Hemodynamic alterations in anterior segment of liver graft after right-lobe living-donor liver transplantation: computed tomography perfusion imaging findings

Congestion Area of the Right Lobe Graft in Living Donor Liver Transplantation: Quantitative Evaluation of Hemodynamics Using Computed Tomography Perfusion

BACKGROUND

The hemodynamics of congestion areas in the right lobe graft after living donor liver transplantation (LDLT) remains unclear. The aim of this study was to elucidate the hemodynamics of congestion areas in the right lobe graft after LDLT using computed tomography (CT) perfusion imaging and the dual-input maximum slope method.

METHODS

Sixteen recipients underwent CT perfusion of the liver and portal phase abdominal to pelvic CT 1week after LDLT using a right lobe graft. The attenuation of segments V and VIII on the portal venous phase abdominal to the pelvic CT scan was classified into 3 categories: hyperattenuation, iso-attenuation, and hypoattenuation. Mean arterial blood flow (AF, mL/min/100 mL tissue), portal blood flow (PF, mL/min/100 mL tissue), and perfusion index (%) [PI = AF/(AF + PF) × 100] were compared between the hyperattenuation group and iso-attenuation group. The independent t test was used for these statistical analyses.

RESULTS

On the portal phase abdominal scan, 15 segments, 16 segments, and 1 segment showed hyperattenuation, iso-attenuation, and hypoattenuation, respectively. The mean AF and PI of the hyperattenuation group (44.4 ± 24.4, 30.2 ± 13.5) were significantly higher than those of the iso-attenuation group (28.0 ± 7.8, 19.9 ± 6.2) (P < .05, P < .05).

CONCLUSIONS

The congested liver segments showed high AF and high PI on CT perfusion imaging. This method enables the feasible quantification of the hemodynamics and the description of focal hemodynamic change in the graft after LDLT.

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.

Perfusion CT imaging of the liver: review of clinical applications

Perfusion computed tomography (CT) has a great potential for determining hepatic and portal blood flow; it offers the advantages of quantitative determination of lesion hemodynamics, distinguishing malignant and benign processes, as well as providing morphological data. Many studies have reported the use of this method in the assessment of hepatic tumors, hepatic fibrosis associated with chronic liver disease, treatment response following radiotherapy and chemotherapy, and hepatic perfusion changes after radiological or surgical interventions. The main goal of liver perfusion imaging is to improve the accuracy in the characterization of liver disorders. In this study, we reviewed the clinical application of perfusion CT in various hepatic diseases.

Clinical utility of hepatic-perfusion computerized tomography in living-donor liver transplantation: a preliminary study

BACKGROUND

Vascular complications are a primary diagnostic consideration in liver transplant recipients, with an overall incidence of 9%. Cross-sectional imaging techniques provide information regarding vascular structure and luminal patency but can not quantitatively assess hepatocyte damage in the liver graft parenchyma. Perfusion computerized tomography (CT) is a recently developed method that allows for quantitative evaluation of hemodynamic changes in tissue. Our objective was to evaluate the clinical utility of perfusion CT in assessing vascular complications during living-donor liver transplantation (LDLT).

METHODS

The 33 recipients were divided into 3 groups according to Doppler ultrasonographic findings: hepatic arterial complication group, portal venous complication group, and hepatic venous complication group. Blood volume (BV), blood flow (BF), arterial liver perfusion (ALP), portal venous perfusion (PVP), and hepatic perfusion index (HPI) were calculated for the affected vascular territory regions.

RESULTS

Compared with normal liver parenchyma, BV, BF, ALP, and HPI were significantly lower in the hepatic arterial complication group. Although PVP and BV were significantly lower, ALP, HPI, and BF were higher in the affected vascular territory region than in normal liver parenchyma for the portal venous complication group. In the hepatic venous complication group, PVP was significantly higher and BF, ALP, and HPI significantly lower in the affected vascular territory regions than in normal liver parenchyma.

CONCLUSIONS

Perfusion CT imaging is a noninvasive technique that enables the quantitative evaluation of vascular complications in the graft parenchyma after LDLT and permits a quantitative evaluation of the treatment response.

Abdominal perfusion computed tomography

The purpose of this article is to provide an up to date review on the spectrum of applications of perfusion computed tomography (CT) in the abdomen. New imaging techniques have been developed with the objective of obtaining a structural and functional analysis of different organs. Recently, perfusion CT has aroused the interest of many researchers who are studying the applicability of imaging modalities in the evaluation of abdominal organs and diseases. Per-fusion CT enables fast, non-invasive imaging of the tumor vascular physiology. Moreover, it can act as an in vivo biomarker of tumor-related angiogenesis.

Hepatic blood volume imaging with the use of flat-detector CT perfusion in the angiography suite: comparison with results of conventional multislice CT perfusion

PURPOSE

To prospectively determine the feasibility of flat-detector (FD) computed tomography (CT) perfusion to measure hepatic blood volume (BV) in the angiography suite in patients with hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Twenty patients with HCC were investigated with conventional multislice and FD CT perfusion. CT perfusion was carried out on a multislice CT scanner, and FD CT perfusion was performed on a C-arm angiographic system, before transarterial chemoembolization procedures. BV values of conventional and FD CT perfusion were measured within tumors and liver parenchyma. The arterial perfusion portion of CT perfusion BV was extracted from CT perfusion BV by multiplying it by a hepatic perfusion index. Relative values (RVs) for CT perfusion arterial BV and FD CT perfusion BV (FD BV) were defined by dividing BV of tumor by BV of parenchyma. Relationships between BV and RV values of these two techniques were analyzed.

