Hepatic perfusion changes after transcatheter arterial embolization (TAE) of hepatocellular carcinoma: measurement by dynamic computed tomography (CT)

Computed Tomography Perfusion Following Transarterial Chemoembolization of Hepatocellular Carcinoma: A Feasibility Study in the Early Period

OBJECTIVES

The aim of this study was to assess the feasibility of computed tomography (CT) perfusion in early follow-up after transarterial chemoembolization (TACE) of hepatocellular carcinoma (HCC).

METHODS

Fifteen patients with a total of 16 HCC who were referred to our institution for TACE were included in the study. Computed tomography perfusion was performed within 1 to 3 days before and 4 to 7 days after TACE. Multiphase contrast-enhanced CT was performed 35 (SD, 20) days after TACE. Hepatic arterial blood flow and portal venous blood flow, as well as the perfusion index (PI), were calculated for each HCC using the dual input maximum slope method. Visual grading of the PI and visual grading of the amount of deposition of embolic material within the HCC were performed using a 6-step scale. Differences in perfusion before and after TACE and correlation of perfusion before TACE with the amount of embolization material depositions 1 week and 1 month after TACE were tested.

RESULTS

No statistically significant correlation was found between pre-TACE perfusion parameters and the amount of embolization material deposition in the post-TACE studies. There was no statistically significant difference between pre- and post-TACE arterial blood flow and portal venous blood flow, whereas PI was significantly lower after TACE. Congruently, visual grading of PI was statistically significantly lower after TACE. There was no statistically significant difference in quantitative pre-TACE and post-TACE PI between tumors, which showed hypervascularization in the multiphase follow-up CT and tumors that did not show hypervascularization. However, tumors that showed hypervascularization in the multiphase follow-up CT had significantly higher visual grading of PI after TACE than tumors that did not show hypervascularization.

CONCLUSIONS

Our findings indicate that visual interpretation of the PI of HCC derived from dual-input maximum slope CT perfusion may be an early predictor of response to TACE.

Therapeutic response assessment of transcatheter arterial chemoembolization for hepatocellular carcinoma: ultrasonography, CT and MR imaging

Two randomized controlled trials identified that transcatheter arterial chemoembolization (TACE) for hepatocellular carcinoma (HCC) shows a significant survival benefit compared with controls, after a long-term controversy. Thus, TACE is the current standard of care for patients presenting with multinodular HCC. Monitoring tumor response to TACE is part of the clinical management of HCC patients. Imaging, including ultrasonography, computed tomography and magnetic resonance imaging, has an important role in assessing therapeutic effects earlier and more objectively. Imaging assessment needs to detect not only a reduction in overall tumor load but also a reduction in viable tumor. Here, we give an overview of the current status of the imaging assessment of HCC response to TACE.

Pseudolesion of the liver on gadoxetate disodium-enhanced MR images obtained after transarterial chemoembolization for hepatocellular carcinoma: clinicoradiologic correlation

OBJECTIVE

The purpose of this study was to elucidate the clinicoradiologic characteristics of pseudolesions of the liver in patients with hepatocellular carcinoma (HCC) treated with transarterial chemoembolization (TACE) as observed on gadoxetate disodium-enhanced MR images. A particular interest was correlation between the pseudolesion characteristics and TACE-MRI interval, during which sequential changes in pseudolesions may be revealed after TACE.

MATERIALS AND METHODS

Forty-eight patients with HCC who underwent gadoxetate disodium-enhanced MRI after TACE were retrospectively recruited. Pseudolesions were defined as areas of decreased signal intensity in treated areas on hepatocellular phase images that were confirmed to be nontumorous areas at follow-up. The prevalence and MRI features of pseudolesions were correlated with various clinical parameters, including TACE-MRI interval.

