Liver perfusion studied with ultrafast CT

Perfusão por tomografia computadorizada do abdome: aplicações clínicas, princípios e técnica do exame

Novas técnicas de exames têm sido desenvolvidas com o objetivo de se obter não apenas uma avaliação estrutural, mas também uma análise funcional e metabólica de diversos órgãos e tipos de lesões. Entre estas ferramentas, a perfusão por tomografia computadorizada (PTC) tem despertado o interesse de muitos pesquisadores em estudar a sua aplicabilidade em órgãos e doenças abdominais. Entre estas aplicações podemos citar a avaliação do comportamento biológico de tecidos sadios e doentes, a diferenciação de processos inflamatórios de tumorais e o diagnóstico da recidiva tumoral após terapêuticas minimamente invasivas. A principal característica da PTC reside na sua capacidade de caracterizar comportamentos perfusionais distintos e que traduzem alterações biológicas de determinadas lesões e tecidos doentes. Dessa forma, o nosso objetivo foi realizar uma ampla revisão da literatura, mostrando as principais técnicas e protocolos utilizados nos exames de PTC, as principais indicações, vantagens e desvantagens do método, além de propor um protocolo de exame que possa ser introduzido na rede privada e pública de saúde, com reprodutibilidade e simplicidade de implementação.

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.

Hepatic perfusion imaging: concepts and application

Hepatic perfusion imaging with magnetic resonance (MR) imaging is an emerging technique for quantitative assessment of diffuse hepatic disease and hepatic lesion blood flow. The principal method that has been used is based on T1 dynamic contrast-enhanced MR imaging. Perfusion imaging shows promise in the assessment of tumor therapy response, staging of liver fibrosis, and evaluation of hepatocellular carcinoma. The future standardization of imaging protocols and MR imaging pulse sequences will allow for broader clinical applications.

Protocol modifications for CT perfusion (CTp) examinations of abdomen-pelvic tumors: impact on radiation dose and data processing time

PURPOSE

To evaluate the effect of CT perfusion (CTp) protocol modifications on quantitative perfusion parameters, radiation dose and data processing time.

MATERIALS & METHODS

CTp datasets of 30 patients (21M:9F) with rectal (n = 24) or retroperitoneal (n = 6) tumours were studied. Standard CTp protocol included 50 sec cine-phase (0.5 sec/rotation) and delayed-phase after 70 ml contrast bolus at 5-7 ml/sec. CTp-data was sub-sampled to generate modified datasets (n = 105) with cine-phase(n = 15) alone, varying cine-phase duration (20-40 sec, n = 45) and varying temporal sampling-interval (1-3 sec, n = 45). The estimated CTp parameters (BF,BV,MTT&PS) and radiation dose of standard CTp served as reference for comparison.

RESULTS

CTp with 50 sec cine-phase showed moderate to high correlation with standard CTp for BF&MTT (r = 0.96&0.85) and low correlation for BV (0.75, p = 0.04). Limiting cine-phase duration to 30 sec demonstrated comparable results for BF&MTT, while considerable variation in CTp values existed at 20 sec. There was moderate-to-high correlation of CTp parameters with sampling interval of 1&2 sec (r = 0.83-0.97, p > 0.05), while at 3 sec only BF showed high correlation (r = 0.96, p = 0.05). Increasing sampling interval (47-60%) and reducing cine-phase duration substantially reduced dose(30.8-65%) which paralleled reduced data processing time (3-10 min).

CONCLUSION

Limiting CTp cine-phase to 30 sec results in comparable BF&MTT values and increasing cine-phase sampling interval to 2 sec provides good correlation for all CTp parameters with substantial dose reduction and improved computational efficiency.

Quantitative 4D transcatheter intraarterial perfusion MRI for monitoring chemoembolization of hepatocellular carcinoma

PURPOSE

To develop a fully quantitative 4D transcatheter intraarterial perfusion (TRIP) magnetic resonance imaging (MRI) technique and prospectively test the hypothesis that quantitative 4D TRIP-MRI can be used clinically to monitor intraprocedural liver tumor perfusion reductions during transcatheter arterial chemoembolization (TACE).

MATERIALS AND METHODS

TACE was performed within an x-ray digital subtraction angiography (DSA)-MRI procedure suite in 16 patients with hepatocellular carcinoma. Quantitative 4D TRIP-MRI with targeted radiofrequency field mapping and dynamic longitudinal relaxation rate mapping was used to monitor changes in tumor perfusion during TACE. First-pass perfusion analysis was performed to produce intraprocedural blood flow (Frho) maps. Mean liver tumor perfusions before and after TACE were compared with a paired t-test (alpha = 0.05).

RESULTS

Perfusion reductions were successfully measured with quantitative 4D TRIP-MRI in 22 separate tumors during 18 treatment sessions. Mean tumor perfusion Frho decreased from 16.3 (95% confidence interval [CI]: 10.7-21.9) before TACE to 5.0 (95% CI: 3.5-6.5) (mL/min/100 mL) after TACE. Tumor perfusion reductions were statistically significant (P < 0.0005), with a mean absolute perfusion change of 11.4 (95% CI: 5.6-17.1) (mL/min/100 mL) and a mean percentage reduction of 61.0% (95% CI: 48.3%-73.6%).

CONCLUSION

Quantitative 4D TRIP-MRI can be successfully performed within clinical interventional settings to monitor intraprocedural changes in liver tumor perfusion during TACE.

Liver fibrosis in chronic hepatitis C virus infection: differentiating minimal from intermediate fibrosis with perfusion CT

PURPOSE

To prospectively assess the utility of perfusion computed tomography (CT) for differentiating minimal from intermediate fibrosis in treatment-naïve patients with chronic hepatitis C virus (HCV) infection.

MATERIALS AND METHODS

This study was approved by the Institutional Review Board, and informed consent was obtained. Fifty-two patients with treatment-naïve HCV infection underwent perfusion CT and percutaneous liver biopsy on the same day. Portal vein, arterial, and total liver perfusion; mean transit time; and distribution volumes for the right and left liver lobes were measured. Liver samples were scored for fibrosis, and fibrosis area was determined. Differences in quantitative perfusion parameters between patients with minimal fibrosis (score of F1) and those with intermediate fibrosis (score of F2 or F3) were tested.

