Effects of TIPS on liver perfusion measured by dynamic CT

Computed tomography perfusion in differentiating portal hypertension: A correlation study with hepatic venous pressure gradient

BACKGROUND

Hepatic venous pressure gradient (HVPG) is the gold standard for diagnosis of portal hypertension (PH), invasiveness and potential risks in the process of measurement limited its widespread use.

AIM

To investigate the correlation of computed tomography (CT) perfusion parameters with HVPG in PH, and quantitatively assess the blood supply changes in liver and spleen parenchyma before and after transjugular intrahepatic portosystemic shunt (TIPS).

METHODS

Twenty-four PH related gastrointestinal bleeding patients were recruited in this study, and all patients were performed perfusion CT before and after TIPS surgery within 2 wk. Quantitative parameters of CT perfusion, including liver blood volume (LBV), liver blood flow (LBF), hepatic arterial fraction (HAF), spleen blood volume (SBV) and spleen blood flow (SBF), were measured and compared before and after TIPS, and the quantitative parameters between clinically significant PH (CSPH) and non-CSPH (NCSPH) group were also compared. Then the correlation of CT perfusion parameters with HVPG were analyzed, with statistical significance as P < 0.05.

RESULTS

For all 24 PH patients after TIPS, CT perfusion parameters demonstrated decreased LBV, increased HAF, SBV and SBF, with no statistical difference in LBF. Compared with NCSPH, CSPH showed higher HAF, with no difference in other CT perfusion parameters. HAF before TIPS showed positive correlation with HVPG (r = 0.530, P = 0.008), while no correlation was found in other CT perfusion parameters with HVPG and Child-Pugh scores.

CONCLUSION

HAF, an index of CT perfusion, was positive correlation with HVPG, and higher in CSPH than NCSPH before TIPS. While increased HAF, SBF and SBV, and decreased LBV, were found after TIPS, which accommodates a potential non-invasive imaging tool for evaluation of PH.

The Relationship and Changes of Liver Blood Supply, Portal Pressure Gradient, and Liver Volume following TIPS in Cirrhosis

AIM

Transjugular intrahepatic portosystemic shunt (TIPS) alters the liver blood supply and reduces portal pressure. This study was to investigate the changes and associations of the hepatic blood flow, liver volume, and portal pressure gradient (PPG) after TIPS in liver cirrhosis.

METHODS

Twenty-one patients with liver cirrhosis who received TIPS were recruited. The contrast CT images were used to assess the iodine density (ID) of liver parenchymal and liver volume. The ID of the liver parenchyma was used to reflect hepatic blood flow. We used a paired t-test and regression analysis to investigate the effect of TIPS on hepatic blood flow, liver volume, and PPG in individuals with cirrhosis and the factors that affect changes in liver volume.

RESULTS

After TIPS, there was a significant improvement in the ID of liver parenchyma at arterial phase (AP) and PPG in individuals with cirrhosis (P < 0.05). Each 1 unit increase in the ID change of whole liver parenchyma at the venous phase (VP) was significantly associated with a 269.44 cm³ increase in the liver volume after TIPS (b = 269.44, P = 0.012). With an increasing ID change of whole liver parenchyma at VP, the change in liver volume followed an increasing trend (P for overall association = 0.005).

CONCLUSIONS

Our data indicate that there was a significant improvement in hepatic blood flow, especially at AP, after TIPS and the change in hepatic blood supply from the portal vein is positively associated with the change in liver volume after TIPS. Increasing the blood supply to the liver from the portal vein may improve the reduction of liver volume.

Computed tomography perfusion in liver and spleen for hepatitis B virus-related portal hypertension: A correlation study with hepatic venous pressure gradient

BACKGROUND

Hepatic venous pressure gradient (HVPG) is the gold standard for diagnosis of portal hypertension (PH). However, its use can be limited because it is an invasive procedure. Therefore, it is necessary to explore a non-invasive method to assess PH.

AIM

To investigate the correlation of computed tomography (CT) perfusion of the liver with HVPG and Child-Pugh score in hepatitis B virus (HBV)-related PH.

METHODS

Twenty-eight patients (4 female, 24 male) with gastroesophageal variceal bleeding induced by HBV-related PH were recruited in our study. All patients received CT perfusion of the liver before transjugular intrahepatic portosystemic stent-shunt (TIPS) therapy. Quantitative parameters of CT perfusion of the liver, including liver blood flow (LBF), liver blood volume (LBV), hepatic artery fraction, splenic blood flow and splenic blood volume were measured. HVPG was recorded during TIPS therapy. Correlation of liver perfusion with Child-Pugh score and HVPG were analyzed, and the receiver operating characteristic curve was analyzed. Based on HVPG (> 12 mmHg vs ≤ 12 mmHg), patients were divided into moderate and severe groups, and all parameters were compared.

RESULTS

Based on HVPG, 18 patients were classified into the moderate group and 10 patients were classified into the severe group. The Child-Pugh score, HVPG, LBF and LBV were significantly higher in the moderate group compared to the severe group (all P < 0.05). LBF and LBV were negatively associated with HVPG (r = -0.473, P < 0.05 and r = -0.503, P < 0.01, respectively), whereas splenic blood flow was positively associated with hepatic artery fraction (r = 0.434, P < 0.05). LBV was negatively correlated with Child-Pugh score. Child-Pugh score was not related to HVPG. Using a cutoff value of 17.85 mL/min/100 g for LBV, the sensitivity and specificity of HVPG ≥ 12 mmHg for diagnosis were 80% and 89%, respectively.

