LI-RADS: Looking Back, Looking Forward.

Since its initial release in 2011, the Liver Imaging Reporting and Data System (LI-RADS) has evolved and expanded in scope. It started as a single algorithm for hepatocellular carcinoma (HCC) diagnosis with CT or MRI with extracellular contrast agents and has grown into a multialgorithm network covering all major liver imaging modalities and contexts of use. Furthermore, it has developed its own lexicon, report templates, and supplementary materials. This article highlights the major achievements of LI-RADS in the past 11 years, including adoption in clinical care and research across the globe, and complete unification of HCC diagnostic systems in the United States. Additionally, the authors discuss current gaps in knowledge, which include challenges in surveillance, diagnostic population definition, perceived complexity, limited sensitivity of LR-5 (definite HCC) category, management implications of indeterminate observations, challenges in reporting, and treatment response assessment following radiation-based therapies and systemic treatments. Finally, the authors discuss future directions, which will focus on mitigating the current challenges and incorporating advanced technologies. Tha authors envision that LI-RADS will ultimately transform into a probability-based system for diagnosis and prognostication of liver cancers that will integrate patient characteristics and quantitative imaging features, while accounting for imaging modality and contrast agent.

Responsiveness of Magnetic Resonance Enterography Indices for Evaluation of Luminal Disease Activity in Crohn's Disease.

BACKGROUND & AIMS: Magnetic resonance enterography (MRE) is having an increasing role in Crohn's disease; however, fully validated indices are needed. We evaluated the responsiveness of 4 MRE indices in luminal Crohn's disease. METHODS: Paired MRE images (pretreatment and post-treatment at weeks 12 or 14) from 41 patients were scored by 3 blinded radiologists. Disease activity was scored for 4 MRE indices (magnetic resonance index of activity [MaRIA], simplified MaRIA, London index, and London extended index) and a 100-mm visual analog scale (VAS) of overall disease activity. The criterion for change was an improvement by at least one half of an SD in the VAS after treatment. Responsiveness was evaluated using the standardized effect size (SES). Longitudinal validity was evaluated using correlations between changes in MRE index scores and disease activity measures including endoscopy and the VAS. RESULTS: The SES was 1.17 (95% CI, 0.56-1.77) for the simplified MaRIA, 0.98 (95% CI, 0.42-1.55) for the MaRIA, 0.95 (95% CI, 0.38-1.51) for the London extended index, and 0.85 (95% CI, 0.31-1.39) for the London index. The simplified MaRIA was significantly more responsive than the London index (ΔSES, 0.32; 95% CI, 0.05-0.58) but not the MaRIA (ΔSES, 0.18; 95% CI, -0.01 to 0.38) or the London extended index (ΔSES, 0.22; 95% CI, -0.05 to 0.50). Correlations with endoscopy (simplified MaRIA: r = 0.72) were not different from correlations with the VAS (London extended index: r = 0.70). CONCLUSIONS: Evaluated MRE indices showed moderate-to-large responsiveness and are suitable for use in clinical trials. The simplified MaRIA may be preferred because of its responsiveness and nonreliance on gadolinium administration.

Liver imaging: it is time to adopt standardized terminology.

Liver imaging plays a vital role in the management of patients at risk for hepatocellular carcinoma (HCC); however, progress in the field is challenged by nonuniform and inconsistent terminology in the published literature. The Steering Committee of the American College of Radiology (ACR)'s Liver Imaging Reporting And Data System (LI-RADS), in conjunction with the LI-RADS Lexicon Writing Group and the LI-RADS International Working Group, present this consensus document to establish a single universal liver imaging lexicon. The lexicon is intended for use in research, education, and clinical care of patients at risk for HCC (i.e., the LI-RADS population) and in the general population (i.e., even when LI-RADS algorithms are not applicable). We anticipate that the universal adoption of this lexicon will provide research, educational, and clinical benefits. KEY POINTS: •To standardize terminology, we encourage authors of research and educational materials on liver imaging to use the standardized LI-RADS Lexicon. •We encourage reviewers to promote the use of the standardized LI-RADS Lexicon for publications on liver imaging. •We encourage radiologists to use the standardized LI-RADS Lexicon for liver imaging in clinical care.

