MR imaging of hepatocellular carcinomas: effect of Cu and Fe contents on signal intensity

Current Imaging Diagnosis of Hepatocellular Carcinoma

Simple Summary

The role of imaging in the management of hepatocellular carcinoma (HCC) has significantly evolved and expanded beyond the plain radiological confirmation of the tumor based on the typical appearance in a multiphase contrast-enhanced CT or MRI examination. The introduction of hepatobiliary contrast agents has enabled the diagnosis of hepatocarcinogenesis at earlier stages, while the application of ultrasound contrast agents has drastically upgraded the role of ultrasound in the diagnostic algorithms. Newer quantitative techniques assessing blood perfusion on CT and MRI not only allow earlier diagnosis and confident differentiation from other lesions, but they also provide biomarkers for the evaluation of treatment response. As distinct HCC subtypes are identified, their correlation with specific imaging features holds great promise for estimating tumor aggressiveness and prognosis. This review presents the current role of imaging and underlines its critical role in the successful management of patients with HCC.

Abstract

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer related death worldwide. Radiology has traditionally played a central role in HCC management, ranging from screening of high-risk patients to non-invasive diagnosis, as well as the evaluation of treatment response and post-treatment follow-up. From liver ultrasonography with or without contrast to dynamic multiple phased CT and dynamic MRI with diffusion protocols, great progress has been achieved in the last decade. Throughout the last few years, pathological, biological, genetic, and immune-chemical analyses have revealed several tumoral subtypes with diverse biological behavior, highlighting the need for the re-evaluation of established radiological methods. Considering these changes, novel methods that provide functional and quantitative parameters in addition to morphological information are increasingly incorporated into modern diagnostic protocols for HCC. In this way, differential diagnosis became even more challenging throughout the last few years. Use of liver specific contrast agents, as well as CT/MRI perfusion techniques, seem to not only allow earlier detection and more accurate characterization of HCC lesions, but also make it possible to predict response to treatment and survival. Nevertheless, several limitations and technical considerations still exist. This review will describe and discuss all these imaging modalities and their advances in the imaging of HCC lesions in cirrhotic and non-cirrhotic livers. Sensitivity and specificity rates, method limitations, and technical considerations will be discussed.

Expression of zinc transporters ZIP4, ZIP14 and ZnT9 in hepatic carcinogenesis-An immunohistochemical study

INTRODUCTION

Dysregulation of both, systemic zinc levels and tissue-specific zinc transporters, is reported in chronic inflammatory and malignant liver disease (hepatocellular carcinoma, HCC). Aim of this study is to assess the expression level of three zinc transporters in liver tissue and HCC: ZIP4, ZIP14 and ZnT9.

METHODS

The study is based on tissue samples obtained from 138 patients with histologically proven HCC. Tissue specimens from tumor (n = 138) and extra-lesional specimens (n = 72) were assessed immunohistochemically for the expression of the three zinc transporters. Expression levels were semi-quantitatively scored and statistically analyzed with respect to the etiology of HCC (alcohol, AFLD; non-alcoholic fatty liver disease, NAFLD; virus-hepatitis, VH) and survival.

RESULTS

Overall, expression levels of ZIP4, ZIP14 and ZnT9 were significantly higher in HCC tissue than in adjacent extra-lesional liver tissue. Expression levels in tumor tissue and survival time revealed a negative correlation for ZIP4 and ZIP14, and in part for ZnT9 (nuclear staining) (p < 0.05), whereas cytoplasmic staining of ZnT9 did not correlate with survival. Furthermore, the expression level of ZIP4 in extra-lesional tissue showed inverse correlation with survival time.

CONCLUSION

The upregulation of zinc transporters in hepatic carcinogenesis and its negative correlation with survival time implies a regulatory/functional link between zinc-homeostasis and development/progression of HCC that deserves to be further explored.

Hepatic Relaxation Times from Postmortem MR Imaging of Adult Humans

Purpose:

To measure T₁ and T₂ values of hepatic postmortem magnetic resonance (PMMR) imaging.