CONCLUSION

LBV and LBF were negatively correlated with HVPG and Child-Pugh scores. CT perfusion imaging is a potential non-invasive quantitative predictor for PH in HBV-related liver cirrhosis.

Efficacy and safety of transjugular intrahepatic portosystemic shunt combined with transcatheter embolization/chemoembolization in hepatocellular carcinoma with portal hypertension and arterioportal shunt

OBJECTIVES

This study seeks to assess the efficacy and safety of transjugular intrahepatic portosystemic shunt (TIPS) combined with transarterial embolization/transarterial chemoembolization (TAE/TACE) in hepatocellular carcinoma (HCC) with portal hypertension and arterioportal shunt (APS).

METHODS

Consecutive hospitalized patients having HCC accompanied by portal hypertension and APS were retrospectively analyzed. A total of 103 patients were enrolled. Of them, 26 patients were in Group A and 77 patients were in Group B according to the treatment protocol (Group A: TIPS plus TAE/TACE; Group B: TAE/TACE alone). The clinical outcomes and survival rate were compared between the two groups.

RESULTS

The mean survival time in Group A and Group B were 14 mo and 9.9 mo, respectively, with statistical difference (p = 0.043). The immediate APS improvement rate was 95.2% in Group A and 91.9% in Group B, respectively, with no signficant difference (p = 1.000). However, the first follow-up consultation revealed that APS improvement rate in Group A was more obvious (66.7% vs 27.4%, p = 0.001). Objective response rate of HCC tended to be greater in Group A compared with Group B (65.4% vs 38.7%, p = 0.019). Liver function parameters significantly increased in Group A than those in Group B. After TIPS placement, the mean portal pressure gradient decreased from 32.61 ± 8.87 mmHg to 15.61 ± 8.15 mmHg, with significant difference (p = 0.000). The rate of absorption of ascites and control of variceal bleeding were statistically different between the two groups (p = 0.045 and 0.039, respectively).

CONCLUSION

Our research suggests that TIPS combined with TAE/TACE seems to be safe and efficacious in patients with HCC accompanied by portal hypertension and APS, albeit may be accompanied by liver function damage.

Hepatic parenchyma and vascular blood flow changes after TIPS with spectral CT iodine density in HBV-related liver cirrhosis

To compare changes in spectral CT iodine densities of hepatic parenchyma and vessels before and after transjugular intrahepatic portosystemic shunt (TIPS) in hepatitis B virus (HBV)-related liver cirrhosis. Twenty-five patients with HBV-related liver cirrhosis who received TIPS for gastroesophageal varices bleeding were recruited. Each patient underwent three phases contrast CT before and after TIPS within 4 weeks, with the raw data reconstructed at 1.25-mm-thick slices. Iodine density (in milligrams per milliliter) was measured on iodine-based material decomposition image. Multiple regions of interest (ROIs) in liver parenchyma, aorta and portal vein were selected from three slices of images. Portal vein trunk was set as the central one, and mean liver parenchymal iodine densities from arterial phase (AP), venous phase (VP) and equilibrium phase (EP) were recorded. Quantitative indices of iodine density (ID), including normalized ID in liver parenchyma for arterial phase (NIDLAP), ID of liver parenchyma for venous phase (IDLVP), ID of portal vein in venous phase (IDPVP) and liver arterial iodine density fraction (AIF), were measured and compared before and after TIPS. Based on Child–Pugh stage, 4, 12 and 9 patients were classified as grade A, B, and C, respectively. Liver volume was comparable before and after TIPS (1110.5 ± 287.4 vs. 1092.0 ± 276.3, P = 0.28). After TIPS, ID was decreased in aorta (146.0 ± 34.5 vs. 120.9 ± 30.7, P < 0.01) whereas increased in liver parenchyma at arterial phase, as demonstrated by IDAP (9.3 ± 3.1 vs. 13.4 ± 4.4 mg/mL) and AIF (0.40 ± 0.11 vs. 0.58 ± 0.11, P < 0.01). For venous or equilibrium phase, quantitative indices remained stable (23.1 ± 4.5 vs. 23.0 ± 5.3, 19.8 ± 4.1 vs. 19.4 ± 4.6) mg/mL (Ps > 0.05). For portal vein, ID and NID were increased after TIPS (23.1 ± 11.7 vs. 36.5 ± 13.0, 16.4 ± 8.5 vs. 31.8 ± 12.8) (P < 0.01). No positive correlation between iodine density and preoperative Child–Pugh score was observed. Based on iodine density measurement, spectral CT as a noninvasive imaging modality may assess hepatic parenchyma and vascular blood flow changes before and after TIPS in HBV-related liver cirrhosis.

Clinical registration number: ChiCTR- DDC-16009986.

Pathological Features of Mitochondrial Ultrastructure Predict Susceptibility to Post-TIPS Hepatic Encephalopathy

BACKGROUND

Post-TIPS hepatic encephalopathy (PSE) is a complex process involving numerous risk factors; the root cause is unclear, but an elevation of blood ammonia due to portosystemic shunt and metabolic disorders in hepatocytes has been proposed as an important risk factor.

AIMS

The aim of this study was to investigate the impact of pathological features of mitochondrial ultrastructure on PSE via transjugular liver biopsy at TIPS implantation.

