Current MR imaging lipid detection techniques for diagnosis of lesions in the abdomen and pelvis

Adrenal washout CT in patients with no history of cancer: a waste of time?

PURPOSE

To validate the diagnostic performance of adrenal washout CT in patients without known malignancy in a Western Australian population.

METHODS

A radiology information system (RIS) search for CT reports containing "adrenal" and "washout" across six networked metropolitan public hospitals between January 2005 and November 2021. Homogenous nodules ≥ 1 cm, ≥ 10 HU without a suspected functional component in patients without a history of malignancy were included. Reported absolute and relative washout percentages were recorded and re-measured from unenhanced, 60-s portal venous and 15-min delayed phase imaging and compared to either histopathological or CT follow up for growth (≥ 12 months) reference standards.

RESULTS

2653 studies were screened with 191 meeting inclusion criteria. 105 nodules underwent washout CT and then had either histopathological (12 patients) or CT follow up (93 patients) reference standards available. Reported absolute washout (aWO) estimated sensitivity and specificity for malignant/indeterminate nodules was low at 33% (95% CI 25-43%) and 77% (95% CI 68-84%) respectively. Reported relative washout (rWO) sensitivity and specificity were 56% (95% CI 46-65%) and 69% (95% CI 60-77%) respectively. Negative predictive values for both aWO and rWO were reassuring at 92% (95% CI 86-96%) and 94% (95%CI 88-97%).

CONCLUSION

Our study validates a recent report suggesting that adrenal washout has poor sensitivity for and consequent limited utility to exclude malignancy in patients with no cancer history. However, patients with incidental adrenal nodules < 4 cm in size with benign washout can be reassured by the high negative predictive value and worked up to exclude functional adenoma and re-imaged in a year to confirm no growth.

Lipomatoses

Lipomatoses are benign proliferation of adipose tissue. Lipomas (benign fat tumors) are the most common component of lipomatosis. They may be unique or multiple, encapsulated or not, subcutaneous or sometimes visceral. In some cases, they form large areas of non-encapsulated fat hypertrophy, with a variable degree of fibrosis. They can develop despite the absence of obesity. They may be familial or acquired. At difference with lipodystrophy syndromes, they are not associated with lipoatrophy areas, except in some rare cases such as type 2 familial partial lipodystrophy syndromes (FPLD2). Their metabolic impact is variable in part depending on associated obesity. They may have functional or aesthetic consequences. Lipomatosis may be isolated, be part of a syndrome, or may be visceral. Isolated lipomatoses include multiple symmetrical lipomatosis (Madelung disease or Launois-Bensaude syndrome), familial multiple lipomatosis, the painful Dercum's disease also called Adiposis Dolorosa or Ander syndrome, mesosomatic lipomatosis also called Roch-Leri lipomatosis, familial angiolipomatosis, lipedema and hibernomas. Syndromic lipomatoses include PIK3CA-related disorders, Cowden/PTEN hamartomas-tumor syndrome, some lipodystrophy syndromes, and mitochondrial diseases, especially MERRF, multiple endocrine neoplasia type 1, neurofibromatosis type 1, Wilson disease, Pai or Haberland syndromes. Finally, visceral lipomatoses have been reported in numerous organs and sites: pancreatic, adrenal, abdominal, epidural, mediastinal, epicardial… The aim of this review is to present the main types of lipomatosis and their physiopathological component, when it is known.

Fat-containing hepatocellular carcinoma in patients with cirrhosis: proposal of a diagnostic modification regarding enhancement characteristics

OBJECTIVES

The aim of this study was to develop and validate an algorithm for the non-invasive diagnosis of these fat-containing HCCs.

METHODS

Eighty-four cirrhotic patients with 77 fat-containing HCCs and 11 non-HCC fat-containing nodules were retrospectively included. All MRIs were reviewed; nodule characteristics, European Association for the Study of the Liver (EASL) and LI-RADS classifications, and survival were collected. One of the major features of LI-RADS v2018 (non-rim-like arterial phase hyperenhancement [APHE]) was changed to include different enhancing patterns at arterial phase and a new fat-LI-RADS algorithm was created for fat-containing nodules in cirrhosis. Its diagnostic performance was evaluated in both a derivation and external validation cohort (external cohort including 58 fat-containing HCCs and 10 non-HCC fat nodules). Reproducibility of this new algorithm was assessed.

RESULTS

In the derivation cohort, 54/77 (70.1%) fat-containing HCCs had APHE, 62/77 (80.5%) had enhancement compared to the nodule itself at arterial phase (APE), 43/77 (55.8%) had washout, and 20/77 (26.0%) had an enhancing capsule. EASL and LI-RADS had a sensitivity of 37.7% (29/77) and 36.4% (28/77), respectively, for the diagnosis of fat-containing HCC and both had a specificity of 100% (11/11). The new fat-LI-RADS algorithm increased sensitivity to 50.6% (39/77) without decreasing the specificity of 100% (11/11). The validation cohort confirmed the increased sensitivity, with a slight decrease in specificity. The concordance for the diagnosis of HCC for fat-LR5 was 85.3% (58/68).

CONCLUSION

The new fat-LI-RADS algorithm proposed here significantly improves the performance of the non-invasive diagnosis of fat-containing HCC and thus could reduce the number of biopsies conducted for fat-containing HCCs.

CLINICAL RELEVANCE STATEMENT

The European Association for the Study of the Liver and LI-RADS guidelines are poorly sensitive for the diagnosis of fat-containing HCC, mainly because of the low rate of arterial phase hyperenhancement (APHE) displayed by fat-containing HCC. Using all types of enhancement instead of APHE improves sensitivity of LI-RADS.

KEY POINTS

• Fat-containing HCCs on MRI account for 7.5% of HCCs and have different imaging characteristics from non-fatty HCCs. • The European Association for the Study of the Liver and LI-RADS algorithms for the non-invasive diagnosis of HCC have low sensitivity for the diagnosis of fat-containing HCC with MRI (37.7% and 36.4%, respectively). • The new fat-LI-RADS, which includes a slight modification of the "arterial enhancement" criterion, improves the sensitivity for the diagnosis of fat-containing HCC using MRI, without degrading the specificity.

Gut microbiota and its therapeutic implications in tumor microenvironment interactions

The development of cancer is not just the growth and proliferation of a single transformed cell, but its tumor microenvironment (TME) also coevolves with it, which is primarily involved in tumor initiation, development, metastasis, and therapeutic responses. Recent years, TME has been emerged as a potential target for cancer diagnosis and treatment. However, the clinical efficacy of treatments targeting the TME, especially its specific components, remains insufficient. In parallel, the gut microbiome is an essential TME component that is crucial in cancer immunotherapy. Thus, assessing and constructing frameworks between the gut microbiota and the TME can significantly enhance the exploration of effective treatment strategies for various tumors. In this review the role of the gut microbiota in human cancers, including its function and relationship with various tumors was summarized. In addition, the interaction between the gut microbiota and the TME as well as its potential applications in cancer therapeutics was described. Furthermore, it was summarized that fecal microbiota transplantation, dietary adjustments, and synthetic biology to introduce gut microbiota-based medical technologies for cancer treatment. This review provides a comprehensive summary for uncovering the mechanism underlying the effects of the gut microbiota on the TME and lays a foundation for the development of personalized medicine in further studies.

