Comparison of Gadobenate-Enhanced MRI and Gadoxetate-Enhanced MRI for Hepatocellular Carcinoma Detection Using LI-RADS Version 2018: A Prospective Intraindividual Randomized Study.

BACKGROUND. Gadobenate and gadoxetate show different degrees of intracellular accumulation within hepatocytes, potentially impacting these agents' relative performance for hepatocellular carcinoma (HCC) diagnosis. OBJECTIVE. The purpose of this article was to perform an intraindividual comparison of gadobenate-enhanced MRI and gadoxetate-enhanced MRI for detection of HCC and to assess the impact of inclusion of hepatobiliary phase images on HCC detection for both agents. METHODS. This prospective study enrolled 126 patients (112 men, 14 women; mean age, 52.3 years) at high risk for HCC who consented to undergo two 3-T liver MRI examinations (one using gadobenate [0.05 mmol/kg], one using gadoxetate [0.025 mmol/kg]) separated by 7-14 days. The order of the two contrast agents was randomized. All examinations included postcontrast dynamic and hepatobiliary phase images (120 minutes for gadobenate, 20 minutes for gadoxetate). Three radiologists independently reviewed the gadobenate and gadoxetate examinations in separate sessions and recorded the location of detected observations. Observations were classified using LI-RADS version 2018 and using a LI-RADS modification whereby hepatobiliary phase hypointensity may upgrade observations from category LR-4 to LR-5. Observations classified as LR-5 were considered positive interpretations for HCC. Diagnostic performance for histologically confirmed HCC (n = 96) was assessed. RESULTS. Across readers, sensitivity for HCC for gadobenate versus gadoxetate was 74.0-80.2% versus 54.2-67.7% using dynamic images alone and 82.1-87.4% versus 66.3-81.1% using dynamic and hepatobiliary phase images. For HCCs measuring 1.0-2.0 cm, sensitivity for gadobenate versus gadoxetate was 61.9% (all readers) versus 38.1-57.1% using dynamic images alone and 76.2-85.7% versus 52.4-61.9% using dynamic and hepatobiliary phase images. PPV for HCC ranged from 88.6% to 97.4% across readers, agents, and image sets. CONCLUSION. Sensitivity for HCC was higher for gadobenate than for gadoxetate, whether using dynamic images alone or dynamic and hepatobiliary phase images; the improved sensitivity using gadobenate was more pronounced for small HCCs. Whereas hepatobiliary phase images improved sensitivity for both agents, sensitivity of gadobenate using dynamic images alone compared favorably with that of gadoxetate using dynamic and hepatobiliary phase images. CLINICAL IMPACT. The findings support gadobenate as a preferred agent over gadoxetate when performing liver MRI in patients at high risk for HCC.

Editorial for "Utility of Diffusion-Weighted Imaging for Guiding Clinical Management of Patients With Kidney Transplant: A Prospective Study".

LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY STAGE: 5 J. Magn. Reson. Imaging 2020;52:575-576.

Liver-Directed Therapy for Hepatocellular Carcinoma: An Overview of Techniques, Outcomes, and Posttreatment Imaging Findings.

OBJECTIVE: The purposes of this article are to describe the indications, techniques, and results of arterially directed therapies and ablation and to review the imaging assessment of response and complications. CONCLUSION: Most patients with hepatocellular carcinoma are not eligible for surgery, and systemic treatments are suboptimal. Therefore, locoregional therapy plays a large role in this disease. Locoregional therapies include arterially directed therapies, ablation, and radiation therapy.

A Review and Update of Treatment Options and Controversies in the Management of Hepatocellular Carcinoma.