METHODS

We evaluated the pathological damage of mitochondrial ultrastructure on recruited patients by the Flameng classification system. A score ≤2 (no or low damage) was defined as group A, and a score >2 (high damage level) was defined as group B; routine follow-up was required at 1 and 2 years; the incidence of PSE and multiple clinical data were recorded.

RESULTS

A total of 78 cases in group A and 42 in group B completed the study. The incidence of PSE after 1 and 2 years in group B (35.7% and 45.2%, respectively) was significantly higher than that in group A (16.7% and 24.4%, respectively); the 1- and 2-year OR (95% CI) were 2.778 (1.166-6.615) and 2.565 (1.155-5.696), respectively, for groups A and B. Importantly, group B had worse incidence of PSE than group A [P=0.014, hazard ratio (95%CI): 2.172 (1.190-4.678)].

CONCLUSION

Aggressive damage to mitochondrial ultrastructure in liver shunt predicts susceptibility to PSE. The registration number is NCT02540382.

A model of blood-ammonia homeostasis based on a quantitative analysis of nitrogen metabolism in the multiple organs involved in the production, catabolism, and excretion of ammonia in humans

Increased blood ammonia (NH₃) is an important causative factor in hepatic encephalopathy, and clinical treatment of hepatic encephalopathy is focused on lowering NH₃. Ammonia is a central element in intraorgan nitrogen (N) transport, and modeling the factors that determine blood-NH₃ concentration is complicated by the need to account for a variety of reactions carried out in multiple organs. This review presents a detailed quantitative analysis of the major factors determining blood-NH₃ homeostasis – the N metabolism of urea, NH₃, and amino acids by the liver, gastrointestinal system, muscle, kidney, and brain – with the ultimate goal of creating a model that allows for prediction of blood-NH₃ concentration. Although enormous amounts of NH₃ are produced during normal liver amino-acid metabolism, this NH₃ is completely captured by the urea cycle and does not contribute to blood NH₃. While some systemic NH₃ derives from renal and muscle metabolism, the primary site of blood-NH₃ production is the gastrointestinal tract, as evidenced by portal vein-NH₃ concentrations that are about three times that of systemic blood. Three mechanisms, in order of quantitative importance, release NH₃ in the gut: 1) hydrolysis of urea by bacterial urease, 2) bacterial protein deamination, and 3) intestinal mucosal glutamine metabolism. Although the colon is conventionally assumed to be the major site of gut-NH₃ production, evidence is reviewed that indicates that the stomach (via Helicobacter pylori metabolism) and small intestine and may be of greater importance. In healthy subjects, most of this gut NH₃ is removed by the liver before reaching the systemic circulation. Using a quantitative model, loss of this “first-pass metabolism” due to portal collateral circulation can account for the hyperammonemia observed in chronic liver disease, and there is usually no need to implicate hepatocyte malfunction. In contrast, in acute hepatic necrosis, hyperammonemia results from damaged hepatocytes. Although muscle-NH₃ uptake is normally negligible, it can become important in severe hyperammonemia. The NH₃-lowering actions of intestinal antibiotics (rifaximin) and lactulose are discussed in detail, with particular emphasis on the seeming lack of importance of the frequently emphasized acidifying action of lactulose in the colon.

Is de novo hepatocellular carcinoma after transjugular intrahepatic portosystemic shunt increased?

BACKGROUND

Portal hypertension is a major complication of liver cirrhosis. Transjugular intrahepatic portosystemic shunt is effective in treatment of portal hypertension. However, decreased parenchymal portal venous flow after transjugular intrahepatic portosystemic shunt insertion favours ischaemic liver injury which has been discussed to induce hepatocarcinogenesis causing hepatocellular cancer.

AIM

This study aimed to explore the association between transjugular intrahepatic portosystemic shunt placement and the development of hepatocellular cancer.

METHODS

A total of 1338 consecutive liver cirrhosis patients were included in this retrospective study between January 2004-December 2015. Data were analysed with regard to development of hepatocellular cancer during follow-up. Binary logistic regression and Kaplan-Meier analyses were conducted for the assessment of risk factors for hepatocellular cancer development. In a second step, to rule out confounders of group heterogeneity, case-control matching was performed based on gender, age, model of end-stage liver disease score and underlying cause of cirrhosis (non-alcoholic steatohepatitis, alcoholic liver disease and viral hepatitis).

RESULTS

Besides established risk factors such as older age, male gender and underlying viral hepatitis, statistical analysis revealed the absence of transjugular intrahepatic portosystemic shunt insertion as a risk factor for hepatocellular cancer development. Furthermore, matched-pair analysis of 432 patients showed a significant difference (p = 0.003) in the emergence of hepatocellular cancer regarding transjugular intrahepatic portosystemic shunt placement versus the non-transjugular intrahepatic portosystemic shunt cohort.

CONCLUSION

In patients with end-stage liver disease, transjugular intrahepatic portosystemic shunt insertion is significantly associated with reduced rates of hepatocellular cancer development.

