Three-dimensional dynamic liver MR imaging using sensitivity encoding for detection of hepatocellular carcinomas: comparison with superparamagnetic iron oxide-enhanced mr imaging

Iron Sucrose as MRI Contrast Agent in Ischemic Stroke Model

BACKGROUND

Despite the growing concern about the safety of gadolinium-based contrast agents (GBCAs), they are still the most commonly used. Ferumoxytol, as an off-label alternative MRI contrast agent, cannot be administered by a rapid bolus for dynamic susceptibility contrast perfusion-weighted imaging (DSC-PWI).

PURPOSE

To assess the feasibility of iron sucrose (IS) as a contrast agent for MR angiography (MRA) and DSC-PWI.

STUDY TYPE

Prospective animal model.

ANIMAL MODEL

Thirty-six normal rats (16 for MRA, 20 for biocompability tests) and 36 occlusion of the middle cerebral artery (MCAO) model rats.

FIELD STRENGTH/SEQUENCE

3.0T; head and neck angiography, using a fast spoiled gradient-recalled-echo (FSPGR) sequence and DSC-MRI using echo planar imaging(EPI) sequence.

ASSESSMENT

MRA was performed on normal rats to examine the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of different doses of IS. DSC-PWI was performed on MCAO rats at 0, 24, 48, and 72 hours postreperfusion to investigate the lesion detectability of IS. Arterial spin labeling (ASL) and DSC-PWI enhanced by GBCAs were conducted on MCAO rats as controls.

STATISTICAL TESTS

Kruskal-Wallis test was used to compare qualitative assessment. One-way analysis of variance (ANOVA) was used to compare the parametric data. Pearson's r values were evaluated between relative cerebral blood flow(rCBF)-ASL, rCBF-DSC_IS , and rCBF obtained from DSC-PWI enhanced by GBCA.

RESULTS

The mean SNR and CNR of the common carotid artery at doses of 10 mg Fe/kg of IS were comparable with the standard dose of GBCAs (SNR: 68.04 ± 12.55 vs. 67.72 ± 14.66; CNR: 23.78 ± 7.21vs. 21.63 ± 6.83). In MCAO rat models, rCBF and relative cerebral blood volume (rCBV) of ipsilateral striatum declined (0.72 ± 0.14, 0.86 ± 0.11) with prolonged relative mean transit time (rMTT) and relative time-to-peak (rTTP) (1.27 ± 0.24, 1.07 ± 0.03) following occlusion. Hyperperfusion was observed in all rats at 48 and 72 hours postreperfusion, in 4/6 rats at 24 hours postreperfusion for IS-mediated DSC-PWI.

DATA CONCLUSION

IS may be an effective contrast agent for both MRA and DSC-PWI in ischemic stroke models.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY STAGE: 1 J. Magn. Reson. Imaging 2020;52:836-849.

Detecting GPC3-Expressing Hepatocellular Carcinoma with L5 Peptide-Guided Pretargeting Approach: In Vitro and In Vivo MR Imaging Experiments

Objective

To investigate the potential of L5 peptide-guided pretargeting approach to identify GPC3-expressing hepatocellular carcinoma (HCC) using ultrasmall superparamagnetic iron oxide (USPIO) as the MR probe.

Methods

Immunofluorescence with carboxyfluorescein- (FAM-) labeled L5 peptide was performed in HepG2 cells. Polyethylene glycol-modified USPIO (PEG-USPIO) and its conjugation with streptavidin (SA-PEG-USPIO) were synthesized, and their hydrodynamic diameters, zeta potential, T₂ relaxivity, and cytotoxicity were measured. In vitro and in vivo two-step pretargeting MR imaging was performed on HepG2 cells and tumor-bearing mice after the administration of biotinylated L5 peptide (first step), followed by SA-PEG-USPIO (second step). Prussian blue staining was performed to assess iron deposition in tumors.

Results

The high specificity of L5 peptide for GPC3 was demonstrated. Generation of SA-PEG-USPIO nanoparticles with good biocompatibility (an average hydrodynamic diameter of 35.97 nm and a zeta potential of -7.91 mV), superparamagnetism (R ₂ = 0.1039 × 10³ mM^-1s^-1), and low toxicity was achieved. The pretargeting group showed more enhancement than the nonpretargeting group both in vitro (60% vs 20%, P < 0.05) and in vivo (32% vs 6%, P < 0.001). Substantial iron deposition was only observed in HepG2 cells and tumors in the pretargeting group.

Conclusion

L5 peptide-guided, two-step pretargeting approach with USPIO as the MR imaging probe is a lucrative strategy to specifically identify GPC3-expressing HCC.

Challenges and opportunities in developing targeted molecular imaging to determine inner ear defects of sensorineural hearing loss

The development of inner ear gene carriers and delivery systems has enabled genetic defects to be repaired and hearing to be restored in mouse models. Today, promising advances in translational therapies provide confidence that targeted molecular therapy for inner ear diseases will be developed. Unfortunately, the currently available non-invasive modalities, such as Computerized Tomography scan or Magnetic Resonance Imaging provide insufficient resolution to identify most pathologies of the human inner ear, even when the current generation of contrast agents is utilized. The development of targeted contrast agents may play a critical role in determining the cause of, and treatment for, sensorineural hearing loss. Such agents should be able to pass through the cochlea barriers, possess minimal cytotoxicity, and easily conjugate to a targeting agent, without distorting the anatomic details. This review focuses on a series of contrast agents which may fit these criteria for potential clinical application.