RESULTS

In patients with intermediate fibrosis (F2 and F3) compared with those with minimal fibrosis (F1), the portal venous perfusion (87 mL min(-1) 100 mL(-1) +/- 27 [standard deviation] vs 138 mL min(-1) 100 mL(-1) +/- 112, P = .042) and total liver perfusion (107 mL min(-1) 100 mL(-1) +/- 31 vs 169 mL min(-1) 100 mL(-1) +/- 137, P = .02) were significantly decreased, and the mean transit time was significantly increased (16 seconds +/- 4 vs 13 seconds +/- 5, P = .025). At multivariate analysis, only the mean transit time was an independent factor (odds ratio, 1.18; 95% confidence interval: 1.02, 1.37; P = .030). Receiver operating characteristic curve analysis showed that a mean transit time threshold of 13.4 seconds allowed discrimination between minimal and intermediate fibrosis with a sensitivity of 71% and a specificity of 65%.

CONCLUSION

The results of this study show that perfusion changes occur early during fibrosis in chronic HCV infection and can be detected with perfusion CT. Perfusion CT may help to discriminate minimal from intermediate fibrosis. Mean transit time appears to be the most promising perfusion parameter for differentiating between fibrosis stages, although the large amount of overlap in the measured parameters limits the clinical utility of this test at present.

Estimation of tissue perfusion by dynamic contrast-enhanced imaging: simulation-based evaluation of the steepest slope method

OBJECTIVE

Tissue perfusion is frequently determined from dynamic contrast-enhanced CT or MRI image series by means of the steepest slope method. It was thus the aim of this study to systematically evaluate the reliability of this analysis method on the basis of simulated tissue curves.

METHODS

9600 tissue curves were simulated for four noise levels, three sampling intervals and a wide range of physiological parameters using an axially distributed reference model and subsequently analysed by the steepest slope method.

RESULTS

Perfusion is systematically underestimated with errors becoming larger with increasing perfusion and decreasing intravascular volume. For curves sampled after rapid contrast injection with a temporal resolution of 0.72 s, the bias was less than 23% when the mean residence time of tracer molecules in the intravascular distribution space was greater than 6 s. Increasing the sampling interval and the noise level substantially reduces the accuracy and precision of estimates, respectively.

CONCLUSIONS

The steepest slope method allows absolute quantification of tissue perfusion in a computationally simple and numerically robust manner. The achievable degree of accuracy and precision is considered to be adequate for most clinical applications.

Perfusion magnetic resonance imaging of the liver

Perfusion magnetic resonance imaging (MRI) studies quantify the microcirculatory status of liver parenchyma and liver lesions, and can be used for the detection of liver metastases, assessing the effectiveness of anti-angiogenic therapy, evaluating tumor viability after anti-cancer therapy or ablation, and diagnosis of liver cirrhosis and its severity. In this review, we discuss the basic concepts of perfusion MRI using tracer kinetic modeling, the common kinetic models applied for analyses, the MR scanning techniques, methods of data processing, and evidence that supports its use from published clinical and research studies. Technical standardization and further studies will help to establish and validate perfusion MRI as a clinical imaging modality.

An Introduction to MR Perfusion Imaging of the Liver

This article introduces the basic principles of magnetic resonance (MR) perfusion imaging of liver and summarized the currently available literature. Perfusion magnetic resonance imaging (MRI) is a functional imaging technique that quantifies the microcirculatory status of liver parenchyma and liver lesions such as flow, permeability, fractional intravascular volume and fractional interstitial volume. It potentially allows one to (i) detect liver metastases, (ii) assess effectiveness of anti-angiogenic therapy, (iii) assess viable tumour after therapy or ablation, and (iv) diagnose cirrhosis and assess its severity. Further work is required to establish and validate perfusion MRI as a clinical modality.

New imaging techniques for non-alcoholic steatohepatitis

No imaging modality has yet been proven to reliably differentiate simple hepatic steatosis from steatohepatitis. This review focuses on the predominant non-nuclear imaging modalities available to clinicians at the present time. The key feature of the techniques outlined in this review that demonstrate the most interesting results have one thing in common: imaging is not performed in a passive manner but is undertaken as a method to investigate functional differences between simple hepatic steatosis and steatohepatitis based upon the current working model for pathogenesis and progression. The purpose of this article is to review the strengths and weakness of current clinical and experimental imaging modalities for noninvasive detection of NAFLD, with an emphasis on NASH.

Hepatic transit time analysis using contrast-enhanced ultrasound with BR1: A prospective study comparing patients with liver metastases from colorectal cancer with healthy volunteers

We prospectively compared hepatic transit time (HTT) measurements in subjects with liver metastases from colorectal cancer (group a) and healthy volunteers (group b) using contrast-enhanced ultrasound with BR1. The purpose of this study was to verify our hypothesis that the hemodynamic changes of the liver, which occur during metastasis seeding, would shorten the HTT, and we expect that such changes could be used for the detection of occult liver metastases from colorectal cancer in the future. The study had institutional review board approval and all subjects gave informed written consent. Group a and group b consisted of 22 subjects each. Baseline and post contrast images were acquired starting 10 s before and ending 40 s after administration of BR1, using nonlinear imaging at a frame rate of 5/s. The baseline images were used to determine the signal intensity without contrast enhancement as the reference signal. Arrival times (AT) of the contrast agent for the hepatic artery, the portal vein and one hepatic vein were determined using (i) quantitative analysis and (ii) subjective analysis by two blinded readers. HTT was calculated based on arrival time measurements. Quantitative and subjective analysis showed significantly shorter arterial to venous and portal to venous HTT in group a compared with group b (p < 0.001). Arterial to venous HTT (quantitative analysis) was < or = 9 s in 19 of 22 subjects of group a and >9 s in 18 of 22 subjects of group b (sensitivity 86%, specificity 82%, positive predictive value 83%, negative predictive value 86%, area under the curve [AUC] 0.87). Portal to venous HTT (quantitative analysis) was < 7 s in 21 of 22 subjects of group a and > 7s in 15 of 22 subjects of group b (sensitivity 95%, specificity 68%, PPV 75%, NPV 94%, AUC 0.85). There was an inverse relation with number of liver segments involved for arterial to venous and portal to venous HTT in group a (p < 0.05), but no correlation between HTT and overall volume of metastases (group a) or subject age (group b). From the results of our study, we conclude that HTT measurements using contrast-enhanced ultrasound with BR1 can detect hemodynamic changes caused by metastatic liver disease from colorectal cancer. However, comparison with the literature suggests that the use of other contrast agents might provide better results. Comparison of different contrast agents for the purpose of transit time analysis would therefore be useful before embarking on a prospective trial looking at the detection of occult liver metastases in patients with colorectal cancer. (E-mail: jhohmann@uhbs.ch).

