Perfusion computed tomographic assessment of early hepatocellular carcinoma in cirrhotic liver disease: initial observations

Baseline parenchymal blood volume is a potential prognostic imaging biomarker in patients with malignant liver tumors treated with transarterial chemoembolization

PURPOSE

To assess the prognostic value of Parenchymal Blood Volume (PBV) in predicting survival, tumor response, and PBV response after transarterial chemoembolization (TACE).

METHODS

A total of 137 patients with malignant liver tumors who were treated with TACE between 07/2016 and 07/2018 were evaluated. Computed tomography illustrations were reworked at a dedicated workstation to create a PBV map which was overlapped with the associated magnetic resonance image to determine tumor diameter and PBV. Patients were divided into two groups according to their initial PBV value: PBV < 50 or ≥ 50 ml/l.

RESULTS

Retrospectively, for patients with at least 2 TACE and initial PBV < 50 ml/l (n = 27), the tumor volume, regardless of the primary tumor type, decreased by 13.26%, and PBV showed a decrease of 23.11%. For 84 patients with PBV ≥ 50 ml/l, the tumor volume decreased by 24.01%, and PBV showed a more substantial decrease of 44.69% (both p < 0.001). In the overall study population (n = 137), patients with an initial PBV ≥ 50 ml/l (n = 101) survived for an average of 15.05 months, while patients with an initial PBV < 50 ml/l (n = 36) survived for 10.01 months (p < 0.002). Subgroup analysis indicated that median survival in the HCC group was longer at PBV ≥ 50 ml/l. For CRC and other primary tumors, the survival time for high and low initial PBV was almost identical.

CONCLUSION

Our study reveals a noteworthy correlation between high initial PBV values and a significant reduction in both relative and absolute tumor volume. This association suggests a potential prognostic indicator, indicating that elevated PBV may signify a more favorable response to transarterial chemoembolization (TACE). Additionally, patients with high initial PBV values experienced an extended overall survival time. Notably, the subgroup analysis highlighted a prolonged survival time in the HCC group with elevated initial PBV values. These findings underscore the potential significance of assessing PBV as a predictive factor in the context of TACE, especially in specific tumor entities such as HCC. Further investigations are essential to validate and extrapolate these observations to optimize patient outcomes.

Role of Computed Tomography Perfusion in Patients with Liver Cirrhosis and Hepatocellular Carcinoma

Background

There is a lack of data on computed tomography (CT) perfusion parameters in patients with cirrhosis and the vascular changes that occur with increasing severity of cirrhosis, as well as changes that can occur in the remote/background liver parenchyma when hepatocellular carcinoma (HCC) develops. This study aimed to evaluate the association between CT perfusion parameters in the background liver parenchyma in cirrhotic patients with and without HCC.

Methods

This prospective study comprised consecutive patients with cirrhosis with or without HCC. A CT perfusion scan of the whole liver was done on a 128-detector row CT scanner in the four-dimensional spiral mode. Arterial liver perfusion (ALP), portal venous perfusion (PVP), hepatic perfusion index (HPI), blood flow (BF), blood volume (BV), and time to peak (TTP) were assessed. The perfusion parameters of the background liver parenchyma (bALP, bPVP, bHPI, bBF, bBV, and bTTP) were compared between the patients with cirrhosis (group I) and cirrhosis with HCC (group II). Perfusion parameters were also compared between the background liver parenchyma and the HCC in group II.

Results

Of the 93 patients evaluated during the study period, 60 patients (30 in group I and 30 in group II, mean age, 54.5 years, 53 men) were included in the analysis. Among the perfusion parameters in the background parenchyma, bPVP was lower and bHPI was higher in group II, suggesting increased hepatic arterial perfusion of even the remote background liver parenchyma in patients with HCC (P = 0.001 and P = 0.01, respectively). Perfusion parameters were significantly altered with increasing severity of cirrhosis (based on Child-Pugh class) both within and between groups. Additionally, there were significant differences in all the perfusion parameters between HCC and the background cirrhotic liver.