A comprehensive literatures update of clinical researches of superparamagnetic resonance iron oxide nanoparticles for magnetic resonance imaging

This paper aims to update the clinical researches using superparamagnetic iron oxide (SPIO) nanoparticles as magnetic resonance imaging (MRI) contrast agent published during the past five years. PubMed database was used for literature search, and the search terms were (SPIO OR superparamagnetic iron oxide OR Resovist OR Ferumoxytol OR Ferumoxtran-10) AND (MRI OR magnetic resonance imaging). The literature search results show clinical research on SPIO remains robust, particularly fuelled by the approval of ferumoxytol for intravenously administration. SPIOs have been tested on MR angiography, sentinel lymph node detection, lymph node metastasis evaluation; inflammation evaluation; blood volume measurement; as well as liver imaging. Two experimental SPIOs with unique potentials are also discussed in this review. A curcumin-conjugated SPIO can penetrate brain blood barrier (BBB) and bind to amyloid plaques in Alzheime's disease transgenic mice brain, and thereafter detectable by MRI. Another SPIO was fabricated with a core of Fe3O4 nanoparticle and a shell coating of concentrated hydrophilic polymer brushes and are almost not taken by peripheral macrophages as well as by mononuclear phagocytes and reticuloendothelial system (RES) due to the suppression of non-specific protein binding caused by their stealthy ''brush-afforded'' structure. This SPIO may offer potentials for the applications such as drug targeting and tissue or organ imaging other than liver and lymph nodes.

Alternatives to GBCA: Are We There Yet?

Gadolinium has been widely used as the contrast agent of choice for magnetic resonance imaging (MRI). However, gadolinium administration is not always desired due to its inherent enhancement properties and potential side effects (nephrogenic systemic fibrosis). This article reviews gadolinium alternatives, iron-, and manganese- based agents, and their current clinical usage for contrast-enhanced MRI examinations.

Current status of superparamagnetic iron oxide contrast agents for liver magnetic resonance imaging

Five types of superparamagnetic iron oxide (SPIO), i.e. Ferumoxides (Feridex^® IV, Berlex Laboratories), Ferucarbotran (Resovist^®, Bayer Healthcare), Ferumoxtran-10 (AMI-227 or Code-7227, Combidex^®, AMAG Pharma; Sinerem^®, Guerbet), NC100150 (Clariscan^®, Nycomed,) and (VSOP C184, Ferropharm) have been designed and clinically tested as magnetic resonance contrast agents. However, until now Resovist^® is current available in only a few countries. The other four agents have been stopped for further development or withdrawn from the market. Another SPIO agent Ferumoxytol (Feraheme^®) is approved for the treatment of iron deficiency in adult chronic kidney disease patients. Ferumoxytol is comprised of iron oxide particles surrounded by a carbohydrate coat, and it is being explored as a potential imaging approach for evaluating lymph nodes and certain liver tumors.

Exponential growth of publications on carbon nanodots by Chinese authors

Publication statistics was retrieved on carbon nanodots (C-dots) from 2004 up till 2014 using the web of Science(TM) search engine. The number of publications from Chinese authors increased exponentially during this period. Till 2014 China mainland authors contributed 47% of the total publications. Publications on pharmacology and toxicology lagged far behind the publications on chemistry and material science, indicating that research is not solidly moving toward the direction of application.

Magnetic resonance imaging of the cirrhotic liver: An update

Noninvasive imaging has become the standard for hepatocellular carcinoma (HCC) diagnosis in cirrhotic livers. In this review paper, we go over the basics of MR imaging in cirrhotic livers and describe the imaging appearance of a spectrum of hepatic nodules marking the progression from regenerative nodules to low- and high-grade dysplastic nodules, and ultimately to HCCs. We detail and illustrate the typical imaging appearances of different types of HCC including focal, multi-focal, massive, diffuse/infiltrative, and intra-hepatic metastases; with emphasis on the diagnostic value of MR in imaging these lesions. We also shed some light on liver imaging reporting and data system, and the role of different magnetic resonance imaging (MRI) contrast agents and future MRI techniques including the use of advanced MR pulse sequences and utilization of hepatocyte-specific MRI contrast agents, and how they might contribute to improving the diagnostic performance of MRI in early stage HCC diagnosis.

Performance of gadoxetic acid-enhanced MRI for detecting hepatocellular carcinoma in recipients of living-related-liver-transplantation: comparison with dynamic multidetector row computed tomography and angiography-assisted computed tomography

PURPOSE

To clarify the diagnostic performance of gadoxetic acid-enhanced MRI for the detection of hepatocellular carcinoma (HCC) in recipients of living related-liver transplantation (LRLT).

MATERIALS AND METHODS

This retrospective study group consisted of 15 patients with 61 HCCs who each underwent multidetector row computed tomography (MDCT), gadoxetic acid-enhanced MRI, and angiography-assisted computed tomography (CT) before LRLT. The three modalities were compared for their ability to detect HCC. Two blinded readers independently reviewed the images obtained by each modality for the presence of HCC on a segment-by-segment basis using a 5-point confidence scale. The diagnostic performance of the modalities was evaluated in a receiver operating characteristic (ROC) analysis. The area under the ROC curve (Az), sensitivity, specificity, and accuracy were compared for the three modalities.