LI-RADS categorization of benign and likely benign findings in patients at risk of hepatocellular carcinoma: a pictorial atlas.

OBJECTIVE: The purpose of this article is to review the imaging features and Liver Imaging Reporting and Data System (LI-RADS) categorization of benign and likely benign entities, including typical cirrhotic nodules, distinctive nodular observations, and benign entities that may simulate hepatocellular carcinoma. CONCLUSION: LI-RADS is a system of standardized criteria for interpreting liver CT and MR images of patients at risk of hepatocellular carcinoma. Most of the observations in these patients are not malignant. With the development of fibrosis and cirrhosis, these benign entities may take on an altered appearance.

ACR Appropriateness Criteria® Left Lower Quadrant Pain: 2023 Update.

The differential diagnosis for left lower quadrant pain is wide and conditions range from the benign and self-limited to life-threatening surgical emergencies. Along with patient history, physical examination, and laboratory tests, imaging is often critical to limit the differential diagnosis and identify life-threatening abnormalities. This document will discuss the guidelines for the appropriate use of imaging in the initial workup for patients who present with left lower quadrant pain, patients with suspected diverticulitis, and patients with suspected complications from diverticulitis. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

ACR Appropriateness Criteria® Hernia.

Abdominopelvic hernias are common clinical entities composed of a wide variety of congenital, traumatic, and iatrogenic etiologies. Any weakness in the body wall may result in hernia of cavity contents with concomitant risks of morbidity and mortality. Presentations may be specific, palpable body wall mass/bulge, or vague, nonspecific pain through bowel obstruction. This document focuses on initial imaging of the adult population with signs of symptoms prompting suspicion of abdominopelvic hernia. Imaging of the abdomen and pelvis to evaluate defects is essential for prompt diagnosis and treatment. Often CT and ultrasound are the first-line modalities to quickly evaluate the abdomen and pelvis, providing for accurate diagnoses and management of patients. MRI protocols may be useful as first-line imaging studies, especially in patients with orthopedic instrumentation. Although often performed, abdominal radiographs and fluorographic procedures may provide indirect evidence of hernias but are usually not indicated for initial diagnosis of hernia. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer-reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer-reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

ACR Appropriateness Criteria® Staging of Colorectal Cancer: 2021 Update.

Preoperative imaging of rectal carcinoma involves accurate assessment of the primary tumor as well as distant metastatic disease. Preoperative imaging of nonrectal colon cancer is most beneficial in identifying distant metastases, regardless of primary T or N stage. Surgical treatment remains the definitive treatment for colon cancer, while organ-sparing approach may be considered in some rectal cancer patients based on imaging obtained before and after neoadjuvant treatment. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

ACR Appropriateness Criteria® Right Lower Quadrant Pain: 2022 Update.

This document focuses on imaging in the adult and pregnant populations with right lower quadrant (RLQ) abdominal pain, including patients with fever and leukocytosis. Appendicitis remains the most common surgical pathology responsible for RLQ abdominal pain in the United States. Other causes of RLQ pain include right colonic diverticulitis, ureteral stone, and infectious enterocolitis. Appropriate imaging in the diagnosis of appendicitis has resulted in decreased negative appendectomy rate from as high as 25% to approximately 1% to 3%. Contrast-enhanced CT remains the primary and most appropriate imaging modality to evaluate this patient population. MRI is approaching CT in sensitivity and specificity as this technology becomes more widely available and utilization increases. Unenhanced MRI and ultrasound remain the diagnostic procedures of choice in the pregnant patient. MRI and ultrasound continue to perform best in the hands of the experts. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer-reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer-reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Incidental Liver Findings on Cross-sectional Imaging.

Hepatic incidental findings often are seen on cross-sectional imaging examinations of the chest, spine, pelvis, or other nondedicated hepatic imaging. Radiologists are tasked with appropriately triaging, which requires further evaluation, even in the setting of an otherwise limited evaluation. This article reviews common benign entities encountered on ultrasound, computed tomography, or magnetic resonance imaging, along with their characteristic imaging features. Imaging features that are suspicious for malignancy or suggest the need for further evaluation also are discussed. Two algorithms are proposed to guide radiologists in their recommendations based on patient risk factors, focal hepatic abnormality size, and available imaging features.

