Irene Cruite

Gadoxetate Disodium–Enhanced MRI of the Liver: Part 2, Protocol Optimization and Lesion Appearance in the Cirrhotic Liver

OBJECTIVE The purpose of this article is to review the pharmacokinetic and pharmacodynamic properties of gadoxetate disodium (Gd-EOB-DTPA), to describe a workflow-optimized pulse sequence protocol, and to illustrate the imaging appearance of focal lesions in the noncirrhotic liver. CONCLUSION Gd-EOB-DTPA allows a comprehensive evaluation of the liver with the acquisition of both dynamic and hepatocyte phase images. This provides potential additional information, especially for the detection and characterization of small liver lesions. However, protocol optimization is necessary for improved image quality and workflow.

In vivo characterization of the liver fat 1H MR spectrum

A theoretical triglyceride model was developed for in vivo human liver fat 1H MRS characterization, using the number of double bonds (CHCH), number of methylene‐interrupted double bonds (CHCHCH2CHCH) and average fatty acid chain length. Five 3 T, single‐voxel, stimulated echo acquisition mode spectra (STEAM) were acquired consecutively at progressively longer TEs in a fat–water emulsion phantom and in 121 human subjects with known or suspected nonalcoholic fatty liver disease. T2‐corrected peak areas were calculated. Phantom data were used to validate the model. Human data were used in the model to determine the complete liver fat spectrum. In the fat–water emulsion phantom, the spectrum predicted by the model (based on known fatty acid chain distribution) agreed closely with spectroscopic measurement. In human subjects, areas of CH2 peaks at 2.1 and 1.3 ppm were linearly correlated (slope, 0.172; r = 0.991), as were the 0.9 ppm CH3 and 1.3 ppm CH2 peaks (slope, 0.125; r = 0.989). The 2.75 ppm CH2 peak represented 0.6% of the total fat signal in high‐liver‐fat subjects. These values predict that 8.6% of the total fat signal overlies the water peak. The triglyceride model can characterize human liver fat spectra. This allows more accurate determination of liver fat fraction from MRI and MRS. Copyright

Reproducibility of MRI-Determined Proton Density Fat Fraction Across Two Different MR Scanner Platforms

To evaluate magnetic resonance imaging (MRI)‐determined proton density fat fraction (PDFF) reproducibility across two MR scanner platforms and, using MR spectroscopy (MRS)‐determined PDFF as reference standard, to confirm MRI‐determined PDFF estimation accuracy.

Imaging-based diagnostic systems for hepatocellular carcinoma.

OBJECTIVE Noninvasive imaging plays critical roles in the treatment of patients with cirrhosis or other risk factors for the development of hepatocellular carcinoma. In recognition of the critical roles played by imaging, numerous international scientific organizations and societies have, in the past 12 years, proposed diagnostic systems for the interpretation of liver imaging examinations performed of at-risk patients. CONCLUSION Although these imaging-based diagnostic systems represent important advances, they have limitations and they are not perfectly consistent with each other. The limitations and inconsistencies potentially cause confusion and may impair the integration of the systems into clinical practice as well as their utilization in research studies. The purpose of this article is to synthesize and critically appraise the current published imaging-based diagnostic systems endorsed by major societies for the noninvasive diagnosis and staging of hepatocellular carcinoma and to propose future directions that we hope may be helpful in further advancing the field.

Noninvasive classification of hepatic fibrosis based on texture parameters from double contrast-enhanced magnetic resonance images

To demonstrate a proof of concept that quantitative texture feature analysis of double contrast‐enhanced magnetic resonance imaging (MRI) can classify fibrosis noninvasively, using histology as a reference standard.

Toward a standardized system for hepatocellular carcinoma diagnosis using computed tomography and MRI

Contrast-enhanced computed tomography and MRI are frequently used for the noninvasive diagnosis of hepatocellular carcinoma (HCC). Despite their important role in diagnosis and management of HCC, until recently, there has been no standardized system for their interpretation, reporting and data collection. In 2008, the American College of Radiology convened a committee to develop such a standardized system. This article reviews the role of computed tomography and MRI in the diagnosis and management of HCC; the need for a standardized imaging interpretation system; current HCC imaging criteria included in management guidelines endorsed by the European Association for the Study of Liver, American Association for Study of Liver Diseases, United Network for Organ Sharing and Asian Pacific Association for the Study of the Liver; and the limitations of these criteria. The article then provides an overview of the Liver Imaging Reporting and Data System and discusses future directions.

