MR imaging of hypervascular lesions in the cirrhotic liver: a diagnostic dilemma

Lesion or Pseudolesion? A Comprehensive Description of Perfusion-Based Liver Alterations on Contrast-Enhanced Computed Tomography and Literature Review

ABSTRACT

Pseudolesions on contrast-enhanced computed tomography represent a diagnostic challenge for radiologists because they could be difficult to distinguish from true space-occupying lesions. This article aims to provide a detailed overview of these entities based on radiological criteria (hyperattenuation or hypoattenuation, localization, morphology), as well as a brief review of the hepatic vascular anatomy and pathophysiological process. Relevant examples from hospital case series are reported as helpful hints to assist radiologists in recognizing and correctly diagnosing these abnormalities.

Evaluation of the efficacy of transcatheter arterial embolization combined with apatinib on rabbit VX2 liver tumors by intravoxel incoherent motion diffusion-weighted MR imaging

Background and purpose

It is crucial to evaluate the efficacy, recurrence, and metastasis of liver tumors after clinical treatment. This study aimed to investigate the value of Introvoxel Incoherent Motion (IVIM) imaging in the evaluation of rabbit VX2 liver tumors treated with Transcatheter Arterial Embolization (TAE) combined with apatinib.

Methods

Twenty rabbit VX2 liver tumor models were established and randomly divided into either the experimental group (n=15) or the control group (n=5). The experimental group was treated with TAE combined with oral apatinib after successful tumor inoculation, while no treatment was administered following inoculation in the control group. IVIM sequence scan was performed in the experimental group before treatment, at 7 and 14 days after treatment. All rabbits were sacrificed after the last scan of the experimental group. Marginal tissues from the tumors of both groups were excised for immunohistochemical analysis to observe and compare the expression of microvessel density (MVD). The alterations of IVIM-related parameters of tumor tissues in the experimental group, including Apparent Diffusion Coefficient (ADC), True Diffusion Coefficient (D), Pseudodiffusion Coefficient (D*), and Perfusion Fraction (f) were compared at different periods, and the correlation between these parameters and MVD was analyzed.

Results

After treatment, ADC and D values significantly increased, whereas D* and f values both decreased, with statistically significant differences.(P<0.05). The average tumor MVD of the experimental group after TAE combined with apatinib ((33.750 ± 6.743) bars/high power field (HPF)) was significantly lower than that in the control group ((64.200 ± 10.164) bars/HPF)). Moreover, D and f were positively correlated with tumor MVD in the experimental group (r=0.741 for D and r=0.668 for f, P<0.05). However, there was no significant correlation between ADC and D* values of the experimental group and tumor MVD (r=0.252 for ADC and r=0.198 for D*, P>0.05).

Conclusion

IVIM imaging can be employed to evaluate the efficacy of TAE combined with apatinib in rabbit VX2 liver tumors. Alterations in D and f values were closely related to the MVD of liver tumor tissues.

The value of intra-operative ultrasonography on safety margin and outcome during liver resection and radio-frequency ablation in the management of hepatocellular carcinoma patients

Background

Hepatocellular carcinoma (HCC) is an important health issue worldwide. Liver resection is the optimal management for early compensated HCC patients, but the majority of HCC patients are not candidates for resection. Several nonsurgical treatment modalities such as radio-frequency ablation (RFA), microwave ablation (MWA), trans-arterial chemoembolization, and immune therapy have been established. Intra-operative ultrasound (IOUS) is essential for accurate staging and secures both resection and RFA. We aimed to detect the value of using IOUS on safety margin and outcome during liver resection and RFA in the management of HCC patients. In the current study, 76 HCC patients, 58 males and 18 females, were included. Patients' age ranged from 49 to 69 years. Patients were divided into two groups: 52 open surgery liver resections (open resection group) and 24 laparoscopic-assisted RFA guided with laparoscopic IOUS (LARFA group). The open resection group was further subdivided into 32 cases for whom IOUS was performed and 20 patients studied retrospectively without IOUS. Surgical decisions were based on preoperative ultrasonography, computed tomography, and/or magnetic resonance imaging (MRI). We determined the size, number of lesions, and location by IOUS and compared them with preoperative imaging. Histopathology was done for resected lesions and follow-up CT for all patients.