OBJECTIVE: To review the current management, outline recent advances and address controversies in the management of hepatocellular carcinoma (HCC). SUMMARY OF BACKGROUND DATA: The treatment of HCC is multidisciplinary involving hepatologists, surgeons, medical oncologists, radiation oncologists, radiologists, interventional radiologists, and other disciplines. Each of these disciplines brings its unique perspective and differing opinions that add to controversies in the management of HCC. METHODS: A focused literature review was performed to identify recent studies on the management of HCC and thereby summarize relevant information on the various therapeutic modalities and controversies involved in the treatment of HCC. RESULTS: The main treatment algorithms continue to rely on hepatic resection or transplantation with controversies involving patients harboring early stage disease and borderline hepatic function. The other treatment strategies include locoregional therapies, radiation, and systemic therapy used alone or in combination with other treatment modalities. Recent advances in locoregional therapies, radiation, and systemic therapies have provided better therapeutic options with curative intent potential for some locoregional therapies. Further refinements in combination therapies such as algorithms consisting of locoregional therapies and systemic or radiation therapies are likely to add additional options and improve survival. CONCLUSIONS: The management of HCC has witnessed significant strides with advances in existing options and introduction of several new treatment modalities of various combinations. Further refinements in these treatment options combined with enrollment in clinical trials are essential to improve the management and outcomes of patients with HCC.

Magnetic resonance imaging of acute appendicitis in pregnancy: a 5-year multiinstitutional study.

OBJECTIVE: The purpose of this study was to determine the diagnostic performance of magnetic resonance imaging (MRI) in the diagnosis of acute appendicitis during pregnancy in a multiinstitutional study. STUDY DESIGN: In this multicenter retrospective study, the cases of pregnant women who underwent MRI evaluation of abdominal or pelvic pain and who had clinical suspicion of acute appendicitis between June 1, 2009, and July 31, 2014, were reviewed. All MRI examinations with positive findings for acute appendicitis were confirmed with surgical pathologic information. Sensitivity, specificity, negative predictive values, and positive predictive values were calculated. Receiver operating characteristic curves were generated, and area under the curve analysis was performed for each participating institution. RESULTS: Of the cases that were evaluated, 9.3% (66/709) had MRI findings of acute appendicitis. Sensitivity, specificity, accuracy, positive predictive value, and negative predictive values were 96.8%, 99.2%, 99.0%, 92.4%, and 99.7%, respectively. There was no statistically significant difference between centers that were included in the study (pair-wise probability values ranged from 0.12-0.99). CONCLUSION: MRI is useful and reproducible in the diagnosis of suspected acute appendicitis during pregnancy.

Two fully automated data-driven 3D whole-breast segmentation strategies in MRI for MR-based breast density using image registration and U-Net with a focus on reproducibility.

Presence of higher breast density (BD) and persistence over time are risk factors for breast cancer. A quantitatively accurate and highly reproducible BD measure that relies on precise and reproducible whole-breast segmentation is desirable. In this study, we aimed to develop a highly reproducible and accurate whole-breast segmentation algorithm for the generation of reproducible BD measures. Three datasets of volunteers from two clinical trials were included. Breast MR images were acquired on 3 T Siemens Biograph mMR, Prisma, and Skyra using 3D Cartesian six-echo GRE sequences with a fat-water separation technique. Two whole-breast segmentation strategies, utilizing image registration and 3D U-Net, were developed. Manual segmentation was performed. A task-based analysis was performed: a previously developed MR-based BD measure, MagDensity, was calculated and assessed using automated and manual segmentation. The mean squared error (MSE) and intraclass correlation coefficient (ICC) between MagDensity were evaluated using the manual segmentation as a reference. The test-retest reproducibility of MagDensity derived from different breast segmentation methods was assessed using the difference between the test and retest measures (Δ2-1), MSE, and ICC. The results showed that MagDensity derived by the registration and deep learning segmentation methods exhibited high concordance with manual segmentation, with ICCs of 0.986 (95%CI: 0.974-0.993) and 0.983 (95%CI: 0.961-0.992), respectively. For test-retest analysis, MagDensity derived using the registration algorithm achieved the smallest MSE of 0.370 and highest ICC of 0.993 (95%CI: 0.982-0.997) when compared to other segmentation methods. In conclusion, the proposed registration and deep learning whole-breast segmentation methods are accurate and reliable for estimating BD. Both methods outperformed a previously developed algorithm and manual segmentation in the test-retest assessment, with the registration exhibiting superior performance for highly reproducible BD measurements.