Understanding LI-RADS: a primer for practical use.

The Liver Imaging-Reporting and Data System (LI-RADS) is a comprehensive system for standardized interpretation and reporting of computed tomography and magnetic resonance examinations performed in patients at risk for hepatocellular carcinoma. LI-RADS includes a diagnostic algorithm, lexicon, and atlas as well as suggestions for reporting, management, and imaging techniques. This primer provides an introduction to LI-RADS for radiologists including an explanation of the diagnostic algorithm, descriptions of the categories, and definitions of the major imaging features used to categorize observations with case examples.

Evidence Supporting LI-RADS Major Features for CT- and MR Imaging–based Diagnosis of Hepatocellular Carcinoma: A Systematic Review

The Liver Imaging Reporting and Data System (LI-RADS) standardizes the interpretation, reporting, and data collection for imaging examinations in patients at risk for hepatocellular carcinoma (HCC). It assigns category codes reflecting relative probability of HCC to imaging-detected liver observations based on major and ancillary imaging features. LI-RADS also includes imaging features suggesting malignancy other than HCC. Supported and endorsed by the American College of Radiology (ACR), the system has been developed by a committee of radiologists, hepatologists, pathologists, surgeons, lexicon experts, and ACR staff, with input from the American Association for the Study of Liver Diseases and the Organ Procurement Transplantation Network/United Network for Organ Sharing. Development of LI-RADS has been based on literature review, expert opinion, rounds of testing and iteration, and feedback from users. This article summarizes and assesses the quality of evidence supporting each LI-RADS major feature for diagnosis of HCC, as well as of the LI-RADS imaging features suggesting malignancy other than HCC. Based on the evidence, recommendations are provided for or against their continued inclusion in LI-RADS.

Risk of nephrogenic systemic fibrosis is low in patients with chronic liver disease exposed to gadolinium-based contrast agents.

To determine the risk of nephrogenic systemic fibrosis (NSF) in a cohort of patients with chronic liver disease.

Diagnostic Accuracy of Preoperative Gadoxetic Acid–enhanced 3-T MR Imaging for Malignant Liver Lesions by Using Ex Vivo MR Imaging–matched Pathologic Findings as the Reference Standard

PURPOSE To determine per-lesion sensitivity and positive predictive value (PPV) of gadoxetic acid-enhanced 3-T magnetic resonance (MR) imaging for the diagnosis of malignant lesions by using matched (spatially correlated) hepatectomy pathologic findings as the reference standard. Materials and METHODS In this prospective, institutional review board-approved, HIPAA-compliant study, 20 patients (nine men, 11 women; mean age, 59 years) with malignant liver lesions who gave written informed consent underwent preoperative gadoxetic acid-enhanced 3-T MR imaging for surgical planning. Two image sets were independently analyzed by three readers to detect liver lesions (set 1 without and set 2 with hepatobiliary phase [HBP] images). Hepatectomy specimen ex vivo MR imaging assisted in matching gadoxetic acid-enhanced 3-T MR imaging findings with pathologic findings. Interreader agreement was assessed by using the Cohen κ coefficient. Per-lesion sensitivity and PPV were calculated. RESULTS Cohen κ values were 0.64-0.76 and 0.57-0.84, and overall per-lesion sensitivity was 45% (42 of 94 lesions) to 56% (53 of 94 lesions) and 58% (55 of 94 lesions) to 64% (60 of 94 lesions) for sets 1 and 2, respectively. The addition of HBP imaging did not affect interreader agreement but significantly improved overall sensitivity for one reader (P < .05) and almost for another (P = .05). Sensitivity for 0.2-0.5-cm lesions was 0% (0 of 26 lesions) to 8% (two of 26 lesions) for set 1 and 4% (one of 26 lesions) to 12% (three of 26 lesions) for set 2. Sensitivity for 0.6-1.0-cm lesions was 28% (nine of 32 lesions) to 59% (19 of 32 lesions) for set 1 and 66% (21 of 32 lesions) to 69% (22 of 32 lesions) for set 2. Sensitivity for lesions at least 1.0 cm in diameter was at least 81% (13 of 16 lesions) for set 1 and was not improved for set 2. PPV was 98% (56 of 57 lesions) to 100% (60 of 60 lesions) for all readers without differences between image sets or lesion size. CONCLUSION Gadoxetic acid-enhanced 3-T MR imaging provides high per-lesion sensitivity and PPV for preoperative malignant liver lesion detection overall, although sensitivity for 0.2-0.5-cm malignant lesions is poor.