Conclusion

HPI and PVP of background liver parenchyma were significantly different in cirrhosis with and without HCC and also showed a worsening trend with increasing grades of cirrhosis.

Response Assessment of Primary Liver Tumors to Novel Therapies: an Imaging Perspective

The latest developments in cancer immunotherapy, namely the introduction of immune checkpoint inhibitors, have led to a fundamental change in advanced cancer treatments. Imaging is crucial to identify tumor response accurately and delineate prognosis in immunotherapy-treated patients. Simultaneously, advances in image acquisition techniques, notably functional and molecular imaging, have facilitated more accurate pretreatment evaluation, assessment of response to therapy, and monitoring for tumor recurrence. Traditional approaches to assessing tumor progression, such as RECIST, rely on changes in tumor size, while new strategies for evaluating tumor response to therapy, such as the mRECIST and the EASL, rely on tumor enhancement. Moreover, the assessment of tumor volume, enhancement, cellularity, and perfusion are some novel techniques that have been investigated. Validation of these novel approaches should rely on comparing their results with those of standard evaluation methods (EASL, mRECIST) while considering the ultimate outcome, which is patient survival. More recently, immunotherapy has been used in the management of primary liver tumors. However, little is known about its efficacy. This article reviews imaging modalities and techniques for assessing tumor response and survival in immunotherapy-treated patients with primary hepatic malignancies.

Evaluation of dual-energy and perfusion CT parameters for diagnosing solitary pulmonary nodules

Background

To evaluate the correlation and accuracy of dual‐energy CT (DECT) (70/Sn150) and low‐dose volume perfusion CT (VPCT) parameters for the diagnosis of solitary pulmonary nodules (SPN).

Methods

A total of 15 patients with benign SPN (mean age 56 ± 7 years) and 34 patients with malignant SPN and clinical indication for surgery (mean age 58 ± 6 years) were enrolled from July 2017 to September 2019 at a single institution. All the patients underwent low‐dose VPCT with a scan volume of 114 mm on the z‐axis and a venous phase enhancement DECT (70/150 Sn) scan just before surgery on the same day. All CT findings were studied in comparison with the pathological results after surgery. Perfusion and dual‐energy CT parameters such as blood flow (BF), blood volume (BV), mean transit time (MTT), flow extraction product (FED), pulmonary nodule enhancement peak (PPnod) and iodine concentration (IC) were evaluated as well as t‐test, chi‐square test, Pearson correlation analysis, and ROC curve analysis to determine the significance of study parameters.

Results

The effective radiation dosage of the VPCT and DECT scans were 4.67 ± 0.26 mSv and 0.32 ± 0.10 mSv, respectively. Significant correlations were found between iodine concentration from DECT and VPCT parameters (r = 0.376–0.533, p < 0.05). The sensitivity and specificity of IC to differentiate the SPN were 86.67% and 72.73%, which was slightly lower than that of BV (94.44%, 73.33%), FED (88.89%, 80.00%) and PPnod (94.44%, 80.00%).

Conclusions

VPCT scans have low radiation dosage achieved by shortening the z‐axis scan range for assessment of SPN. IC from DECT is significantly correlated with VPCT parameters, and VPCT parameters have better diagnostic performance for SPN than DECT parameters.

Dynamic Computed Tomography Perfusion Imaging: Complementary Diagnostic Tool in Hepatocellular Carcinoma Assessment From Diagnosis to Treatment Follow-up

Early diagnosis of HCC is of paramount importance in order to enable the application of curative treatments. Among these, radiofrequency ablation (RFA) is actually considered the most effective ablative therapy for early stage hepatocellular carcinoma (HCC) not suitable for surgery. On the other hand, transarterial chemoembolization (TACE) represents the standard of care for intermediate stage HCC and compensated liver function. Finally, sorafenib, an oral antiangiogenic targeted drug, is the only approved systemic therapy for advanced HCC with vascular invasion, extrahepatic spread, and well-preserved liver function. Beside traditional radiological techniques, new functional imaging tools have been introduced in order to provide not only morphological information but also quantitative functional data. In this review, we analyze perfusion-CT (pCT) from a technical point of view, describing the main different mathematical analytical models for the quantification of tissue perfusion from acquired CT raw data, the most commonly acquired perfusion parameters, and the technical parameters required to perform a standard pCT examination. Moreover, a systematic review of the literature was performed to assess the role of pCT as an emerging imaging biomarker for HCC diagnosis, response evaluation to RFA, TACE, and sorafenib, and we examine its challenges in HCC management.