Materials and Methods:

We performed hepatic PMMR imaging of 22 deceased adults (16 men, 6 women; mean age, 56.3 years) whose deaths were for reasons other than liver injury or disease at a mean of 27.7 hours after death. Before imaging, the bodies were kept in cold storage at 4°C (mean rectal temperature, 17.6°C). We measured T₁ and T₂ values in the liver at two sites (the anterior segment of the right lobe and the lateral segment of the left lobe). We also investigated the influence of the body temperature and postmortem interval on T₁ and T₂ values.

Results:

In the anterior segment of the right lobe and the lateral segment of the left lobe, T₁ values of PMMR imaging were 524 ± 112 ms and 472 ± 104 ms (mean ± standard deviation), respectively; while T₂ values were 42 ± 6 ms and 43 ± 8 ms, respectively. T₁ and T₂ values did not differ significantly between the two sites (P ≧ 0.05). Regarding temperature, the T₂ values of hepatic PMMR imaging were linearly correlated with the body temperature, but the T₁ values were not. The T₁ and T₂ values of the two sites in the liver did not correlate with the postmortem interval.

Conclusion:

Reduction in body temperature after death is considered to induce T₁ and T₂ value changes in the liver on PMMR imaging.

Small hepatocellular carcinoma: MRI findings for predicting tumor growth rates

RATIONALE AND OBJECTIVES

Current clinical practice favors imaging rather than biopsy to diagnose hepatocellular carcinoma (HCC). There is a need to better understand tumor biology and aggressiveness of HCC. Our goal is to investigate magnetic resonance imaging (MRI) features of HCC that are associated with faster growth rates (GRs).

MATERIALS AND METHODS

After approval from institutional review board, a retrospective evaluation was performed of pre-liver transplant patients. Fifty-two patients who developed a >2 cm HCC on serial imaging were included in the study group, with a total of 60 HCCs seen. Precursor foci were identified on serial MRIs before the specific diagnostic features of >2 cm HCC could be made, and GRs and MRI features, including signal on T1- and T2-weighted images (WI), the presence of intralesional steatosis on chemical shift imaging, and enhancement pattern were analyzed. GRs were correlated with imaging features.

RESULTS

The average GR of precursor lesions to >2 cm HCC was determined to be 0.23 cm/mo (standard deviation [SD], 0.32), with a doubling time of 5.26 months (SD, 5.44). The presence of increased signal intensity (SI) on T2-WI was associated with significantly higher growth (P = .0002), whereas increased intensity on T1-WI at the initial study was associated with a significantly lower GR (P = .0162). Furthermore, lesions with hypervascular enhancement with washout pattern had significantly higher GR (P = .0164). There is no evidence of differences in GRs seen in lesions with steatosis.

CONCLUSIONS

Small precursor lesions with increased SI on T2-WI and a washout pattern of enhancement are associated with faster GRs, which may suggest more aggressive tumor biology. These features may be helpful in patient management and surveillance for HCC.

Imaging of hepatocellular carcinoma: current concepts

Hepatocellular carcinoma (HCC) is the most common primary hepatic malignancy, and usually develops in the setting of liver cirrhosis. The early diagnosis of HCC is essential as curative treatment (including surgical resection and liver transplantation) improves survival. While screening and surveillance are traditionally performed with ultrasound, reported accuracies of ultrasound vary greatly, and poor sensitivity for small nodules is a uniformly recognized concern. Advances in computed tomography (CT) and magnetic resonance imaging (MRI), including multidetector technology and fast breath hold sequences now allow dynamic multiphasic enhanced imaging of the liver with excellent spatial and temporal resolution, holding much promise for improved HCC detection.