Imaging modalities for measuring body composition in patients with cancer: opportunities and challenges

Body composition assessment (ie, the measurement of muscle and adiposity) impacts several cancer-related outcomes including treatment-related toxicities, treatment responses, complications, and prognosis. Traditional modalities for body composition measurement include body mass index, body circumference, skinfold thickness, and bioelectrical impedance analysis; advanced imaging modalities include dual energy x-ray absorptiometry, computerized tomography, magnetic resonance imaging, and positron emission tomography. Each modality has its advantages and disadvantages, thus requiring an individualized approach in identifying the most appropriate measure for specific clinical or research situations. Advancements in imaging approaches have led to an abundance of available data, however, the lack of standardized thresholds for classification of abnormal muscle mass or adiposity has been a barrier to adopting these measurements widely in research and clinical care. In this review, we discuss the different modalities in detail and provide guidance on their unique opportunities and challenges.

Does Chemical Shift Magnetic Resonance Imaging Improve Visualization of Pars Interarticularis Defect?

Introduction A unilateral or bilateral pars interarticularis defect (spondylolysis) is a leading cause of axial back pain in adolescent athletes. Currently, a spectrum of imaging modalities is used for assessment of pars interarticularis defects.

Objectives The aim of this study is to compare the accuracy of chemical shift sequence (magnetic resonance imaging [MRI]) technique to conventional MRI sequences in the detection of pars defects.

Patients and Methods Conventional T1, T2, and short tau inversion recovery sagittal and axial, as well as “in-” and “out-” phase chemical shift sagittal MRI sequences of 70 consecutive patients referred for low back pain were reviewed. Demographic details, clinical indication, and presence/diagnosis of pars defects using a 5-point Likert scale on both conventional and chemical shift MRI sequences. Spearman's correlation was used for statistical analysis. Intraclass correlation coefficient analysis was evaluated to assess the intraclass reliability between observers. Data were analyzed using DATAtab web-based statistics software (2022).

Results A total of 70 patients with an average age of 54.34 years with a female predominance were included. There were 11 pars defects in the cohort. Both in and out phases of chemical shift imaging were able to identify pars defect and intact pars. However, out phase was relatively better in delineating pars defects, while the in phase was superior in identifying an intact pars, though this was not statistically significant. There was good intra- and interobserver reliabilities.

Conclusion Chemical shift MRI sequence is a quicker, complementary technique to assess and analyze pars interarticularis confidently than conventionally utilized MRI sequences in patients being evaluated for axial back pain.

Comparison of ability of lesion detection of two MRI sequences of T2WI HASTE and T2WI BLADE for hepatocellular carcinoma

We investigated the diagnostic accuracy of 2 magnetic resonance imaging (MRI) sequences of T2 weighted image (T2WI) half-Fourier acquired single turbo spin-echo (HASTE) and BLADE, for hepatocellular carcinoma (HCC) detection. From November 2010 to August 2018, patients diagnosed with HCC and regularly followed up, and who underwent MRI with 2 kinds of T2WI, were included in this study. The diagnosis of HCC was established based on histopathological findings or LI-RADS 4 and 5 by image. The sensitivities and positive predictive value for the detection of HCC by T2WI HASTE and BLADE were compared for each sequence. Quantitative assessment with lesion contrast-to-noise ratio and visual rating scoring of image quality, based on factors such as artifact, margin of organs, and vessel sharpness of the 2 sequences, were compared. No significant differences in lesion detection were observed based on paired comparison of all lesions and lesions larger than 1 cm across both sequences. The sensitivity was higher in larger than 1cm group in all sequences. The HASTE sequence had less motion artifact, but the BLADE images had advantage in edge sharpness of organs and vessels. The HASTE without fat-saturation seems to have better overall image quality. The lesions contrast-to-noise ratio of the 2 image modalities were not significantly different. Compared with T2 BLADE, T2 HASTE may be a more effective protocol for detecting HCC larger than 1 cm without loss of sensitivity. The accuracy of data from 2 T2WI protocols could be applied to streamline MRI protocols of HCC screening and surveillance.

Water/fat separation for self-navigated diffusion-weighted multishot echo-planar imaging

The purpose of this study was to develop a self-navigation strategy to improve scan efficiency and image quality of water/fat-separated, diffusion-weighted multishot echo-planar imaging (ms-EPI). This is accomplished by acquiring chemical shift-encoded diffusion-weighted data and using an appropriate water-fat and diffusion-encoded signal model to enable reconstruction directly from k-space data. Multishot EPI provides reduced geometric distortion and improved signal-to-noise ratio in diffusion-weighted imaging compared with single-shot approaches. Multishot acquisitions require corrections for physiological motion-induced shot-to-shot phase errors using either extra navigators or self-navigation principles. In addition, proper fat suppression is important, especially in regions with large B₀ inhomogeneity. This makes the use of chemical shift encoding attractive. However, when combined with ms-EPI, shot-to-shot phase navigation can be challenging because of the spatial displacement of fat signals along the phase-encoding direction. In this work, a new model-based, self-navigated water/fat separation reconstruction algorithm is proposed. Experiments in legs and in the head-neck region of 10 subjects were performed to validate the algorithm. The results are compared with an image-based, two-dimensional (2D) navigated water/fat separation approach for ms-EPI and with a conventional fat saturation approach. Compared with the 2D navigated method, the use of self-navigation reduced the shot duration time by 30%-35%. The proposed algorithm provided improved diffusion-weighted water images in both leg and head-neck regions compared with the 2D navigator-based approach. The proposed algorithm also produced better fat suppression compared with the conventional fat saturation technique in the B₀ inhomogeneous regions. In conclusion, the proposed self-navigated reconstruction algorithm can produce superior water-only diffusion-weighted EPI images with less artefacts compared with the existing methods.

The diagnostic value of magnetic resonance imaging compared to computed tomography in the evaluation of fat-containing thoracic lesions

Intrathoracic fat-containing lesions may arise in the mediastinum, lungs, pleura, or chest wall. While CT can be helpful in the detection and diagnosis of these lesions, it can only do so if the lesions contain macroscopic fat. Furthermore, because CT cannot demonstrate microscopic or intravoxel fat, it can fail to identify and diagnose microscopic fat-containing lesions. MRI, employing spectral and chemical shift fat suppression techniques, can identify both macroscopic and microscopic fat, with resultant enhanced capability to diagnose these intrathoracic lesions non-invasively and without ionizing radiation. This paper aims to review the CT and MRI findings of fat-containing lesions of the chest and describes the fat-suppression techniques utilized in their assessment.

In Vivo Renal Lipid Quantification by Accelerated Magnetic Resonance Spectroscopic Imaging at 3T: Feasibility and Reliability Study

A reliable and practical renal-lipid quantification and imaging method is needed. Here, the feasibility of an accelerated MRSI method to map renal fat fractions (FF) at 3T and its repeatability were investigated. A 2D density-weighted concentric-ring-trajectory MRSI was used for accelerating the acquisition of 48 × 48 voxels (each of 0.25 mL spatial resolution) without respiratory navigation implementations. The data were collected over 512 complex-FID timepoints with a 1250 Hz spectral bandwidth. The MRSI sequence was designed with a metabolite-cycling technique for lipid–water separation. The in vivo repeatability performance of the sequence was assessed by conducting a test–reposition–retest study within healthy subjects. The coefficient of variation (CV) in the estimated FF from the test–retest measurements showed a high degree of repeatability of MRSI-FF (CV = 4.3 ± 2.5%). Additionally, the matching level of the spectral signature within the same anatomical region was also investigated, and their intrasubject repeatability was also high, with a small standard deviation (8.1 ± 6.4%). The MRSI acquisition duration was ~3 min only. The proposed MRSI technique can be a reliable technique to quantify and map renal metabolites within a clinically acceptable scan time at 3T that supports the future application of this technique for the non-invasive characterization of heterogeneous renal diseases and tumors.