Low-Dose CT Perfusion of the Liver using Reconstruction of Difference

Liver CT perfusion (CTP) is used in the detection, staging, and treatment response analysis of hepatic diseases. Unfortunately, CTP radiation exposures is significant, limiting more widespread use. Traditional CTP data processing reconstructs individual temporal samples, ignoring a large amount of shared anatomical information between temporal samples, suggesting opportunities for improved data processing. We adopt a prior-image-based reconstruction approach called Reconstruction of Difference (RoD) to enable low-exposure CTP acquisition. RoD differs from many algorithms by directly estimating the attenuation changes between the current patient state and a prior CT volume. We propose to use a high-fidelity unenhanced baseline CT image to integrate prior anatomical knowledge into subsequent data reconstructions. Using simulation studies based on a 4D digital anthropomorphic phantom with realistic time-attenuation curves, we compare RoD with conventional filtered-backprojection, penalized-likelihood estimation, and prior image penalized-likelihood estimation. We evaluate each method in comparisons of reconstructions at individual time points, accuracy of estimated time-attenuation curves, and in an analysis of common perfusion metric maps including hepatic arterial perfusion, hepatic portal perfusion, perfusion index, and time-to-peak. Results suggest that RoD enables significant exposure reductions, outperforming standard and more sophisticated model-based reconstruction, making RoD a potentially important tool to enable low-dose liver CTP.

Impact of transjugular intrahepatic portosystemic shunt implantation on liver perfusion measured by volume perfusion CT

Background Implantation of a transjugular intrahepatic portosystemic shunt (TIPS) induces changes of liver perfusion. Purpose To determine the changes in arterial, portal venous, and total perfusion of the liver parenchyma induced by TIPS using the technique of volume perfusion computed tomography (VPCT) and compare results with invasively measured hepatic intravascular pressure values. Material and Methods VPCT quantification of liver perfusion was performed in 23 patients (mean age, 62.5 ± 8.8 years) with portal hypertension in the pre-TIPS and post-TIPS setting, respectively. A commercially available software package was used for post-processing, enabling separate calculation of the dual (arterial [ALP] and portal venous [PVP]) blood supply and additionally of the hepatic perfusion index (HPI) (HPI = ALP/(ALP + PVP)*100%). Invasive pressure measurements were performed during the intervention, before and after TIPS placement. Liver function tests performed before and after the procedure were compared. Results Mean decrease of pressure gradient through TIPS was 13.3 mmHg. Mean normal values for ALP, PVP, and total perfusion (ALP + PVP) before TIPS were 15.9, 37.7, and 53.5 mL/100 mL/min, respectively, mean HPI was 35.4%. After TIPS, ALP increased to a mean value of 37.7 mL/100 mL/min, PVP decreased (15.7 mL/100 mL/min, P < 0.05), whereas total perfusion remained unchanged (53.4 mL/100 mL/min, P = 0.97). HPI increased (71.9%; P < 0.05). No correlation between invasive pressure measurement and VPCT parameters was observed. After TIPS, liver function tests were found to worsen with a significant increase of bilirubin ( P < 0.05). Conclusion Following TIPS placement, ALP and HPI increased in all patients, whereas PVP markedly decreased. Interestingly, the magnitude of decrease in portosystemic pressure gradients was not found to correlate with VPCT parameters.

Arterial pressure suffices to increase liver stiffness

Noninvasive measurement of liver stiffness (LS) has been established to screen for liver fibrosis. Since LS is also elevated in response to pressure-related conditions such as liver congestion, this study was undertaken to learn more about the role of arterial pressure on LS. LS was measured by transient elastography (μFibroscan platform, Echosens, Paris, France) during single intravenous injections of catecholamines in anesthetized rats with and without thioacetamide (TAA)-induced fibrosis. The effect of vasodilating glycerol trinitrate (GTN) on LS was also studied. Pressures in the abdominal aorta and caval and portal veins were measured in real time with the PowerLab device (AD Instruments, Dunedin, New Zealand). Baseline LS values in all rats (3.8 ± 0.5 kPa, n = 25) did not significantly differ from those in humans. Epinephrine and norepinephrine drastically increased mean arterial pressure (MAP) from 82 to 173 and 156 mmHg. Concomitantly, LS almost doubled from 4 to 8 kPa, while central venous pressure remained unchanged. Likewise, portal pressure only showed a slight and delayed increase. In the TAA-induced fibrosis model, LS increased from 9.5 ± 1.0 to 25.6 ± 14.7 kPa upon epinephrine injection and could efficiently be decreased by GTN. We finally show a direct association in humans in a physiological setting of elevated cardiac output and MAP. During continuous spinning at 200 W, MAP increased from 84 ± 8 to 99 ± 11 mmHg while LS significantly increased from 4.4 ± 1.8 to 6.7 ± 2.1 kPa. In conclusion, our data show that arterial pressure suffices to increase LS. Moreover, lowering MAP efficiently decreases LS in fibrotic livers that are predominantly supplied by arterial blood.

Contrast-enhanced ultrasound and computerized tomography perfusion imaging of a liver fibrosis-early cirrhosis in dogs

BACKGROUND AND AIM

To assess liver fibrosis stages in a liver fibrosis-early cirrhosis model in dogs, the clinical efficiency of contrast-enhanced ultrasound (CEUS) and computed tomography (CT) perfusion imaging were compared.

METHODS

Hepatic vein arriving time (HVAT), hepatic artery arriving time, and hepatic artery to vein transit time (HA-VTT) were measured on CEUS. Total liver perfusion (TLP), portal vein perfusion (PVP), hepatic artery perfusion, and hepatic perfusion index (HPI) were measured on CT perfusion imaging. Histologic examination of liver specimens of the animals was performed to assess the fibrosis stage.

