Hepatic perfusion parameters in chronic liver disease: dynamic CT measurements correlated with disease severity

OBJECTIVE: The aim of our study was to determine if hepatic perfusion parameters measured with CT change in relation to disease severity in patients with chronic liver disease. SUBJECTS AND METHODS: Dynamic contrast-enhanced single-section CT scans of the liver were obtained in 40 individuals who included six control subjects, 16 patients with noncirrhotic chronic liver disease, and 18 patients with cirrhosis. Hepatic, aortic, and portal venous time-density curves were fitted to a dual-input one-compartment model to calculate the liver perfusion, arterial fraction, distribution volume, and mean transit time. RESULTS: Liver perfusion decreased in patients with cirrhosis (67 +/- 23 mL. min(-1). 100 mL(-1) versus 108 +/- 34 mL. min(-1). 100 mL(-1) in control subjects [p = 0.009] and 98 +/- 36 mL. min(-1). 100 mL(-1) in patients with noncirrhotic chronic liver disease [p = 0.003]), and the arterial fraction and the mean transit time increased (41 +/- 27% and 51 +/- 79 sec versus 17 +/- 16% and 16 +/- 5 sec in control subjects, and 19 +/- 6% and 17 +/- 8 sec in patients with noncirrhotic chronic liver disease [p < 0.05]). A significant correlation was seen between these three perfusion parameters and the severity of chronic liver disease based on clinical and biologic data (p < 0.001). No significant change in distribution volume was observed. CONCLUSION: Hepatic perfusion parameters measured with CT were significantly altered in cirrhosis and correlated with the severity of chronic liver disease.     

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。     

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。     

Scintigraphic evaluation of hepatic blood flow after intrahepatic portosystemic shunt (TIPS)

In patients with liver cirrhosis a transjugularly placed intrahepatic portocaval shunt (TIPS) is a non-surgical portosystemic device which aims to reduce portal venons pressure. In comparison with Doppler sonography, we evaluated in 28 patients the diagnostic impact of liver perfusion scintigraphy (with technetium-99m diethylene triamine penta-acetic acid) in the assessment of changes in the hepatic blood flow after TIPS shunting. The arterial and portal contributions to hepatic flow were calculated from the areas under the biphasic timeactivity curve. In the course of TIPS shunting, patency is threatened by reocclusion. Angiography is the gold standard for TIPS shunt reassessment. However, there is a need for a less invasive diagnostic procedure, such as scintigraphy or Doppler sonography, for the early detection of shunt insufficiency. Scintigraphy demonstrated that prior to TIPS shunting the portal venons contribution to hepatic perfusion was reduced to 29.2%, this reduction being due to portal hypertension. After TIPS placement a significant increase in portal venous perfusion was observed (38.2%;P<0.02). TIPS shunt occlusion was identified in patients by a significant reduction in the scintigraphically measured portal venons contribution to hepatic blood flow. Hepatic perfusion scintigraphy appears to be a valuable method to determine the immediate effect of TIPS on hepatic blood flow. Post-TIPS follow-up studies of hepatic haemodynamics by liver perfusion scintigraphy appear able to contribute to the detection of TIPS shunt occlusion before the clinical consequences of this complication have become apparent.     