Assessment of the hepatic microvascular changes in liver cirrhosis by perfusion computed tomography

AIM: To assess the hepatic microvascular parameters in patients with liver cirrhosis by perfusion computed tomography (CT).

METHODS: Perfusion CT was performed in 29 patients without liver disease (control subjects) and 39 patients with liver cirrhosis, including 22 patients with compensated cirrhosis and 17 patients with decompensated cirrhosis, proved by clinical and laboratory parameters. CT cine-scans were obtained over 50 s beginning with the injection of 50 mL of contrast agent. Hepatic microvascular parameters, mean transit time (MTT) and permeability surface area product (PS) were obtained with the Perfusion 3 software (General Electric, ADW 4.2).

RESULTS: The overall differences of MTT and PS between control subjects, patients with compensated cirrhosis and those with decompensated cirrhosis were statistically significant (P = 0.010 and P = 0.002, respectively). MTT values were 15.613 ± 4.1746 s, 12.592 ± 4.7518 s, and 11.721 ± 4.5681 s for the three groups, respectively, while PS were 18.945 ± 7.2347 mL/min per 100 mL, 22.767 ± 8.3936 mL/min per 100 mL, and 28.735 ± 13.0654 mL/min per 100 mL. MTT in decompensated cirrhotic patients were significantly decreased compared to controls (P = 0.017), whereas PS values were remarkably increased (P = 0.001).

CONCLUSION: The hepatic microvascular changes in patients with liver cirrhosis can be quantitatively assessed by perfusion CT. Hepatic microvascular parameters (MTT and PS), as measured by perfusion CT, were significantly altered in decompensated cirrhosis.

Body perfusion CT: technique, clinical applications, and advances

Perfusion CT has made tremendous progress since its inception and is gradually broadening its applications from the research realm into routine clinical care. This has been particularly noteworthy in the oncological setting, where perfusion CT is emerging as a valuable tool in tissue characterization, risk stratification and monitoring treatment effects especially assessing early response to novel targeted therapies. Recent technological advancements in CT have paved ways to overcome the initial limitations of restricted tissue coverage and radiation dose concerns. In this article, the authors review the basic principles and technique of perfusion CT and discuss its various oncologic and non-oncological clinical applications in body imaging.

Optimizing functional parameter accuracy for breath-hold DCE-MRI of liver tumours

Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) is a valuable tool for assessing treatment response to novel cancer therapeutics. With appropriate data acquisition, quantitative functional parameter estimates can be obtained by fitting a model to the data. This research focuses on applying a dual-input single-compartment pharmacokinetic model to breath-hold DCE-MRI imaging of the liver. In this paper, the use of two breath-holds, providing greater temporal information, is compared with a single breath-hold approach. Computer simulations are used to assess the accuracy, precision and sensitivity to input function errors obtained for parameters estimated from the two imaging protocols. Data from ten patients were analysed to assess the noise statistics obtained from the two breath-hold protocols. The noise statistics were used with a pharmacokinetic liver model to simulate data, from which the estimation accuracy, precision and sensitivity for the two protocols were assessed. Data from the ten patients were also analysed, and the estimates were compared with literature values. This work demonstrates the feasibility of obtaining functional liver perfusion estimates over a 3D volume using a sequential breath-hold protocol. The simulation results show that the protocol consisting of two images per breath-hold is to be preferred as it requires identical patient co-operation, but provides parameter estimates that have superior accuracy and precision.

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.

Evaluation of liver reserve function with multi-slice spiral CT perfusion imaging

AIM: To measure and assess the features of hepatic hemodynamics in patients with hepatocirrhosis using multi-slice spiral CT (MSCT), and to investigate the value in determining reserve function in liver cirrhosis with CT perfusion imaging.

METHODS: A total of 32 patients with varying liver cirrhosis and hepatocellular carcinoma were classified into three groups based on CT morphologic classification: 17 were classified as light liver cirrhosis group, 8 as moderate group and 7 as severe group. The parameters of CT perfusion including BF, BV, MTT, HAF, IRF To, PVP and A/V were analyzed by the CT perfusion 3 software package (GE) with deconvolution method, and the correlations of CT perfusion parameters, CT morphologic classification and Child-pugh's hepatic functional classification were analyzed.

RESULTS: There were significantly statistical difference and correlation of CT morphologic classification of hepatocirrhosis and BF, BV, IRF To, PVP, MTT, HAF, A/V ratio (r = -0.848, -0.801, -0.652, -0.864, 0.612, 0.822, 0.824, all P < 0.05), and the CT morphologic classification of hepatocirrhosis degree was positively correlated with Child-Pugh classification (r = 0.877, P = 0.001). Based on canonical discriminate function, 90.6% were correctly classified by hepatic perfusion parameters, while according to ROC curve, the CT perfusion parameters of BF, BV and PVP in judging Child-pugh's hepatic functional classification were 90.6%, 87.5% and 93.8%, respectively.

CONCLUSION: Hepatic perfusion imaging with MSCT should be valuable to evaluate the cirrhosis degree and hepatic functional reserve in patients with hepatocellular carcinoma.