Perfusion-CT analysis for assessment of hepatocellular carcinoma lesions: diagnostic value of different perfusion maps

BACKGROUND

Computed tomography liver perfusion (CTLP) has been improved in recent years, offering a variety of perfusion-parametric maps. A map that better discriminates hepatocellular carcinoma (HCC) is still to be found.

PURPOSE

To compare different CTLP maps, regarding their ability to differentiate cirrhotic or non-cirrhotic parenchyma from malignant HCC.

MATERIAL AND METHODS

Twenty-six patients (11 cirrhotic) with 50 diagnosed HCC lesions, underwent CTLP on a 128-row dual-energy CT system. Nine different maps were generated. Regions of interest (ROIs) were positioned on non-tumorous parenchyma and on HCCs found on previous magnetic resonance imaging. Perfusion parameters for non-cirrhotic and cirrhotic livers were compared. Receiver operating characteristic (ROC) analysis was employed to evaluate each map's ability to discriminate HCCs from non-tumorous livers. Comparison of ROC curves was performed to evaluate statistical significance of differences in the discriminating efficiency of derived perfusion maps.

RESULTS

Perfusion parameters for non-tumorous liver and HCCs recorded in cirrhotic patients did not significantly differ from corresponding values recorded in non-cirrhotic patients ( P > 0.05). The highest power for HCC discrimination was found for the maximum-slope-of-increase (MSI) parametric map, with estimated the area under ROC curve of 0.997. An MSI cut-off criterion of 2.2 HU/s was found to provide 96% sensitivity and 100% specificity. Time to peak, blood flow, and transit time to peak were also found to have high discriminating power.

CONCLUSION

Among available CTLP-derived perfusion parameters, MSI was found to provide the highest diagnostic accuracy in discriminating HCCs from non-tumorous parenchyma. Perfusion parameters for non-tumorous livers and HCCs were not found to significantly differ between cirrhotic and non-cirrhotic patients.

Evaluation of liver lesions by use of shear wave elastography and computed tomography perfusion imaging after radiofrequency ablation in clinically normal dogs

OBJECTIVE To evaluate acute changes of the liver by use of shear wave elastography (SWE) and CT perfusion after radiofrequency ablation (RFA). ANIMALS 7 healthy Beagles. PROCEDURES RFA was performed on the liver (day 0). Stiffness of the ablation lesion, transitional zone, and normal parenchyma were evaluated by use of SWE, and blood flow, blood volume, and arterial liver perfusion of those regions were evaluated by use of CT perfusion on days 0 and 4. All RFA lesions were histologically examined on day 4. RESULTS Examination of the SWE color-coded map distinctly revealed stiffness of the liver tissue, which increased from the normal parenchyma to the transitional zone and then to the ablation zone. For CT perfusion, blood flow, blood volume, and arterial liver perfusion decreased from the transitional zone to the normal parenchyma and then to the ablation zone. Tissue stiffness and CT perfusion variables did not differ significantly between days 0 and 4. Histologic examination revealed central diffuse necrosis and peripheral hyperemia with infiltration of lymphoid cells and macrophages. CONCLUSIONS AND CLINICAL RELEVANCE Coagulation necrosis induced a loss of blood perfusion and caused tissue hardening (stiffness) in the ablation zone. Hyperemic and inflammatory changes of the transitional zone resulted in increased blood perfusion. Acute changes in stiffness and perfusion of liver tissue after RFA could be determined by use of SWE and CT perfusion. These results can be used to predict the clinical efficacy of RFA and to support further studies, including those involving hepatic neoplasia.