RESULTS

No significant difference in Az, sensitivity, specificity, or accuracy was obtained among gadoxetic acid-enhanced MRI, MDCT, and angiography-assisted CT for both readers. For reader 1, the sensitivity (55.6%) and the accuracy (84.7%) of angiography-assisted CT were significantly higher than those of MDCT (33.3% and 78.0%) (P < 0.05).

CONCLUSION

Gadoxetic acid-enhanced MRI has a relatively high diagnostic ability to detect HCC even in recipients of LRLT, equivalent to the abilities of MDCT and angiography-assisted CT.

In vivo magnetic resonance imaging of mice liver tumors using a new gadolinium-based contrast agent

We compared the enhancement effect between a newly synthesized tissue-specific contrast agent, [Gd-DOTA-FPβG], and a commercially available agent, [Gd(DOTA)](-), in a murine model of liver tumor using a clinical magnetic resonance imaging scanner. The colon cancer cell lines with and without β-glucuronidase (βG) expression were implanted into the liver of mice. Self-synthesized gadolinium-based magnetic resonance contrast agent, [Gd(DOTA-FPβG)], was administered to measure enhancement on magnetic resonance images using a commercially available agent, [Gd(DOTA)](-), as control in a clinical 3.0 tesla (T) magnetic resonance scanner. In vivo fluorescence imaging and histopathology of the liver were also performed to compare and correlate with the magnetic resonance studies. The in vivo fluorescence imaging failed to depict a sufficiently intense signal for liver or liver tumor of mice without exposure of the liver following an incision on the abdominal wall. The tissue-specific magnetic resonance agent, [Gd(DOTA-FPβG)], caused significantly stronger enhancement in tumors expressing βG (CT26/mβG-eB7) than in tumors not expressing βG (CT26) (p < 0.05). In the magnetic resonance imaging studies using control agent [Gd(DOTA)](-), the tumors with and without βG expression depicted no significant difference in enhancement on the T1-weighted images. The [Gd(DOTA-FPβG)] also provided significantly more contrast uptake in the CT26/mβG-eB7 tumor than in the normal liver parenchyma, whereas the [Gd(DOTA)](-) did not. This study confirms that better contrast enhancement can be readily detected in vivo by the use of a tissue-specific magnetic resonance contrast agent to target tumor cells with specific biomarkers in a clinical magnetic resonance imaging scanner.

MR characterization of focal nodular hyperplasia: gadoxetic acid versus superparamagnetic iron oxide imaging

PURPOSE

We evaluated the diagnostic efficacy of gadoxetic acid- and superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging for focal nodular hyperplasia (FNH).

MATERIALS AND METHODS

We retrospectively evaluated 11 patients with 11 FNHs. Both gadoxetic acid- and SPIO-enhanced MR imaging were performed. A 3-dimensional (3D) volumetric interpolated breath-hold examination was used with the gadoxetic acid dynamic study. SPIO-enhanced MR imaging included T₂- and T₂*-weighted images. We quantitatively and qualitatively compared lesion-specific enhancement of both contrast media.

RESULTS

The mean signal-to-noise (S/N) ratio of the FNH lesions differed significantly on pre- and postenhanced imaging of each contrast medium (P<0.05); mean contrast-to-noise (C/N) ratio did not (P>0.05). All observers described all lesions as hyperintense in the arterial phase on gadoxetic acid-enhanced MR imaging and observed the presence of central scar, fibrous septa, and rim most clearly in gadoxetic acid-enhanced hepatobiliary phase images.

CONCLUSION

Gadoxetic acid-enhanced MR imaging was more useful than SPIO-enhanced MR imaging in characterizing FNH.

Contrast agents as a biological marker in magnetic resonance imaging of the liver: conventional and new approaches

Liver imaging is an important clinical area in everyday practice. The clinical meaning of different lesion types in the liver can be quite different. Therefore, the result of imaging studies of the liver can change therapeutic concepts fundamentally. Contrast agents are used in the majority of MR examinations of the liver parenchyma-despite the already good soft-tissue contrast in plain MRI. This can be explained by the advantages in lesion detection and characterization of contrast-enhanced MRI of the liver. Beyond the qualitative evaluation of contrast-enhanced liver MR examinations, quantification of parameters will be the demand of the future. This can be achieved by perfusion MRI, also called dynamic contrast-enhanced MRI (DCE-MRI) of the liver. Its basic principles and different clinical applications will be discussed in this article. Definite cut-off values to determine disease or therapeutic response will help to increase the objectivity and reliability of liver MRI in future. This is especially important in the oncological setting, where modern therapies cannot be assessed based on changes in size only.

Hepatobiliary MR imaging with gadolinium-based contrast agents

The advent of gadolinium-based "hepatobiliary" contrast agents offers new opportunities for diagnostic magnetic resonance imaging (MRI) and has triggered great interest for innovative imaging approaches to the liver and bile ducts. In this review article we discuss the imaging properties of the two gadolinium-based hepatobiliary contrast agents currently available in the U.S., gadobenate dimeglumine and gadoxetic acid, as well as important pharmacokinetic differences that affect their diagnostic performance. We review potential applications, protocol optimization strategies, as well as diagnostic pitfalls. A variety of illustrative case examples will be used to demonstrate the role of these agents in detection and characterization of liver lesions as well as for imaging the biliary system. Changes in MR protocols geared toward optimizing workflow and imaging quality are also discussed. It is our aim that the information provided in this article will facilitate the optimal utilization of these agents and will stimulate the reader's pursuit of new applications for future benefit.