Dynamic contrast-enhanced CT imaging of hepatocellular carcinoma in cirrhosis: feasibility of a prolonged dual-phase imaging protocol with tracer kinetics modeling

Dynamic contrast-enhanced (DCE) CT imaging of four patients with hepatocellular carcinoma (HCC) was performed using a dual-phase imaging protocol designed with initial rapid dynamic imaging to capture the initial increase in contrast medium enhancement in order to assess perfusion, followed by a delayed imaging phase with progressively longer intervals to monitor subsequent tissue enhancement behaviour in order to assess tissue permeability. The DCE CT images were analysed using a dual-input two-compartment distributed parameter model to yield separate estimates for blood flow and permeability, as well as fractional intravascular and extravascular volumes. The HCCs and surrounding cirrhotic liver tissues were found to exhibit enhancement curves that can be appropriately described by two distinct compartments separated by a semipermeable barrier. Early contrast arrival was also found for HCC as compared with background liver. These findings are consistent with the current understanding of sinusoidal capillarization and hepatocarcinogenesis.

Can imaging modalities diagnose and stage hepatic fibrosis and cirrhosis accurately?

The accurate diagnosis and staging of hepatic fibrosis is crucial for prognosis and treatment of liver disease. The current gold standard, liver biopsy, cannot be used for population-based screening, and has well known drawbacks if used for monitoring of disease progression or treatment success. Our objective was to assess performance and promise of radiologic modalities and techniques as alternative, noninvasive assessment of hepatic fibrosis. A systematic review was conducted. Six hundred twenty-eight studies were identified via electronic search. One hundred fifty-three papers were reviewed. Most described techniques that could differentiate between cirrhosis or severe fibrosis and normal liver. Accurate staging of fibrosis or diagnosis of mild fibrosis was often not achievable. Ultrasonography is the most common modality used in the diagnosis and staging of hepatic fibrosis. Elastographic measurements, either ultrasonography-based or magnetic resonance-based, and magnetic resonance diffusion weighted imaging, show the most promise for accurate staging of hepatic fibrosis. Most currently available imaging techniques can detect cirrhosis or significant fibrosis reasonably accurately. However, to date only magnetic resonance elastography has been able to stage fibrosis or diagnose mild disease. Utrasonographic elastography and magnetic resonance diffusion weighted appear next most promising.

The usefulness of CT perfusion in differentiation between neoplastic and tuberculous disease of the spine

INTRODUCTION

Routine diagnostic techniques are not sufficient to confidently differentiate diseases of the axial skeleton. Purpose of study was to determine whether CT perfusion (CTP) can differentiate inflammatory diseases like tuberculosis from neoplastic diseases of spine.

METHODS

Fifty-one patients with vertebrdraft%freshal body lesions associated with paraspinal mass underwent CT guided bone biopsy and histopathological evaluation. CTP was done before doing bone biopsy. Perfusion parameters like blood volume (BV), blood flow (BF), and time to peak (TTP) were calculated. Values are correlated with histopathological report of bone biopsy. Statistical analysis was done using Mann-Whitney test. P value < .05 was considered significant.

RESULTS

Of 51, 32 had infective osteomyelitis and 19 neoplastic disease (9 metastasis, 5 plasmacytoma, 4 lymphoma and 1 chordoma. Mean rBF was [inflammatory lesions, 1.79 and neoplastic lesions, 9.42 (P < .000)]. Mean rBV was [inflammatory disease, 1.63 and neoplastic lesions, 9.37 (P < .000)].

CONCLUSION

CTP technique has potential for differentiating inflammatory from neoplastic lesions affecting spine associated with paraspinal mass noninvasively.

Error analysis of the quantification of hepatic perfusion using a dual-input single-compartment model

We performed an error analysis of the quantification of liver perfusion from dynamic contrast-enhanced computed tomography (DCE-CT) data using a dual-input single-compartment model for various disease severities, based on computer simulations. In the simulations, the time-density curves (TDCs) in the liver were generated from an actually measured arterial input function using a theoretical equation describing the kinetic behavior of the contrast agent (CA) in the liver. The rate constants for the transfer of CA from the hepatic artery to the liver (K(1a)), from the portal vein to the liver (K(1p)), and from the liver to the plasma (k(2)) were estimated from simulated TDCs with various plasma volumes (V(0)s). To investigate the effect of the shapes of input functions, the original arterial and portal-venous input functions were stretched in the time direction by factors of 2, 3 and 4 (stretching factors). The above parameters were estimated with the linear least-squares (LLSQ) and nonlinear least-squares (NLSQ) methods, and the root mean square errors (RMSEs) between the true and estimated values were calculated. Sensitivity and identifiability analyses were also performed. The RMSE of V(0) was the smallest, followed by those of K(1a), k(2) and K(1p) in an increasing order. The RMSEs of K(1a), K(1p) and k(2) increased with increasing V(0), while that of V(0) tended to decrease. The stretching factor also affected parameter estimation in both methods. The LLSQ method estimated the above parameters faster and with smaller variations than the NLSQ method. Sensitivity analysis showed that the magnitude of the sensitivity function of V(0) was the greatest, followed by those of K(1a), K(1p) and k(2) in a decreasing order, while the variance of V(0) obtained from the covariance matrices was the smallest, followed by those of K(1a), K(1p) and k(2) in an increasing order. The magnitude of the sensitivity function and the variance increased and decreased, respectively, with increasing disease severity and decreased and increased, respectively, with increasing stretching factor except for V(0). Identifiability analysis showed that the identifiability between K(1)(p) and k(2) was lower than that between K(1)(a) and k(2) or between K(1a) and K(1p). In conclusion, this study will be useful for understanding the accuracy and reliability of the quantitative measurement of liver perfusion using a dual-input single-compartment model and DCE-CT data.