Correlation between acoustic radiation force impulse (ARFI)-based tissue elasticity measurements and perfusion parameters acquired by perfusion CT in cirrhotic livers: a proof of principle

PURPOSE

To investigate whether liver stiffness measured by acoustic radiation force impulse (ARFI) sonoelastography always correlates with the liver perfusion parameters quantified by perfusion CT in patients with known liver cirrhosis.

METHODS

Sonoelastography and perfusion CT were performed in 50 patients (mean age 65.5; range 45-87 years) with liver cirrhosis, who were classified according to Child-Pugh into class A (30/50, 60%), B (17/50, 34%), and C (3/50, 6%). For standardized ARFI measurements in the left liver lobe at a depth of 4 cm, a convex 6-MHz probe was used. CT examinations were performed using 80 kV, 100 mAs, and 50 ml of iodinated contrast agent injected at 5 ml/s. Using standardized region-of-interest measurements, we quantified arterial, portal venous, and total liver perfusion.

RESULTS

There was a significant linear correlation between tissue stiffness and arterial liver perfusion (p = 0.015), and also when limiting the analysis to patients with histology (p = 0.019). In addition, there was a positive correlation between the total blood supply (arterial + portal-venous liver perfusion) to the liver and tissue stiffness (p = 0.001; with histology, p = 0.027). Shear wave velocity increased with higher Child-Pugh stages (p = 0.013).

CONCLUSION

The degree of tissue stiffness in cirrhotic livers correlates expectedly-even if only moderately-with the magnitude of arterial liver perfusion and total liver perfusion. As such, liver elastography remains the leading imaging tool in assessing liver fibrosis.

Noninvasive imaging of hepatocellular carcinoma: From diagnosis to prognosis

Hepatocellular carcinoma (HCC) is the most common primary liver cancer and a major public health problem worldwide. Hepatocarcinogenesis is a complex multistep process at molecular, cellular, and histologic levels with key alterations that can be revealed by noninvasive imaging modalities. Therefore, imaging techniques play pivotal roles in the detection, characterization, staging, surveillance, and prognosis evaluation of HCC. Currently, ultrasound is the first-line imaging modality for screening and surveillance purposes. While based on conclusive enhancement patterns comprising arterial phase hyperenhancement and portal venous and/or delayed phase wash-out, contrast enhanced dynamic computed tomography and magnetic resonance imaging (MRI) are the diagnostic tools for HCC without requirements for histopathologic confirmation. Functional MRI techniques, including diffusion-weighted imaging, MRI with hepatobiliary contrast agents, perfusion imaging, and magnetic resonance elastography, show promise in providing further important information regarding tumor biological behaviors. In addition, evaluation of tumor imaging characteristics, including nodule size, margin, number, vascular invasion, and growth patterns, allows preoperative prediction of tumor microvascular invasion and patient prognosis. Therefore, the aim of this article is to review the current state-of-the-art and recent advances in the comprehensive noninvasive imaging evaluation of HCC. We also provide the basic key concepts of HCC development and an overview of the current practice guidelines.

Functional imaging in liver tumours

Functional imaging encompasses techniques capable of assessing physiological parameters of tissues, and offers useful clinical information in addition to that obtained from morphological imaging. Such techniques may include magnetic resonance imaging with diffusion-weighted sequences or hepatobiliary contrast agents, perfusion imaging, or molecular imaging with radiolabelled tracers. The liver is of major importance in oncological practice; not only is hepatocellular carcinoma one of the malignancies with steadily rising incidence worldwide, but hepatic metastases are regularly observed with a range of solid neoplasms. Within the realm of hepatic oncology, different functional imaging modalities may occupy pivotal roles in lesion characterisation, treatment selection and follow-up, depending on tumour size and type. In this review, we characterise the major forms of functional imaging, discuss their current application to the management of patients with common primary and secondary liver tumours, and anticipate future developments within this field.

Iodine concentration as a perfusion surrogate marker in oncology: Further elucidation of the underlying mechanisms using Volume Perfusion CT with 80 kVp

OBJECTIVES

To assess the value of iodine concentration (IC) in computed tomography data acquired with 80 kVp, as a surrogate for perfusion imaging in hepatocellular carcinoma (HCC) and lymphoma by comparing iodine related attenuation (IRA) with quantitative Volume Perfusion CT (VPCT)-parameters.