肝硬化基础上肝癌肝血流变化功能CT灌注成像研究

目的对正常肝实质、肝硬化和肝硬化基础上肝癌患者的64层螺旋CT灌注成像进行分析,评价多层螺旋CT灌注成像对肝硬化基础上肝癌肝血流变化的诊断价值。资料与方法无肝脏疾病的30例作为对照组。实验组包括49例肝硬化疾病患者,其中27例确诊为原发性肝癌(HCC)。所有研究对象知情同意后,选择癌灶中心层面或肝门层面行CT灌注扫描,采用低剂量扫描:120 kV,60 mA,扫描范围为40 mm。以4～5 ml/s流率,按照1.0ml/kg体重用量静脉团注对比剂。在注入对比剂5 s后行50 s连续的扫描,360°旋转/s,5 mm层厚进行图像重组,矩阵大小512×512像素。利用去卷积数学模型获得与肝血流变化相关的灌注参数值:肝血流量(HBF),肝血容量(HBV),肝动脉灌注分数(HAF),肝动脉灌注量(HAP),门静脉灌注量(HPP)。对不同的感兴趣区进行三次灌注参数测量后取平均值进行灌注结果分析。感兴趣区包括:对照组的正常肝实质、癌灶边缘区、癌灶周围的肝实质和无癌灶的肝硬化肝实质。结果与对照组灌注参数比较,癌周围肝实质的HBF、HAP、HPP、HBV及癌灶边缘区的HBF、HAP、HPP有统计学差异(P<0.05)。与对照组相对应灌注参数比较,癌周的HAP、HPP及对照组的HBF、HAP、HPP有统计学差异(P<0.05)。与癌边缘区HAF对比,癌灶周围肝实质、对照组和无癌灶的肝硬化组均有统计学差异(P<0.05)。对照组和无癌灶的肝硬化组间灌注参数无明显差异(P>0.05)。结论 CT灌注成像能很好地反映肝硬化基础上肝癌的肝血流变化信息,为肝血流动力学变化的影像研究提供新的方法。     

Multidetector multiphase contrast-enhanced liver CT: prospective study comparing two contrast material injection rates on vascular and liver parenchyma enhancement in patients with varied cirrhotic status

BACKGROUND: To compare 2 rates of contrast material injection, with dose tailored to patient body weight (bw) and automatic bolus triggering system, on vascular and liver parenchyma enhancement at multidetector multiphase contrast-enhanced liver computed tomography (CT) of patients with varied cirrhotic status. METHODS: One hundred and thirty consecutive patients with varied cirrhotic status, referred for contrast-enhanced liver CT evaluation of focal liver nodule(s), were prospectively and randomly assigned to 1 of 2 routine contrast-enhanced liver CT protocols: 2 mL/kg of bw of a nonionic contrast agent (300 mg I/mL) injected at a 3 mL/sec, versus 2 mL/kg of bw of the same contrast agent injected at 4 mL/sec. Quantitative vascular and liver parenchyma enhancements were obtained. Attenuation values of the abdominal aorta during the arterial phase CT, of the main portal vein during the portal venous phase CT, and of the liver parenchyma during the arterial, the portal venous, and the equilibrium phases liver CT, were compared with multiple 2-way analysis of variance. RESULTS: Significantly higher attenuation values were noted in the abdominal aorta with a 4-mL/sec-flow rate. Attenuation values were not significantly different in the portal vein and in the liver parenchyma, whatever was the patient cirrhotic status. CONCLUSIONS: With dose tailored to body weight and automatic bolus triggering system, adjusting flow rate makes no difference in patients with regard to liver or portal vein enhancement, regardless of presence/absence of cirrhosis.     

Hepatic enhancement in multiphasic contrast-enhanced MDCT: comparison of high- and low-iodine-concentration contrast medium in same patients with chronic liver disease

OBJECTIVE: The aim of this study was to evaluate the degree of hepatic enhancement and image quality in patients with cirrhosis or chronic hepatitis who underwent multiphasic contrast-enhanced dynamic imaging on MDCT at least twice using standard (300 mg I/mL) and higher (370 mg I/mL) iodine concentrations in contrast medium during follow-up periods. MATERIALS AND METHODS: This study included 20 patients with chronic liver diseases who underwent at least two multiphasic contrast-enhanced dynamic MDCT examinations using 100 mL of standard (300 mg I/mL = group A) and higher (370 mg I/mL = group B) iodine concentrations in contrast medium. After we obtained unenhanced CT scans, we performed multiphasic scanning at 30 sec (arterial phase), 60 sec (portal phase), and 180 sec (late phase) after the start of contrast medium injection. The CT values of hepatic parenchyma, abdominal aorta, and portal vein were measured. The mean enhancement value was defined as the difference in CT values between unenhanced and contrast-enhanced images. Visual image quality was also assessed on the basis of the degree of hepatic and vascular enhancement, rated on a 4-point scale. RESULTS: The mean hepatic parenchyma enhancement values in group B was significantly greater (p < 0.001) than those in group A during the portal phase (43.8 +/- 8.2 H vs 36.2 +/- 7.3 H) and the late phase (33.7 +/- 7.0 H vs 27.3 +/- 3.9 H), but the difference on the arterial phase images between the two groups (9.4 +/- 3.2 H vs 8.3 +/- 2.5 H) was not significant. The mean aorta-to-liver contrast during the arterial phase in group B was significantly higher (p < 0.001) than that in group A (236 +/- 40 H vs 193 +/- 32 H). For qualitative analysis, the mean visual scores for hepatic parenchyma and vasculature enhancement in group B were significantly higher than those in group A in arterial phase (p < 0.018), portal phase (p < 0.0001), and late phase (p < 0.0001). CONCLUSION: In the same patients with chronic liver diseases, a higher iodine concentration (370 mg I/mL) in the contrast medium improves contrast enhancement of liver parenchyma in the portal phase and late phase images, improves overall image quality, and helps improve diagnostic accuracy for liver diseases on multiphasic contrast-enhanced dynamic MDCT.     