Results

In the open resection group, the 32 cases of 52 for whom IOUS was performed, all had free surgical margin (100%) while 18 of 20 patients studied retrospectively without IOUS had free surgical margin (90%). Patients operated guided by IOUS had less morbidity and mortality with less operative time and hospital stay. In the LARFA group (24 patients with 37 lesions), the one-month follow-up showed complete ablation for all lesions in the 24 patients, while 12-month follow-up proved two cases of recurrence.

Conclusions

IOUS is a cornerstone in liver surgery. It improves outcomes with less morbidity and mortality and helps to achieve free surgical margin. Using IOUS allows the performance of radical but conservative hepatic resection.

MR Imaging Contrast Agents: Role in Imaging of Chronic Liver Diseases

Contrast-enhanced MR imaging plays an important role in the evaluation of patients with chronic liver disease, particularly for detection and characterization of liver lesions. The two most commonly used contrast agents for liver MR imaging are extracellular agents (ECAs) and hepatobiliary agents (HBAs). In patients with liver disease, the main advantage of ECA-enhanced MR imaging is its high specificity for the diagnosis of progressed HCCs. Conversely, HBAs have an additional contrast mechanism, which results in high liver-to-lesion contrast and highest sensitivity for lesion detection in the hepatobiliary phase. Emerging data suggest that features depicted on contrast-enhanced MR imaging scans are related to tumor biology and are predictive of patients' prognosis, likely to further expand the role of contrast-enhanced MR imaging in the clinical care of patients with chronic liver disease.

Can gadoxetic acid–enhanced magnetic resonance imaging be used to avoid liver biopsy in patients with nonalcoholic fatty liver disease?

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a major cause of liver disease worldwide. The diagnosis of nonalcoholic steatohepatitis (NASH), the most severe form of NAFLD, is crucial and has prognostic and therapeutic implications. However, currently this diagnosis is based on liver biopsy and has several limitations.

AIM

To evaluate the performance of gadoxetic acid–enhanced magnetic resonance imaging (GA-MRI) in differentiating isolated steatosis from NASH in patients with NAFLD.

METHODS

In this prospective study, 56 patients with NAFLD (18 with isolated steatosis and 38 with NASH) underwent GA-MRI. The contrast enhancement index (CEI) was calculated as the rate of increase of the liver-to-muscle signal intensity ratio from before and 20 min after intravenous GA administration. Between-group differences in mean CEI were examined using Student's t test. The area under the receiver operator characteristic curve and the diagnostic performance of gadoxetic acid–enhanced magnetic resonance imaging were evaluated.

RESULTS

The mean CEI for all subjects was 1.82 ± 0.19. The mean CEI was significantly lower in patients with NASH than in those with isolated steatosis (P = 0.008). Two CEI cut-off points were used: < 1.66 (94% specificity) to characterize NASH and > 2.00 (89% sensitivity) to characterize isolated steatosis. CEI values between 1.66 and 2.00 indicated liver biopsy, and the procedure could be avoided in 40% of patients with NAFLD.

CONCLUSION

GA-MRI is an effective noninvasive method that may be useful for the differentiation of NASH from isolated steatosis, and could help to avoid liver biopsy in patients with NAFLD.

Pathognomonic imaging signs in abdominal radiology

The imaging evaluation of the abdomen is of crucial importance for every radiologist. In addition to ultrasound, conventional radiographs and contrast-enhanced computed tomography (CT) are the most common imaging procedures in the abdominal region. Numerous pathognomonic signs should be known in this context by every radiologist. Radiographs of the abdomen are an often used first step in radiologic imaging, while CT examinations are carried out for further differentiation, in oncological settings and in time-critical emergency situations. A fast and clear assignment of these signs to a specific disease is the basis for a correct diagnosis. This pictorial review describes the most common pathognomonic signs in abdominal imaging. The knowledge of these pictograms is therefore essential for radiologists interested in abdominal medicine and should also be addressed in training and further education.