Cirrhosis and lesion characterization at MR imaging

Magnetic resonance (MR) imaging has emerged as an important imaging modality for the assessment of cirrhosis and its complications. Faster sequences now allow high-quality liver imaging with high intrinsic soft-tissue contrast. Automated contrast detection methods in combination with faster sequences allow reproducible capture of the arterial phase, which is essential for the detection and characterization of hepatocellular carcinoma. The lack of ionizing radiation permits routine use of gadolinium-enhanced three-dimensional (3D) fat-suppressed multiphasic imaging with high temporal and spatial resolution. In addition, MR imaging allows simultaneous evaluation of the background liver parenchyma and the liver lesions with the combined use of sequences that include T2-weighted sequences, T1-weighted sequences (including chemical shift imaging), echoplanar diffusion-weighted sequences, dynamic gadolinium-enhanced 3D multiphasic imaging, and liver-specific delayed phase sequences (if contrast agents with hepatobiliary excretion are used). The combination of findings from different sequences often helps pinpoint the nature of the liver abnormalities.

Diffuse liver disease: strategies for hepatic CT and MR imaging

The liver plays several complex but essential roles in the metabolism of amino acids, carbohydrates, and lipids, as well as synthesis of proteins. The basic pathophysiology of diffuse parenchymal hepatic diseases usually represents a failure in one of these metabolic pathways. Specific parenchymal diseases can be categorized as storage, vascular, and inflammatory diseases. Cross-sectional hepatic imaging techniques, specifically multidetector computed tomography (CT) and magnetic resonance (MR) imaging, have roles in evaluation of diffuse liver disease. The prominent role of multidetector CT is primarily defined by its excellent morphologic visualization capabilities, in particular of diffuse or focal intrahepatic lesions as well as of anatomic relationships between the liver and adjacent organs. The variety of available multidetector CT scanners covers a huge spectrum of detector configurations ranging from equally sized and equally spaced detector arrays to asymmetric detector configurations, resulting in imaging protocols with unique parameters for almost each multidetector CT system. In addition to 64-detector row imaging, hepatic multidetector CT can be performed with emerging techniques such as dual-energy CT. Hepatic MR imaging has been proved to be a comprehensive modality for assessing the morphology and functional characteristics of the liver. Concurrent technical improvements as well as implementation of advanced imaging sequence designs permit high-quality examination of the liver with T1-, T2-, and diffusion-weighted pulse sequences. Three basic demands remain if MR imaging is chosen for hepatic imaging: to improve parenchymal contrast, to suppress respiratory motion, and to ensure complete anatomic coverage. Supplemental material available at http://radiographics.rsna.org/content/29/6/1591/suppl/DC1.

Advances in imaging diagnosis of small hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide. Early diagnosis and treatment of small hepatocellular carcinoma (SHCC) are key to improvement of the survival of HCC patients. The advances in imaging technology have led to an increase in the detection rate of SHCC. For patients who are not suitable for surgical treatment, early detection of SHCC can not only help avoid unnecessary operation and improve survival and prognosis but also help alleviate the patient's physical and mental burden. Nowadays, intervention therapies, such as radiofrequency catheter ablation (RFCA), percutaneous ethanol injection, and superselective transcatheter arterial chemoembolization (S-TACE), show satisfactory efficacy in the treatment of SHCC. As the five-year survival rate achieved after RFCA (58.22%) is comparable to that after surgery (55.51%), RFCA has become a primary non-surgical therapy for SHCC. In this article, we will review the recent advances in imaging diagnosis of SHCC.

Surveillance and diagnosis of hepatocellular carcinoma in patients with cirrhosis

Early identification of hepatocellular carcinoma (HCC) is more frequent because of surveillance programs for HCC worldwide. The optimal strategy of surveillance in cirrhosis is a current topical issue. In terms of diagnosis, recent advances in non-invasive imaging technology, including various techniques of harmonic ultrasound, new ultrasound contrast agents, multi-slice helical computed tomography and rapid high quality magnetic resonance, have all improved the accuracy of diagnosis. Consequently the role of liver biopsy in diagnosis of HCC has declined. The imaging diagnosis relies on the hallmark of arterial hypervascularity with portal venous washout. However, with recent advances in genomics and proteomics a great number of potential serum and tissue markers have been identified and are being developed as new candidate markers for both diagnosis and prognosis of hepatocellular carcinoma, and may increase the need for liver biopsy.

Preoperative evaluation of pancreatic cancer: comparison of gadolinium-enhanced dynamic MRI with MR cholangiopancreatography versus MDCT

PURPOSE

To determine the accuracy of magnetic resonance imaging (MRI) including dynamic imaging using three-dimensional gradient-echo (3D-GRE) sequences and MR cholangiopancreatograpy (MRCP) compared with that of multidetector row CT (MDCT) with regard to resectability in pancreas cancer.