Multi-detector row helical CT of the liver: quantitative assessment of iodine concentration of intravenous contrast material on multiphasic CT--a prospective randomized study

PURPOSE: The purpose of this study was to assess the quantitative effects of contrast material concentration on hepatic parenchymal and vascular enhancement in multiphasic computed tomography (CT), using multi-detector row helical CT. MATERIALS AND METHODS: We designed a prospective randomized study to test two different concentrations of contrast material on five phasic scans of the liver. One hundred patients were randomly assigned to two groups: an iodine concentration of 300 mg/mL in group A and 370 mg/mL in group B. All patients received a fixed volume of 100 mL at a 4 mL/sec injection rate. Enhancement values for the hepatic parenchyma and aorta at three levels (upper, middle, and lower level of the liver), and values for portal and hepatic veins were statistically compared between the two groups. RESULTS: Hepatic parenchymal enhancement values at all levels of the liver in portal phase (PP) and equilibrium phase (EP) were significantly higher in group B than in group A (p<0.01). Aortic enhancement values at two levels of the liver (middle and lower) in early hepatic arterial phase (EAP) were significantly higher in group B than in group A (p<0.05), however, there was no significant difference between groups A and B in aortic enhancement during the delayed hepatic arterial phase (DAP). Portal and hepatic venous enhancement values in PP and EP were significantly higher in group B than in group A (p<0.01). CONCLUSION: On multiphasic dynamic CT, the use of a higher iodine concentration of contrast material results in higher hepatic parenchymal enhancement and aortic enhancement, as well as higher portal and hepatic venous enhancement.     

Measurement of hepatic perfusion with dynamic computed tomography: assessment of normal values and comparison of two methods to compensate for motion artifacts

RATIONALE AND OBJECTIVES: To assess normal values of hepatic perfusion by dynamic, single-section computed tomography, to compare two methods of data processing (a smoothing with a fitting procedure), and to evaluate the influence of motion artifacts. METHODS: Twenty-five volunteers with no history or suspicion of liver disease were examined (age range, 32.8-81.1 years). All examinations were subjectively ranked into groups 1 through 3 according to the degree of motion artifacts (negligible, moderate, severe). All data were processed with a smoothing procedure and a pharmacokinetic fitting procedure (TopFit). The arterial, portal venous, and total hepatic perfusion; the hepatic perfusion index (HPI); and the arterial/portal venous ratio (A/P ratio) were calculated with both procedures. RESULTS: Mean hepatic perfusion, as assessed with the fitting procedure and the smoothing procedure, respectively, was as follows: arterial, 0.20 and 0.22 mL x min(-1) x mL(-1); portal venous, 1.02 and 1.24 mL x min(-1) x mL(-1); total perfusion, 1.22 and 1.47 mL x min(-1) x mL(-1); HPI, 16.4% and 15.4%; and A/P ratio, 0.20 and 0.19. The differences were significant for the portal venous and total hepatic perfusion. The portal venous and total hepatic perfusion values showed significant differences between group 1 and groups 2 and 3 for both procedures. HPI and the A/P ratio showed no significant differences at all. CONCLUSIONS: Motion artifacts and the type of data processing influence the assessment of the arterial, portal venous, and total hepatic perfusion but do not influence measurement of the HPI and the A/P ratio.     