RESULTS

For assessment of liver fibrosis, the area under the receiver operating characteristic curve of CEUS indexes HVAT and HA-VTT were 0.865 and 0.930, respectively; the perfusion CT indexes TLP, PVP, and HPI were 0.797, 0.800, and 0.220, respectively; the serological index hyaluronic acid was 0.793. While for assessment of early cirrhosis, the area under the receiver operating characteristic curve of CEUS indexes HVAT and HA-VTT were 0.915 and 0.948, respectively; the perfusion CT indexes TLP, PVP, and HPI were 0.737, 0.765, and 0.218, respectively; the serological index hyaluronic acid was 0.627.

CONCLUSIONS

This study showed that both CEUS and CT perfusion imaging have the potential to be complementary imaging tools in the evaluation of liver fibrosis. While CEUS is the better choice and the index HA-VTT can be considered as non-invasive semi-quantitative indexes for diagnosing liver fibrosis and early cirrhosis.

Quantification of liver perfusion using multidelay pseudocontinuous arterial spin labeling

PURPOSE

To develop a free-breathing multidelay pseudocontinuous arterial spin labeling (pCASL) technique for quantitative measurement of liver perfusion of the hepatic artery and portal vein, respectively.

MATERIALS AND METHODS

A navigator-gated pCASL sequence with balanced steady-state free precession (bSSFP) readout was developed and applied on five healthy young volunteers at 3T. Two labeling schemes were performed with the labeling plane applied on the descending aorta above the liver, and perpendicular to the portal vein before its entry to liver to label the hepatic artery and portal vein, respectively. For each labeling scheme, pCASL scans were performed at five or six postlabeling delays between 200 and 2000 msec or 2500 msec with an interval of 400 or 500 msec. Multidelay pCASL images were processed offline with nonrigid motion correction, outlier removal, and fitted for estimation of liver perfusion and transit time.

RESULTS

Estimated liver perfusion of the hepatic artery and hepatic portal vein were 21.8 ± 1.9 and 95.1 ± 8.9 mL/100g/min, with the corresponding transit time of 1227.3 ± 355.5 and 667.2 ± 85.0 msec, respectively. The estimated liver perfusion and transit time without motion correction were less reliable with greater residual variance compared to those processed with motion correction (P < 0.05).

CONCLUSION

The liver perfusion measurement using multidelay pCASL showed good correspondence with values noted in the literature. The capability to noninvasively and selectively label the hepatic artery and portal vein is a unique strength of pCASL as compared to other liver perfusion imaging techniques, such as computed tomography perfusion and dynamic contrast-enhanced MRI.

The evaluation of haemodynamics in cirrhotic patients with spectral CT

OBJECTIVE

To evaluate haemodynamics in cirrhotic patients with portal hypertension using spectral CT imaging.

METHODS

118 cirrhotic patients with portal hypertension were included in the study group (further divided into Child-Pugh A, B and C subgroups). The control group consisted of 21 subjects with normal liver functionality. All subjects underwent three-phase spectral CT scans. Material decomposition images with water and iodine as basis material pairs were reconstructed. The iodine concentrations for the hepatic parenchyma in both arterial and portal venous phases were measured. The arterial iodine fraction (AIF) was obtained by dividing the iodine concentration in the hepatic arterial phase by that in the portal venous phase. AIF values from the study and control groups were compared using analysis of variance and between subgroups using a post-hoc test with Bonferroni correction, with a statistical significance of p<0.05.

RESULTS

The AIF was 0.25±0.05 in the control group, and 0.29±0.10, 0.37±0.12 and 0.43±0.14 in the study group with Child-Pugh Grades A, B and C, respectively. The difference in AIF between the control and study groups was statistically significant. The differences were statistically significant between the subgroups with multiple comparisons except between the control group and the Child-Pugh A group (p=0.685).

CONCLUSION

AIF measured in spectral CT could be used to evaluate the liver haemodynamics of cirrhotic patients.

ADVANCES IN KNOWLEDGE

The AIF, provided by spectral CT, could be used as a new parameter to observe liver haemodynamics.

Quantitative hepatic CT perfusion measurement: comparison of Couinaud's hepatic segments with dual-source 128-slice CT

PURPOSE

To compare the quantitative liver computed tomography perfusion (CTP) differences among eight hepatic segments.

MATERIALS AND METHODS

This retrospective study was based on 72 acquired upper abdomen CTP scans for detecting suspected pancreas tumor. Patients with primary or metastatic liver tumor, any focal liver lesions except simple cyst (<3 cm in diameter), history of liver operation or splenectomy, evidence of liver cirrhosis or invasion of portal vein were excluded. The final analysis included 50 patients (M:F=21:29, mean age=43.2 years, 15-76 years). Arterial liver perfusion (ALP), portal-venous perfusion (PVP), total hepatic perfusion (THP=ALP+PVP), and hepatic perfusion index (HPI) of each hepatic segment were calculated and compared by means of one-way analysis of variance (ANOVA) and the Bonferonni correction method.

RESULTS

Compared to hepatic segments 5, 6, 7 and 8, segments 2 and 3 showed a tendency of higher ALPs, lower PVPs, and higher HPIs, most of which were statistically significant (p<0.05). Hepatic segments 1 and 4 had higher mean values of ALP and HPI and lower mean values of PVP than segments 5, 6, 7 and 8 as well, although no significant differences were detected except for ALP and HPI for liver segments 1 and 7 (p=0.001 and 0.035 respectively), and ALP for liver segments 1 and 5 (p=0.039). Higher ALP and HPI were showed in hepatic segment 3 compared to segment 4 (p=0.000 and 0.000 respectively). No significant differences were found for THP among eight segments.

