Multidetector CT: contributions in liver imaging

In Vivo Evaluation of Feeding Arteries of Tumors in Dorsal Sector of the Liver

Background:

The identification of the dorsal sector of the liver and its detailed vascular anatomy is of primary importance for surgical practice and segmental transcatheter arterial chemoembolization.

Objectives:

This study aimed to investigate the feeding arteries of tumors in dorsal sector of the liver.

Patients and Methods:

Computed tomography (CT) and digital subtraction angiography (DSA) images of eleven patients with tumors of the dorsal sector of the liver were analyzed retrospectively. The hepatic arteries that probably supplied the tumors were observed in DSA images. The case number of each hepatic artery feeding to the tumors was calculated. A scoring method was used to estimate each hepatic artery contribution to the tumor stain in DSA images. The accumulative scores were employed to evaluate the blood supply of feeding arteries of the tumors.

Results:

The data of the study revealed that right posterior hepatic artery (RPHA) (n = 9), middle hepatic artery (MHA) (n = 8), left medial hepatic artery (LMHA) (n = 6), right anterior hepatic artery (RAHA) (n = 5), and caudate hepatic artery (CaHA) (n = 3) were the feeding arteries of the tumors in dorsal sector in eleven patients. The accumulative scores of RPHA, MHA, RAHA, and LMHA were 23, 17, 11, and 7 points, respectively (χ² = 6.827, P = 0.078, Friedman test). The total scores of right hepatic artery (RHA) branches and left hepatic artery (LHA) branches were 51 and 11 points, respectively (Z = -2.764, P = 0.006, Wilcoxon rank test).

Conclusion:

The RPHA, MHA, RAHA, and LMHA might be the main feeding arteries of the tumors in dorsal sector of the liver.

Detection and classification of different liver lesions: comparison of Gd-EOB-DTPA-enhanced MRI versus multiphasic spiral CT in a clinical single centre investigation

OBJECTIVE

To compare the diagnostic efficacy of Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI) vs. multidetector computed tomography (MDCT) for the detection and classification of focal liver lesions, differentiated also for lesion entity and size; a separate analysis of pre- and postcontrast images as well as T2-weighted MRI sequences of focal and exclusively solid lesions was integrated.

METHODS

Twenty-nine patients with 130 focal liver lesions underwent MDCT (64-detector-row; contrast medium iopromide; native, arterial, portalvenous, venous phase) and MRI (1.5-T; dynamic and tissue-specific phase 20 min after application of Gd-EOB-DTPA). Hepatic lesions were verified against a standard of reference (SOR). CT and MR images were independently analysed by four blinded radiologists on an ordinal 6-point-scale, determining lesion classification and diagnostic confidence.

RESULTS

Among 130 lesions, 68 were classified as malignant and 62 as benign by SOR. The detection of malignant and benign lesions differed significantly between combined and postcontrast MRI vs. MDCT; overall detection rate was 91.5% for combined MRI and 80.4% for combined MDCT (p<0.05). Considering all four readers together, combined MDCT achieved sensitivity of 66.2%, specificity of 79.0%, and diagnostic accuracy of 72.3%; combined MRI reached superior diagnostic efficacy: sensitivity 86.8%, specificity 94.4%, accuracy 90.4% (p<0.05). Differentiated for lesion size, in particular lesions <20mm revealed diagnostic benefit by MRI. Postcontrast MRI also achieved higher overall sensitivity, specificity, and accuracy compared to postcontrast MDCT for focal and exclusively solid liver lesions (p<0.05).

CONCLUSION

Combined and postcontrast Gd-EOB-DTPA-enhanced MRI provided significantly higher overall detection rate and diagnostic accuracy, including low inter-observer variability, compared to MDCT in a single centre study.

[Radiological diagnosis of primary hepatic malignancy]

Modern radiology offers countless opportunities both in the detection but also in the characterization of primary liver malignancies. Ultrasound remains usually the first exploratory overview study whereat using ultrasound contrast agent for a further characterization of liver lesions improves this technique considerably. Advanced cross-sectional imaging methods can, in most cases, already provide an exact diagnosis. Thus, the CT is already considered a standard technique for liver imaging and magnetic resonance imaging has gained in recent years due to liver-specific contrast agents and faster sequences a central role in liver imaging. The following article provides an overview of these various radiological procedures and describes the different primary liver malignancies and their imaging characteristics.