Effect of electrocardiogram triggering on reproducibility of coronary artery calcium scoring

PURPOSE: To determine the prevalence of arterioportal shunt associated with hepatic hemangiomas, describe the two-phase spiral computed tomographic (CT) findings, and correlate the presence of arterioportal shunt with the size and rapidity of enhancement of hemangiomas. MATERIALS AND METHODS: The study group consisted of 109 hepatic hemangiomas in 69 patients who underwent two-phase spiral CT during 1 year. CT scans were obtained during the hepatic arterial (30-second delay) and portal venous (65-second delay) phases after injection of 120 mL of contrast material (3 mL/sec). Arterioportal shunts were diagnosed when hepatic arterial phase CT scans showed a wedge-shaped or irregularly shaped homogeneous enhancement in the liver parenchyma adjacent to the tumor and when portal venous phase CT scans showed isoattenuation or slight hyperattenuation, compared with normal liver in that area, and when there was no demonstrable cause of these attenuation differences. The presence of arterioportal shunt in hemangioma was correlated with the size of the tumor and the rapidity of intratumoral enhancement. RESULTS: Arterioportal shunt was found in 28 (25.7%) of 109 hemangiomas. There was no statistically significant relationship between lesion size and presence of the arterioportal shunt (P =.653). Arterioportal shunt was more frequently found in hemangiomas with rapid enhancement (P <.01). CONCLUSION: Arterioportal shunts are not uncommonly seen in hepatic hemangiomas at two-phase spiral CT. Hemangiomas with arterioportal shunts tend to show rapid enhancement.     

Computed tomography perfusion of the liver: assessment of pure portal blood flow studied with CT perfusion during superior mesenteric arterial portography

Purpose: To quantitatively assess the portal component of hepatic blood flow using computed tomography (CT) perfusion studies during superior mesenteric arterial portography. Material and Methods: Thirty-four patients with hepatocellular carcinoma and liver cirrhosis (LC) and 13 patients with liver metastasis without chronic liver disease were enrolled in this study. Ten milliliters of a non-ionic contrast medium (150 mgI) was injected at a rate of 5 ml/s via a catheter placed in the superior mesenteric artery. Single-slice cine CT images at the level of the main trunk or the right/left main trunk of the portal vein were acquired over 40 s. The deconvolution method was then used on these CT images to measure blood flow (BF), blood volume (BV), and mean transit time (MTT) in (a) liver parenchyma in patients with HCC and liver cirrhosis; (b) liver parenchyma in patients with liver metastasis without cirrhosis; (c) directly in the HCC; and (d) directly in one of the metastases. Results: In 34 LC patients (a), BF, BV, and MTT in the liver parenchyma were 44.7±24.5 ml/min/100 g, 3.9±2.4 ml/100 g, and 10.9±5.5 s, respectively. In 13 patients without cirrhosis (b), BF, BV, and MTT in the liver parenchyma were 89.6±52.0 ml/min/100 g, 6.3 ±3.2 ml/100 g, and 8.7±3.6 sec, respectively. A significant difference in BF and BV was seen in patients with liver cirrhosis compared to those without cirrhosis. BF, BV, and MTT measured directly in HCC (c) were 6.5±4.5 ml/min/100 g, 0.4±0.4 ml/100 g, and 3.0±3.1 sec respectively, and BF, BV, and MTT in liver metastases (d) were 19.3 ± 21.7 ml/min/100 g, 0.6±0.8 ml/100 g, and 1.8±1.6 s, respectively. Conclusion: CT perfusion studies during superior mesenteric arterial portography allow quantitative assessment of pure portal blood flow in the liver.     