Fat-containing liver lesions: a pictorial review

The aim of this pictorial essay is to review the spectrum of fat-containing liver lesions and their characterisation on magnetic resonance imaging with focus on the radiological features that aid in the differential diagnoses. Fat-containing liver lesions comprise a heterogeneous group of tumours with variable imaging findings. Magnetic resonance imaging clearly displays the micro- and macroscopic fat components of the lesions and other characteristic features that are helpful tools to make the differential diagnosis.

Magnetic resonance imaging of the cirrhotic liver: diagnosis of hepatocellular carcinoma and evaluation of response to treatment - Part 1

Magnetic resonance imaging (MRI) is the modern gold standard for the noninvasive evaluation of the cirrhotic liver. The combination of arterial phase hyperenhancement and delayed wash-out allows a definitive diagnosis of hepatocellular carcinoma (HCC) in patients with liver cirrhosis or chronic liver disease, without the requirement for confirmatory biopsy. That pattern is highly specific and has been endorsed in Western and Asian diagnostic guidelines. However, the sensitivity of the combination is relatively low for small HCCs. In this two-part review paper, we will address MRI of the cirrhotic liver. In this first part, we provide a brief background on liver cirrhosis and HCC, followed by descriptions of imaging surveillance of liver cirrhosis and the diagnostic performance of the different imaging modalities used in clinical settings. We then describe some of the requirements for the basic MRI technique, as well as the standard MRI protocol, and provide a detailed description of the appearance of various types of hepatocellular nodules encountered in the setting of the carcinogenic pathway in the cirrhotic liver, ranging from regenerative nodules to HCC.

Ongoing challenges in the diagnosis of hepatocellular carcinoma

In 2001, the European Association for the Study of the Liver (EASL) endorsed the possibility of achieving a non-invasive diagnosis of Hepatocellular Carcinoma (HCC) for the first time. Since then, various refinements of the criteria and techniques capable of achieving this diagnosis and the role of plasma and tissue oncomarkers have been reported in the literature and have been accepted to different extents in various geographical areas. Such tools can also potentially imply prognostic significance. The present article critically discusses some of the most relevant and debated challenges which have emerged in this field, including the role of contrast-enhanced ultrasound, and of hepatocyte-specific magnetic resonance contrast agents, the pitfall of transient hepatic attenuation differences, the reliability of biopsy and the status of biomarkers.

Acute myeloid leukemia masquerading as hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is often diagnosed on the basis of high quality imaging without a biopsy in the cirrhotic liver. This is a case of a 64-year-old Caucasian man with no history of liver disease or cirrhosis that presented with fatigue, weight loss, and abdominal distension and was found to have a large, isolated liver mass with arterial enhancement and portal venous washout on triple-phase computed tomography (CT) suspicious for HCC. The patient was initially referred for a surgical evaluation. Meanwhile, he developed fevers, pancytopenia, and worsening back pain, and a subsequent spinal MRI revealed a heterogeneous bone marrow signal suspicious for metastatic disease. A bone marrow biopsy that followed was diffusely necrotic. A core biopsy of the patient's liver mass was then performed and was diagnostic of acute monocytic-monoblastic leukemia. Findings from peripheral flow cytometry and a repeat bone marrow biopsy were also consistent with this diagnosis, and induction chemotherapy with cytarabine and idarubicin was initiated. This case describes a rare presentation of myeloid sarcoma (MS) as an isolated, hypervascular liver mass that mimics HCC in its radiographic appearance. Due to the broad differential for a liver mass, a confirmatory biopsy should routinely be considered prior to surgical intervention.