METHODS

VPCT-parameters were compared with intra-tumoral IC at 5 time points after the aortic peak enhancement (APE) with a temporal resolution of 3.5 sec in untreated 30 HCC and 30 lymphoma patients.

RESULTS

Intra-tumoral perfusion parameters for HCC showed a blood flow (BF) of 52.7 ± 17.0 mL/100 mL/min, blood volume (BV) 12.6 ± 4.3 mL/100 mL, arterial liver perfusion (ALP) 44.4 ± 12.8 mL/100 mL/min. Lesion IC 7 sec after APE was 133.4 ± 57.3 mg/100 mL. Lymphoma showed a BF of 36.8 ± 13.4 mL/100 mL/min, BV of 8.8 ± 2.8 mL/100 mL and IC of 118.2 ± 64.5 mg/100 mL 3.5 sec after APE. Strongest correlations exist for VPCT-derived BF and ALP with IC in HCC 7 sec after APE (r = 0.71 and r = 0.84) and 3.5 sec after APE in lymphoma lesions (r = 0.77). Significant correlations are also present for BV (r = 0.60 and r = 0.65 for HCC and lymphoma, respectively).

CONCLUSIONS

We identified a good, time-dependent agreement between VPCT-derived flow values and IC in HCC and lymphoma. Thus, CT-derived ICs 7 sec after APE in HCC and 3.5 sec in lymphoma may be used as surrogate imaging biomarkers for tumor perfusion with 80 kVp.

KEY POINTS

• Iodine concentration derived from low kVp CT is regarded as perfusion surrogate • Correlation with Perfusion CT was performed to elucidate timing and histology dependencies • Highest correlation was present 7 sec after aortic peak enhancement in hepatocellular carcinoma • In lymphoma, highest correlation was calculated 3.5 sec after aortic peak enhancement • With these results, further optimization of Dual energy CT protocols is possible.

Characterization of hepatocellular carcinoma (HCC) lesions using a novel CT-based volume perfusion (VPCT) technique

OBJECTIVE

To characterize hepatocellular carcinoma (HCC) in terms of perfusion parameters using volume perfusion CT (VPCT) and two different calculation methods, compare their results, look for interobserver agreement of measurements and correlation between tumor arterialization and lesion size.

MATERIAL AND METHODS

This study was part of a prospective monitoring study in patients with HCC undergoing TACE, which was approved by the local Institutional Review Board. 79 HCC-patients (mean age, 64.7) with liver cirrhosis were enrolled. VPCT was performed for 40s covering the involved liver (80 kV, 100/120 mAs) using 64 mm × 0.6 mm collimation, 26 consecutive volume measurements, 50 mL iodinated contrast IV and 5 mL/s flow rate. Mean/maximum blood flow (BF; ml/100mL/min), blood volume (BV) and k-trans were determined both with the maximum slope+Patlak vs. deconvolution method. Additionally, the portal venous liver perfusion (PVP), the arterial liver perfusion (ALP) and the hepatic perfusion index (HPI) were determined for each tumor including size measurements. Interobserver agreement for all perfusion parameters was calculated using intraclass correlation coefficients (ICC).

RESULTS

The max. slope+Patlak method yielded: BFmean/max=37.8/57 mL/100g-tissue/', BVmean/max=9.8/11.1 mL/100g-tissue, k-trans-mean/max=34.4/44.5 mL/100g-tissue/'. For the deconvolution method BFmean/max, BVmean/max and, k-trans-mean/max were 68.3/106.1 mL/100g-tissue/', 12.6/15.5 mL/100g-tissue and 24/33.8 mL/100g-tissue/'. Mean ALP, PVP, HPI and size were 53.7 mL/100g-tissue/', 2.4 mL/100g-tissue/', 96.4 and 3.5 cm, respectively. Interobserver agreement measured with intraclass coefficient correlation (ICC) was very good for all perfusion parameters (≥ 0.99). Best correlation between calculation methods was achieved for measurements of BF, while BV and k-trans values were less correlated. There was no relationship between HPI and lesion size.