Signal intensity patterns in health and disease: basics of abdominal magnetic resonance imaging in children

Magnetic resonance imaging (MRI) is playing an increasing role in pediatric abdominal imaging, especially in the evaluation of diffuse parenchymal disease where other imaging modalities might be less sensitive. While quantitative imaging is slowly being incorporated into clinical imaging, qualitative assessment of visceral signal intensity should be part of the routine clinical workflow of all radiologists. Based on their T1 and T2 weighting, the liver, spleen, kidneys and pancreas have characteristic signal intensity patterns with respect to one another and to skeletal muscle. It is important to recognize normal signal intensity patterns of viscera and their evolution with patient age to be able to identify age-related variations and accurately identify diffuse parenchymal disease. Knowledge of normal signal intensity patterns can also help identify ectopic locations of normal tissue such as splenic rests and splenosis. In this review, we discuss normal signal intensity patterns of upper abdominal viscera and their variations on commonly used sequences in pediatric abdominal MRI. We also review normal variations in the perinatal period. Knowledge of these patterns can help pediatric radiologists become more astute in their interpretation of diffuse parenchymal disease in the abdomen.

Radiomics Based on Contrast-Enhanced MRI in Differentiation Between Fat-Poor Angiomyolipoma and Hepatocellular Carcinoma in Noncirrhotic Liver: A Multicenter Analysis

Objective

This study aims to develop and externally validate a contrast-enhanced magnetic resonance imaging (CE-MRI) radiomics-based model for preoperative differentiation between fat-poor angiomyolipoma (fp-AML) and hepatocellular carcinoma (HCC) in patients with noncirrhotic livers and to compare the diagnostic performance with that of two radiologists.

Methods

This retrospective study was performed with 165 patients with noncirrhotic livers from three medical centers. The dataset was divided into a training cohort (n = 99), a time-independent internal validation cohort (n = 24) from one center, and an external validation cohort (n = 42) from the remaining two centers. The volumes of interest were contoured on the arterial phase (AP) images and then registered to the venous phase (VP) and delayed phase (DP), and a total of 3,396 radiomics features were extracted from the three phases. After the joint mutual information maximization feature selection procedure, four radiomics logistic regression classifiers, including the AP model, VP model, DP model, and combined model, were built. The area under the receiver operating characteristic curve (AUC), diagnostic accuracy, sensitivity, and specificity of each radiomics model and those of two radiologists were evaluated and compared.

Results

The AUCs of the combined model reached 0.789 (95%CI, 0.579-0.999) in the internal validation cohort and 0.730 (95%CI, 0.563-0.896) in the external validation cohort, higher than the AP model (AUCs, 0.711 and 0.638) and significantly higher than the VP model (AUCs, 0.594 and 0.610) and the DP model (AUCs, 0.547 and 0.538). The diagnostic accuracy, sensitivity, and specificity of the combined model were 0.708, 0.625, and 0.750 in the internal validation cohort and 0.619, 0.786, and 0.536 in the external validation cohort, respectively. The AUCs for the two radiologists were 0.656 and 0.594 in the internal validation cohort and 0.643 and 0.500 in the external validation cohort. The AUCs of the combined model surpassed those of the two radiologists and were significantly higher than that of the junior one in both validation cohorts.

Conclusions

The proposed radiomics model based on triple-phase CE-MRI images was proven to be useful for differentiating between fp-AML and HCC and yielded comparable or better performance than two radiologists in different centers, with different scanners and different scanning parameters.

RAVE-T2/T1 - Feasibility of a new hybrid MR-sequence for free-breathing abdominal MRI in children and adolescents

BACKGROUND

The new radial volumetric encoding RAVE-T₂/T₁ hybrid sequence is a modern three-dimensional sequence with multiparametric approach, which includes T₂- and T₁-weighted contrasts obtained in identical slice position during one measurement. However, the RAVE-T₂/T₁ hybrid sequence is not yet being used in clinical routine.

PURPOSE

The aim of this study was to evaluate the RAVE-T₂/T₁ hybrid sequence in a pediatric population with a clinical indication for an abdominal MRI examination to demonstrate that the hybrid imaging may be less challenging to perform on children.

MATERIALS AND METHODS

Our retrospective observational study included pediatric patients of all age groups and required for an abdominal MRI examination. Non-contrast standard axial T₁ DIXON and non-contrast RAVE-T₂/T₁ hybrid sequence were obtained at 3 T. MRI studies were analyzed independently by two pediatric radiologists using a 5-point Likert-type scale in five different categories. T₁- and T₂-weighted sequences were each compared with the RAVE-T₂/T₁-sequence using a Wilcoxon signed-rank test.

RESULTS

The analysis included 15 children (mean age, 11 years and 4 months, 7 girls and 8 boys). The Cohens Kappa of interrater agreement measured 0.62. The T₂ weighted part of the RAVE-T₂/T₁ sequence was significantly better than the standard T₂ HASTE sequence in four of five image quality categories: overall image quality (2.2 ± 0.7 vs 1.8 ± 0,7, p = 0.03), respiratory motion artefacts (3.8 ± 0.4 vs 2.0 ± 0.7, p <= 0.01), portal vein clarity (3.3 ± 0.8 vs 2.2 ± 0.7, p <= 0.01), hepatic margin sharpness (2.4 ± 1,0 vs 1.8 ± 0.7, p <= 0.01). The T₁ weighted part of the RAVE-T₂/T₁ sequence was significantly better than the standard T₁ DIXON weighted sequence in three of five image quality categories: respiratory motion artefacts (4.0 ± 0.2 vs 3.6 ± 0.8, p = 0.01), portal vein clarity (2.7 ± 0.9 vs 2.1 ± 0.7, p <= 0.01), hepatic margin sharpness (3.2 ± 0.7 vs 2.6 ± 0.9, p <= 0.01).

CONCLUSIONS

The RAVE-T₂/T₁ hybrid sequence is feasible and equal compared to standard T₁- and T₂-weighted sequences in the assessment of abdominal organs in a pediatric population. Due to non-inferiority to the current standard sequences for abdominal imaging, the RAVE-T₂/T₁ hybrid sequence is a good alternative for children who cannot be examined in breath-hold technique.

Spindle Cell Lipoma Revisited: Common and Unusual Magnetic Resonance Imaging Findings in 54 Patients With New Observations

ABSTRACT

The aims of the study were to study demographic data of patients with spindle cell lipoma and describe a spectrum of magnetic resonance imaging features of the tumor.

Regularized joint water-fat separation with B0 map estimation in image space for 2D-navigated interleaved EPI based diffusion MRI

Purpose

To develop a new water–fat separation and B₀ estimation algorithm to effectively suppress the multiple resonances of fat signal in EPI. This is especially relevant for DWI where fat is often a confounding factor.

Methods

Water–fat separation based on chemical‐shift encoding enables robust fat suppression in routine MRI. However, for EPI the different chemical‐shift displacements of the multiple fat resonances along the phase‐encoding direction can be problematic for conventional separation algorithms. This work proposes a suitable model approximation for EPI under B₀ and fat off‐resonance effects, providing a feasible multi‐peak water–fat separation algorithm. Simulations were performed to validate the algorithm. In vivo validation was performed in 6 volunteers, acquiring spin‐echo EPI images in the leg (B₀ homogeneous) and head‐neck (B₀ inhomogeneous) regions, using a TE‐shifted interleaved EPI sequence with/without diffusion sensitization. The results are numerically and statistically compared with voxel‐independent water–fat separation and fat saturation techniques to demonstrate the performance of the proposed algorithm.