Discrimination of cirrhotic nodules, dysplastic lesions and hepatocellular carcinoma by their vibrational signature

Background

Hepatocarcinogenesis is a multistep process characterized in patients with chronic liver diseases by a spectrum of hepatic nodules that mark the progression from regenerative nodules to dysplastic lesions followed by hepatocellular carcinoma (HCC). The differential diagnosis between precancerous dysplastic nodules and early HCC still represents a challenge for both radiologists and pathologists. We addressed the potential of Fourier transform-infrared (FTIR) microspectroscopy for grading cirrhotic nodules on frozen tissue sections.

Methods

The study was focused on 39 surgical specimens including normal livers (n = 11), dysplastic nodules (n = 6), early HCC (n = 1), progressed HCC on alcoholic cirrhosis (n = 10) or hepatitis C virus cirrhosis (n = 11). The use of the bright infrared source emitted by the synchrotron radiation allowed investigating the biochemical composition at the cellular level. Chemical mapping on whole tissue sections was further performed using a FTIR microscope equipped with a laboratory-based infrared source. The variance was addressed by principal component analysis.

Results

Profound alterations of the biochemical composition of the pathological liver were demonstrated by FTIR microspectroscopy. Indeed, dramatic changes were observed in lipids, proteins and sugars highlighting the metabolic reprogramming in carcinogenesis. Quantifiable spectral markers were characterized by calculating ratios of areas under specific bands along the infrared spectrum. These markers allowed the discrimination of cirrhotic nodules, dysplastic lesions and HCC. Finally, the spectral markers can be measured using a laboratory FTIR microscope that may be easily implemented at the hospital.

Conclusion

Metabolic reprogramming in liver carcinogenesis can constitute a signature easily detectable using FTIR microspectroscopy for the diagnosis of precancerous and cancerous lesions.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0763-6) contains supplementary material, which is available to authorized users.

Differentiation of hepatocellular carcinoma from its various mimickers in liver magnetic resonance imaging: What are the tips when using hepatocyte-specific agents?

Hepatocellular carcinoma is the most common primary hepatic malignant tumor. With widespread use of liver imaging, various cirrhosis-related nodules are frequently detected in patients with chronic liver disease, while diverse hypervascular hepatic lesions are incidentally detected but undiagnosed on dynamic computed tomography and magnetic resonance imaging (MRI). However, use of hepatocyte-specific MR contrast agents with combined perfusion and hepatocyte-selective properties have improved diagnostic performance in detection and characterization of focal liver lesions. Meanwhile, the enhancement patterns observed during dynamic phases using hepatocyte-specific agents may be different from those observed during MRI using conventional extracellular fluid agents, leading to confusion in diagnosis. Therefore, we discuss useful tips for the differentiation of hepatocellular carcinoma from similar lesions in patients with and without chronic liver disease using liver MRI with hepatocyte-specific agents.

Multiparametric Gd-EOB-DTPA magnetic resonance in diagnosis of HCC: dynamic study, hepatobiliary phase, and diffusion-weighted imaging compared to histology after orthotopic liver transplantation

PURPOSE

To evaluate Gd-EOB-DTPA-enhanced magnetic resonance (MR) performance during dynamic (DYN) phases, hepatobiliary (HB) phase and diffusion-weighted imaging (DWI) compared with pathological findings in patients undergoing orthotopic liver transplantation (OLT) for hepatocellular carcinoma (HCC) associated with different conditions, such as stage of chronic liver disease, histological grading, nodule size, and occurrence of previous treatments.

METHODS

Retrospective analysis of 64 nodules reported as HCC at pathological analysis on 28 explanted livers, examined about 3 months before OLT using a 1.5 T device and 16 channels array after intravenous GD-EOB-DTPA injection. Lesions features and hepatic functional values were recorded for each patient. Two radiologists performed in consensus the analysis of nodules on DYN, HB, and DWI. MR findings were compared with those of pathological anatomy. Diagnostic indicators were calculated for each technique.