CONCLUSION

VPCT can measure tumor volume perfusion non-invasively and enables quantification of the degree of HCC arterialization. Results are dependent on the technique used with best inter-method correlation for BF. Tumor HPI did not proved size-dependent.

Hepatocellular carcinoma: diagnostic criteria by imaging techniques

Imaging plays a very important role in the diagnosis of HCC. Indeed, in high-risk patients a noninvasive diagnosis can only be obtained by imaging in presence of typical features. These features include arterial enhancement followed by washout during the portal venous and/or delayed phases on CT scan or MRI. This pattern is quite specific and has been endorsed by both Western and Asian diagnostic guidelines. However, its sensitivity is not very high, especially for small lesions. Therefore ancillary signs may be needed to increase the reliability of the diagnosis. Recent hepatobiliary MRI contrast agents seem to be interesting to improve characterization of small nodules in the cirrhotic liver.

DCE-MRI in hepatocellular carcinoma-clinical and therapeutic image biomarker

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) enables tumor vascular physiology to be assessed. Within the tumor tissue, contrast agents (gadolinium chelates) extravasate from intravascular into the extravascular extracellular space (EES), which results in a signal increase on T1-weighted MRI. The rate of contrast agents extravasation to EES in the tumor tissue is determined by vessel leakiness and blood flow. Thus, the signal measured on DCE-MRI represents a combination of permeability and perfusion. The semi-quantitative analysis is based on the calculation of heuristic parameters that can be extracted from signal intensity-time curves. These enhancing curves can also be deconvoluted by mathematical modeling to extract quantitative parameters that may reflect tumor perfusion, vascular volume, vessel permeability and angiogenesis. Because hepatocellular carcinoma (HCC) is a hypervascular tumor, many emerging therapies focused on the inhibition of angiogenesis. DCE-MRI combined with a pharmacokinetic model allows us to produce highly reproducible and reliable parametric maps of quantitative parameters in HCC. Successful therapies change quantitative parameters of DCE-MRI, which may be used as early indicators of tumor response to anti-angiogenesis agents that modulate tumor vasculature. In the setting of clinical trials, DCE-MRI may provide relevant clinical information on the pharmacodynamic and biologic effects of novel drugs, monitor treatment response and predict survival outcome in HCC patients.

Hepatocellular carcinoma: perfusion quantification with dynamic contrast-enhanced MRI

OBJECTIVE

The objective of our study was to report our initial experience with dynamic contrast-enhanced MRI (DCE-MRI) for perfusion quantification of hepatocellular carcinoma (HCC) and surrounding liver.

SUBJECTS AND METHODS

DCE-MRI of the liver was prospectively performed on 31 patients with HCC (male-female ratio, 26:5; mean age, 61 years; age range, 41-83 years). A dynamic coronal 3D FLASH sequence was performed at 1.5 T before and after injection of gadolinium-based contrast agent with an average temporal resolution of 3.8 seconds. Regions of interest were drawn on the abdominal aorta, portal vein, liver parenchyma, and HCC lesions by two observers in consensus. Time-activity curves were analyzed using a dual-input single-compartment model. The following perfusion parameters were obtained: arterial flow, portal venous flow, arterial fraction, distribution volume, and mean transit time (MTT).

RESULTS

Thirty-three HCCs (mean size, 3.9 cm; range, 1.1-12.6 cm) were evaluated in 26 patients. When compared with liver parenchyma, HCC showed significantly higher arterial hepatic blood flow and arterial fraction (p < 0.0001) and significantly lower distribution volume and portal venous hepatic blood flow (p < 0.0001-0.023), with no difference in MTT. Untreated HCCs (n = 16) had a higher arterial fraction and lower portal venous hepatic blood flow value than chemoembolized HCCs (n = 17, p < 0.04).

CONCLUSION

DCE-MRI can be used to quantify perfusion metrics of HCC and liver parenchyma and to assess perfusion changes after HCC chemoembolization.