Hepatic perfusion before and after the transjugular intrahepatic portosystemic shunt procedure: impact on survival

PURPOSE: This study correlates transjugular intrahepatic portosystemic shunt (TIPS) mortality with flow patterns in the cirrhotic liver. MATERIALS AND METHODS: Twenty-seven TIPS patients and 10 control subjects were used for this study. The authors evaluated hepatic perfusion with venous injections of Tc-99m pertechnetate before and after TIPS. Hepatic time-activity curves were analyzed for type and amount of liver perfusion. These parameters were correlated with survival for a mean follow-up of 18 months. RESULTS: The mean arterial contribution to liver blood flow was 25.4% in the normal control patients, 39.9% in patients prior to TIPS, and increased to 48.3% after TIPS. Although the proportion of arterial supply to the cirrhotic liver varied widely, TIPS mortality did not correlate with the preprocedure hepatic artery/portal venous perfusion ratio. However, patients with both an "arterialized" flow pattern and low total hepatic perfusion had higher mortality, with a mean survival of 2 months compared to patients with a more favorable perfusion profile (mean survival, 28.4 months). CONCLUSIONS: The proportion of arterial perfusion to the liver before TIPS did not affect survival. However, patients with a combination of reduced total hepatic perfusion and an arterial flow pattern had poorer survival, suggesting that both the quantity and quality of hepatic perfusion predicts TIPS outcome.     

Multidetector CT of the liver and hepatic neoplasms: effect of multiphasic imaging on tumor conspicuity and vascular enhancement

OBJECTIVE: Our aim was to determine which of three contrast-enhanced phases (early arterial, late arterial, or portal venous) was optimal for achieving maximal enhancement of the celiac artery, portal vein, and hepatic parenchyma. We also wanted to learn which phase provided the maximal tumor-to-parenchyma difference when using multidetector CT (MDCT) with fixed timing delays. MATERIALS AND METHODS: Fifty-two patients with suspected or known hepatic tumors underwent multiphasic contrast-enhanced MDCT using double arterial (early and late arterial) and venous phase acquisitions with fixed timing delays. All patients were administered 150 mL of IV contrast material at an injection rate of 4 mL/sec. Images were acquired at 20 sec for the early arterial phase, 35 sec for the late arterial phase, and 60 sec for the portal venous phase. Attenuation measurements of the celiac artery, portal vein, normal hepatic parenchyma, and the hepatic tumor were compared. Three reviewers independently and subjectively rated tumor conspicuity for each of the three phases. Ratings were compared using kappa statistics. RESULTS: Late arterial phase images showed maximal celiac axis attenuation, whereas portal venous phase images revealed the highest portal vein and normal hepatic parenchymal attenuation. Maximal tumor-to-parenchyma differences for hypovascular tumors was superior in the portal venous phase, but we found no significant differences in maximal tumor-to-parenchyma differences for hypervascular tumors among the evaluated phases. On subjective analysis, interobserver agreement was moderate to very good for the three phases. All three reviewers graded both hypovascular and hypervascular tumor conspicuity as superior in either the late arterial phase or the portal venous phase in most patients. In only one patient was the early arterial phase graded as superior to the late arterial and portal venous phases (by two of the three reviewers). CONCLUSION: When MDCT of the liver is performed using fixed timing delays, maximal vascular and hepatic parenchymal enhancement is achieved on either late arterial phase or portal venous phase imaging. In most patients, early arterial phase imaging does not improve tumor conspicuity by either quantitative or subjective analysis.     

CT perfusion of the liver during selective hepatic arteriography: pure arterial blood perfusion of liver tumor and parenchyma

PURPOSE: To quantify pure arterial blood perfusion of liver tumor and parenchyma by using CT perfusion during selective hepatic arteriography. METHODS: A total of 44 patients underwent liver CT perfusion study by injection of contrast medium via the hepatic artery. CT-perfusion parameters including arterial blood flow, arterial blood volume, and arterial mean transit time in the liver parenchyma and liver tumor were calculated using the deconvolution method. The CT-perfusion parameters and vascularity of the tumor were compared. RESULTS: A complete analysis could be performed in 36 of the 44 patients. For liver tumor and liver parenchyma, respectively, arterial blood flow was 184.6 +/- 132.7 and 41.0 +/- 27.0 ml/min/ 100 g, arterial blood volume was 19.4 +/- 14.6 and 4.8 +/- 4.2 ml/100 g, and arterial mean transit time was 8.9 +/- 4.2 and 10.2 +/- 5.3 sec. Arterial blood flow and arterial blood volume correlated significantly with the vascularity of the tumor; however no correlation was detected between arterial mean transit time and the vascularity of the tumor. CONCLUSION: This technique could be used to quantify pure hepatic arterial blood perfusion.     