RESULTS

DYN and HB showed no statistically significant difference in sensitivity (88% and 98%, respectively), diagnostic accuracy (90.6% and 99.9%), and specificity (both 100%), for all Child-Pugh scores, gradings, sizes, and presence or absence of previous treatments. DWI had a statistically significant lower sensitivity compared to DYN (p = 0.001) and HB (p < 0.0001); its sensitivity was significantly inferior for Child-Pugh Class B nodules than for Child-Pugh Class A ones (p = 0.00005). DWI sensitivity presented a significant increase (p = 0.03) with grading and presence of previous treatments (p = 0.0006). ADC values showed no statistically significant changes with Child-Pugh score, grading and nodules size; statistically significant increase was instead found for treated vs. untreated nodules (p = 0.016).

CONCLUSIONS

In a multiparametric HCC MRI assessment, DYN and HB play the leading role, with DWI faring acceptably well for Child-Pugh Class A nodules and treated ones.

Focal liver lesions: Practical magnetic resonance imaging approach

With the widespread of cross-sectional imaging, a growth of incidentally detected focal liver lesions (FLL) has been observed. A reliable detection and characterization of FLL is critical for optimal patient management. Maximizing accuracy of imaging in the context of FLL is paramount in avoiding unnecessary biopsies, which may result in post-procedural complications. A tremendous development of new imaging techniques has taken place during these last years. Nowadays, Magnetic resonance imaging (MRI) plays a key role in management of liver lesions, using a radiation-free technique and a safe contrast agent profile. MRI plays a key role in the non-invasive correct characterization of FLL. MRI is capable of providing comprehensive and highly accurate diagnostic information, with the additional advantage of lack of harmful ionizing radiation. These properties make MRI the mainstay for the noninvasive evaluation of focal liver lesions. In this paper we review the state-of-the-art MRI liver protocol, briefly discussing different sequence types, the unique characteristics of imaging non-cooperative patients and discuss the role of hepatocyte-specific contrast agents. A review of the imaging features of the most common benign and malignant FLL is presented, supplemented by a schematic representation of a simplistic practical approach on MRI.

Hepatobiliary contrast agents: differential diagnosis of focal hepatic lesions, pitfalls and other indications

The characterization of focal liver lesions is very important. Magnetic resonance imaging is considered the best imaging method for evaluating such lesions, but does not allow for the diagnosis in all cases. The use of hepatobiliary contrast agents increases the diagnostic accuracy of magnetic resonance imaging and reduces the number of non-specific liver lesions. The main indications for the method include: differentiation between focal nodular hyperplasia and adenoma; characterization of hepatocellular carcinomas in cirrhotic patients; detection of small liver metastases; evaluation of biliary anatomy; and characterization of postoperative biliary fistulas. The use of hepatobiliary contrast agents may reduce the need for invasive diagnostic procedures and further investigations with other imaging methods, besides the need for imaging follow-up.

Diffusion-weighted imaging of the liver in patients with chronic liver disease: comparison of monopolar and bipolar diffusion gradients for image quality and lesion detection

OBJECTIVE

The objective of our study was to compare diffusion-weighted imaging (DWI) sequences using a bipolar versus a monopolar single-shot echo-planar imaging (EPI) gradient design for image quality and for lesion detection and characterization in patients with liver disease.

MATERIALS AND METHODS

In this retrospective study, 77 patients with chronic liver disease who underwent MRI including bipolar and monopolar DWI at 1.5 T were assessed. Two independent observers reviewed the DWI studies for image quality and the detection and characterization of liver lesions. The reference standard for diagnosis was established by consensus review of two different observers using imaging characteristics on conventional MRI sequences, lesion stability over time, pathologic correlation, or a combination of these findings. The estimated signal-to-noise ratio (SNR) of liver parenchyma and apparent diffusion coefficients (ADCs) of the liver and lesions were calculated for both sequences. ROC analysis was conducted to evaluate the performance of ADC for the diagnosis of hepatocellular carcinoma (HCC).