CONCLUSIONS

Intra-hepatic perfusion differences exist in normal hepatic parenchyma especially between lateral sector (segments 2 and 3) and right lobe (segments 5, 6, 7 and 8). This might have potential clinical significance in liver-perfusion-related protocol design and result analysis.

Hepatic CT perfusion measurements: a feasibility study for radiation dose reduction using new image reconstruction method

OBJECTIVES

To assess the effects of image reconstruction method on hepatic CT perfusion (CTP) values using two CT protocols with different radiation doses.

MATERIALS AND METHODS

Sixty patients underwent hepatic CTP and were randomly divided into two groups. Tube currents of 210 or 250 mA were used for the standard dose group and 120 or 140 mA for the low dose group. The higher currents were selected for large patients. Demographic features of the groups were compared. CT images were reconstructed by using filtered back projection (FBP), image filter (quantum de-noising, QDS), and adaptive iterative dose reduction (AIDR). Hepatic arterial and portal perfusion (HAP and HPP, ml/min/100ml) and arterial perfusion fraction (APF, %) were calculated using the dual-input maximum slope method. ROIs were placed on each hepatic segment. Perfusion and Hounsfield unit (HU) values, and image noises (standard deviations of HU value, SD) were measured and compared between the groups and among the methods.

RESULTS

There were no significant differences in the demographic features of the groups, nor were there any significant differences in mean perfusion and HU values for either the groups or the image reconstruction methods. Mean SDs of each of the image reconstruction methods were significantly lower (p<0.0001) for the standard dose group than the low dose group, while mean SDs for AIDR were significantly lower than those for FBP for both groups (p=0.0006 and 0.013). Radiation dose reductions were approximately 45%.

CONCLUSIONS

Image reconstruction method did not affect hepatic perfusion values calculated by dual-input maximum slope method with or without radiation dose reductions. AIDR significantly reduced images noises.

Perfusion measurement of the whole upper abdomen of patients with and without liver diseases: initial experience with 320-detector row CT

OBJECTIVES

To report initial experience of upper abdominal perfusion measurement with 320-detector row CT (CTP) for assessment of liver diseases and therapeutic effects.

MATERIALS AND METHODS

Thirty-eight patients who were suspected of having a liver disease underwent CTP. There were two patients with liver metastases, two with hemangiomas, and four with cirrhosis (disease group). CTP was repeated for four patients with cirrhosis or hepatocellular carcinoma (HCC) after therapy. Hepatic arterial and portal perfusion (HAP and HPP) and arterial perfusion fraction (APF), and arterial perfusion (AP) of pancreas, spleen, stomach, and intra-portal HCC were calculated. For disease-free patients (normal group), the values were compared among liver segments and among pancreatic and gastric parts. The values were compared between groups and before and after therapy.

RESULTS

No significant differences were found in the normal group except between APFs for liver segments 3 and 5, and fundus and antrum. Mean HAP and APF for the disease group were significantly higher than for the normal group. APF increased after partial splenic embolization or creation of a transjugular intrahepatic portosystemic shunt. HPP increased and AP of intra-portal HCC decreased after successful radiotherapy.

CONCLUSIONS

320-Detector row CT makes it possible to conduct perfusion measurements of the whole upper abdomen. Our preliminary results suggested that estimated perfusion values have the potential to be used for evaluation of hepatic diseases and therapeutic effects.

CT hepatic perfusion measurement: comparison of three analytic methods

OBJECTIVES

To compare the efficacy of three analytic methods, maximum slope (MS), dual-input single-compartment model (CM) and deconvolution (DC), for CT measurements of hepatic perfusion and assess the effects of extra-hepatic systemic factors.

MATERIALS AND METHODS

Eighty-eight patients who were suspected of having metastatic liver tumors underwent hepatic CT perfusion. The scans were performed at the hepatic hilum 7-77 s after administration of contrast material. Hepatic arterial and portal perfusions (HAP and HPP, ml/min/100 ml) and arterial perfusion fraction (APF, %) were calculated with the three methods, followed by correlation assessment. Partial correlation analysis was used to assess the effects on hepatic perfusion values by various factors such as age, sex, risk of cardiovascular diseases, arrival time of contrast material at abdominal aorta, transit time from abdominal aorta to hepatic parenchyma, and liver dysfunction.

RESULTS

Mean HAP of MS was significantly higher than DC. HPP of CM was significantly higher than MS and CM, and HPP of MS was significantly higher than DC. There was no significant difference in APF. HAP and APF showed significant and moderate correlations among the methods. HPP showed significant and moderate correlations between CM and DC, and poor correlation between MS and CM or DC. All methods showed weak correlations between HAP or APF and age or sex. Finally, MS showed weak correlations between HAP or HPP and arrival time or cardiovascular risks.

CONCLUSIONS

Hepatic perfusion values arrived at with the three methods are not interchangeable. CM and DC are less susceptible to extra-hepatic systemic factors.

Low-dose hepatic computed tomography perfusion imaging and its preliminary study

OBJECTIVE

Computed tomography perfusion imaging (CTPI) is a rapid and non-invasive functional imaging method that reflects hemodynamic changes of liver diseases. However, its large radiation dosage limits its clinical application. We aimed to evaluate the feasibility of low-dose CTPI in normal liver and its preliminary application in hepatocellular carcinoma (HCC).