Multiphase hepatic CT with a multirow detector CT scanner

OBJECTIVE: The aim of this study was to evaluate a new injection-acquisition technique performed using a multirow detector CT scanner for separation of three distinct hepatic circulatory phases (hepatic artery, portal venous inflow, hepatic venous) and to determine which of these phases is optimal for detecting hypervascular neoplasm. MATERIALS AND METHODS: Two sequential acquisitions were performed during a single breath-hold followed by a third acquisition beginning 60 sec after injection. Injection-to-scan delay for the first acquisition was the individual patient's circulation time, which was determined by a preliminary mini bolus. The mean attenuation of the upper abdominal aorta, portal vein, and hepatic parenchyma were determined for each imaging pass in 20 patients with cirrhosis and 20 patients without cirrhosis. Tumor-to-liver contrast for hypervascular primary and metastatic neoplasm was evaluated in a different set of 16 cirrhotic patients and nine noncirrhotic patients. Three-dimensional CT arteriograms were obtained from first-pass data. RESULTS: Three distinct circulatory phases (hepatic artery, portal vein inflow or late arterial, and hepatic venous) were seen in cirrhotic and noncirrhotic patients. Maximum tumor-to-liver contrast for hypervascular primary and metastatic neoplasm occurred during the second pass for both cirrhotic (p < 0.006) and noncirrhotic (p < 0. 001) patients. A three-dimensional hepatic-mesenteric CT arteriogram of normal or anomalous hepatic vessels without venous overlay was obtained from first-pass data in all patients. CONCLUSION: Rapid-sequence hepatic helical CT allows selection of the optimal time interval for hypervascular tumor detection. A new paradigm for rapid hepatic CT acquisition-namely, hepatic arterial, portal vein inflow, and hepatic venous phases-is recommended to replace hepatic artery dominant and portal venous phases.     

Multiphase multislice spiral CT for liver assessment: optimization in cirrhotic patients

PURPOSE: The aim of our study was to optimize a multiphase study protocol with double arterial phase acquisition in a patient population with cirrhosis using a multislice spiral CT scanner. MATERIAL AND METHODS: Thirteen patients (10 males, 3 females, mean age 58 years) with known cirrhosis were selected for the study. All examinations were performed with a multislice spiral CT scanner (Somatom Plus 4 Volume Zoom; Siemens, Erlangen, Germany). Images were acquired using the following parameters: slice collimation, 2.5 mm; slice thickness, 3.0 mm; table feed, 10.8 mm/sec; mAs, 165; kVp, 120. Four scans of the hepatic parenchyma were obtained after the administration of contrast material. The first pass (early arterial phase) was acquired in a cranio-caudal direction; the second pass (late arterial phase) was acquired in a caudo-cranial direction. Early and late arterial phases were obtained during a single breath-hold of 24 sec. The third pass (portal-venous phase) was acquired with a 60-sec delay time after contrast material injection. The fourth pass (equilibrium phase) was obtained with a 180-sec delay time. Optimal delay time to start CT acquisition was assessed by means of injecting a 20-ml minibolus of contrast material and by performing serial dynamic scans every two sec at the level of the hepatic hilum. The time of peak aortic enhancement was used as the start time for the early arterial phase. Attenuation values of aorta, portal vein, and liver parenchyma were calculated in all the acquisitions. CT data from the early arterial phase were used to produce three-dimensional angiographic images of the hepatic and mesenteric circulation. RESULTS: The enhancement of liver parenchyma progressively increased from pre-contrast phase to portal-venous and equilibrium phases. The highest difference in attenuation values between aorta and hepatic parenchyma was observed during the second acquisition (early arterial phase, 247.78+/-106.29 HU) rather than during the third acquisition (late arterial phase, 185.72+/-109.23 HU); this difference was statistically significant (p<0.01). DISCUSSION: Results from our study emphasize the potential of multiphase acquisition in the evaluation of cirrhotic patients; in particular, the use of an early arterial phase is useful for studying the hepatic and mesenteric vascular anatomy, whereas the late arterial and the portal-venous phases are of paramount importance for adequate evaluation of liver parenchyma and focal lesions. Further studies are needed to evaluate whether the benefits deriving from double arterial phase acquisition would justify the increase in cost and patient radiation exposure.     