Quantitative (19)F imaging of nmol-level F-nucleotides/-sides from 5-FU with T(2) mapping in mice at 9.4T

A unique acquisition method is proposed for quantitative, high-sensitivity (19)F MR spectroscopic imaging for the study of drug distribution aiming at nmol-level metabolite information in mice. The use of fast spin echo (FSE) at 9.4T allowed us to obtain whole-body images with minimal effect of magnetic susceptibility and to acquire several metabolite signals simultaneously by the method of interleaved multifrequency selection. Modified 2-shot FSE was designed for simultaneous, high-sensitivity (19)F imaging and T(2) mapping. A time course study including all the main metabolites at 10-minute resolution was attained with an oral dose of 1-2 mmol 5-fluorouracil (5-FU) (130-260 mg)/kg in mice. With acquisition parameters optimized for in vivo T(2) of 40 ms, images of F-nucleotides/-sides, effective anabolites of the anticancer drug 5-FU, were obtained at the level of 200 nmol in the tumor for all the mice studied with a linear correlation (R = 0.96) between image intensity and the quantity determined in the excised tissue. The method exhibits potential capability of molecular imaging with a variety of (19)F-labeled compounds and drug evaluation.

Focal liver lesions hyperintense on T1-weighted magnetic resonance images

This article reviews focal liver lesions hyperintense on T1-weighted magnetic resonance (MR) images and describes the underlying etiologies associated with their T1 signal intensity. Although focal liver lesions are commonly detected because of their iso- or hypointensity on T1-weighted images, lesions (benign or malignant) may present with T1 hyperintensity when they contain T1 shortening elements--such as fat, hemorrhage, copper, melanin, and highly concentrated proteins. Our discussion includes the description of state-of-the-art T1-weighted MR sequences and the imaging features of lesions on pre- and postcontrast MR images that are characteristic for lesion composition and useful for making accurate diagnosis.

The hypointense liver lesion on T2-weighted MR images and what it means

The vast majority of focal liver lesions are hyperintense on T2-weighted magnetic resonance (MR) images. Rarely, however, hepatic nodules may appear totally or partially hypointense on those images. Causes for this uncommon appearance include deposition of iron, calcium, or copper and are related to the presence of blood degradation products, macromolecules, coagulative necrosis, and other conditions. Although rare, low signal intensity relative to surrounding liver on T2-weighted images may be seen in a wide spectrum of lesions. Examples include cases of focal nodular hyperplasia, hepatocellular adenoma, hepatocellular carcinoma, metastases, leiomyoma, siderotic or dysplastic nodules, nodules in Wilson disease, granuloma, and hydatid cyst. On fat-suppressed T2-weighted images, nodules with a lipomatous component, such as lipoma, angiomyolipoma, hepatocellular adenoma, and hepatocellular carcinoma may also appear partially or totally hypointense. The conjunction of other MR imaging findings and their integration in the clinical setting may allow a correct diagnosis in a considerable proportion of cases. The cause for T2-weighted hypointensity may not be, however, always recognized, and only pathologic correlation may provide the answer. The aims of this work are to discuss the causes and mechanisms of hypointensity of liver lesions on T2-weighted images and proposing an algorithm for classification that may be useful as a quick reminder for the interested reader.

Trace element concentration in primary liver cancers--a systematic review

BACKGROUND

The incidence of primary liver cancer varies between countries. Many of the etiological factors contributing to the geographical variations in incidence are unknown. Development of hepatocellular carcinoma has been linked to levels of trace elements. This review summarizes the evidence associating HCC with trace elements.

METHODS

MEDLINE, EMBASE, and CENTRAL databases were searched. Various inclusion and exclusion criteria were applied to select the articles for inclusion. Data extraction was performed using a custom designed data extraction form.

RESULTS

A total of 12,344 references were identified. Duplicates, 1,597, were excluded. Clearly irrelevant references, 10,676, were excluded through reading titles and abstracts. Some references (59) were excluded by applying the exclusion criteria. Twelve studies including 646 patients and measuring iron content (8), copper content (11), zinc (9), and selenium (2) qualified for the review. Although a meta-analysis was not possible due to heterogeneity between the studies, a clear pattern of distribution of the trace elements was discernible.