RESULTS

Pseudolesions were found in 14 patients (29%). Within 1 month of TACE, the prevalence of pseudolesions was 83%. All of the pseudolesions had arterial enhancement, mimicking residual HCC. After 1 month, the prevalence of pseudolesions decreased, and these pseudolesions tended to exhibit no abnormality in any sequence other than the hepatocellular phase. Results of multivariate analysis suggested that size of HCC (p < 0.0001), duration of postembolization syndrome (p = 0.012), and TACE-MRI interval (p = 0.038) are independent indicators of the presence of pseudolesions.

CONCLUSION

The prevalence and appearance of pseudolesions differ at different intervals from TACE. Radiologists need to recognize the clinicoradiologic characteristics to differentiate pseudolesions from true residual or recurrent HCC.

The role of perfusion CT as a follow-up modality after transcatheter arterial chemoembolization: an experimental study in a rabbit model

OBJECTIVES

To prospectively evaluate the feasibility of perfusion CT as a follow-up modality after transcatheter arterial chemoembolization (TACE) and to compare these findings with those of histopathology as the reference standard in a VX2 tumor rabbit model.

MATERIALS AND METHODS

VX2 carcinoma tumors were implanted into the liver of 20 rabbits 3 weeks prior to TACE. Perfusion CT was performed prior to TACE and 1- and 4-week after TACE. After obtaining perfusion index maps on perfusion CT, 2 radiologists measured the parametric perfusion indices of blood flow (BF), blood volume (BV), mean transit time (MTT), permeability of the capillary vessel surface (PS), and hepatic arterial fraction (HAF) of primary tumors on pre-TACE perfusion CT, chemoembolized primary tumors on 1-week perfusion CT, and recurred tumors on 4-week perfusion CT. The normal liver parenchyma indices were also recorded. In addition, the radiologists investigated the presence of a recurred tumor adjacent to the chemoembolized area on perfusion index maps of 4-week CT images. The areas of higher hepatic blood flow (HBF), hepatic blood volume (HBV), PS, and HAF, and lower MTT on 4-week perfusion CT than the normal liver parenchyma and the identical area on 1-week perfusion CT were considered as recurred tumors. Histopathology revealed the presence of a recurred tumor, and mean vessel density (MVD) was determined by immunochemical staining for CD31. CT perfusion indices were compared by use of the t test. Comparisons were made for the primary tumor versus normal liver parenchyma on pre-TACE CT, the primary tumor on pre-TACE CT versus the chemoembolized tumor on 1-week CT, the recurred tumor on 4-week CT versus the identical area on 1-week CT, and the primary tumor on pre-TACE CT versus the recurred tumor on 4-week CT. For the detection of recurred tumors, the sensitivity and specificity for 4-week perfusion CT were calculated. Correlation analysis between the recurred tumor perfusion indices and the MVD of the corresponding tumor region was performed. Among 20 rabbits, 6 were excluded from the analysis, and results were based on 14 rabbits.

RESULTS

Recurred tumors were histologically proven in 8 of 14 rabbits (57.1%). The BF, BV, PS, and HAF indices of primary tumors were significantly higher, whereas the MTT was significantly lower than that of the normal liver parenchyma on pre-TACE perfusion CT and that of chemoembolized areas on 1-week perfusion CT (P < 0.05). In addition, recurred tumors also showed significantly higher BF, BV, PS, and HAF, and lower MTT indices than the identical areas on 1-week perfusion CT (P < 0.05). The perfusion indices of recurred tumors were not significantly different from the indices of primary tumors (P > 0.05). Both sensitivity and specificity were 100% for 4-week perfusion CT. There were significant positive correlations between BF (r = 0.947), BV (r = 0.758), PS (r = 0.759), HAF (r = 0.955), and MVD in recurred tumors, and a significant inverse correlation between MTT (r = -0.782) and MVD was observed (P < 0.05).

CONCLUSIONS

We believe that perfusion CT is a feasible alternative modality for the successful early response assessment and early detection of a marginally recurred tumor after TACE. However, perfusion CT has limitations for the prediction of tumor recurrence after TACE.