RESULTS

Eighty-five lesions, 50 HCCs and 35 benign lesions, were detected with the reference standard in 38 patients. There was equivalent image quality for the bipolar and monopolar sequences (p = 0.24-0.42). The HCC detection rate for observers 1 and 2 was slightly better with bipolar DWI (50.0% and 52.0%, respectively) compared with monopolar DWI (44.0% and 46.0%); however, this difference did not reach statistical significance. The estimated SNR was higher with the monopolar sequence than with the bipolar sequence (p ≤ 0.001). The AUC for the ROC curve was 0.691 for bipolar DWI and 0.649 for monopolar DWI when ADC was used for the characterization of HCC, which is not a statistically significant difference (p = 0.59).

CONCLUSION

The higher estimated SNR yielded by the monopolar DWI sequence did not translate into better HCC detection compared with the bipolar DWI sequence. ADC has a limited role for HCC characterization in patients with liver disease.

Diagnosis and management of solid benign liver lesions

More and more asymptomatic benign liver tumours are discovered incidentally and can be divided into regenerative lesions and true neoplastic lesions. The most common regenerative lesions include hemangioma, focal nodular hyperplasia and inflammatory pseudotumours of the liver. Neoplastic lesions include hepatocellular adenomas and angiomyolipomas. Regenerative lesions rarely increase in volume, do not yield a higher risk of complications and usually do not require treatment. By contrast, hepatocellular adenomas and angiomyolipomas can increase in volume and are associated with a risk of complications. Large hepatocellular adenomas (>5 cm in diameter) are undoubtedly associated with a risk of bleeding and malignant transformation, particularly the inflammatory (also known as telangiectatic) and β-catenin mutated subtypes. Accurate diagnosis needs to be obtained to select patients eligible for surgical resection. MRI has markedly improved diagnosis and can identify the major hepatocellular adenomas subtypes. The use of biopsy results to inform the indication for resection remains questionable. However, when diagnosis remains uncertain after imaging, percutaneous biopsy could help improve diagnostic accuracy.

Radiological features of hepatocellular carcinoma

Present article is a review of radiological features of hepatocellular carcinoma on various imaging modalities. With the advancement in imaging techniques, biopsy is rarely needed for diagnosis of hepatocellular carcinoma (HCC), unlike other malignancies. Imaging is useful not only for diagnosis but also for surveillance, therapy and assessing response to treatment. The classical and the atypical radiological features of HCC have been described.

Using intravoxel incoherent motion (IVIM) MR imaging to predict lipiodol uptake in patients with hepatocellular carcinoma following transcatheter arterial chemoembolization: a preliminary result

PURPOSE

To assess the usefulness of intravoxel incoherent motion diffusion weighted imaging (IVIM-DWI) for predicting lipiodol uptake in patients with hepatocellular carcinoma (HCC) after transcatheter arterial chemoembolization (TACE).

MATERIALS AND METHODS

The institutional review board approved this study. 44 HCC patients underwent IVIM-DWI and Gd-EOB-DTPA-enhanced MRI prior to TACE. Using post-TACE CT as a reference standard, each HCC was classified into either lipiodol good uptake (LGU) or poor uptake (LPU) group. Apparent diffusion coefficient (ADC), true diffusion coefficient (D), perfusion coefficient (D*), and perfusion fraction (f) in HCC were calculated. Arterial enhancement ratio (AER) and IVIM parameters were compared between those two groups using the Mann-Whitney U test.

RESULTS

Of the 51 HCCs, 37 (72.5%) were LGU group and 14 (27.5%) were LPU group. AER of HCC was significantly higher in LGU than LPU (0.99±0.54 and 0.67±0.45; P=.034). ADC, D, and f values were not significantly different (P=.073, .059, and .196, respectively) between these two groups. D* was significantly elevated in LGU than LPU (48.10±15.33 and 26.75±9.55; P=.001).

CONCLUSION

Both AER derived from contrast enhanced MRI and D* values derived from IVIM-DWI for HCC were significantly higher in LGU than in LPU. These parameters would be helpful for predicting the lipiodol uptake.