Imaging techniques to evaluate the response to treatment in oncology: current standards and perspectives

Response evaluation in solid tumours currently uses radiological imaging techniques to measure changes under treatment. Imaging requires a well-defined anatomical lesion to be viewed and relies on the measurement of a reduction in tumour size during treatment as the basis for presumed clinical benefit. However, with the development of anti-angiogenesis agents, anatomical imaging has became inappropriate as certain tumours would not reduce in size. Functional studies are therefore necessary and dynamic contrast enhanced magnetic resonance imaging (DCE-MRI), DCE-computed tomography (CT) and DCE-ultrasonography (US) are currently being evaluated for monitoring treatments. Diffusion-weighted MR imaging (DW-MRI) and magnetic resonance spectroscopy (MRS) are also capable of detecting changes in cell density and metabolite content within tumours. In this article, we review anatomical and functional criteria currently used for monitoring therapy. We review the published data on DCE-MRI, DCE-CT, DCE-US, DW-MRI and MRS. This literature review covers the following area: basic principles of the technique, clinical studies, reproducibility and repeatability, limits and perspectives in monitoring therapy. Anatomical criteria such as response evaluation criteria in solid tumours (RECIST) will require adaptation to employ not only new tools but also different complementary techniques such as functional imaging in order to monitor therapeutic effects of conventional and new anti-cancer agents.

Hepatic metastases: in vivo assessment of perfusion parameters at dynamic contrast-enhanced MR imaging with dual-input two-compartment tracer kinetics model

This study was institutional review board approved, with waived patient consent for retrospective analysis of the data. The hepatic perfusion at dynamic contrast material-enhanced magnetic resonance (MR) imaging was commonly described and assessed by using a dual-input one-compartment tracer kinetics model. Although the tracer kinetics in normal liver parenchyma can be described by using a single compartment, functional changes in the tumor microenvironment can result in distinctly different tracer behavior that entails a second tissue compartment. A dual-input two-compartment model is proposed to describe the tracer behavior in hepatic metastases. The authors applied this model to the dynamic MR imaging data obtained in three patients. Perfusion parameter maps and region-of-interest analysis revealed that tracer behavior in hepatic metastases-in contrast to that in surrounding normal liver tissue, which effectively involves one compartment-can be described by using two compartments.

A quantitative method for estimating hepatic blood flow using a dual-input single-compartment model

The purpose of this study was to investigate the accuracy of a quantitative method for estimating arterial hepatic blood flow and portal hepatic blood flow separately using a dual-input single-compartment model compared with the maximum slope method using computer simulations and clinical data. In computer simulations, the rate constants for the transfer of contrast agent (CA) from the hepatic artery to the liver (K(1a)), from the portal vein to the liver (K(1p)) and from the liver to the blood (k(2)) were estimated from simulated time-density curves with various transit times of CA from the aorta to the liver (tau(a)) and from the portal vein to the liver (tau(p)) using the linear least-squares (LLSQ) method. In clinical studies, dynamic CT data were acquired from 27 patients, and parametric maps of K(1a), K(1p) and k(2) were generated by applying the LLSQ method pixel by pixel. In simulation studies, tau(a) and tau(p) were found to have a large and a small effect on the estimates of K(1a) and K(1p), respectively. In clinical studies, the K(1a) and K(1p) values estimated with the maximum slope method were underestimated by 60+/-29% and 37+/-12%, respectively, compared with those estimated by the LLSQ method. In conclusion, our results suggest that correction of tau(a) is necessary for accurately estimating K(1a) and K(1p). Our method is therefore promising for the evaluation of hepatic blood flow in various liver diseases because it allows us to evaluate arterial hepatic blood flow and portal hepatic blood flow separately and visually.

CT coronary angiography: quantitative assessment of myocardial perfusion using test bolus data-initial experience

The aim of this study is to quantify myocardial perfusion during coronary CT angiography using data from a modified timing test-bolus acquisition. Institutional review board approval and informed consent were obtained. Nineteen patients with suspected coronary artery disease underwent combined coronary CT angiography and cardiac (82)Rubidium-PET perfusion. Prior to the CT angiogram a retrospectively ECG-gated dynamic test bolus was obtained following 25 mls of IV contrast medium injected at 5 ml/s. Images were acquired every 1.5 s for 30 s using 4 x 1.25-mm slices at 120 kV, 35 mAs. Regions of interest were drawn to delineate the myocardium and aorta on the resulting transaxial images. Time density curves were created and perfusion calculated using two simple approaches: maximum-slope method and peak method. In patients with normal PET myocardial perfusion, the mean (SD) resting myocardial perfusion estimated by CT using the maximum-slope method was 0.89 (+/-0.27) ml/min/g and 0.93 (+/-0.21) ml/min/g at end-systole and end-diastole, respectively, and 0.69 (+/-0.11) ml/min/g and 0.79 (+/-0.19) at end-systole and end-diastole, respectively, for the peak method. Thus quantification of myocardial perfusion from a routine coronary CT angiography test bolus is possible. CT-derived myocardial perfusion values are consistent with published values derived from other techniques.

Non-invasive estimation of hepatic blood perfusion from H2 15O PET images using tissue-derived arterial and portal input functions

PURPOSE

The liver is perfused through the portal vein and the hepatic artery. When its perfusion is assessed using positron emission tomography (PET) and (15)O-labeled water (H(2) (15)O), calculations require a dual blood input function (DIF), i.e., arterial and portal blood activity curves. The former can be generally obtained invasively, but blood withdrawal from the portal vein is not feasible in humans. The aim of the present study was to develop a new technique to estimate quantitative liver perfusion from H(2) (15)O PET images with a completely non-invasive approach.

METHODS

We studied normal pigs (n=14) in which arterial and portal blood tracer concentrations and Doppler ultrasonography flow rates were determined invasively to serve as reference measurements. Our technique consisted of using model DIF to create tissue model function and the latter method to simultaneously fit multiple liver time-activity curves from images. The parameters obtained reproduced the DIF. Simulation studies were performed to examine the magnitude of potential biases in the flow values and to optimize the extraction of multiple tissue curves from the image.

RESULTS

The simulation showed that the error associated with assumed parameters was <10%, and the optimal number of tissue curves was between 10 and 20. The estimated DIFs were well reproduced against the measured ones. In addition, the calculated liver perfusion values were not different between the methods and showed a tight correlation (r=0.90).