Assessment of blood flow in hepatocellular carcinoma: correlations of computed tomography perfusion imaging and circulating angiogenic factors

Hepatocellular carcinoma (HCC) is a highly vascular tumor through the process of angiogenesis. To evaluate more non-invasive techniques for assessment of blood flow (BF) in HCC, this study examined the relationships between BF of HCC measured by computer tomography (CT) perfusion imaging and four circulating angiogenic factors in HCC patients. Interleukin 6 (IL-6), interleukin 8 (IL-8), vascular endothelial growth factor (VEGF), and platelet derived growth factor (PDGF) in plasma were measured using Bio-Plex multiplex immunoassay in 21 HCC patients and eight healthy controls. Circulating IL-6, IL-8 and VEGF showed higher concentrations in HCC patients than in controls (p < 0.05), and predicted HCC occurrence better than chance (p < 0.01). Twenty-one patients with HCC received 21-phase liver imaging using a 64-slice CT. Total BF, arterial BF, portal BF, arterial fraction (arterial BF/total BF) of the HCC and surrounding liver parenchyma, and HCC-parenchyma ratio were measured using a dual-vessel model. After analyzing the correlations between BF in HCC and four circulating angiogenic factors, we found that the HCC-parenchyma ratio of arterial BF showed a significantly positive correlation with the level of circulating IL-8 (p < 0.05). This circulating biomarker, IL-8, provides a non-invasive tool for assessment of BF in HCC.

Viable residual tumor tissue after radiofrequency ablation treatment in hepatocellular carcinoma: evaluation with CT perfusion

PURPOSE

To assess the role of CT perfusion technique in detection of blood flow changes related to the therapeutic effects in HCC lesion treated with RFA.

METHODS

14 cirrhotic patients with known HCC underwent a perfusion study about 4 months (range 1-13 months) after RFA on a 16-slice MDCT scanner (Brilliance, Philips). Dynamic CT was performed acquiring 8 dynamic slice/scan, after injection of 50 mL of contrast media. In treated lesion, surrounding parenchyma and hypervascular tissue suspicious for residual disease/recurrence, the following perfusion parameters were analyzed: perfusion (P, mL/100 g min); arterial perfusion (AP, mL/min); blood volume (BV, mL/100 mg); hepatic perfusion index (HPI, %), and time to peak (TTP, s). Univariate Wilcoxon signed rank test was used for statistical analysis.

RESULTS

In patients with residual disease (8/14) values of perfusion parameters measured within tumor were: P, median = 45.2; AP, median = 48.2; BV, median = 18.9; HPI, median = 35.8; and TTP, median = 19.4. The values calculated in ablated area were: P, median = 10.9; AP, median = 9.6; BV, median = 5.5; HPI, median = 14.6; TTP, median = 39.6. The parameters calculated in the surrounding parenchyma were: P, median = 15.8; AP, median = 14.2; BV, median = 12.0; HPI, median = 17.9; TTP, median = 43.2. A significant difference (P < 0.05) was observed in mean values of P, AP, and HPI, calculated between treated lesions with residual tumor and those successfully treated.

CONCLUSION

Perfusion CT enables assessment of HCC vascularity after RFA treatment, by adding quantitative information about the presence of residual arterial vessels within the viable residual neoplastic tissue.

Functional imaging of the liver

Anatomical-based imaging is used widely for the evaluation of diffuse and focal liver, including detection, characterization, and therapy response assessment. However, a limitation of anatomical-based imaging is that structural changes may occur relatively late in a disease process. By applying conventional anatomical-imaging methods in a more functional manner, specific pathophysiologic alterations of the liver may be assessed and quantified. There has been an increasing interest in both the clinical and research settings, with the expectation that functional-imaging techniques may help solve common diagnostic dilemmas that conventional imaging alone cannot. This review considers the most common functional magnetic resonance imaging, computed tomography, and ultrasound imaging techniques that may be applied to the liver.