MATERIALS AND METHODS

From February 2004 to July 2008, 54 patients (32 men, 22 women: age range, 28-83 years; mean age, 63.1 years old) with surgically proven pancreatic carcinoma, who had undergone preoperative gadolinium-enhanced 3D-GRE MRI with MRCP and triple-phase MDCT, were included in this retrospective study. Two, clinically experienced attending radiologists independently reviewed the two image sets. These readers evaluated the tumor conspicuity, presence of vascular invasion, choledochal and duodenal invasion, lymph node metastases, distant metastasis, and tumor resectability. The results were compared with the surgical and histopathologic findings using receiver operating characteristic analysis (Az) and kappa statistics.

RESULTS

Curative resections were performed on 42 patients. Regarding the tumor conspicuity, MRI had a significantly higher Az value compared with MDCT according to both reviewers (P < 0.05). The accuracy of resectability was Az = 0.753 and 0.768 on MRI and Az = 0.829 and 0.762 on MDCT for each reviewer, and the difference in the accuracy of resectability was not significant between MRI and MDCT for either reviewer (P > 0.05). Two imaging sets showed a similar diagnostic performance in the evaluation of vascular involvement, lymph node metastasis, and distant metastasis.

CONCLUSION

Dynamic 3D-GRE MRI with MRCP shows superior tumor conspicuity and similar diagnostic performance compared with MDCT in evaluating the resectability of pancreatic cancer.

Diagnostic performance of multidetector row computed tomography, superparamagnetic iron oxide-enhanced magnetic resonance imaging, and dual-contrast magnetic resonance imaging in predicting the appropriateness of a transplant recipient based on milan criteria: correlation with histopathological findings

PURPOSE

To retrospectively evaluate the diagnostic performance of multidetector row CT (MDCT), superparamagnetic iron oxide (SPIO)-enhanced MRI (S-MRI), and dual-contrast MRI (DC-MRI) in predicting the appropriateness of recipients with hepatocellular carcinoma (HCC) for liver transplantation (LT), based on Milan criteria.

MATERIALS AND METHODS

This retrospective study received Institutional Review Board approval. Requirement for patient informed consent was waived. During a 3-year period, 80 patients who underwent LT were enrolled in this study. However, 2 patients in whom >10 HCCs were present were excluded from the analysis of detection performance of imaging modalities for HCC. MDCT and DC-MRI examinations with the sequential use of SPIO and gadolinium were performed in all patients. Interval readings for MDCT, S-MRI, and DC-MRI were performed. Two radiologists independently recorded confidence levels using a 4- and 5-point scale for the presence of HCC and for the appropriateness regarding LT, respectively. Image interpretation was compared with histopathological results on a lesion-by-lesion basis. Diagnostic performance of the 3 imaging techniques was compared using jackknife alternative free-response receiver operating characteristic and ROC analyses.

RESULTS

Eighty-two HCCs were detected in 38 of 78 patients. Twenty-seven HCCs were larger than 2 cm in diameter and 55 HCCs were smaller than 2 cm in diameter. Among 80 patients included for the assessment of eligibility for LT, 69 recipients were categorized as appropriate and the remaining 11 patients were found to be inappropriate for LT based on Milan criteria. In terms of detecting HCCs, the reader-averaged figure of merit was highest for DC-MRI (0.764), followed by S-MRI (0.702) and MDCT (0.672). The use of DC-MRI was significantly better than the use of the other 2 modalities specifically for HCCs smaller than 2 cm in diameter (P < 0.001) although not for those larger than or equal to 2 cm (P = 0.125-1). The AZ value for predicting the appropriateness for LT was highest with the use of S-MRI (0.841), followed by the use of DC-MRI (0.830) and the use of MDCT (0.790). However, significant differences were not seen for the predictions determined by both radiologists (P = 0.384-1). This result might be because of the small number of patients who had a critical number of HCCs (ie, 2 approximately 4 HCCs).

CONCLUSION

DC-MRI showed significantly better diagnostic performance in transplantation candidates for the detection of HCCs, particularly small HCCs, than both MDCT and S-MRI. However, for assessing the appropriateness of a transplantation recipient based on Milan criteria, MDCT, S-MRI, and DC-MRI showed comparable diagnostic accuracy without a statistical difference.

Small hypervascular hepatocellular carcinomas: value of "washout" on gadolinium-enhanced dynamic MR imaging compared to superparamagnetic iron oxide-enhanced imaging

The aim of this study was to retrospectively compare the value of "washout" on dynamic MR imaging with superparamagnetic iron oxide (SPIO)-enhanced imaging features of small hepatocellular carcinoma (HCC). A total of 74 small (5-30 mm) hypervascular HCCs in 42 cirrhotic patients who underwent double contrast material-enhanced MR imaging were evaluated to determine the presence of washout in the portal or equilibrium phase of gadolinium-enhanced dynamic imaging and decreased uptake of SPIO on T2*-weighted imaging. HCCs were verified histologically (n = 13) or by serial follow-up imaging studies (n = 61). According to the size of the lesions, 27 vs. 73% (<10 mm, n = 15; P = 0.016 on McNemar test), 39 vs. 79% (10-14 mm, n = 28; P = 0.002), 50 vs. 93% (15-20 mm, n = 14; P = 0.031), and 82 vs. 100% (>20 mm, n = 17; P = 0.250) of the lesions showed washout vs. decreased SPIO accumulation respectively. The larger the lesion, the higher the prevalence of washout or decreased SPIO uptake (P = 0.004 or P = 0.036, respectively, on Mantel-Haenszel test). In many small hypervascular HCCs up to 2 cm, SPIO-enhanced MR imaging offers essential information for early diagnosis in the absence of washout on dynamic imaging.