CONCLUSION

In conclusion, our results demonstrate that DIF can be estimated directly from tissue curves obtained through H(2) (15)O PET imaging. This suggests the possibility to enable completely non-invasive technique to assess liver perfusion in patho-physiological studies.

Quantitative mapping of hepatic perfusion index using MR imaging: a potential reproducible tool for assessing tumour response to treatment with the antiangiogenic compound BIBF 1120, a potent triple angiokinase inhibitor

Hepatic metastases are arterially supplied, resulting in an elevated hepatic perfusion index (HPI). The purpose of this study was to use dynamic contrast-enhanced (DCE) MR imaging to quantify the HPI of metastases and the liver before and after treatment with a novel antiangiogenic drug. Ten patients with known metastatic liver disease underwent DCE-MR studies. HPIs of metastases and whole liver were derived using regions of interest (ROIs) and calculated on a pixel-by-pixel basis from quantified changes in gadopentetate dimeglumine (Gd-DTPA) concentration. The HPI measurement error prior to treatment was derived by the Bland-Altman analysis. The median HPI before and after treatment with antiangiogenic drug BIBF 1120 were compared using the Wilcoxon signed rank test. Prior to treatment, the median HPI of metastases, 0.75 +/- 0.14, was significantly higher than that of the whole liver, 0.66 +/- 0.16 (p < 0.01). Bland-Altman reproducibility coefficients of the median HPI from metastases and whole liver were 13.0 and 5.1% respectively. The median HPI of metastases decreased significantly at 28 days after treatment with BIBF 1120 (p < 0.05). This pilot study demonstrates that HPI determined using quantified Gd-DTPA concentration is reproducible and may be useful for monitoring antiangiogenic treatment response of hepatic metastases.

Dynamic T(1) mapping predicts outcome of chemoradiation therapy in primary rectal carcinoma: sequence implementation and data analysis

PURPOSE

To describe details about the implementation of a dynamic T(1)-mapping technique and a simple data analysis strategy that can be used to predict therapy outcome in primary rectal carcinoma and to investigate the physiologic meaning of the obtained parameter.

MATERIALS AND METHODS

Contrast-enhanced dynamic T(1) mapping was achieved with a snapshot fast low-angle shot (FLASH) T(1) mapping sequence implemented on a 1.5 T MR scanner. This method was applied to 58 patients with primary rectal cancer before onset of chemoradiation therapy. A simple data analysis strategy based on the calculation of the maximum slope of the tissue concentration-time curve divided by the maximum of the arterial input function (AIF) was used as a measure of tumor microcirculation (PI values).

RESULTS

The snapshot FLASH (SFL) T(1)-mapping technique is accurate and sensitive enough to detect inhomogeneous uptake kinetics within tumor tissue. Classifying the patients into two groups according to therapy response showed lower mean PI values for responders as compared to nonresponders. PI was found to combine information about permeability surface area product (PS) and blood volume.

CONCLUSIONS

The described method based on dynamic T(1) mapping has the potential to be a clinical tool for predicting therapy outcome of preoperative chemoradiation in patients with primary rectal carcinoma.

Colorectal cancer: imaging surveillance following resection of primary tumour

Most patients with colorectal cancer undergo treatment with curative intent and subsequently enter a surveillance programme. The primary aim of surveillance is to identify patients with disease relapse at a resectable stage. However, the identification of local recurrence and metachronous carcinoma are also important aspects of follow up. Patients under observation may be referred for imaging either because regular imaging forms part of the surveillance strategy, or because tumour relapse is suggested by the development of new symptoms or a rise in tumour markers. This paper reviews the use of new and existing imaging techniques during surveillance following resection of primary colorectal cancer. The use of imaging for this surveillance is an application of cancer imaging that is supported by evidence-based clinical guidelines. Computed tomography provides the mainstay modality on grounds of good overall diagnostic performance combined with high availability and low cost. Improvements in survival with more aggressive follow up and treatment are likely to demand more accurate imaging techniques in the future.

Dynamic computed tomographic quantitation of hepatic perfusion in dogs with and without portal vascular anomalies

OBJECTIVE

To compare hepatic, pancreatic, and gastric perfusion on dynamic computed tomography (CT) scans of clinically normal dogs with those of dogs with portal vascular anomalies.

SAMPLE POPULATION

Dynamic computed tomography (CT) scans of 10 clinically normal dogs and 21 dogs with portal vascular anomalies.

PROCEDURES

Retrospective analysis of dynamic CT scans. Hepatic arterial perfusion, hepatic portal perfusion, total hepatic perfusion, hepatic perfusion index, gastric perfusion, and pancreatic perfusion were calculated from time attenuation curves.

RESULTS

Mean +/- hepatic arterial perfusion was significantly higher in affected dogs (0.57 +/- 0.27 mL/min x mL(-1)) than in clinically normal dogs (0.23 +/- 0.11 mL/min x mL(-1)), and hepatic portal perfusion was significantly lower in affected dogs (0.52 +/- 0.47 mL/min x mL(-1)) than in clinically normal dogs (1.08 +/- 0.45 mL/min x mL(-1)). This was reflected in the hepatic perfusion index, which was significantly higher in affected dogs (0.59 +/- 0.34), compared with clinically normal dogs (0.19 +/- 0.07). Gastric perfusion was significantly higher in dogs with portal vascular anomalies (0.72 +/- 0.44 mL/min x mL(-1)) than in clinically normal dogs (0.41 +/- 0.21 mL/min x mL(-1)), but total hepatic perfusion and pancreatic perfusion were not significantly different. Among subgroups, dogs with congenital intrahepatic portosystemic shunts and dogs with arterioportal fistulae had higher hepatic arterial perfusion than did clinically normal dogs. Dogs with congenital intrahepatic portosystemic shunts also had an increase in gastric perfusion and hepatic perfusion index.

CONCLUSIONS AND CLINICAL RELEVANCE

Hepatic perfusion variables measured on CT scans revealed differences in hemodynamics between clinically normal dogs and those with portal vascular anomalies.