A comparison of hepatic segmental anatomy as revealed by cross-sections and MPR CT imaging

To compare the areas of human liver horizontal sections with computed tomography (CT) images and to evaluate whether the subsegments determined by CT are consistent with the actual anatomy. Six human cadaver livers were made into horizontal slices with multislice spiral CT three-dimensional (3D) reconstruction was used during infusion process. Each liver segment was displayed using different color, and 3D images of the portal and hepatic vein were reconstructed. Each segmental area was measured on CT-reconstructed images, which were compared with the actual area on the sections of the same liver. The measurements were performed at four key levels namely: (1) the three hepatic veins, (2) the left, and (3) the right branch of portal vein (PV), and (4) caudal to the bifurcation of the PV. By dividing the sum of these areas by the total area of the liver, the authors got the percentage of the incorrectly determined subsegmental areas. In addition to these percentage values, the maximum distances of the radiologically determined intersegmental boundaries from the true anatomic boundaries were measured. On the four key levels, an average of 28.64 ± 10.26% of the hepatic area of CT images was attributed to an incorrect segment. The mean-maximum error between artificial segments on images and actual anatomical segments was 3.81 ± 1.37 cm. The correlation between radiological segmenting method and actual anatomy was poor. The hepatic segments being divided strictly according to the branching point of the PV could be more informative during liver segmental resection.

Application of multi-slice spiral CT three-dimensional reconstruction technique in liver resection for hepatic carcinoma

Hepatic carcinoma is a very common disease across the world, and hepatic resection is still the best treatment. As the liver has complex anatomy and frequent vascular variations, it is of great importance to obtain some preoperative data, such as the position of liver cancer and its relationship with liver vessels and adjacent structures. Now, three-dimensional reconstruction technique allows to clearly show the relationship of the hepatic artery, portal vein, hepatic vein and tumor with surrounding strctures and accurately calculate the remnant liver volume, providing valuable preoperative imaging data for liver resection. This article will give an overview of three-dimensional reconstruction technique and discuss its ability to display liver vascularity, show the relationship between tumors and liver blood vessels, and predict liver resection volume.

Recent advances in imaging hepatic fibrosis and steatosis

Liver disease is an increasing cause of morbidity and mortality worldwide. Currently, the gold standard for diagnosis and assessment of parenchymal disease is histopathological assessment of a percutaneous or transjugular liver biopsy. The risks and limitations of this technique are well recognized and as a result, significant effort has gone into the development of novel noninvasive methods of diagnosis and longitudinal assessment. Imaging techniques have improved significantly over the past decade and new technologies are beginning to enter clinical practice. Ultrasound, computed tomography and MRI are the main modalities currently used, but novel MRI-based techniques will have an increasing role. While there has been extensive research into the imaging of focal liver disease, the evidence base for imaging in diffuse disease has also undergone recent rapid development, particularly in the assessment of fibrosis and steatosis. Both of these abnormalities of the parenchyma can lead to cirrhosis and/or hepatocellular carcinoma and represent an important opportunity for detection of early liver disease. We discuss the recent advances in liver imaging techniques and their role in the diagnosis and monitoring of diffuse liver disease, with a focus on their current and potential clinical relevance and whether they may replace or augment liver biopsy. We also discuss techniques currently under development and their potential clinical applications in the future.

Definition of contrast enhancement phases of the liver using a perfluoro-based microbubble agent, perflubutane microbubbles

To define the contrast enhancement phases in the liver with perflubutane microbubbles, the liver enhancement time-intensity curves were investigated in 14 healthy volunteers. The agent was injected intravenously as a bolus and the liver was imaged with an ultrasound scanner as long as 4h after the injection. Time-intensity curves from the hepatic artery, the intrahepatic portal vein, the hepatic vein and the parenchyma of the liver were obtained from the liver ultrasound images. The arrival of the agent in the hepatic artery, the portal vein and the hepatic vein were visually distinguishable and the mean arrival times were 19.2, 24.3 and 32.2 s after the injection, respectively. The signal intensity in these vessels increased rapidly after the arrival of the contrast and gradually reverted to baseline after the peak. In contrast, within 5 min after the injection, the intensity in the parenchyma increased and reached a plateau, which persisted for at least 2h. The contrast enhancement phases in the liver with perflubutane microbubbles could be defined as two major phases-a vascular phase, in which the vessels are enhanced between 15 s and 10 min after injection, and a Kupffer phase, in which the parenchyma is enhanced 10 min after injection. The vascular phase is divided into three subphases: the arterial phase (15 to 45 s after injection); the portal phase (45 s to 1 min after injection); and the vasculo-Kupffer phase (1 to 10 min after injection).

Area extraction of the liver and hepatocellular carcinoma in CT scans

In Korea, hepatocellular carcinoma is the third frequent cause of cancer death, occupying 17.2% among the whole deaths from cancer, and the rate of death from hepatocellular carcinoma comes to about 21 out of 100,000. This paper proposes an automatic method for the extraction of areas being suspicious as hepatocellular carcinoma from computed tomography (CT) scans and evaluates the availability as an auxiliary tool for the diagnosis of hepatocellular carcinoma. For detecting tumors in the internal of the liver from a CT scan, first, an area of the liver is extracted from about 45-50 CT slices obtained by scanning in 2.5-mm intervals starting from the lower part of the chest. In the extraction of an area of the liver, after the unconcerned areas outside of the bony thorax are removed, areas of the internal organs are segmented by using information on the intensity distribution of each organ, and an area of the liver is extracted among the segmented areas by using information on the position and morphology of the liver. Because hepatocellular carcinoma is a hypervascular tumor, the area corresponding to hepatocellular carcinoma appears more brightly than the surroundings in a CT scan, and also takes a spherical shape if the tumor shows expansile growth pattern. By using these features, areas being brighter than the surroundings and globe-shaped are segmented as candidate areas for hepatocellular carcinoma in the area of the liver, and then, areas appearing at the same position in successive CT slices among the candidates are discriminated as hepatocellular carcinoma. For the performance evaluation of the proposed method, experimental results obtained by applying the proposed method to CT scans were compared with the diagnoses by radiologists. The evaluation results showed that all areas of the liver and hypervascular tumors were extracted exactly and the proposed method has a high availability as an auxiliary diagnosis tool for the discrimination of liver tumors.