Results

The reference separation algorithm without the proposed spatial shift correction caused water–fat ambiguities in simulations and in vivo experiments. Some spectrally selective fat saturation approaches also failed to suppress fat in regions with severe B₀ inhomogeneities. The proposed algorithm was able to achieve improved fat suppression for DWI data and ADC maps in the head–neck and leg regions.

Conclusion

The proposed algorithm shows improved suppression of the multi‐peak fat components in multi‐shot interleaved EPI applications compared to the conventional fat saturation approaches and separation algorithms.

Canadian Society of Thoracic Radiology/Canadian Association of Radiologists Clinical Practice Guidance for Non-Vascular Thoracic MRI

Historically thoracic MRI has been limited by the lower proton density of lung parenchyma, cardiac and respiratory motion artifacts and long acquisition times. Recent technological advancements in MR hardware systems and improvement in MR pulse sequences have helped overcome these limitations and expand clinical opportunities for non-vascular thoracic MRI. Non-vascular thoracic MRI has been established as a problem-solving imaging modality for characterization of thymic, mediastinal, pleural chest wall and superior sulcus tumors and for detection of endometriosis. It is increasingly recognized as a powerful imaging tool for detection and characterization of lung nodules and for assessment of lung cancer staging. The lack of ionizing radiation makes thoracic MRI an invaluable imaging modality for young patients, pregnancy and for frequent serial follow-up imaging. Lack of familiarity and exposure to non-vascular thoracic MRI and lack of consistency in existing MRI protocols have called for clinical practice guidance. The purpose of this guide, which was developed by the Canadian Society of Thoracic Radiology and endorsed by the Canadian Association of Radiologists, is to familiarize radiologists, other interested clinicians and MR technologists with common and less common clinical indications for non-vascular thoracic MRI, discuss the fundamental imaging findings and focus on basic and more advanced MRI sequences tailored to specific clinical questions.

Hepatocellular Carcinoma With Atypical Imaging Features: Review of the Morphologic Hepatocellular Carcinoma Subtypes With Radiology-Pathology Correlation

Hepatocellular carcinoma (HCC) is the fastest growing cause of cancer death in the United States with the incidence rate more than doubling in 20 years. HCC is unique since a noninvasive diagnosis can be achieved with imaging alone when specific clinical criteria and imaging characteristics are met, obviating the need for tissue sampling. However, HCC is a highly heterogeneous neoplasm. Atypical HCC subtypes vary significantly in their morphology, which can be attributed to specific histologic and molecular features, and can cause deviations from the classic imaging characteristics. The different morphologic subtypes of HCC frequently present a diagnostic challenge for radiologists and pathologists since their imaging and pathologic features can overlap with those of non-HCC malignancies. Identifying an atypical subtype can have important clinical implications. Liver transplant, albeit a scarce and limited resource, is the optimal treatment for conventional HCC, potentially curing both the tumor and the underlying pre-malignant condition. Some HCC subtypes as well as mimickers are associated with unacceptably high recurrence and poor outcome after transplant, and there remains limited data on the role and prognosis of liver transplantation for treatment of rare HCC subtypes. Other subtypes tend to recur later than classic HCC, potentially requiring a different follow-up scheme. This review will discuss the appearance of different HCC subtypes in relation to their histopathologic features. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY: Stage 3.

Lexicon for renal mass terms at CT and MRI: a consensus of the society of abdominal radiology disease-focused panel on renal cell carcinoma

PURPOSE

There is substantial variation in the radiologic terms used to characterize renal masses, leading to ambiguity and inconsistency in clinical radiology reports and research studies. The purpose of this study was to develop a standardized lexicon to describe renal masses at CT and MRI.

MATERIALS AND METHODS

This multi-institutional, prospective, quality improvement project was exempt from IRB oversight. Thirteen radiologists belonging to the Society of Abdominal Radiology (SAR) disease-focused panel on renal cell carcinoma representing nine academic institutions participated in a modified Delphi process to create a lexicon of terms used to describe imaging features of renal masses at CT and MRI. In the first round, members voted on terms to be included and proposed definitions; subsequent voting rounds and a teleconference established consensus. One non-voting member developed the questionnaire and consolidated responses. Consensus was defined as ≥ 80% agreement.

RESULTS

Of 37 proposed terms, 6 had consensus to be excluded. Consensus for inclusion was reached for 30 of 31 terms (13/14 basic imaging terms, 8/8 CT terms, 6/6 MRI terms and 3/3 miscellaneous terms). Despite substantial initial disagreement about definitions of 'renal mass,' 'necrosis,' 'fat,' and 'restricted diffusion' in the first round, consensus for all was eventually reached. Disagreement remained for the definition of 'solid mass.'

CONCLUSIONS

A modified Delphi method produced a lexicon of preferred terms and definitions to be used in the description of renal masses at CT and MRI. This lexicon should improve clarity and consistency of radiology reports and research related to renal masses.

Overview of spontaneous intraabdominal tumor hemorrhage: etiologies, imaging findings, and management

Hemorrhage is a potential complication of benign and malignant tumors and tumor-like conditions in the abdomen. Patients often have non-specific presentations, although they may present critically ill and hemodynamically unstable. Imaging plays an important role not only in the diagnosis of hemorrhage but also in the detection and characterization of an underlying mass. Ultrasound, computed tomography, and magnetic resonance imaging are utilized in evaluating these patients, with each having particular strengths and limitations. Spontaneous tumor hemorrhage is most commonly seen in hepatic and renal lesions, although it can arise from nearly every abdominal organ. In this article, we will review principles of tumor hemorrhage, illustrate common and uncommon imaging features, and highlight different options for management.

Vanishing washout of hepatocellular carcinoma according to the presence of hepatic steatosis: diagnostic performance of CT and MRI

OBJECTIVES

To compare the presence of washout and the diagnostic performance of computed tomography (CT) and magnetic resonance imaging (MRI) for hepatocellular carcinoma (HCC) according to the presence of hepatic steatosis.

METHODS

This retrospective study included 566 patients with chronic liver disease who had undergone hepatic resection for hepatic tumors (482 HCCs and 84 non-HCCs) between January 2016 and June 2018 and had available multiphasic CT and MR images. Patients were allocated in the fatty liver (n = 141) or non-fatty liver (n = 425) group according to the presence of hepatic steatosis, defined as lipid droplets in at least 5% of hepatocytes on pathological examination. The presence of HCC washout and the diagnostic performance of CT and MRI for HCC were compared between the groups.

RESULTS

HCC washout was less frequently seen in the fatty liver group than in the non-fatty liver group on CT (61.5% vs. 88.9%, p < 0.001), whereas it was similarly present on MRI in both groups (77.0% vs. 74.4%, p = 0.565). For diagnosis of HCC, the sensitivity (53.3% vs. 80.0%, p < 0.001) and accuracy (53.9% vs. 80.9%, p < 0.001) of CT were lower in the fatty liver group than in the non-fatty liver group. However, for MRI, these values were not significantly different between the groups (p > 0.05).

CONCLUSIONS

Hepatic steatosis significantly decreased the performance of CT for the diagnosis of HCC, whereas it did not significantly alter the performance of MRI.