MR imaging findings of early bile duct cancer

PURPOSE

To retrospectively evaluate the MR imaging features of early bile duct cancer and to correlate them with the clinicopathologic findings.

MATERIALS AND METHODS

This retrospective study was approved by our institutional review board, and informed consent was waived. Seventeen patients with surgically proven early bile duct cancer who had undergone preoperative MR cholangiopancreatography with gadolinium-enhanced MR imaging, were included in this study. Two, experienced radiologists evaluated the MR images in consensus regarding the following findings: tumor number and morphology; signal intensity of the tumor; sharpness of the outer border of the bile duct wall; enhancement pattern of the tumor; and the presence of enlarged peribiliary lymph nodes. Another radiologist measured the SNR of the tumor and bile duct wall on gadolinium-enhanced MRI during the dynamic phases to evaluate the tumor enhancement degree.

RESULTS

In all patients, MR imaging demonstrated single or multiple intraluminal bile duct masses showing a sharply defined outer margin. The most common enhancement pattern of the biliary lesions showed heterogeneous amorphous enhancement or heterogeneous enhancement with central, dot-like structures or vascular structures (76.5%, 13/17 patients). The difference of SNR between bile duct and tumor was greatest in the equilibrium phase (P < 0.05).

CONCLUSION

MRCP combined with dynamic contrast-enhanced MRI can be useful for detecting early bile duct cancers. Common MR findings of early bile duct cancer include one or more inhomogeneously enhancing intraductal masses with clear outer margins and preservation of the bile duct wall.

Detection of small hepatocellular carcinoma: comparison of conventional gadolinium-enhanced MRI with gadolinium-enhanced MRI after the administration of ferucarbotran

We compared the diagnostic efficacy of gadolinium (Gd)-enhanced MRI with that of Gd-enhanced MRI after administration of ferucarbotran for revealing small hypervascular hepatocellular carcinomas (HCCs). 24 patients with 34 HCCs (ranging in size from 0.6-2.0 cm) underwent Gd-enhanced three-dimensional dynamic MRI followed, after an interval of 5-11 days (mean, 7 days), by Gd-enhanced three-dimensional dynamic MRI after administration of ferucarbotran. The two Gd-enhanced arterial-phase MRI scans were compared quantitatively by measuring the tumour-liver contrast-to-noise ratio (CNR) and qualitatively by evaluating the tumour-liver contrast using matched-pairs analysis. The tumour-liver CNR with Gd-enhanced arterial-phase imaging after ferucarbotran (250.3 +/- 103.7) was higher than that with Gd-enhanced arterial-phase imaging (221.1 +/- 96.1) (p < 0.001). Matched-pairs analysis indicated that, for three lesions, the relative tumour-liver contrast was slightly better with Gd-enhanced arterial-phase imaging after ferucarbotran than with conventional Gd-enhanced arterial-phase imaging; however, in the case of the remaining 31 lesions, the two images were equivalent. We concluded that, although Gd-enhanced arterial-phase imaging after ferucarbotran results in better tumour-liver CNR than Gd-enhanced arterial-phase imaging, the ability of the two techniques to reveal small hypervascular HCCs is the same.

Evidence-based diagnosis and locoregional therapy for hepatocellular carcinoma

Early identification of hepatocellular carcinoma (HCC) is crucial to improving the results of therapy and for patients to be eligible for liver transplantation. Recent advances in noninvasive imaging technology include various techniques of harmonic ultrasound, new ultrasound contrast agents, multislice helical computed tomography and rapid high-quality magnetic resonance. The imaging diagnosis relies on the hallmark of arterial hypervascularity with portal venous washout. Since the use of better radiological techniques has improved the accuracy of noninvasive diagnosis, the role of liver biopsy in the diagnosis of HCC has declined. With recent advances in genomics and proteomics, a great number of potential markers have been identified and developed as new candidate markers for HCC. Locoregional therapies currently constitute the best options for early nonsurgical treatment of HCC. Percutaneous ethanol injection shows similar results to resection surgery for single tumors less than 3 cm in diameter. Radiofrequency ablation is superior to percutaneous ethanol injection in terms of local recurrence. Transarterial chemoembolization is currently the most common approach for the management of HCC without curative options since it improves patient survival, but the optimal embolizing agent, length of interval between sessions and whether the chemotherapeutic agent has any effect have not yet been determined. Combining transarterial chemoembolization with antiangiogenic agents, as well as with other techniques, such as radiofrequency ablation, may improve the results. Injection of radioisotopes such as yttrium-90, via the hepatic artery, may be particularly useful in patients with portal vein thrombosis. Comparisons with other transarterial techniques are needed.