Comparison of liver perfusion parameters studied with conventional extravascular and experimental intravascular CT contrast agents

RATIONALE AND OBJECTIVES

To compare liver perfusion parameters obtained by using an extravascular contrast agent and a blood-pool agent.

MATERIALS AND METHODS

Fifteen rabbits were imaged with a continuous 40-second single-slice computed tomography acquisition after a bolus injection of contrast agent (physiologic bolus duration 4-5 seconds, extravascular iohexol, n = 7; experimental nanoparticulated blood-pool agent WIN8883, n = 8). Time-density curves were generated for the aorta, portal vein, and liver. From the curves, arterial, portal, and total blood flows and hepatic perfusion index (HPI, arterial-to-total perfusion ratio) were determined by using two commonly applied fundamentally different analyzing methods: the single-compartment model and the peak gradient (PG) method. Also, the gamma variate fitting method was used.

RESULTS

By using the single-compartment model, the obtained HPI and total blood flow were 0.14 +/- 0.04 and 2.29 +/- 0.40 (mL/min/mL(tissue)) for WIN8883, and 0.15 +/- 0.06 (P = .54) and 4.60 +/- 1.14 (mL/min/mL(tissue)) (P = .0002) for iohexol, respectively. With the PG, HPI and total blood flow were 0.15 +/- 0.08 and 1.27 +/- 0.24 (mL/min/mL(tissue)) for WIN8883, and 0.20 +/- 0.06 (P = .12) and 2.11 +/- 0.25 (mL/min/mL(tissue)) (P = .00002) for iohexol, respectively. With the blood pool agent, similar contrast enhancement to the conventional agent was achieved with about 36% reduced dosage of iodine per body weight (mg I/kg).

CONCLUSIONS

HPI was found to be quite insensitive to different contrast agent types and analyzing methods. However, the arterial, portal and total liver blood flow values strongly depend on contrast agent type and modeling method.

CT perfusion for determination of pharmacologically mediated blood flow changes in an animal tumor model

PURPOSE

To prospectively compare single- and multisection computed tomographic (CT) perfusion for tumor blood flow determination in an animal model.

MATERIALS AND METHODS

All animal protocols and experiments were approved by the institutional animal care and use committee before the study was initiated. R3230 mammary adenocarcinoma was implanted in 11 rats. Tumors (18-20 mm) were scanned with dynamic 16-section CT at baseline and after administration of arsenic trioxide, which is known to cause acute reduction in blood flow. The concentration of arsenic was titrated (0-6 mg of arsenic per kilogram of body weight) to achieve a defined blood flow reduction (0%-75%) from baseline levels at 60 minutes, as determined with correlative laser Doppler flowmetry. The mean blood flow was calculated for each of four 5-mm sections that covered the entire tumor, as well as for the entire tumor after multiple sections were processed. Measurements obtained with both methods were correlated with laser Doppler flowmetry measurements. Interobserver agreement was determined for two blinded radiologists, who calculated the percentage of blood flow reduction for the "most representative" single sections at baseline and after arsenic administration. These results were compared with the interobserver variability of the same radiologists obtained by summing blood flow changes for the entire tumor volume.

RESULTS

Overall correlations for acute blood flow reduction were demonstrated between laser Doppler flowmetry and the two CT perfusion approaches (single-section CT, r=0.85 and r(2)=0.73; multisection CT, r=0.93 and r(2)=0.87; pooled data, P=.01). CT perfusion disclosed marked heterogeneity of blood flow, with variations of 36% +/- 13 between adjacent 5-mm sections. Given these marked differences, interobserver agreement was much lower for single-section CT (standard deviation, 0.22) than for multisection CT (standard deviation, 0.10; P=.01).

CONCLUSION

Multisection CT perfusion techniques may provide an accurate and more reproducible method of tumor perfusion surveillance than comparison of single representative tumor sections.

Assessment of Hepatic Perfusion in Transplanted Livers by Pharmacokinetic Analysis of Dynamic Magnetic Resonance Measurements

OBJECTIVE

The purpose of this study was to validate the assessment of hepatic perfusion by pharmacokinetic analysis of dynamic contrast-enhanced magnetic resonance image series.

MATERIALS AND METHODS

Dynamic measurements were performed with a saturation recovery turbo fast low angle shot (ie, FLASH) sequence over the course of approximately 4 minutes in 17 patients with transplanted livers. By pharmacokinetic analysis using an open 2-compartment model, we estimated and correlated an amplitude of signal enhancement, A, and the perfusion rate, kp, with invasive perfusion measurements from implanted thermo-diffusion probes (FTDP).

RESULTS

Data analysis for segment IV of the transplanted livers yielded a mean blood flow of 81 +/- 19 mL/min/100g and a mean perfusion rate of 13 +/- 6 minutes. There was a significant correlation between FTDP and kp (rS = 0.64, P = 0.01) but not with A.

CONCLUSIONS

Although our open 2-compartment model oversimplifies the complexity of hepatic perfusion, it allows a numerically robust estimation of regional blood flow per unit of blood volume. Thus, dynamic magnetic resonance imaging represents a noninvasive method to assess hepatic perfusion rate which can be visualized in color coded images.

Quantitative tumor perfusion assessment with multidetector CT: are measurements from two commercial software packages interchangeable?

PURPOSE

To prospectively determine the level of agreement between tumor blood volume and permeability measurements obtained with two commercially available perfusion computed tomographic (CT) software packages.

MATERIALS AND METHODS

This study was performed with institutional review board approval; informed consent was obtained from all participants. A total of 44 patients (24 men, 20 women; mean age, 68 years; range, 28-87 years) with proved colorectal cancer were examined prospectively with multi-detector row CT. A 65-second tumor perfusion study was performed after intravenous bolus injection of contrast material. Tumor blood volume and permeability were determined with two methods: adiabatic approximation of distributed parameter analysis and Patlak analysis. Agreement between the results was determined by using Bland-Altman statistics. Within-patient variation was determined by using analysis of variance.

