepatic arterial and portal venous components of blood flow on a global and regional basis constitutes the primary goal of liver perfusion imaging. Earlier detection of primary and metastatic hepatic malignancies and cirrhosis may be possible on the basis of relative increases in hepatic arterial blood flow associated with these diseases. To date, liver flow scintigraphy and flow quantification at Doppler ultrasonography have focused on characterization of global abnormalities. Computed tomography (CT) and magnetic resonance (MR) imaging can provide regional and global parameters, a critical goal for tumor surveillance. Several challenges remain: reduced radiation doses associated with CT perfusion imaging, improved spatial and temporal resolution at MR imaging, accurate quantification of tissue contrast material at MR imaging, and validation of parameters obtained from fitting enhancement curves to biokinetic models, applicable to all perfusion methods. Continued progress in this new field of liver imaging may have profound implications for large patient groups at risk for liver disease.     

Measurement of liver blood flow using oxygen-15 labelled water and dynamic positron emission tomography: Limitations of model description

To date no satisfactory method has been available for the quantitative in vivo measurement of the complex hepatic blood flow. In this study two modelling approaches are proposed for the analysis of liver blood flow using positron emission tomography (PET). Five experiments were performed on three foxhounds. The anaesthetised dogs were each given an intravenous bolus injection of oxygen-15 labelled water, and their livers were then scanned using PET. Radioactivity in the blood from the aorta and portal vein was measured directly and simultaneously using closed external circuits. Time-activity curves were constructed from sequential PET data. Data analysis was performed by assuming that water behaves as a freely diffusible tracer and adapting the standard one-compartment blood flow model to describe the dual blood supply of the liver. Two particular modelling approaches were investigated: the dual-input model used both directly measured input functions (i.e. using the hepatic artery and the portal vein input, determined from the radioactivity detected in the aorta and portal vein respectively) whereas the single-input model used only the measured arterial curve and predicted the corresponding portal input function. Hepatic arterial flow, portal flow and blood volume were fitted from the PET data in several regions of the liver. The resulting estimates were then compared with reference blood flow measurements, obtained using a standard microsphere technique. The microspheres were injected in a separate experiment on the same dogs immediately prior to PET scanning. Whilst neither the single- nor the dual-input models accurately reproduced the arterial reference flow values, the flow values from the single-input model were closer to the microsphere flow values. The proposed single-input model would be a good approximation for liver blood flow measurements in man. The observed discrepancies between the PET and microsphere flow values may be due to the inherent temporal and spatial heterogeneity of liver blood flow. The results presented suggest that adaptation of the standard one-compartment blood flow model to describe the dual blood supply of the liver is limited and other flow tracers have to be considered for quantitative PET measurements in the liver.     

Hepatic blood flow measurements with arterial and portal blood flow mapping in the human liver by means of xenon CT

PURPOSE: The purpose of this work was to quantify arterial and portal blood flows in the human liver and to create blood flow maps by means of xenon CT. METHOD: Mathematical procedures were developed based on a simplified model having two tissue components: liver tissue and portal organ tissue. Xe-CT studies were performed on 10 healthy volunteers (ages 33.4 +/- 9.8 years), a patient with hepatocellular carcinoma (HCC), and a liver transplant recipient. RESULTS: Arterial and portal blood flows for the healthy subjects were 36.7 +/- 5.2 and 65.2 +/- 22.0 ml/100 ml/min. In the HCC patient, arterial blood flow was shown to be dominant in the tumoral area. From the results of the liver recipient, it was demonstrated that obtaining lambda values is important for proper evaluation of blood flows. CONCLUSION: Xe-CT can provide substantial information on hepatic blood flow quantitatively and visually with separation of arterial and portal components.     

肝移植术前MSCT血管造影检查

目的 :评价肝移植术前多层螺旋CT血管造影 (MSCTA)检查的应用价值。方法 :对 5 7例拟行肝移植术患者行多层螺旋CT(MSCT)肝脏多期扫描。分别于肝动脉期和门脉期进行血管 3D成像 ,重建方法包括MPR、SSD、VR系列图像显示。统计肝动脉期和门脉期各主要相关血管及其分支的显示率 ,并比较各 3D重建方法的优劣。结果 :肝动脉期血管成像可清晰显示扫描范围内的腹主动脉、腹腔干及其分支 ,SSD和VR对胃十二指肠动脉 ,肝固有动脉 ,肝左、右动脉的显示率分别为 85 .9%和 64 .9%。门静脉期血管成像能清晰显示门静脉系统情况 ,VR优于SSD。利用MPR能准确测量有门脉高压影像表现患者与对照组患者门静脉系统管径 ,两者相比差异有显著性意义 (P <0 .0 5 )。结论 :肝脏MSCTA双期血管成像是了解肝脏供血动脉和门静脉系统情况的无创性检查方法 ,以VR血管成像最佳 ,MPR可提供必要的数据补充 ,联合应用可为临床提供更多的有关肝动脉和门静脉方面的信息。