KEY POINTS

• Unlike MRI, there is vanishing HCC washout on CT caused by the background hepatic steatosis. • The diagnostic performance of CT for the diagnosis of HCC was significantly altered by hepatic steatosis. • The optimal cutoff HU value of the liver parenchyma for the vanishing washout of HCC was < 50 HU on unenhanced CT images.

Pictorial Review of Mediastinal Masses with an Emphasis on Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) has become a crucial tool for evaluating mediastinal masses considering that several lesions that appear indeterminate on computed tomography and radiography can be differentiated on MRI. Using a three-compartment model to localize the mass and employing a basic knowledge of MRI, radiologists can easily diagnose mediastinal masses. Here, we review the use of MRI in evaluating mediastinal masses and present the images of various mediastinal masses categorized using the International Thymic Malignancy Interest Group's three-compartment classification system. These masses include thymic hyperplasia, thymic cyst, pericardial cyst, thymoma, mediastinal hemangioma, lymphoma, mature teratoma, bronchogenic cyst, esophageal duplication cyst, mediastinal thyroid carcinoma originating from ectopic thyroid tissue, mediastinal liposarcoma, mediastinal pancreatic pseudocyst, neurogenic tumor, meningocele, and plasmacytoma.

MRI in the assessment of adipose tissues and muscle composition: how to use it

Body composition analysis based on the characterization of different tissue compartments is currently experiencing increasing attention by a broad range of medical disciplines for both clinical and research questions. However, body composition profiling (BCP) can be performed utilizing different modalities, which all come along with several technical and diagnostic strengths and limitations, respectively. Magnetic resonance imaging (MRI) demonstrates good soft tissue resolution, high contrast between fat and water, and is free from ionizing radiation. This review article represents an overview of imaging techniques for body composition assessment, focussing on qualitative and quantitative methods of assessing adipose tissue and muscles in MRI.

Advanced MR imaging of bone marrow: quantification of signal alterations on T1-weighted Dixon and T2-weighted Dixon sequences in red marrow, yellow marrow, and pathologic marrow lesions

OBJECTIVES

To quantify and compare signal intensity (SI) changes on T1-weighted (W) and T2W Dixon imaging in yellow marrow, red marrow, and bone marrow lesions.

MATERIALS AND METHODS

A total of 141 patients (77 controls, 64 lesions-33 benign, 31 malignant) between January 2016 and December 2017 were retrospectively identified. For the control group, fixed 2-cm² region of interests (ROI) were drawn at L5, bilateral ilium and femurs on in-phase and opposed-phase T1W and T2W Dixon images. For the lesion group, ROIs of best fit were drawn around each lesion on in-phase and opposed-phase T2W Dixon images. SI changes between in-phase and opposed phase maps for each group were compared. Inter-reader analysis was performed.

RESULTS

Yellow marrow exhibited smaller SI changes as compared to red marrow on both T1W and T2W Dixon imaging at all locations (p < 0.0001) except at L5 on T2W Dixon imaging (p = 0.206). Both benign and malignant lesions showed significantly smaller SI changes as compared to both yellow (p = 0.0087, p < 0.0001) and red marrow (p = 0.0004, p < 0.0001) on T2W Dixon imaging. Malignant lesions exhibited smaller SI change as compared to benign lesions on T2W Dixon imaging (p = 0.0005). Signal intensity loss on both red and yellow marrow were smaller on T1W Dixon as compared to T2W Dixon (0.49-0.64, 0.27-0.31 vs. 0.70-0.74, 0.48-0.71). Inter-reader agreements were excellent (0.91-0.97).

CONCLUSIONS

SI change calculated from T2-weighted Dixon imaging can adequately differentiate between yellow marrow, red marrow, and osseous lesions, both benign and malignant.

Infiltrative non-mass-like hepatocellular carcinoma initially presenting with isolated malignant portal vein thrombosis: A case report and review of the literature

Hepatocellular carcinoma (HCC) shows a rising incidence and mortality rates worldwide. HCC is divided into several distinct subtypes, both morphologically and histopathologically. Among these subtypes, infiltrative HCC may be the most challenging subtype to diagnose, given its characteristic myriad of tumor nodules blended with normal hepatocytes without a distinct mass-like lesion. Herein, we report an unusual case of an infiltrative HCC initially presenting with isolated malignant portal vein thrombosis and provide a brief review of the literature regarding the infiltrative HCC subtype. Additionally, we demonstrate how sonoelastography could aid in detecting the appropriate biopsy area in the infiltrative HCC subtype. To our knowledge, there have not been previously reported cases describing the use of sonoelastography in the evaluation of the appropriate area for the targeted liver biopsy.

State-of-the-art MR Imaging of Fat-containing Focal Lesions of the Liver

BACKGROUND

Fat can be identified in numerous liver lesions, and usually is not a specific finding. Distinguishing between different kinds of fatty deposits is an important part of differential diagnosis. Magnetic Resonance Imaging (MRI) is superior to other imaging techniques because it allows distinguishing intracellular from macroscopic fat.

DISCUSSION

Intracellular lipid may be found in focal hepatic steatosis, hepatic adenoma, hepatocellular carcinoma and, less commonly, in focal nodular hyperplasia as well as regenerative and dysplastic nodules. Macroscopic fat is seen in angiomyolipoma, lipoma, metastases from fatcontaining neoplasms, primary or metastatic liposarcoma, hydatid cyst, pseudolipoma of the Glisson capsule, pericaval fat collection, lipopeliosis, hepatic teratoma, focal hepatic extramedullary haematopoiesis and adrenal rest tumour.

CONCLUSION

Liver nodules should be characterised with regard to underlying liver condition, MRI characteristics and contrast enhancement pattern, including hepatobiliary phase. In many cases, identification of fatty content may help narrowing the differential diagnosis.

Pelvic hemorrhagic lesions in women: MRI findings and differential diagnosis

A large spectrum of pathologic pelvic conditions can present with hemorrhage in structures or organs. These may present acutely, subacutely, chronically or as incidental findings. Clinical history and MRI characteristics can often narrow the differential diagnosis and guide management. The purpose of this article is to showcase a wide array of pelvic lesions, in which the presence of blood is a key imaging feature, and their differential diagnosis.

Photoacoustic imaging as a tool to probe the tumour microenvironment

The tumour microenvironment (TME) is a complex cellular ecosystem subjected to chemical and physical signals that play a role in shaping tumour heterogeneity, invasion and metastasis. Studying the roles of the TME in cancer progression would strongly benefit from non-invasive visualisation of the tumour as a whole organ in vivo, both preclinically in mouse models of the disease, as well as in patient tumours. Although imaging techniques exist that can probe different facets of the TME, they face several limitations, including limited spatial resolution, extended scan times and poor specificity from confounding signals. Photoacoustic imaging (PAI) is an emerging modality, currently in clinical trials, that has the potential to overcome these limitations. Here, we review the biological properties of the TME and potential of existing imaging methods that have been developed to analyse these properties non-invasively. We then introduce PAI and explore the preclinical and clinical evidence that support its use in probing multiple features of the TME simultaneously, including blood vessel architecture, blood oxygenation, acidity, extracellular matrix deposition, lipid concentration and immune cell infiltration. Finally, we highlight the future prospects and outstanding challenges in the application of PAI as a tool in cancer research and as part of a clinical oncologist's arsenal.

Summary: This Review details the potential of photoacoustic imaging to visualise features of the tumour microenvironment such as blood vessels, hypoxia, fibrosis and immune infiltrate to provide unprecedented insight into tumour biology.