METHODS

CTPI was performed in 34 healthy volunteers randomly divided into three groups with different applications of tube current, including a conventional dose group, a median-dose group and a low-dose group. The perfusion parameters of each group were compared and a low-dose CTPI was performed in 13 patients with HCC.

RESULTS

Relatively satisfying images and perfusion parameters of liver CTPI were acquired with the different tube currents. There were no significant differences between the parameters of the three groups (P>0.05). The effective dosage of conventional, median and low-dose liver CTPI were 19.62 mSv, 12.61 mSv, and 7.01 mSv, respectively. The radiation dosage of low-dose liver CTPI was reduced to 64.27% compared with that of the conventional group. The hepatic blood flow, hepatic blood volume and hepatic perfusion index of HCC were higher than background liver parenchyma and normal liver.

CONCLUSIONS

Low-dose liver CTPI obtained similar perfusion parameters result to that of the conventional-dose, whereas the radiation dosage was reduced by 2/3. Low-dose liver CTPI can reflect the hemodynamic change of HCC. Low-dose liver CTPI has potential clinical value for diagnosis and differential diagnosis of liver diseases.

Morphological and functional MDCT: problem-solving tool and surrogate biomarker for hepatic disease clinical care and drug discovery in the era of personalized medicine

This article explains the significant role of morphological and functional multidetector computer tomography (MDCT) in combination with imaging postprocessing algorithms served as a problem-solving tool and noninvasive surrogate biomarker to effectively improve hepatic diseases characterization, detection, tumor staging and prognosis, therapy response assessment, and novel drug discovery programs, partial liver resection and transplantation, and MDCT-guided interventions in the era of personalized medicine. State-of-the-art MDCT depicts and quantifies hepatic disease over conventional CT for not only depicting lesion location, size, and extent but also detecting changes in tumor biologic behavior caused by therapy or tumor progression before morphologic changes. Color-encoded parameter display provides important functional information on blood flow, permeability, leakage space, and blood volume. Together with other relevant biomarkers and genomics, the imaging modality is being developed and validated as a biomarker to early response to novel, targeted anti-VEGF(R)/PDGFR or antivascular/angiogenesis agents as its parameters correlate with immunohistochemical surrogates of tumor angiogenesis and molecular features of malignancies. MDCT holds incremental value to World Health Organization response criteria and Response Evaluation Criteria in Solid Tumors in liver disease management. MDCT volumetric measurement of future remnant liver is the most important factor influencing the outcome of patients who underwent partial liver resection and transplantation. MDCT-guided interventional methods deliver personalized therapies locally in the human body. MDCT will hold more scientific impact when it is fused with other imaging probes to yield comprehensive information regarding changes in liver disease at different levels (anatomic, metabolic, molecular, histologic, and other levels).

Liver failure after an uncovered TIPS procedure associated with hepatic infarction

Transjugular intrahepatic portosystemic shunt (TIPS) is a safe and effective procedure for the treatment of complications of liver cirrhosis, such as refractory ascites, hepatic hydrothorax and refractory variceal bleeding. The aim of this paper is to describe a rare case of liver failure after a TIPS procedure. A 38-year-old diabetic male with Child-Pugh C liver cirrhosis due to chronic hepatitis C infection who had developed refractory ascites was scheduled for a TIPS procedure. Within 24 h following TIPS placement, the patient developed distributive shock, jaundice, persistentgrade 3 hepatic encephalopathy, severe coagulopathy and acute renal failure. He was treated with lactulose enemas, broad-spectrum antibiotics and blood-derived products. Laboratory data revealed a 100-fold increase in aminotransferases and a non-enhanced computed tomography showed an irregular hypodense area in the right posterior segment of the liver. Despite being initially being in a stable condition, the patient developed progressive liver failure and died 2 mo later. Hepatic infarction is an uncommon phenomenon after a TIPS procedure; however, it can greatly complicate the course of a disease in a patient with an already compromised liver function.

Evaluation of gastric fundic and oesophageal varices by 64-row multidetector computed tomography before and after transjugular intrahepatic portosystemic shunt with concurrent left gastric vein embolization

OBJECTIVE

To determine the utility of 64-row multidetector computed tomography (MDCT) in assessing the changes of gastric fundic and oesophageal varices before and after transjugular intrahepatic portosystemic shunt (TIPS) with concurrent left gastric vein embolization.

METHODS

Twenty-eight consecutive patients with gastric fundic and oesophageal varices resulted from posthepatitic cirrhosis, clinically confirmed with endoscopy, were enrolled into our study. All the patients underwent thoracicoabdominal triphasic enhancement scans with 64-row MDCT 2 weeks before TIPS along with embolizing left gastric vein, and 6 months after the therapy. Before and after the therapy, the varices shown on multiplanar reconstruction (MPR) were compared by Fisher's exact test to evaluate the changes.

RESULTS

Gastric fundic and oesophageal varices were shown in 26 patients (92.9%) and 25 (89.3%) on MPR before the therapy, respectively. After the therapy, these varices diminished markedly, and were illustrated in six (21.4%) and 10 patients (35.7%), respectively (all P<0.05). As for the main inflowing vessel of the varices (left gastric vein), it was illustrated in 28 patients (100.0%) on preoperative CT-MPR. After the embolization, the left gastric vein had been completely occluded on postoperative CT-MPR.