CONCLUSION

Iron and zinc content are lower in HCC than in surrounding tissues or normal controls. Copper content is lower in HCC than in surrounding tissues and cirrhotic controls. Epidemiological and physiological reasons for the trace element alterations should be further investigated.

Evaluation of MR signal index for the assessment of occupational manganese exposure of welders by measurement of local proton T1 relaxation time

Magnetic resonance (MR) imaging has become a useful tool for the estimation of occupational exposure to manganese (Mn). However, validity of signal indices on T1-weighted imaging, a proxy measurement of T1 relaxation time shortening due to Mn deposition, needs to be evaluated in an occupationally exposed population. We performed MR imaging on 20 male welders and 10 age- and gender-matched, non-office workers in a shipyard. We measured the relative signal intensity ratio of the globus pallidus (GP) to the frontal white matter on T1-weighted MR images (pallidal index, PI). We also assessed the visual scale for the relative signal intensity of the GP, which was graded as 0-2 by a radiologist. We evaluated both signal index and visual scale in relation to the T1 relaxation time measured at the GP. Both PI and T1 relaxation time were significantly increased in the welders compared to the non-welders. T1 relaxation time began to decrease from visual scale 2, while PI began to increase from visual scale 1. Environmental Mn exposure indices correlated well with both T1 relaxation time and PI. However, blood Mn level correlated only with T1 relaxation time, and not with PI. T1 relaxation time correlated with PI only at the higher level of PI. These results indicate the possible inaccuracy of visual scoring and the discrepancy between T1 relaxation time and PI, especially at the lower level of signal intensity. Although both T1 and PI are good biomarkers for the environmental Mn exposure, non-linearity of the relationship between T1 and PI must be considered in the assessment of Mn exposure using MRI.

Magnetic resonance imaging of hepatocellular carcinoma

Hepatocellular carcinoma (HCC), the most common primary hepatic malignancy, usually develops in patients with cirrhosis, growing sequentially from low-grade dysplastic nodules to frank malignant HCC. Its recognition is critical because curative treatment and prognosis require early diagnosis. Survival in patients with HCC relates directly to the number, size, and extent of lesions at diagnosis. Imaging of HCC is complicated because the tumor has a varied imaging appearance and frequently coexists with other cirrhotic nodules. Magnetic resonance imaging (MRI), the best available diagnostic technique, offers good contrast resolution and diagnostic sensitivity ranging from 33% to 77%. The main difficulty is not in diagnosing large tumors, but rather small tumors (<2 cm), because of considerable overlap on imaging between benign (regenerative), borderline (dysplastic), and malignant nodules. Increasing degrees of histological malignancy are associated with increasing arterialization and loss of portal blood supply; therefore, recognition of HCC requires dynamic imaging with gadolinium-enhanced T1-weighted sequence. Typically, HCC is a focal lesion with high signal intensity on T2-weighted images, variable signal intensity on T1-weighted images, intense arterial phase enhancement after gadolinium injection, and isointensity or hypointensity at the portal venous phase. The sensitivity of MRI for detecting small lesions is low, and improvement is still needed. Newer contrast agents, higher field strength (3 Tesla) imaging, and perfusion and diffusion MRI techniques possibly will provide greater sensitivity and specificity for detecting small HCCs in the future.

Small nodule detection in cirrhotic livers: evaluation with US, spiral CT, and MRI and correlation with pathologic examination of explanted liver

PURPOSE

The purpose of this work was to evaluate the detection and characterization of nodules > or = 8 mm and small hepatocellular carcinomas (HCCs) in liver cirrhosis.

METHOD

Pathologic examination and results of US, helical CT, and dynamic MRI with gadolinium were compared after orthotopic liver transplantation (OLT) of 43 cirrhotic patients. Nodules were classified as macroregenerative nodules (MRNs), borderline nodules (BNs), and HCC.