New MRI series for kidney evaluation: Saving time and money

OBJECTIVES

This study investigates the diagnostic performance of a new T1 imaging series, generated by the digital subtraction of the opposed phase from in phase T ₁ weighted images, in MRI for renal angiomyolipoma (AML) evaluation.

METHODS

This retrospective study involved 96 patients, 63 (65.6%) with at least one renal AML and 33 (34.4%) healthy patients. Two radiologists having different experience retrospectively reviewed two MR imaging series, starting with in and out-phase T ₁ weighted images and then the new subtracted T1 images, in which AML appeared white on black background. The presence, number, location, and dimensions of the AMLs, and reading time were collected separately for the two kidneys. Statistical analysis was carried out using the appropriate tests.

RESULTS

The number of lesions identified and the evaluation of lesion dimension did not statistically differ between the different MR imaging series evaluated, without interobserver variability. Both percentage agreement of the total number of observations and the κ coefficient showed very good agreement between the radiologists. The median time for the diagnosis was statistically lower when using the subtracted T1 imaging series for both observers with a median gain from 6.5 to 15 s per identified lesion, resulting in a total time-saving of more than half (52.9%), in both patients with and without AMLs, and in patients with a single or with more than one AML (p < 0.001).

CONCLUSIONS

The new subtracted T1 imaging series proved to be reliable in identifying fat-containing renal lesions, by both expert and non-expert radiologists, resulting in a saving of both time and money. Moreover, this new subtracted T1 imaging series could be an effective tool in non-dedicated kidney examinations in which a faster reading is advisable.

ADVANCES IN KNOWLEDGE

The opportunity of using a single set of MRI images in kidney evaluation for identifying fat-containing lesions, considerably reducing reading time, resulting in cost-effectiveness.

Clinical experience with two-point mDixon turbo spin echo as an alternative to conventional turbo spin echo for magnetic resonance imaging of the pediatric knee

BACKGROUND

Two-point modified Dixon (mDixon) turbo spin-echo (TSE) sequence provides an efficient, robust method of fat suppression. In one mDixon acquisition, four image types can be generated: water-only, fat-only, in-phase and opposed-phase images.

OBJECTIVE

To determine whether PD mDixon TSE water-only and, by proxy, PD in-phase images generated by one acquisition can replace two conventional PD TSE sequences with and without fat suppression in routine clinical MR examination of the knee.

MATERIALS AND METHODS

This is a retrospective study of 50 consecutive pediatric knee MR examinations. PD mDixon TSE water-only and PD fat-saturated TSE sequences (acquired in the sagittal plane with identical spatial resolution) were reviewed independently by two pediatric radiologists for homogeneity of fat suppression and detection of intra-articular pathology. Thirteen of the 50 patients underwent arthroscopy, and we used the arthroscopic results as a reference standard for the proton-density fat-saturated and proton-density mDixon results. We used the Kruskal-Wallis rank test to assess difference in fat suppression between the proton-density mDixon and proton-density fat-saturated techniques. We used kappa statistics to compare the agreement of detection of intra-articular pathology between readers and techniques. We also calculated sensitivity, specificity and accuracy between arthroscopy and MR interpretations.

RESULTS

Proton-density mDixon water-only imaging showed significant improvement with the fat suppression compared with proton-density fat-saturated sequence (P=0.02). Each observer demonstrated near-perfect agreement between both techniques for detecting meniscal and ligamentous pathology and fair to substantial agreement for bone contusions, and chondral and osteochondral lesions.

CONCLUSION

Two-point mDixon water-only imaging can replace conventional proton-density fat-saturated sequence. When same-plane proton-density fat-saturated and non-fat-saturated sequences are required, proton-density water-only and proton-density in-phase image types acquired in the same acquisition shorten the overall examination time while maintaining excellent intra-articular lesion conspicuity.

Fatty masses of the abdomen and pelvis and their complications

There are numerous common and rare macroscopic fat-containing masses found in the abdomen and pelvis. These include benign masses, such as lipoleiomyoma, ovarian teratoma, mesenteric teratoma, and lipoma, as well as malignant masses, including liposarcoma and malignant transformation of benign entities. Any mass may become symptomatic due to the development of a complication which may range from ovarian torsion to intussusception to hemorrhage. Imaging plays a vital role in diagnosis and treatment planning when confronted with a symptomatic fat-containing mass.

MR fingerprinting with simultaneous T1, T2, and fat signal fraction estimation with integrated B0 correction reduces bias in water T1 and T2 estimates

PURPOSE

MR fingerprinting (MRF) sequences permit efficient T₁ and T₂ estimation in cranial and extracranial regions, but these areas may include substantial fat signals that bias T₁ and T₂ estimates. MRI fat signal fraction estimation is also a topic of active research in itself, but may be complicated by B₀ heterogeneity and blurring during spiral k-space acquisitions, which are commonly used for MRF. An MRF method is proposed that separates fat and water signals, estimates water T₁ and T₂, and accounts for B₀ effects with spiral blurring correction, in a single sequence.

THEORY AND METHODS

A k-space-based fat-water separation method is further extended to unbalanced steady-state free precession MRF with swept echo time. Repeated application of this k-space fat-water separation to demodulated forms of the measured data allows a B₀ map and correction to be approximated. The method is compared with MRF without fat separation across a broad range of fat signal fractions (FSFs), water T₁s and T₂s, and under heterogeneous static fields in simulations, phantoms, and in vivo.

RESULTS

The proposed method's FSF estimates had a concordance correlation coefficient of 0.990 with conventional measurements, and reduced biases in the T₁ and T₂ estimates due to fat signal relative to other MRF sequences by several hundred ms. The B₀ correction improved the FSF, T₁, and T₂ estimation compared to those estimates without correction.

CONCLUSION

The proposed method improves MRF water T₁ and T₂ estimation in the presence of fat and provides accurate FSF estimation with inline B₀ correction.

Can pancreatic steatosis affect exocrine functions of pancreas?

BACKGROUND/AIMS

Pancreatic steatosis (PS) is a generally used term to define accumulation of fat in the pancreas. In theory PS may be able to affect the exocrine function of pancreas. In this study we aimed to determine the effect of PS on exocrine pancreas function.

MATERIALS AND METHODS

Forty-three patients with PS determined by 3 tesla magnetic resonance imaging (MRI) and 48 patients without PS were included in this study. Patients with PS were classified as group 1 and control patients were classified as group 2. Fecal elastase-1 levels were determined. Fecal elastase-1 levels <200 μg/g were defined as exocrine pancreatic insufficiency (EPI). Patients with PS were further grouped according to severity and anatomic distribution of steatosis based on findings of 3 tesla MRI.

RESULTS

Fecal elastase-1 levels was significantly lower in group 1 compared to group 2 (319.76±45.7 vs 549.31±69.4, respectively, p=0.003). Proportion of patients with EPI was significantly higher in group 1 than group 2 (35.5% vs 12% p=0.042). There were no significant differences in terms of severity or the anatomic distribution of PS in patients with PS with EPI based on MRI (p=0.052, p=0.198, p=0.405) Conclusion: Current study demonstrates that PS can cause EPI.

Quantification and visualization of lipid landscape in glioma using in -and opposed-phase imaging

Objectives

This study maps the lipid distributions based on magnetic resonance imaging (MRI) in-and opposed-phase (IOP) sequence and correlates the findings generated from lipid map to histological grading of glioma.