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.

Liver imaging at 3.0 T: diffusion-induced black-blood echo-planar imaging with large anatomic volumetric coverage as an alternative for specific absorption rate-intensive echo-train spin-echo sequences: feasibility study.

Institutional Review Board approval and signed informed consent were obtained by all participants for an ongoing sequence optimization project at 3.0 T. The purpose of this study was to evaluate breath-hold diffusion-induced black-blood echo-planar imaging (BBEPI) as a potential alternative for specific absorption rate (SAR)-intensive spin-echo sequences, in particular, the fast spin-echo (FSE) sequences, at 3.0 T. Fourteen healthy volunteers (seven men, seven women; mean age +/- standard deviation, 32.7 years +/- 6.8) were imaged for this purpose. Liver coverage (20 cm, z-axis) was always performed in one 25-second breath hold. Imaging parameters were varied interactively with regard to echo time, diffusion b value, and voxel size. Images were evaluated and compared with fat-suppressed T2-weighted FSE images for image quality, liver delineation, geometric distortions, fat suppression, suppression of the blood signal, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR). An optimized short- (25 msec) and long-echo (80 msec) BBEPI provided full anatomic, single breath-hold liver coverage (100 and 50 sections, respectively), with resulting voxel sizes of 3.3 x 2.7 x 2.0 mm and 3.3 x 2.7 x 4.0 mm, respectively. Repetition time was 6300 msec, matrix size was 160 x 192, and an acceleration factor of 2.00 was used. b Values of more than 20 sec/mm(2) showed better suppression of the blood signal but b values of 10 sec/mm(2) provided improved volume coverage and signal consistency. Compared with fat-suppressed T2-weighted FSE, the optimized BBEPI sequence provided (a) comparable image quality and liver delineation, (b) acceptable geometric distortions, (c) improved suppression of fat and blood signals, and (d) high CNR and SNR. BBEPI is feasible for fast, low-SAR, thin-section morphologic imaging of the entire liver in a single breath hold at 3.0 T.

MR imaging of the female pelvis at 3T.

The recent development of the transmit-receive body coil and the dedicated torso phased-array radio frequency receive coil for 3.0T MR imaging systems has promoted a move toward higher-field, whole-body MR imaging, including pelvic MR imaging. The female pelvis is an anatomic area that may benefit particularly from the advantages of high-field systems. In this article, the authors present their initial experience with the optimization of sequences for MR imaging of the female pelvis at 3.0T, and include a short description of parallel imaging. They compare some of the physical properties of 1.5T and 3.0T, discuss some of the challenges during sequence optimization for the female pelvis at 3.0T, and give examples of female pelvic abnormalities.

Diagnosis and treatment of benign focal liver lesions.

BACKGROUND: With the routine use of improved imaging modalities, more benign liver lesions are detected nowadays. An accurate characterization of these incidental lesions may be a challenge, and frequently a biopsy or even unnecessary surgery is being performed. However, these interventions are not always to the benefit of the patient. METHODS: A Medline search of studies relevant to imaging diagnosis and management of the most common, benign, solid and non-solid liver lesions was undertaken. References from identified articles were handsearched for further relevant articles. The authors' own experiences with benign liver lesions were also taken into account. RESULTS: Although atypical imaging features are the exception rather than the rule, it is sometimes difficult to differentiate between benign and malignant lesions, and knowledge of their imaging features is essential if unnecessary work-up is to be avoided. The use of tissue-specific contrast media, which has clearly improved the accuracy of highly advanced radiological techniques, may be helpful during differential diagnosis. Once having established an accurate diagnosis, surgery is rarely indicated for a benign liver lesion because of its asymptomatic nature. CONCLUSION: Knowledge of imaging features and a clear management strategy during diagnostic work-up, emphasizing the indications for surgery, will minimize the number of patients who have to undergo biopsy or unnecessary surgery.