Diagnostic accuracy of multi-/single-detector row CT and contrast-enhanced MRI in the detection of hepatocellular carcinomas meeting the milan criteria before liver transplantation

Liver transplantation has been considered to be the only causal treatment for liver cirrhosis patients with hepatocellular carcinoma (HCC) due to its theoretical advantage of eliminating both the tumor and liver disease. However, because of the shortage of donor organs, it is strongly recommended that liver transplantations should be performed on cirrhotic patients with HCCs only when the patients meet the predetermined criteria in terms of number and extent of HCCs. Imaging is thus decisive in the patient inclusion or exclusion from transplantation lists. The imaging techniques used are CT, MRI and ultrasonography. The latter has been proven to be ineffective for HCC surveillance in transplant recipients because of its heavy operator dependence and unreliable detection of small and intermediately sized HCCs. The purpose of this article, then, is to systematically review the diagnostic performances of single-/multidetector row CT, dynamic gadolinium-enhanced MRI, superparamagnetic iron oxide (SPIO)-enhanced MRI and double-contrast MRI using both gadolinium and SPIO for the detection of HCCs with special emphasis on liver transplantation.

Gadolinium-enhanced MRI for tumor surveillance before liver transplantation: center-based experience

OBJECTIVE

The purpose of this study was to evaluate prospectively acquired institutional results to determine the accuracy of gadolinium-enhanced MRI in liver tumor surveillance before transplantation.

SUBJECTS AND METHODS

One hundred fifteen patients underwent MRI of the abdomen within 90 days before liver transplantation. Images were acquired with gadolinium-enhanced 3D gradient-echo sequences in the arterial, venous, and delayed phases. Detection of hepatocellular carcinoma (HCC) was based on the imaging criteria arterial phase enhancement, delayed phase hypointensity, and development of an enhancing outer margin capsule. Imaging findings were compared with findings at histopathologic evaluation of the explanted liver.

RESULTS

Thirty-six HCCs in 27 patients were detected at histopathologic evaluation. Patient-based analysis showed the sensitivity of MRI was 88.9% (24/27); specificity, 97.7% (false-positive findings in two patients); and accuracy, 95.7%. MRI depicted 28 of 36 HCCs, resulting in a lesion-based sensitivity of 77.8%. Although all 18 HCCs 2 cm or larger were depicted with MRI, only 10 of 18 HCCs smaller than 2 cm were correctly diagnosed. However, two HCCs measuring smaller than 2 cm at pathologic examination were rated as dysplastic nodules on MRI.

CONCLUSION

Contrast-enhanced MRI can be used as a primary diagnostic method for accurate detection and characterization of HCC 2 cm or larger as required by the criteria of the Model for End-Stage Liver Disease used by the United Network for Organ Sharing. MRI can be considered a standard tool for surveillance before liver transplantation. Reduction in cost and risk may be derived from the diminished need for other diagnostic imaging studies and biopsy and the avoidance of use of iodinated contrast agents in imaging of patients with cirrhosis, many of whom have impaired renal function.

Usefulness of Combining Sequentially Acquired Gadobenate Dimeglumine-Enhanced Magnetic Resonance Imaging and Resovist-Enhanced Magnetic Resonance Imaging for the Detection of Hepatocellular Carcinoma

OBJECTIVE

To investigate the diagnostic efficacy of sequentially acquired gadobenete dimeglumine-enhanced 3-dimensional dynamic magnetic resonance imaging (MRI) and Resovist-enhanced MRI for detecting hepatocellular carcinoma (HCC) by comparing with combined computed tomography (CT) hepatic arteriography (CTHA) and CT arterioportography (CTAP) using 16-slice multidetector CT.

MATERIALS

Twenty-nine patients with 50 HCCs underwent sequentially acquired double-contrast MRI--gadobenate dimeglumine-enhanced dynamic MRI and Resovist-enhanced MRI--and combined CTHA and CTAP using 16-slice multidetector CT. Dynamic MRI was obtained using volumetric interpolated technique and sensitivity encoding on a 1.5-T unit. Resovist-enhanced MRI was composed of T2-weighted turbo spin-echo and T2*-weighted gradient echo sequences. Sensitivity, positive predictive value, and diagnostic accuracy for double-contrast MRI, gadolinium-enhanced MRI, and combined CTHA and CTAP were calculated by 2 observers using an alternative-free response receiver operating characteristic analysis.

RESULTS

For all observers, the Az values of double-contrast MRI (mean, 0.96) and combined CTHA and CTAP (mean, 0.93) were similar, which tended to be better than that of gadolinium-enhanced MRI (mean, 0.91). The sensitivity of double-contrast MRI (mean, 93%) and combined CTHA and CTAP (mean, 92%) was equivalent for all observers, which was better than that of gadolinium-enhanced MRI (mean, 85%; P < 0.05). The positive predictive value of double-contrast MRI was better than that of combined CTHA and CTAP (P < 0.05).

CONCLUSION

The sequentially acquired double-contrast MRI and combined CTHA and CTAP showed a similar diagnostic accuracy and sensitivity for detecting HCC.

Hepatobiliary MRI: current concepts and controversies

Evaluation of the liver and biliary system is a frequent indication for abdominal MRI. Hepatobiliary MRI comprises a set of noninvasive techniques that are usually very effective in answering most clinical questions. There are significant limitations, however, as well as considerable variation and disagreement regarding the optimal protocols for standard hepatic MRI and magnetic resonance cholangiopancreaticography (MRCP). This review discusses pulse sequences most often used in hepatic MRI and MRCP, examines a few sources of controversy in the current literature, and summarizes some recent and future developments in the field.