RESULTS

In all patients, both perfusion procedures were technically successful, and all 33 HCCs larger than 10 mm were identified with both imaging methods. There were strong correlations between the absolute values of FD BV and CT perfusion arterial BV (tumor, r = 0.903; parenchyma, r = 0.920; both P < .001). Bland-Altman analysis showed a mean difference of -0.15 ± 0.24 between RVs for CT perfusion arterial BV and FD BV.

CONCLUSIONS

The feasibility of FD CT perfusion to assess BV values of liver tumor and surrounding parenchyma in the angiographic suite was demonstrated.

Reconstructing middle hepatic vein tributaries in right-lobe living donor liver transplantation

AIMS

To investigate the effectiveness of our technique and policy in reconstructing middle hepatic vein (MHV) tributaries of patients undergoing right-lobe living donor liver transplantation (LDLT).

METHODS

From January 2001 to December 2010, 186 adult patients underwent right-lobe LDLT without the MHV. Patients were divided into two groups: group A (n = 71) and group B (n = 115) without or with the MHV tributaries reconstruction. We evaluated the serum liver function markers after transplantation and monitored vascular flow in the graft and interpositional vein by Doppler ultrasonography.

RESULTS

The cumulative 1-, 3-, 5-year graft and patient survival rates were not significant between group A and group B (p = 0.287 and p = 0.258). Biliary complications appeared to be more frequent in group A than in group B (16.9 vs. 5.2%, p = 0.009). Liver function impairment was found in patients without MHV reconstruction and those with occluded interpositional vessels early after transplantation. The cumulative 1-, 3-, 6- and 12-month patency rate of the interpositional veins was 81.51, 79.60, 74.69 and 72.68%, respectively.

CONCLUSION

The reconstruction technique based on our policy ensures excellent outflow drainage and favorable recipient outcome, while better criteria for MHV reconstruction should be established.

Vascular communications between donor and recipient tissues after successful full face transplantation

The vascular reorganization after facial transplantation has important implications on future surgical planning. The purpose of this study was to evaluate blood flow (BF) after full face transplantation using wide area-detector computed tomography (CT) techniques. Three subjects with severe craniofacial injury who underwent full face transplantation were included. All subjects underwent a single anastomosis bilaterally of the artery and vein, and the recipient tongue was preserved. Before and after surgery, dynamic volume CT studies were analyzed for vascular anatomy and blood perfusion. Postsurgical CT showed extensive vascular reorganization for external carotid artery (ECA) angiosome; collateral flows from vertebral, ascending pharyngeal or maxillary arteries supplied the branches from the recipient ECAs distal to the ligation. While allograft tissue was slightly less perfused when the facial artery was the only donor artery when compared to an ECA-ECA anastomosis (4.4 ± 0.4% vs. 5.7 ± 0.7%), allograft perfusion was higher than the recipient normal neck tissue. BF for the recipient tongue was maintained from contralateral/donor arteries when the lingual artery was sacrificed. Venous drainage was adequate for all subjects, even when the recipient internal jugular vein was anastomosed in end-to-end fashion on one side. In conclusion, dynamic CT identified adequate BF for facial allografts via extensive vascular reorganization.

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.

Acute outflow obstruction of hepatic veins in rabbits: quantitative analysis of hepatic perfusion with contrast-enhanced sonography

OBJECTIVES

To compare time-enhancement curve parameters of contrast-enhanced sonography in acute partial hepatic venous outflow obstruction with those of a baseline study.

METHODS

Contrast-enhanced sonography was performed in 11 rabbits with bolus administration of a sulfur hexafluoride contrast agent (0.1 mL/kg). After baseline scanning for 3 minutes, a 5.3F balloon catheter was placed into the left hepatic vein. Obstruction was artificially induced by 0.4-mL balloon inflation, and sonography was repeatedly performed thereafter. On images stored with 1-second intervals, 2 × 2-mm regions of interest were placed, and mean luminosity was measured. Time-enhancement curves were plotted, and contrast arrival times, peak enhancement values, peak enhancement times, 50% wash-out times, and 3-minute wash-out rates were obtained. Paired t tests were performed to evaluate the significance of differences in the parameters between baseline and obstruction.

RESULTS

On baseline sonography, the median contrast arrival time, peak enhancement value, peak enhancement time, 50% wash-out time, and 3-minute wash-out rate were 6 (range, 4-8; mean ± SD, 5.9 ± 1.2) seconds, 188.5 (104.7-209.5; 178.4 ± 33.1) arbitrary units, 19 (14-27; 19.8 ± 4.1) seconds, 75 (60-101; 78.2 ± 13.9) seconds, and 89.7% (81.3%-95.1%; 88.4% ± 4.9%), respectively. With obstruction, those values were 7 (5-12; 6.9 ± 2.3) seconds, 202.8 (98.2-215.1; 186.0 ± 39.3) arbitrary units, 31 (17-59; 32 ± 11.6) seconds, 101 (47-136; 96.2 ± 23.6) seconds, and 79.2% (66.2%-88.8%; 79.1% ± 7.6%). Compared with baseline, the peak enhancement time was significantly delayed from 19 to 31 seconds (P = .0027), 50% wash-out time significantly delayed from 75 to 101 seconds (P = .0209), and 3-minute wash-out rate significantly decreased from 89.7% to 79.2% (P < .0001) with obstruction, but there were no significant differences in contrast arrival times and peak enhancement values (P = .0756 and .2179).

CONCLUSIONS

Contrast-enhanced sonography can provide quantitative assessment of microbubble congestion in partial hepatic venous outflow obstruction. The peak enhancement time and 50% wash-out time are delayed and 3-minute wash-out rate is decreased in rabbits with artificially induced obstruction compared with a baseline study.