Methods

Forty histologically proven glioma patients underwent a standard MRI tumour protocol with the addition of IOP sequence. The regions of tumour (solid enhancing, solid non-enhancing, and cystic regions) were delineated using snake model (ITK-SNAP) with reference to structural and diffusion MRI images. The lipid distribution map was constructed based on signal loss ratio (SLR) obtained from the IOP imaging. The mean SLR values of the regions were computed and compared across the different glioma grades.

Results

The solid enhancing region of glioma had the highest SLR for both Grade II and III. The mean SLR of solid non-enhancing region of tumour demonstrated statistically significant difference between the WHO grades (grades II, III & IV) (mean SLR_II = 0.04, mean SLR_III = 0.06, mean SLR_IV = 0.08, & p < .01). A strong positive correlation was seen between WHO grades with mean SLR on lipid map of solid non-enhancing (ρ=0.68, p < .01).

Conclusion

Lipid quantification via lipid map provides useful information on lipid landscape in tumour heterogeneity characterisation of glioma. This technique adds to the surgical diagnostic yield by identifying biopsy targets. It can also be used as an adjunct grading tool for glioma as well as to provide information about lipidomics landscape in glioma development.

•

In- and opposed-phase imaging is useful in gliomas characterisation and grading.

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Signal loss ratio in the solid non-enhancing region is a potential imaging marker for discriminating between the WHO grades.

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Lipid quantification via lipid distribution mapping provides useful information on lipid landscape in tumour heterogeneity.

Chemical shift imaging for evaluation of adrenal masses: a systematic review and meta-analysis

OBJECTIVES

To perform a systematic review and meta-analysis of published data to evaluate the utility of chemical shift imaging (CSI) for differentiating between adrenal adenomas and non-adenomas.

METHODS

A systematic search of the MEDLINE, Web of Science Core Collection, EMBASE and Cochrane Central Register of Controlled Trials electronic databases was performed. The methodological quality of the included studies was assessed by using the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies) tool. A bivariate random effect model was used to determine summary and subgroup sensitivity and specificity and calculate summary receiver operating characteristic curves (SROC).

RESULTS

Eighteen studies with 1138 patients and 1280 lesions (859 adenomas, 421 non-adenomas) in total were included. In addition to summary analysis, quantitative analyses of the adrenal signal intensity index (SII, 978 lesions, 14 studies), adrenal-to-spleen ratio (ASR; 394 lesions, 7 studies) and visual analysis (560 lesions, 5 studies) were performed. The resultant data showed considerable heterogeneity (inconsistency index I² of 94%, based on the diagnostic odds ratio, DOR). The pooled sensitivity of CSI for adenoma was 0.94 [95% confidence interval (CI) 0.88-0.97] and pooled specificity was 0.95 (95% CI 0.89-0.97). The area (AUC) under the SROC curve was 0.98 (95% CI 0.96-0.99). The corresponding AUCs were 0.98, 0.99 and 0.95 for SII, ASR and visual evaluation, respectively.

CONCLUSION

CSI has high sensitivity, specificity and accuracy for adrenal adenoma. Diagnostic performance does not improve when quantitative indices are used.

KEY POINTS

• Inclusion of CSI in abdominal MRI protocols provides an effective solution for classifying adrenal masses discovered on MR exams • Visual evaluation of adrenal CSI is sufficient; use of quantitative indices does not improve diagnostic accuracy.

Fracture of ankle: MRI using opposed-phase imaging obtained from turbo spin echo modified Dixon image shows improved sensitivity

OBJECTIVE

To evaluate if opposed-phase (OP) imaging obtained from the turbo spin echo (TSE) modified Dixon (mDixon) technique can increase the sensitivity of MRI for diagnosing ankle fractures.

METHODS

This study included 95 CT-confirmed ankle fractures with additional MRI of the ankle using a TSE modified Dixon (mDixon) technique. Two groups of images were analyzed independently: Group 1-imaging group without OP imaging; Group 2-imaging group with OP imaging. Readers assessed the images using a 4-point confidence score to detect fractures. During the first review session, the fracture site was blinded. For the second review session, the fracture site was provided. Sensitivity and positive-predictive value were calculated.

RESULTS

In both sessions, the sensitivity for Group 2 was significantly greater than that for Group 1 (Session 1: 76.3% vs 62.6%, p < 0.0001; Session 2: 80.5% vs 65.3%, p < 0.0001). The positive-predictive value of Group 2 was significantly lower in both sessions 1 and 2 (Session 1: 85.8% vs 97.5%, p < 0.0001; Session 2: 90.5% vs 96.9%, p = 0.0068). Among the 28 false-negative fractures missed in Group 1 (Session 1), 12 (9 minimal displaced and 4 small diameter fractures) were identified in Group 2 (Session 1). While 8.9% showed lower movement, 33.6% showed upper movement in Group 2 compared with Group 1. Possible causes of false-positive lesions were subcutaneous fat, bone marrow edema, and intraosseous vessel mimic fractures.

CONCLUSION

OP imaging obtained using the modified Dixon technique provided better sensitivity and improved descriptions of fractures, especially for minimal displaced fractures and small diameter fractures. However, caution is required when diagnosing fractures with OP imaging because pseudofractures can appear as a result of adjacent bone marrow edema, vascular structures, or subcutaneous fat lobules. Advances in knowledge: In MRI, minimal displaced or small chip bone fracture maybe missed, OP imaging obtained using the mDixon technique provided better sensitivity and improved descriptions of fractures using the black boundary artifact.

Basic MRI for the liver oncologists and surgeons

Magnetic resonance imaging (MRI) is the modality of choice for liver imaging due to its superior contrast resolution in comparison with computer tomography and the ability to provide both morphologic and physiologic information. The physics of MR are complex, and a detailed understanding is not required to appreciate findings on an MRI exam. Here, we attempt to introduce the basic principles of MRI with respect to hepatic imaging focusing on various commonly encountered hepatic diseases. The purpose is to facilitate an appreciation of the various diagnostic capabilities of MR among hepatic oncologists and surgeons and to foster an understanding of when MR studies may be appropriate in the care of their patients.

Usefulness of black boundary artifact on opposed-phase imaging from turbo spin-echo two-point mDixon MRI for delineation of an arthroscopically confirmed small fracture of the lateral talar dome: A case report

RATIONALE

A nondisplaced chip fracture can be missed on MRI. Opposed-phase imaging from mDixon MRI produces an interesting artifact called black boundary artifact. This artifact can provide better contrast at the fracture line resulting in better depiction of a small chip fracture on MRI.

PATIENT CONCERNS

We present a case of small nondisplaced chip fracture at the lateral talar dome that was well delineated only with the aid of a black boundary artifact after using T2-weighted opposed-phase imaging from turbo spin-echo two-point modified Dixon ankle MRI. In other sequences, the lesion demonstrated a focal full thickness cartilage defect, subtle cortical irregularity, or subcortical bone marrow edema but the full delineation of the fracture line was not possible.

DIAGNOSES

Opposed-phase imaging from mDixon MRI aided in the diagnosis of lateral talar dome osteochondral fracture (osteochondral lesion), which was confirmed arthroscopically.

INTERVENTIONS

The osteochondral fragment was removed by arthroscopy.

OUTCOMES

The patient did well with recovery of full range of motion after 2 months.

LESSONS

We have identified a black boundary artifact using opposed-phase imaging from mDixon MRI that can aid in detection of small fracture, which can be missed by conventional MRI, by providing a dark linear signal at the fracture line.