Hepatic imaging: comparison of modalities.

This article describes a number of aspects of liver imaging, including the main reasons for imaging of the liver; the current status and recent developments of ultrasound, CT, MR imaging, and PET; and the role of these imaging modalities in the assessment of hepatic abnormalities. Finally, a systematic review of the current relevant literature on studies that compare modalities is presented, and a strategy for the work-up of liver diseases is proposed.

MR imaging of the liver.

MR imaging is establishing a role as a primary diagnostic technique, with increasing evidence showing MR imaging to have advantages over CT regarding diagnostic sensitivity and specificity for many pathologies of solid organs, bile and pancreatic ducts, bowel, peritoneum, and retroperitoneum. In addition, there are increasing concerns regarding the risks of radiation and iodinated contrast associated with CT imaging of the abdomen. The incidence of contrast-induced nephropathy associated with iodinated contrast used for CT scanning is difficult to ascertain because reporting is spurious and variable in interpretation.

Abdominal magnetic resonance imaging at 3.0 T: problem or a promise for the future?

The development of transmit-receive body coils and local and phased-array radiofrequency receive coils for 3.0-T magnetic resonance imaging (MRI) systems, and their recent approval in Europe and North America has promoted a move toward higher field, whole-body MRI. With approximately double the signal-noise ratio of a 1.5-T system, 3.0-T MR systems can substantially improve image quality and image acquisition speed; 3.0 T can potentially deliver square root(2) improvement in resolution in the same acquisition time of a comparable study at 1.5 T or one-half slice thickness with identical coverage or 4-fold speedup in scanning time for identical resolution settings. Parallel imaging, multiple coil elements, specific absorption rate, and altered MR physical properties at 3.0 T (T1 relaxation times, susceptibility, T2*) are important issues during optimization of sequences at high field. Possible future applications in the abdomen include high-resolution, contrast-enhanced imaging of the liver and pancreas; MR angiography; and MR spectroscopy. In this article, we will present our initial experience with optimization of sequences for abdominal MRI at 3.0 T and will include a short description of parallel imaging because of its importance for imaging at 3.0 T, general remarks comparing some of the physical properties of 1.5 T and 3.0 T, and some of the challenges during sequence optimization for the abdomen at 3.0 T with examples of abdominal MRI at 3.0 T with 4- and 8-channel coils.

Magnetic resonance imaging of the gastrointestinal tract.

Comprehensive bowel examination results from the combined use of T2-weighted single-shot and breath hold T1-weighted gradient echo, minus/plus fat suppression, and gadolinium-enhanced 3D gradient echo (3D VIBE, T1 FAME, 3D THRIVE). Gadolinium-enhanced imaging should be performed dynamically, but the venous 60- to 90-second delayed phase images with fat suppression are generally the most valuable. Removal of fat signal for detection of enhancing normal and abnormal structures is critical. Newly available True-FISP (FIESTA, BFFE) sequences obtained in the 2D form can be very helpful in delineation of bowel wall pathology and overall bowel anatomy, particularly when combined with a water-based intraluminal distending agent. Advantages include rapid acquisition, high signal-to-noise, and motion insensitivity. Generalized protocol for comprehensive evaluation of the entire abdomen and pelvis can be used for the following bowel indications: type and severity of inflammatory bowel disease (IBD); identifying enteric abscesses and fistulae; preoperative staging of malignant neoplasms, including rectal carcinoma; differentiating postoperative and radiation therapy changes from recurrent carcinoma; follow-up evaluation of metastases response to localized ablative or systemic chemotherapy. For improved visualization of bowel wall in dedicated examinations, bowel distension should be achieved using either orally or rectally delivered contrast agents to produce either bright or dark lumen. We have found 2D True-FISP without fat suppression superior to 3D True-FISP and to single-shot echo-train sequences to provide a T2-weighted image of bowel morphology. Strengths include: performed without fat suppression results in the very dark bowel wall being sandwiched between intermediate high signal fat adjacent to bowel serosa, and very high lumen signal from water-distending agent; 2D True-FISP provides motion insensitivity that is lost if 3D is used; True-FISP produces better edge sharpness than single-shot echo-train, higher contrast, and resists flow void artifacts commonly seen with single-shot echo-train imaging combined with a water distending agent. Drawbacks of this technique include: artifacts related to extreme sensitivity to field inhomogeneity, including air-soft tissue interfaces at the patient skin surface, and from retained bowel gas; retained bowel gas is dark against dark bowel wall, impairing bowel wall assessment; and True-FISP does not provide sensitivity for edema, which is superior on single-shot echo-train imaging. Small/large bowel indications for MRI include: inflammatory bowel disease, infectious disease including abscess evaluation or for appendicitis, inflammatory conditions including ischemia, and partial obstruction, malnutrition, and neoplasm search.