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.     

Timing of the hepatic arterial phase during contrast-enhanced computed tomography of the liver: assessment of normal values in 25 volunteers

OBJECTIVES: To define normal values of the beginning and duration of the hepatic arterial phase (HAP) during contrast-enhanced computed tomography (CT). METHODS: Twenty-five volunteers (16 men, 9 women; mean age, 60.0 years) without history or suspicion of liver disease were examined with dynamic single-section CT. Scanning was performed at a single level that included the liver, aorta, and portal vein. A series of 25 scans was obtained over a period of 88 seconds (1 baseline scan followed by 16 scans every 2 seconds and 8 scans every 7 seconds) beginning with the injection of a bolus of contrast agent (40 mL, 10 mL/s) and a 40-mL NaCl bolus chaser. Contrast enhancement in the liver, aorta, and portal vein was measured with regions of interest, and time-density curves were obtained. These data were processed with a pharmacodynamic fitting program and the duration of the HAP was calculated. The onsets of the HAP and the portal venous phase were assessed as lag times, referring to the beginning of enhancement in the abdominal aorta. RESULTS: The mean lag time of the HAP was 5.4 seconds after the aorta and the mean duration was 8.6 seconds. The mean lag time of the portal venous phase was 13.9 seconds after the aorta. CONCLUSIONS: These data can be used to optimize protocols for routine CT. Because of the short duration of the HAP, imaging of the entire liver during this phase is possible only with multidetector CT scanners.     

Prevention of hepatic infarction as acute-phase complication of TIPS by temporary balloon occlusion in a patient with primary myelofibrosis

Severe acute liver dysfunction occurred following transjugular intrahepatic portosystemic shunt (TIPS) creation in a patient with massive ascites due to portal hypertension associated with primary myelofibrosis. On US and TIPS venography, we considered that the acute liver ischemia was induced by TIPS. To avoid diffuse hepatic infarction and irreversible liver damage, a balloon catheter was inserted transjugularly into the TIPS tract and occluded it to increase portal venous flow toward the peripheral liver parenchyma. The laboratory data indicating hepatic dysfunction were improved after the procedure. We should pay attention to the possible occurrence of acute hepatic ischemia and infarction after TIPS creation even in a case of noncirrhotic portal hypertension. In such cases, temporary balloon occlusion of TIPS is an effective therapeutic method, probably as a result of inducing the development of arterial compensation through the peribiliary plexus.     

应用DSA、CT和经肠系膜上动脉门静脉灌注CT成像研究肝转移瘤的血液供应

目的 探讨DSA、CT和经肠系膜上动脉门静脉灌注CT成像对肝转移瘤的血液供应显示状况.方法 回顾性分析100例原发病灶经手术和(或)病理证实的肝转移瘤患者资料,均进行了CT平扫、多期CT增强扫描、选择性腹腔动脉和超选择性肝固有动脉DSA检查,其中,56例还经肠系膜上动脉插管行肠系膜上动脉的门静脉灌注CT成像(P(1TAP)检查,计算转移瘤中心区域、肿瘤边缘、门静脉和正常肝实质的时间-密度曲线(TDC)灰度密度(K值),观察肝转移瘤血液供应来源.DSA图像用Photoshop软件进行定量分析,CT图像用去卷积灌注软件进行分析.结果 DSA表现:肝固有动脉造影TDC显示肿瘤中心K值峰值平均为(67±12)%,肿瘤边缘K值峰值平均为(76±15)%,正常肝实质K值峰值平均为(51±10)%.腹腔动脉造影TDC显示,肿瘤中心及肿瘤边缘K值表现为快速上升,然后为缓慢上升的平台,而正常肝实质则呈现持续缓慢上升的态势.PCTAP扫描表现:肿瘤在30 s的时间内,密度变化几乎呈直线,无增强表现.结论 肝动脉是肝转移瘤的主要血液供应来源,门静脉几乎不参与肝转移瘤血液供应.