Fat-Containing Liver Lesions on Imaging: Detection and Differential Diagnosis

OBJECTIVE

The purpose of this article is to review how fat is detected on imaging and to discuss the differential diagnosis of fat-containing liver lesions.

CONCLUSION

Fat is a highly useful feature in characterizing liver lesions on imaging. Although a variety of liver lesions can show fat on cross-sectional imaging, the presence of fat usually indicates that the lesion is of hepatocellular origin. Less commonly, nonhepatocellular fatty lesions may be distinguished by ancillary clinical and imaging features.

Radiology of the adrenal incidentalomas. Review of the literature

The term "adrenal incidentaloma" is a radiological term. Adrenal incidentalomas are adrenal tumors discovered in an imaging study that has been obtained for indications exclusive to adrenal conditions (Udelsman 2001; Linos 2003; Bulow et al. 2006; Anagnostis et al. 2009). This definition excludes patients undergoing imaging testing as part of staging and work-up for cancer (Grumbach et al. 2003; Anagnostis et al. 2009). Papierska et al. (2013) have added the prerequisite that the size of a tumor must be "greater than 1cm in diameter", in order to be called incidentaloma. Although in the most cases these masses are non-hypersecreting and benign, they still represent an important clinical concern because of the risk of malignancy or hormone hyperfunction (Barzon et al. 2003). Th e adrenal tumors belong to the commonest incidental findings having been discovered (Kanagarajah et al. 2012).

Invisible fat on CT: making it visible by MRI

Presence of fat in a lesion significantly narrows the differential diagnosis. Small quantities of macroscopic fat and intracellular fat are invisible on computed tomography (CT) and ultrasonography. Magnetic resonance imaging (MRI) can reveal any fatty change in a lesion and can also differentiate macroscopic fat from intracellular and intravoxel fat. Hypodensity on CT may be a sign of invisible fat and MRI can help to diagnose even minute amounts of fat in liver, pancreas, adrenal, musculoskeletal, and omental pseudolesions and lesions. This article will review the superiority of MRI over CT in demonstrating fat in abdominal lesions.

Imaging of aberrant left gastric vein and associated pseudolesions of segments II and III of the liver and mimickers

We present imaging findings of aberrant left gastric vein (ALGV) and associated pseudolesions and mimickers including metastases and focal nodular hyperplasia. ALGV is formed due to interrupted involution of anastomotic omental veins, and it can drain into left portal vein or segments II and III of the liver as third inflow. Focal fat, focal fat sparing, and perfusion changes can be seen due to the presence of ALGV, which can mimic metastasis in cancer patients. ALGV may also serve as a pathway for direct tumor spread into the liver in patients with gastric cancer. Magnetic resonance imaging can be used as a problem solving tool in the presence of equivocal findings on ultrasonography and computed tomography.

Interpreting body MRI cases: what you need to know to get started

Interpreting body MRI cases can seem overwhelming to an uninitiated radiologist. The standard study includes a variety of pulse sequences, the names of which vary depending on the MR vendor. Pulse sequences may be displayed haphazardly on the picture archiving and communication system (PACS), frequently not synchronized with the imaging protocol. Adding to the complexity is the use of different gadolinium-based contrast agents, which may affect the timing and diagnostic yield of each sequence. The following introductory primer for interpreting body MRI cases is meant to create a basic framework for efficiently reviewing body MRI cases to provide high quality interpretations, fully utilizing the diagnostic information of the modality. There are 4 components that need to be mastered when interpreting body MRI cases including: (1) recognizing the key sequences in a basic body MRI protocol, (2) learning how to best display the key pulse sequences on PACS, (3) understanding the technique and clinical utility of each sequence and learning how to utilize sequences to be an "MR Pathologist", and (4) understanding the key features of the different gadolinium based contrast agents.

Utilization of chemical shift MRI in the diagnosis of disorders affecting pediatric bone marrow

OBJECTIVE

MRI signal intensity of pediatric bone marrow can be difficult to interpret using conventional methods. Chemical shift imaging (CSI), which can quantitatively assess relative fat content, may improve the ability to accurately diagnose bone marrow abnormalities in children.

METHODS

Consecutive pelvis and extremity MRI at a children's hospital over three months were retrospectively reviewed for inclusion of CSI. Medical records were reviewed for final pathological and/or clinical diagnosis. Cases were classified as normal or abnormal, and if abnormal, subclassified as marrow-replacing or non-marrow-replacing entities. Regions of interest (ROI) were then drawn on corresponding in and out-of-phase sequences over the marrow abnormality or over a metaphysis and epiphysis in normal studies. Relative signal intensity ratio for each case was then calculated to determine the degree of fat content in the ROI.

RESULTS

In all, 241 MRI were reviewed and 105 met inclusion criteria. Of these, 61 had normal marrow, 37 had non-marrow-replacing entities (osteomyelitis without abscess n = 17, trauma n = 9, bone infarction n = 8, inflammatory arthropathy n = 3), and 7 had marrow-replacing entities (malignant neoplasm n = 4, bone cyst n = 1, fibrous dysplasia n = 1, and Langerhans cell histiocytosis n = 1). RSIR averages were: normal metaphyseal marrow 0.442 (0.352-0.533), normal epiphyseal marrow 0.632 (0.566-698), non-marrow-replacing diagnoses 0.715 (0.630-0.799), and marrow-replacing diagnoses 1.06 (0.867-1.26). RSIR for marrow-replacing entities proved significantly different from all other groups (p < 0.05). ROC analysis demonstrated an AUC of 0.89 for RSIR in distinguishing marrow-replacing entities.

CONCLUSION

CSI techniques can help to differentiate pathologic processes that replace marrow in children from those that do not.

Noninvasive fat quantification of the liver and pancreas may provide potential biomarkers of impaired glucose tolerance and type 2 diabetes

The aim of the study is to investigate if the fat content of the liver and pancreas may indicate impaired glucose tolerance (IGT) or type 2 diabetes mellitus (T2DM). A total of 83 subjects (34 men; aged 46.5 ± 13.5 years) were characterized as T2DM, IGT, or normal glucose tolerant (NGT). NGT individuals were stratified as <40 or ≥40 years. Standard laboratory tests were conducted for insulin resistance and β-cell dysfunction. The magnetic resonance imaging Dixon technique was used to determine fat distribution in the liver and pancreas. Correlations among liver and pancreatic fat volume fractions (LFVFs and PFVFs, respectively) and laboratory parameters were analyzed. Among the groups, fat distribution was consistent throughout sections of the liver and pancreas, and LFVFs closely correlated with PFVFs. LFVFs correlated more closely than PFVFs with insulin resistance and β-cell function. Both the LFVFs and PFVFs were the highest in the T2DM patients, less in the IGT, and least in the NGT; all differences were significant. The PFVFs of the NGT subjects ≥40 years were significantly higher than that of those <40 years. The fat content of the liver and pancreas, particularly the liver, may be a biomarker for IGT and T2DM.

Common and uncommon pitfalls in pancreatic imaging: it is not always cancer

Despite advances in multimodality imaging of pancreas, there is still overlap between imaging findings of several pancreatic/peripancreatic disease processes. Pancreatic and peripancreatic non-neoplastic entities may mimic primary pancreatic neoplasms on ultrasound, CT, and MRI. On the other hand, primary pancreatic cancer may be overlooked on imaging because of technical and inherent factors. The purpose of this pictorial review is to describe and illustrate pancreatic imaging pitfalls and highlight the basic radiological features for proper differential diagnosis.