Liver masses.

In summary, MR imaging is superior to other imaging modalities, including CT, for the work-up of liver masses. The current challenge is whether the superior performance of MR imaging translates into a beneficial effect on patient management, disease outcome, and health care costs. New MR sequences, phased-array surface coils, and tissue-specific MR contrast agents suggest that MR imaging may exceed further the diagnostic ability of CT.

Approach to abdominal imaging at 1.5 Tesla and optimization at 3 Tesla.

This article reviews fundamental principles and sequence techniques that have been used successfully for imaging diseases of the abdomen and pelvis at 1.5 Tesla. This article also introduces concepts and the specific alteration of sequence parameters for optimization of abdominal-pelvic imaging at 3 Tesla.

Magnetic resonance imaging of perianal fistulas.

Most cases of fistula-in-ano are nonspecific and result from inflammation of anal glands and crypts (cryptoglandular). The classification of cryptoglandular fistulas depends on the degree of involvement of the anal sphincter complex and determines the type of treatment. Studies have shown that preoperative MR imaging revealed important additional information compared with surgery alone and better predicts clinical outcome of patients with fistula-in-ano than initial surgical exploration. With the emergence of novel surgical treatments like MRI-guided surgery, laser, and adhesive treatments, MR imaging is a mainstay for preprocedural and intraoperative evaluation to ensure the adequacy of the procedure.

Hydrogen peroxide-enhanced three-dimensional endoanal ultrasonography and endoanal magnetic resonance imaging in evaluating perianal fistulas: agreement and patient preference.

OBJECTIVES: To determine agreement between hydrogen peroxide-enhanced three-dimensional endoanal ultrasonography (3D HPUS) and endoanal magnetic resonance imaging (MRI) in preoperative assessment of perianal fistulas, and to assess patient preference with regard to these techniques. METHODS: Forty patients (31 males, aged 21-70 years) with symptoms of a perianal fistula and a visible external opening underwent preoperative 3D HPUS and endoanal MRI. The results were assessed separately by experienced observers. Fistulas were described according to the following characteristics: classification of the primary fistula tract according to Parks, location of the internal opening, presence of secondary tracts and fluid collections. Patients were asked to score the amount of discomfort experienced during both procedures and express their preference for either method. RESULTS: The median time interval between 3D HPUS and endoanal MRI was 14 days (range, 0-91 days). The methods agreed in 88% (35/40, kappa = 0.45) for the primary fistula tract, in 90% (36/40, kappa = 0.83) for the location of the internal opening, in 78% (31/40, kappa = 0.62) for secondary tracts, and in 88% (35/40, kappa = 0.63) for fluid collections. Both methods were associated with similar discomfort, and there was no patient preference for one procedure over the other. CONCLUSIONS: 3D HPUS and endoanal MRI are equally adequate for the evaluation of perianal fistulas. Both methods are associated with similar discomfort and patients have no preference for either procedure.