MRI of Perianal Crohn Disease: Technique and Interpretation.

ABSTRACT: Magnetic resonance imaging (MRI) has emerged as the imaging method of choice for evaluation of perianal fistulizing disease. As treatment of Crohn disease and associated perianal fistulas has evolved to include a combination of systemic treatments and surgical interventions, perianal MRI provides critical information to guide treatment selection and timing. Radiologists need to be familiar with the normal regional anatomy to accurately describe perianal fistulas and any associated complications which can then be used to classify fistulas based on several available classification systems. Following treatment, MRI can provide information that suggests treatment success or failure. We propose a perianal fistula reporting template that includes the necessary information to convey fistula complexity, guide treatment, and evaluate treatment response. This review article will also discuss the postoperative appearance of many treatments currently used for management of perianal fistulizing disease and some associated complications.

ACR Appropriateness Criteria® Anorectal Disease.

This review summarizes the relevant literature for the selection of the initial imaging in 4 clinical scenarios in patients with suspected inflammatory disease or postoperative complication of the anorectum. These clinical scenarios include suspected perianal fistula or abscess; rectovesicular or rectovaginal fistula; proctitis or pouchitis; and suspected complication following proctectomy, coloproctectomy, or colectomy with a pouch or other anastomosis. The appropriateness of imaging modalities as they apply to each clinical scenario is rated as usually appropriate, may be appropriate, and usually not appropriate to assist the selection of the most appropriate imaging modality in the corresponding clinical scenarios of anorectal disease. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Deep convolutional neural network applied to the liver imaging reporting and data system (LI-RADS) version 2014 category classification: a pilot study.

PURPOSE: To develop a deep convolutional neural network (CNN) model to categorize multiphase CT and MRI liver observations using the liver imaging reporting and data system (LI-RADS) (version 2014). METHODS: A pre-existing dataset comprising 314 hepatic observations (163 CT, 151 MRI) with corresponding diameters and LI-RADS categories (LR-1-5) assigned in consensus by two LI-RADS steering committee members was used to develop two CNNs: pre-trained network with an input of triple-phase images (training with transfer learning) and custom-made network with an input of quadruple-phase images (training from scratch). The dataset was randomly split into training, validation, and internal test sets (70:15:15 split). The overall accuracy and area under receiver operating characteristic curve (AUROC) were assessed for categorizing LR-1/2, LR-3, LR-4, and LR-5. External validation was performed for the model with the better performance on the internal test set using two external datasets (EXT-CT and EXT-MR: 68 and 44 observations, respectively). RESULTS: The transfer learning model outperformed the custom-made model: overall accuracy of 60.4% and AUROCs of 0.85, 0.90, 0.63, 0.82 for LR-1/2, LR-3, LR-4, LR-5, respectively. On EXT-CT, the model had an overall accuracy of 41.2% and AUROCs of 0.70, 0.66, 0.60, 0.76 for LR-1/2, LR-3, LR-4, LR-5, respectively. On EXT-MR, the model had an overall accuracy of 47.7% and AUROCs of 0.88, 0.74, 0.69, 0.79 for LR-1/2, LR-3, LR-4, LR-5, respectively. CONCLUSION: Our study shows the feasibility of CNN for assigning LI-RADS categories from a relatively small dataset but highlights the challenges of model development and validation.

Hepatocarcinogenesis and LI-RADS.

Hepatocarcinogenesis is a multi-step process characterized by progressive cellular and molecular dedifferentiation of hepatocytes and culminating in the emergence of hepatocellular carcinoma (HCC). Knowledge of hepatocarcinogenesis is important because familiarity with the associated imaging features can lead to improved diagnosis of HCC at its early stages. The article reviews the alterations that accumulate leading to HCC result in abnormal imaging features, many of which are included in LI-RADS v2017 as major and ancillary features.

LI-RADS® algorithm: CT and MRI.