Functional imaging techniques in hepatocellular carcinoma

Novel biological therapies, including tyrosine kinase inhibitors such as sorafenib, improve the survival of patients with unresectable hepatocellular carcinoma. However, assessment of therapeutic efficacy remains challenging with conventional imaging techniques such as ultrasonography, CT or MRI that predominantly rely on size change to detect a treatment response. A beneficial tumour effect may go unrecognized in some patients who do not show tumour shrinkage and conversely, some patients may be maintained on treatment that is not active. This paper explores the use of functional imaging methods that are showing promise in the assessment of hepatocellular carcinoma.

FDG PET/CT early dynamic blood flow and late standardized uptake value determination in hepatocellular carcinoma

PURPOSE

To prospectively determine whether fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) early dynamic blood flow estimates could be used to discriminate hepatocellular carcinoma (HCC) from background liver and to characterize HCC in patients with and those without angioinvasion; and to evaluate the association between blood flow measures at FDG PET/CT with metabolism in HCCs.

MATERIALS AND METHODS

Institutional review board approval and written informed consent were obtained for this prospective study. Twenty-one consecutive patients (mean age, 65 years) with 30 established HCCs (mean size, 5.5 cm; seven lesions in five patients with angioinvasion) underwent a blood flow study with an FDG dynamic scan divided into 18 sequences of 5 seconds each and a standard PET/CT scan. On the dynamic study, three independent operators obtained volumes of interest (VOIs) for which three blood flow estimates were calculated (hepatic perfusion index [HPI], time to peak [TTP], and peak intensity [PI]). On the late study, a VOI was placed on the fused scan for each HCC, and maximum standardized uptake value (SUV(max)) was obtained. By using a mixed-effects model analysis, comparison of blood flow estimates between HCC with and that without angioinvasion and background liver was performed. The association between blood flow estimates and SUV(max) was also assessed.

RESULTS

HPI and TTP showed better performance than did SUV(max) for discriminating HCC and background liver (areas under receiver operating characteristic curve: 0.96, 0.95, and 0.83, respectively; P < .05). HPI was higher in HCC in patients with angioinvasion (0.91 ± 0.15 [standard deviation]) than in those without angioinvasion (0.80 ± 0.18; P = .03). There was no difference in SUV(max) between HCC in patients with and those without angioinvasion (7.8 ± 2.9 vs 6.3 ± 3.4; P = .85). No clear association was found between HPI, PI, or TTP and SUV(max) (P = .49, .77, and .91, respectively).

CONCLUSION

Early dynamic blood flow FDG PET/CT may be used to help discriminate and characterize HCC tumors.

MR-based visualization and quantification of three-dimensional flow characteristics in the portal venous system

PURPOSE

To evaluate the feasibility of time-resolved flow-sensitive MRI for the three-dimensional (3D) visualization and quantification of normal and pathological portal venous (PV) hemodynamics.

MATERIALS AND METHODS

Portal venous hemodynamics were evaluated in 18 healthy volunteers and 5 patients with liver cirrhosis. ECG- and adaptive respiratory navigator gated flow-sensitive 4D MRI (time-resolved 3D MRI with three-directional velocity encoding) was performed on a 3 Tesla MR system (TRIO, Siemens, Germany). Qualitative flow analysis was achieved using 3D streamlines and time-resolved particle traces originating from seven emitter planes precisely placed at anatomical landmarks in the PV system. Quantitative analysis included retrospective extraction of regional peak and mean velocities and vessel area. Results were compared with standard 2D flow-sensitive MRI and to the reference standard Doppler ultrasound.

RESULTS

Qualitative flow analysis was successfully used in the entire PV system. Venous hemodynamics in all major branches in 17 of 18 volunteers and 3 of 5 patients were reliably depicted with good interobserver agreement (kappa = 0.62). Quantitative analysis revealed no significant differences and moderate agreement for peak velocities between 3D MR and 2D MRI (r = 0.46) and Doppler ultrasound (US) (r = 0.35) and for mean velocities between 3D and 2D MRI (r = 0.41). The PV area was significantly (P < 0.01) higher in 3D and 2D MRI compared with US.

CONCLUSION

We successfully applied 3D MR velocity mapping in the PV system, providing a detailed qualitative and quantitative analysis of normal and pathological hemodynamics.