Choosing the best endpoint

Design and endpoints of clinical trials in hepatocellular carcinoma. Llovet JM, Di Bisceglie AM, Bruix J, Kramer BS, Lencioni R, Zhu AX, Sherman M, Schwartz M, Lotze M, Talwalkar J, Gores GJ; for the Panel of Experts in HCC-Design Clinical Trials. The design of clinical trials in hepatocellular carcinoma (HCC) is complex because many patients have concurrent liver disease, which can confound the assessment of clinical benefit. There is an urgent need for high-quality trials in this disease. An expert panel was convened by the American Association for the Study of Liver Diseases to develop guidelines that provide a common framework for designing trials to facilitate comparability of results. According to these guidelines, randomized phase 2 trials with a time-to-event primary endpoint, such as time to progression, are pivotal in clinical research on HCC. Survival remains the main endpoint to measure effectiveness in phase 3 studies, whereas time to recurrence is proposed as an appropriate endpoint in the adjuvant setting. Because progression-free survival and disease-free survival are composite endpoints, they are more vulnerable than others in HCC clinical studies and may not be able to capture clinical benefits. Selection of the target population should be based on the Barcelona Clinic Liver Cancer staging system. New drugs should be tested in patients with well-preserved liver function (Child-Pugh A class). Patients assigned to the control arm should receive standard-of-care therapy, that is, chemoembolization for patients with intermediate-stage disease and sorafenib for patients with advanced-stage disease. Further research is needed to incorporate biomarkers and molecular imaging into clinical research in HCC. These surrogate markers may help to enrich study populations and maximize the cost-benefit ratio of trial execution. Design and conduct of phase 3 trials should be coordinated by centers with appropriate expertise in HCC. [Abstract reproduced by permission of J Natl Cancer Inst 2008;100:698-711.] Link to free abstract at: (http://jnci.oxfordjournals.org/cgi/content/abstract/100/10/698).

Technology Insight: advances in liver imaging

The role of diagnostic imaging in the assessment of liver disease continues to gain in importance. The classic techniques used for liver imaging are ultrasonography, CT and MRI. In the past decade, there have been significant advances in all three techniques. In this article, we discuss the advances in ultrasonography, CT and MRI that have improved assessment of focal and diffuse liver disease, including the development of hardware, software, processing algorithms and procedural innovations.

Venous variants and anomalies on routine abdominal multi-detector row CT

OBJECTIVE

This study aims to determine the types and prevalence rates of anatomic variations of the hepatic veins, portal vein, inferior vena cava and renal veins, and to establish statistical correlations between various anomalies and frequency differences between male and female using multi-detector row computed tomography (CT).

MATERIALS AND METHODS

One thousand one hundred and twenty patients (588 men, 532 women) were evaluated with routine abdominal CT. Frequencies of different variants were noted and compared, and correlations between three categories of variation were tested.

RESULTS

In total, 1261 abdominal vein variants and anomalies were identified in 756 (67.5%) of 1120 patients. Six hundred and forty-two hepatic vein variants were detected in 468 (41.8%) patients. One or more inferior right hepatic veins were identified in 356 (31.8%) individuals, and tributary hepatic veins were detected in 147 (13.1%) patients. Portal vein variations and anomalies were observed in 307 (27.4%) cases. The most frequent of these was trifurcation (139 patients, 12.4%). A total of 311 inferior vena cava and renal vein variants were identified in 258 (23%) cases. Six patients (0.5%) exhibited inferior vena cava anomalies, 62 (5.5%) had circumaortic renal veins, 53 (4.7%) had retroaortic renal veins, and 210 (18.8%) had multiple renal veins.

CONCLUSION

The prevalence of abdominal vein variations is high, and routine abdominal CT demonstrates these abnormalities very well. The data suggest that hepatic vein variants and multiple right renal veins are more frequent in women than in men, and that hepatic vein variation is correlated with portal vein variation.

Multidetector CT Angiography of the Abdomen

Multidetector CT angiography (MDCTA) is redefining traditional imaging strategies of the vascular structures of the abdomen. Angiographic depiction of normal and variant anatomy is becoming the standard for evaluation and has a significant impact in transplant and oncologic surgery. MDCTA is increasingly being used for assessing diseases affecting the vasculature of the abdominal organs, including the abdominal aorta for treatment planning and post therapy follow-up.