RESULTS

The mean values for permeability and blood volume, respectively, were 13.9 mL x 100 mL(-1) x min(-1) +/- 3.7 (standard deviation) and 6.1 mL/100 mL +/- 1.5, as calculated with distributed parameter analysis, and 17.4 mL x 100 mL(-1) x min(-1) +/- 7.3 and 10.1 mL/100 mL +/- 4.2, as calculated with Patlak analysis. The mean difference and 95% limits of agreement, respectively, were -3.6 mL x 100 mL(-1) x min(-1) and -18.4 to 11.2 mL x 100 mL(-1) x min(-1) for permeability and -3.9 mL/100 mL and -10.9 to 3.0 mL/100 mL for blood volume. The coefficient of variation was 37.4% for permeability and 46.5% for blood volume.

CONCLUSION

There was disagreement between the methods used to estimate tumor vascularity, which indicated the measurement techniques were not directly interchangeable.

Xenon computed tomography shows hemodynamic change during the progression of chronic hepatitis C

AIM

Xenon computed tomography (Xe-CT) is a non-invasive method of quantifying and visualizing tissue blood flow (TBF). Xe-CT allows separate measurement of hepatic arterial and portal venous flow. The aim of this study was to investigate correlations between the progression of fibrosis and hemodynamic changes in chronic hepatitis C (CHC) patients using Xe-CT.

METHODS

Separate measurements of portal venous TBF (PVTBF) and hepatic arterial TBF (HATBF) were performed using Xe-CT, and total hepatic TBF (THTBF) was calculated as the sum of PVTBF and HATBF. A total of 50 patients with CHC underwent Xe-CT. Liver biopsy was performed on 42 of the 50 patients, and hepatic fibrosis was classified as mild (F1), moderate (F2), severe (F3) or Child-Pugh class A cirrhosis (F4a). In addition, eight patients with Child-Pugh class B cirrhosis (F4b) were evaluated.

RESULTS

Significant negative correlations were identified between PVTBF and progression of stage (r(s) = -0.622, P < 0.0001) and between THTBF and progression of stage (r(s) = -0.458, P = 0.0041).

CONCLUSION

Separate measurement of PVTBF and HATBF using non-invasive Xe-CT provided quantitative and visual information regarding hemodynamics of the entire liver in CHC patients. PVTBF decreases with the progression of fibrosis, even in CHC patients.

The use of perfusion CT for the evaluation of therapy combining AZD2171 with gefitinib in cancer patients

The purpose of this study was to determine the feasibility of dynamic contrast-enhanced perfusion CT (CTP) in evaluating the hemodynamic response of tumors in the chest and abdomen treated with a combination of AZD2171 and gefitinib. Thirteen patients were examined just before and every 4-6 weeks after starting therapy. Following intravenous injection of a contrast agent, dynamic image acquisition was obtained at the level of a selected tumor location. To calculate perfusion, the maximum-slope method was used. Pre-treatment average perfusion for extra-hepatic masses was 84 ml/min/100 g, for liver masses arterial perfusion was 25 ml/min/100 g, and a portal perfusion of 30 ml/min/100 g was found. After the administration of AZD2171 and gefitinib, in extra-hepatic masses an initial decrease in perfusion of 18% was followed by a plateau and in liver masses an initial decrease of 39% within the lesions and of 36% within a rim region surrounding the lesions was followed by a tendency to recovery of hepatic artery flow. In conclusion, CTP is feasible in showing changes of perfusion induced by anti-angiogenic therapy.

A practical approach for quantitative estimates of voxel-by-voxel liver perfusion using DCE imaging and a compartmental model

Voxel-by-voxel estimation of liver perfusion using nonlinear least-squares fits of dynamic contrast enhanced computed tomography or magnetic resonance imaging data to a compartmental model is a computational expensive process. In this report, a "linear" least-squares method for estimation of liver perfusion is described. Simulated data and the data from an example case of a patient with intrahepatic cancer are presented. Compared to the nonlinear method, the new method can improve computational speed by a factor of approximately 400, which makes it practical for use in clinical trials.

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.

High volume hydrodynamic injection of plasmid DNA via the hepatic artery results in a high level of gene expression in rat hepatocellular carcinoma induced by diethylnitrosamine

BACKGROUND

Hydrodynamic injection of naked plasmid DNA (pDNA) via the tail vein is a safe and effective method of gene transfer to the liver. However, successful gene transfer has yet to be shown for hepatocellular carcinoma (HCC); therefore, we investigated the feasibility and efficacy of hydrodynamic injection via the tail vein and hepatic artery in a diethylnitrosamine (DEN)-induced HCC model in rats.

METHODS

HCC was induced in Sprague-Dawley rats by 100 ppm DEN in drinking water. pCMV-SPORT-beta-galactosidase (beta-gal, 400 microg) was injected (i) via the tail vein in a volume of 0.1 ml/g in 30 s or (ii) via the hepatic artery in a volume of 5 or 10 ml at 1 ml/s, either with or without temporary occlusion of the inferior vena cava (IVC) and portal vein (PV). The liver was harvested 24 h after administration, and beta-gal expression was evaluated with X-gal staining and measurement of enzymatic activity in tissue homogenates.

RESULTS

Hydrodynamic injection via the tail vein achieved transgene expression only in non-cancerous tissue (tumor: 0.16 +/- 0.04%, non-tumor: 5.07 +/- 1.66%). Hydrodynamic injection via the hepatic artery was tolerated, but failed to produce efficient transgene expression in tumor and non-tumor cells. On the other hand, concomitant use of temporary IVC/PV occlusion with hydrodynamic injection via the hepatic artery dramatically increased transgene expression in cancer cells, but tumor-selective gene transfer was not achieved with this procedure (tumor: 7.38 +/- 3.66%, non-tumor: 7.77 +/- 1.06%).

CONCLUSIONS

High-volume hydrodynamic injection of a pDNA solution via the hepatic artery with IVC/PV occlusion achieved a high level of gene expression in a HCC rat model. This gene transfer technique may have potential in clinical gene therapy for HCC.