Pseudolesion of the liver observed on gadoxetate disodium-enhanced magnetic resonance imaging obtained shortly after transarterial chemoembolization for hepatocellular carcinoma

The purpose of this report was to describe pseudolesions of the liver that mimicked residual hypervascular hepatocellular carcinoma (HCC), as observed on gadoxetate disodium-enhanced magnetic resonance imaging (EOB-MRI) obtained shortly after transarterial chemoembolization (TACE). Between June 2008 and December 2008, three patients underwent MRI within 12 days after TACE to rule out remaining viable cancerous tissue or to assess the treatment effect. In all three patients, nontumorous liver tissue adjacent to the treated HCC exhibited focal arterial enhancement on dynamic phase and subsequent diminished uptake of gadoxetate disodium on hepatocellular phase images, which mimicked residual HCC. All three patients had mild postembolization syndrome at the time of EOB-MRI and showed no evidence of residual or recurrent tumors on follow-up. The findings of these areas may represent transient focal hyperemia and damage to the liver cell function caused by TACE. Radiologists should be aware that EOB-MRI obtained shortly after TACE may show pseudolesions around the treated tumors and should not mistake them for residual or recurrent tumors.

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.

Computed tomography perfusion in evaluating the therapeutic effect of transarterial chemoembolization for hepatocellular carcinoma

AIM: To prospectively assess the changes in parameters of computed tomography (CT) perfusion pre- and post-transarterial chemoembolization (TACE) of hepatocellular carcinoma (HCC) in different treatment response groups, and to correlate the changes with various responses of HCC to TACE.

METHODS: Thirty-nine HCC patients underwent CT perfusion examinations pre-(1 d before TACE) and post-treatment (4 wk after TACE). The response evaluation criteria for solid tumors (RECIST) were referred to when treatment responses were distributed. Wilcoxon-signed ranks test was used to compare the differences in CT perfusion parameters pre- and post-TACE for different response groups.

RESULTS: Only one case had treatment response to CR and the CT perfusion maps of post-treatment lesion displayed complete absence of signals. In the PR treatment response group, hepatic artery perfusion (HAP), hepatic arterial fracture (HAF) and hepatic blood volume (HBV) of viable tumors post-TACE were reduced compared with pre-TACE (P = 0.001, 0.030 and 0.001, respectively). In the SD group, all CT perfusion parameters were not significantly different pre- and post-TACE. In the PD group, HAP, HAF, portal vein perfusion (PVP) and hepatic blood flow (HBF) of viable tumors post-TACE were significantly increased compared with pre-TACE (P = 0.005, 0.012, 0.035 and 0.005, respectively).

CONCLUSION: Changes in CT perfusion parameters of viable tumors are correlated with different responses of HCC to TACE. Therefore, CT perfusion imaging is a feasible technique for monitoring response of HCC to TACE.

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Measuring portal venous perfusion with contrast-enhanced CT: comparison of direct and indirect methods

RATIONALE AND OBJECTIVES

Two algorithms can be used to measure portal venous perfusion (PVP) with contrast material-enhanced single-level liver computed tomography. The "direct" and "indirect" algorithms use data from the portal vein and aorta, respectively. This study compared PVP values obtained with direct and with indirect algorithms in a series of patients.

MATERIALS AND METHODS

Both techniques were applied in 27 patients with cirrhosis (14 men and 13 women; mean age, 56.1 years +/- 9.4) and 18 control patients (seven men and 11 women; 52.8 years +/- 12.3). A single section through the liver was scanned after intravenous injection of ioversol (40-mL bolus; 320 mg of iodine per milliliter).

RESULTS

Both techniques showed reduced PVP in patients with cirrhosis (0.63 for direct and 0.17 for indirect method) compared with control patients (1.06 and 0.26, respectively), but only the direct method agreed with physiologic expectations based on animal and human studies. In separating cirrhotic and control patients, the area under the receiver operating characteristic curve was significantly greater for the direct method (0.91 vs 0.78; P = .03).

CONCLUSION

Both direct and indirect methods are feasible and distinguish well between cirrhotic and control patients, but the direct method is more physiologic and is preferable if portal venous data are available.