CONCLUSION

Significant eradication of gastric fundic and oesophageal varices on follow-up CT-MPR portography can be considered to assess the changes of gastric fundic and oesophageal varices before and after TIPS with concurrent left gastric vein embolization, and 64-row MDCT can be an effective modality to evaluate the changes.

Perfusion computed tomography evaluation of angiogenesis in liver cancer

OBJECTIVE

To investigate the value of computed tomography (CT) perfusion imaging for assessment of angiogenesis in liver cancer.

METHODS

Twenty-one patients with histologically proven liver cancer underwent CT perfusion examination. We compared the following perfusion parameters in the tumour area versus the non-tumour area: total blood flow (TBF), hepatic arterial perfusion (HAP), hepatic portal perfusion (HPP) and hepatic arterial perfusion index (HAPI). Slices of postoperative specimen were stained with haematoxylin-eosin and anti-CD34 immunohistochemistry. The slices were evaluated with emphasis on the CD34-positive neovasculature in the tumour parenchyma. Tumour microvascular density (MVD) was calculated according to the Weidner method. Pearson correlation was used to detect correlations between tumour MVD and tumour perfusion parameters.

RESULT

TBF and HPP in the tumour area were lower than in the non-tumour area (P < 0.05). HAP and HAPI in the tumour area were higher than those of the non-tumour area (P < 0.05). TBF and HAP in the tumour area correlated with MVD in the tumour (P < 0.05), with correlation coefficients of 0.849 and 0.829, respectively.

CONCLUSION

CT perfusion imaging can quantitatively assess the blood supply and its distribution in liver cancer. TBF or HAP may be a useful parameter in assessing angiogenesis of liver cancer.

Clinical application of hepatic CT perfusion

Complicated changes occur in hemodynamics of hepatic artery and vein, and portal vein under various kinds of pathologic status because of distinct double hepatic blood supply. This article reviews the clinical application of hepatic computed tomography perfusion in some liver diseases.

Dynamic MR perfusion measurements before and after TIPS in cirrhotic patients with refractory ascites

RATIONALE AND OBJECTIVES

We sought to assess changes in liver perfusion parameters induced by transjugular intrahepatic portosystemic shunt (TIPS) creation in cirrhotic patients with refractory ascites using dynamic MR perfusion measurements.

MATERIALS AND METHODS

MR perfusion measurements were performed before and after TIPS creation in 15 cirrhotic patients all with refractory ascites. Measurements were performed over a time period of 120 seconds providing 60 images for each examination and calculations were done in both liver and splenic parenchyma. Different perfusion parameters were assessed: time to peak (TTP), time to inflow deceleration (TID), maximal or peak perfusion (C-peak) and the wash-in rate.

RESULTS

TIPS procedures were successful in all 15 patients but were complicated by hepatic encephalopathy in 3 patients (20%), and in another 4 patients (26%), persistent refractory ascites was still noted during follow-up. Overall, liver TID values decreased significantly (P = .001) after TIPS creation; liver wash-in values increased significantly (P = .04) after TIPS. TTP values did not decrease significantly (P = .16) and liver C-peak values did not change equally (P = .99).

CONCLUSION

In cirrhotic patients with refractory ascites, TIPS induced a faster, but not an increased, contrast enhancement in the liver.

Nanorod-based flow estimation using a high-frame-rate photoacoustic imaging system

A quantitative flow measurement method that utilizes a sequence of photoacoustic images is described. The method is based on the use of gold nanorods as a contrast agent for photoacoustic imaging. The peak optical absorption wavelength of a gold nanorod depends on its aspect ratio, which can be altered by laser irradiation (we establish a wash-in flow estimation method of this process). The concentration of nanorods with a particular aspect ratio inside a region of interest is affected by both laser-induced shape changes and replenishment of nanorods at a rate determined by the flow velocity. In this study, the concentration is monitored using a custom-designed, high-frame-rate photoacoustic imaging system. This imaging system consists of fiber bundles for wide area laser irradiation, a laser ultrasonic transducer array, and an ultrasound front-end subsystem that allows acoustic data to be acquired simultaneously from 64 transducer elements. Currently, the frame rate of this system is limited by the pulse-repetition frequency of the laser (i.e., 15 Hz). With this system, experimental results from a chicken breast tissue show that flow velocities from 0.125 to 2 mms can be measured with an average error of 31.3%.

Multidetector CT (64 Slices) of the liver: examination techniques

Sixty-four-row MDCT, although developed primarily for cardiac imaging, has the potential to have a great impact on liver imaging as well. Liver-imaging protocols with sub-millimeter collimation improve longitudinal spatial resolution, making the acquired dataset a real isotropic volume perfectly designed for optimal three-dimensional rendering and accurate organ and lesion volumetry. The 64-row detector array offers a wide volumetric coverage (up to 40 mm), suitable not only for shortening scanning time and improving spatial resolution, but also for including a large volume per single rotation, particularly useful for accurate CT perfusion studies. In order to take full benefit from the enormous performance offered by new 64-row MDCT scanners, imaging protocols need to be redesigned. Due to the extremely short scanning window, contrast agent injection should be performed at high flow rate and followed by saline bolus chaser; the use of highly concentrated contrast media might be useful. Timing should be accurately calculated either by a test bolus or, better, by using an automatic bolus-detection technique. Radiation exposure is kept under control, using automatic device-modulating dose delivery according to the patient's anatomy. Finally, the evaluation of acquired volumetric datasets needs the extensive use of a dedicated workstation, with software with sophisticated rendering capabilities.