RESULTS

Pathologic examination classified 69 nodules: 50 MRNs, 6 BNs, and 13 HCCs. Sensitivities of MRN, BN, and HCC detection were, respectively, for US imaging 2% (1/50), 33.3% (2/6), and 46.2% (6/13); for helical CT 2% (1/50), 50% (3/6), and 53.8% (7/13); and for MRI 42% (21/50), 50% (3/6), and 76.9% (10/13). MRI detected 21 MRNs. They presented on T1/T2-weighted images as hyperintense/hypointense (n = 8), hyperintense/isointense (n = 7), hypointense/hypointense (n = 4), hypointense/isointense (n = 1), and hypointense depicted only on echo planar imaging (n = 1). The three detected BNs were hyperintense/hypointense nodules. The 10 detected HCCs appeared hyperintense/isointense (n = 7), hyperintense/hypointense (n = 2), and hypointense/isointense (n = 1). None of the MRNs but eight HCCs and one BN were enhanced after gadolinium injection.

CONCLUSION

Contrast-enhanced MRI is the most sensitive technique for detecting liver nodules. No MR signal intensity pattern characteristic of small HCCs enables differentiation from benign nodules, however. Gadolinium enhancement is the most sensitive and specific characteristic of HCC.

Radiologic diagnosis of hepatocellular carcinoma

Substantial recent technologic improvements in CT scanning, US scanning, and MR imaging, together with advances in the understanding of the optimal application of contrast administration techniques, have facilitated advances in radiologic imaging detection for HCC diagnosis. Despite a large number of earlier publications reporting a high sensitivity for imaging detection of HCC, more recent screening studies of large cirrhotic populations confirm that only 37% to 45% of HCC tumor nodules are detected by CT scanning, US scanning, or MR imaging. Future investigation will include efforts to improve the detection of small tumors and to characterize with greater specificity the spectrum of nodular changes that occur with cirrhosis. Although several small series have attempted to characterize cirrhotic nodules by evaluating the relative arterial or portal blood supply, these preliminary results require substantiation with larger series. Continued technologic advances such as multidetector helical CT scanning and new US and MR contrast agents under investigation may improve the imaging characterization of cirrhotic nodules.

Elucidation of accuracy in calibration of MR signal intensity based on transmission amplitude method

To calibrate magnetic resonance (MR) signal intensity that depends on radio frequency (RF) coil loading, the transmission amplitude (TRA) for the excitation in the transmit-receive RF coil has been used as a good index in the so-called TRA method. As this TRA method needs neither an internal reference nor an additional external reference for the calibration, its accuracy is free from reference measurements. This study elucidated the calibration accuracy of MR signal intensities based on the TRA method. A cylindrical gel phantom was used for accuracy measurements with a 1.5-T MRI unit with conventional T1 imaging as a simple pulse sequence for various loading conditions. The brain parenchyma of eight healthy volunteers also showed calibrated MR signal deviations. The error of the phantom calibration measurements was 2.18% (S.D.%). The background noise intensity of images was theoretically derived to correlate with the impedance mismatching of the RF coil, which is inevitable for fixed tuning, even for automatic tuning that is not always exact. Taking into account this noise intensity, the calibration method was modified to reduce its error to 1.50%. The standard deviations of the calibrated values in the thalamus and frontal white matter were 2.9 and 3.8%, respectively. We suggest that the modified TRA method is a practical and reliable technique to obtain clinical numeric evidence.

Magnetic resonance imaging of focal and diffuse hepatic disease

MRI is a powerful tool in the detection and characterization of both focal and diffuse liver pathology. Because of superior soft tissue characterization, direct multi-planar capabilities and lack of ionizing radiation, current state of the art MRI is useful when contrast CT is relatively contraindicated or not definitive. This article reviews the MRI findings of the most common focal and diffuse liver diseases encountered in clinical practice. Reviews of current MR techniques and MR contrast agents used in liver imaging have been recently published. For this article, discussion of specific techniques and use of contrast is addressed for each pathological entity discussed.