The Liver Imaging Reporting and Data System (LI-RADS®) is an imaging-based diagnostic system applicable in patients at high risk of hepatocellular carcinoma (HCC). In LI-RADS, each liver observation is assigned a category that reflects probability of benignity, HCC, or other malignancy. Familiarity with the LI-RADS diagnostic algorithm is necessary to appropriately implement LI-RADS in clinical practice. This review discusses steps necessary for application of the LI-RADS algorithm and provides examples illustrating each step.

Comparative 13-year meta-analysis of the sensitivity and positive predictive value of ultrasound, CT, and MRI for detecting hepatocellular carcinoma.

PURPOSE: To compare the per-lesion sensitivity and positive predictive value (PPV) of ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI) for the diagnosis of hepatocellular carcinoma (HCC). MATERIALS AND METHODS: The meta-analysis of sensitivity included 242 studies (15,713 patients); 116 studies (7492 patients) allowed calculation of PPV. Pooled per-lesion sensitivity and PPV for HCC detection were compared using empirical Bayes estimates of a beta-binomial model. RESULTS: The pooled per-lesion sensitivity and PPV of contrast-enhanced CT (73.6%, 85.8%) and gadolinium-enhanced MRI (77.5%, 83.6%) are not significantly different (P = 0.08, P = 0.2). However, if the hepatobiliary agent gadoxetate is used, MRI has significantly higher pooled per-lesion sensitivity and PPV (85.6%, 94.2%) than CT (P < 0.0001) or than MRI with other agents (P < 0.0001). Non-contrast-enhanced US has the lowest overall sensitivity and PPV (59.3%, 77.4%). Pooled per-lesion sensitivity and PPV of contrast-enhanced US (84.4%, 89.3%) are relatively high, but no contrast-enhanced US study used the most rigorous reference standards. CONCLUSION: MRI utilizing the hepatobiliary agent gadoxetate has the highest overall sensitivity and PPV, and may be the single optimal method for diagnosis of HCC. Non-contrast-enhanced US has the lowest sensitivity and PPV. More rigorous reference standards are needed to compare the performance of contrast-enhanced US with CT and MRI. Differences in sensitivity and PPV between CT and conventional gadolinium-enhanced MRI are not statistically significant overall.

MR imaging techniques of the bowel.

Due to advances in technology, magnetic resonance is an increasingly popular method for evaluating the small bowel and colon because of the lack of radiation, wealth of information provided by the images, and growing demand from gastroenterologists, surgeons, and oncologists. Careful attention to proper technique, however, is necessary to obtain high-quality images. Factors that need to be considered for successful magnetic resonance of the bowel include method for administration of oral or rectal contrast, patient positioning, need for antiperistaltic medication, and imaging sequences and planes.

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.

Computed tomography of small bowel obstruction.

Multidetector computed tomography (CT) is a powerful tool for the assessment of patients with small bowel obstruction (SBO). CT can provide important information about the cause and site of obstruction and the presence of a closed-loop obstruction or ischemia. Under investigation is the ability of CT to accurately identify patients without clear indications for urgent surgery who may benefit from earlier intervention. This article reviews the appropriate CT technique for assessment of SBO, common causes for obstruction, imaging findings in SBO, and the significance of those findings for determining whether a patient is likely to require surgical management for SBO.

Unusual imaging profile of a solitary splenic lymphangioma.

Splenic lymphangioma is a rare, benign lesion of the spleen that is characterized microscopically by a proliferation of thin-walled vascular channels filled by proteinacious material. Based on microscopic features, three types of lymphangiomas are described as simple capillary, cavernous, and cystic; however, the distinction between these types is not uniformly accepted. The cystic type is the most common type and has well described imaging characteristics. However, little is known about the less common cavernous and capillary forms of lymphangioma. Herein, we present a case of a patient with two synchronous colon cancers that presented with a concomitant splenic mass that was initially suspected to be metastatic disease. Despite the use of multiple imaging modalities including computed tomography (CT), magnetic resonance imaging (MRI), nuclear imaging, and contrast-enhanced ultrasound, the final diagnosis of cavernous lymphangioma was made following core needle biopsy of the lesion. A thorough review of literature and this case now demonstrate the difficulty in differentiating atypical forms of splenic lymphangiomas from other benign lesions such as hemangioma.