Magnetic targeting of mechanosensors in bone cells for tissue engineering applications

Mechanical signalling plays a pivotal role in maintaining bone cell function and remodelling of the skeleton. Our previous work has highlighted the potential role of mechano-induction in tissue engineering applications. In particular, we have highlighted the potential for using magnetic particle techniques for tissue engineering applications. Previous studies have shown that manipulation of integrin attached magnetic particles leads to changes in intracellular calcium signalling within osteoblasts. However, due to the phenomenon of particle internalisation, previous studies have typically focused on short-term stimulation experiments performed within 1-2 h of particle attachment. For tissue engineering applications, bone tissue growth occurs over a period of 3-5 weeks. To date, no study has investigated the cellular responses elicited from osteoblasts over time following stimulation with internalised magnetic particles. Here, we demonstrate the long-term biocompatibility of 4.5 microm RGD-coated particles with osteoblasts up to 21 days in culture, and detail a time course of responses elicited from osteoblasts following mechanical stimulation with integrin attached magnetic particles (<2h post attachment) and internalised particles (>48h post attachment). Mechanical manipulation of both integrin attached and internalised particles were found to induce intracellular calcium signalling. It is concluded that magnetic particles offer a tool for applying controlled mechanical forces to osteoblasts, and can be used to stimulate intracellular calcium signalling over prolonged periods of time. Magnetic particle technology presents a potentially valuable tool for tissue engineering which permits the delivery of highly localised mechano-inductive forces directly to cells.

Double-dose 1.0-M gadobutrol versus standard-dose 0.5-M gadopentetate dimeglumine in revealing small hypervascular hepatocellular carcinomas

The purpose of this study was to compare the diagnostic efficacy of double-dose 1.0-M gadobutrol with that of standard-dose 0.5-M gadopentetate dimeglumine for revealing small hypervascular hepatocellular carcinomas (HCCs). Twenty-three patients with 37 HCCs (mean size: 1.2 cm) that were diagnosed by histology (n = 13) or imaging findings (n = 10) underwent two separate 3D dynamic MRIs with 0.2 mmol/kg of gadobutrol and 0.1 mmol/kg of gadopentetate dimeglumine. Three observers interpreted both MRIs in terms of lesion detection using the alternative-free response receiver operating characteristic method and lesion-to-liver contrast using matched pairs analysis. The two MRIs were also compared quantitatively by measuring the signal-to-noise ratio (SNR) of the liver and lesion as well as the lesion-liver contrast-to-noise ratio (CNR). The SNR of the liver and lesion and lesion-liver CNR with gadobutrol were better than those with gadopentetate dimeglumine (p < 0.01). However, in terms of the diagnostic accuracy (mean Az for gadobutrol: 0.878, and mean Az for gadopentate dimeglumine: 0.873), the sensitivity (92.8%), positive predictive value (92.8% vs. 93.7%) and lesion-liver contrast, the two dynamic MRIs were equivalent. Gadobutrol showed a superior degree of enhancement for hypervascular HCC than did gadopentetate dimeglumine, but the diagnostic capabilities of the two agents for revealing HCCs were equivalent.

Comparison of Gadolinium-BOPTA and Ferucarbotran-Enhanced Three-Dimensional T1-Weighted Dynamic Liver Magnetic Resonance Imaging in the Same Patient

OBJECTIVES

We sought to compare signal changes using Ferucarbotran and gadobenate dimeglumine (Gd-BOPTA) in dynamic 3D T1-weighted (T1w) GRE imaging of the liver.

MATERIAL AND METHODS

Thirty patients were prospectively included in the study. All patients underwent 2 high-field magnetic resonance (MR) examinations: first with Gd-BOPTA (Gd) and then after a mean interval of 4 days with ferucarbotran (Feru). Dynamic MRI was obtained with a 3D T1w GRE sequence (TR 6.33, TE 2.31, flip angle 20 degrees ). Contrast enhanced scans were assessed before intravenous injection of the contrast agent (precontrast), and postcontrast during the arterial phase (30 seconds), portal venous phase (60 seconds), and equilibrium phase (120 seconds). The signal intensities (SIs) of liver, spleen, aorta, and portal vein were defined by region of interest measurements. Signal intensity changes (SICs) and percentage signal intensity change (PSIC) were calculated using the formulas SIC=(SI pre - SI post)/SI pre and PSIC=SIC x 100%.

RESULTS

Positive signal enhancement was observed after intravenous injection of Feru during all dynamic measurements, whereas the mean SI values were lower compared with Gd. During the portal venous phase the mean SI of Gd was up to a factor of 2.1 higher (portal vein). The widest difference of SIC was observed during the equilibrium phase for liver parenchyma (Gd, 1.03; Feru, 0.24). The dynamic signal courses were similar for liver, portal vein and aorta. Different signal courses were obtained for the spleen.

CONCLUSIONS

Feru-enhanced T1w dynamic images demonstrated significant signal increases for liver, vessels, and spleen but overall lower signal intensities than Gd-BOPTA. The dynamic signal courses of ferucarbotran were similar to that of Gd-BOPTA during ll perfusion phases except in the spleen. Thus, it may be possible to detect typical enhancement pattern of focal liver lesions with Feru-enhanced dynamic T1w MRI.