The Liver Imaging Reporting and Data System (LI-RADS) categorizes observations from imaging analyses of high-risk patients based on the level of suspicion for hepatocellular carcinoma (HCC) and ...overall malignancy. The categories range from definitely benign (LR-1) to definitely HCC (LR-5), malignancy (LR-M), or tumor in vein (LR-TIV) based on findings from computed tomography or magnetic resonance imaging. However, the actual percentage of HCC and overall malignancy within each LI-RADS category is not known. We performed a systematic review to determine the percentage of observations in each LI-RADS category for computed tomography and magnetic resonance imaging that are HCCs or malignancies.
We searched the MEDLINE, Embase, Cochrane CENTRAL, and Scopus databases from 2014 through 2018 for studies that reported the percentage of observations in each LI-RADS v2014 and v2017 category that were confirmed as HCCs or other malignancies based on pathology, follow-up imaging analyses, or response to treatment (reference standard). Data were assessed on a per-observation basis. Random-effects models were used to determine the pooled percentages of HCC and overall malignancy for each LI-RADS category. Differences between categories were compared by analysis of variance of logit-transformed percentage of HCC and overall malignancy. Risk of bias and concerns about applicability were assessed with the Quality Assessment of Diagnostic Accuracy Studies 2 tool.
Of 454 studies identified, 17 (all retrospective studies) were included in the final analysis, consisting of 2760 patients, 3556 observations, and 2482 HCCs. The pooled percentages of observations confirmed as HCC and overall malignancy, respectively, were 94% (95% confidence interval CI 92%–96%) and 97% (95% CI 95%–99%) for LR-5, 74% (95% CI 67%–80%) and 80% (95% CI 75%–85%) for LR-4, 38% (95% CI 31%–45%) and 40% (95% CI 31%–50%) for LR-3, 13% (95% CI 8%–22%) and 14% (95% CI 9%–21%) for LR-2, 79% (95% CI 63%–89%) and 92% (95% CI 77%–98%) for LR-TIV, and 36% (95% CI 26%–48%) and 93% (95% CI 87%–97%) for LR-M. No malignancies were found in the LR-1 group. The percentage of HCCs and overall malignancies confirmed differed significantly among LR groups 2–5 (P < .00001). Patient selection was the most frequent factor that affected bias risk, because of verification bias and case–control study design.
In a systematic review, we found that increasing LI-RADS categories contained increasing percentages of HCCs and overall malignancy based on reference standard confirmation. Of observations categorized as LR-M, 93% were malignancies and 36% were confirmed as HCCs. The percentage of HCCs found in the LR-2 and LR-3 categories indicate the need for a more active management strategy than currently recommended. Prospective studies are needed to validate these findings. PROSPERO number CRD42018087441.
While many institutions perform MRI during the work‐up of urinary bladder cancer, others use MRI rarely if at all, possibly due to a variation in the reported staging accuracy and unfamiliarity with ...the potential benefits of performing MRI. Through increased application of functional imaging techniques including diffusion‐weighted imaging (DWI) and dynamic contrast‐enhanced (DCE) imaging, there has been a resurgence of interest regarding evaluation of bladder cancer with MRI. Several recent meta‐analyses have shown that MRI is accurate at differentiating between ≤T1 and T2 disease (with pooled sensitivity/specificity of ∼90/80%) and differentiating between T2 and ≥T3 disease. DWI and DCE, in combination with high‐resolution T2‐weighted images, improves detection and possibly local staging accuracy of bladder cancer. High b value echo‐planar DWI is particularly valuable for tumor detection. Zoomed field of view and segmented readout DWI techniques improve image quality by reducing susceptibility artifact, while methods to extract calculated high b value images save time and improve the contrast‐to‐noise ratio. DCE traditionally required imaging of the pelvis with high temporal but lower spatial resolution; however, advances in parallel and keyhole imaging techniques can preserve spatial resolution. The use of compressed sensing reconstruction may improve utilization of DCE of the bladder, especially when imaging the abdomen simultaneously, as in MR urography. Quantitative imaging analysis of bladder cancer using pharmacokinetic modeling of DCE, apparent diffusion coefficient values, and texture analysis may enable radiomic assessment of bladder cancer grade and stage.
Level of Evidence: 3
Technical Efficacy: Stage 2
J. Magn. Reson. Imaging 2018;48:882–896.
Background
Differentiation of benign and malignant pancreatic cystic lesions on MRI, computed tomography (CT), and endoscopic ultrasound (EUS) is critical for determining management.
Purpose
To ...perform a systematic review evaluating the diagnostic accuracy of MRI for diagnosing malignant pancreatic cystic lesions, and to compare the accuracy of MRI to CT and EUS.
Study Type
Systematic review and meta‐analysis.
Data Sources
MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Web of Science, and Scopus were searched until February 2020 for studies reporting MRI accuracy for assessing pancreatic cystic lesions.
Field Strength
1.5T or 3.0T.
Assessment
Methodologic and outcome data were extracted by two reviewers (AU and MA, 2 years of experience each). All studies of pancreatic cystic lesions on MRI were identified. Studies with incomplete MRI technique were excluded. Risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS)‐2 tool.
Statistical Tests
Sensitivity/specificity was pooled using bivariate random‐effects meta‐analysis with 95% confidence intervals (95%CI). Pairwise‐comparison of MRI to CT and EUS was performed. The impact of gadolinium‐based contrast agents, mucinous lesions, and risk of bias were explored using meta‐regression.
Results
MRI pooled sensitivity was 76% (95%CI 67% to 84%) and specificity was 80% (95%CI 74% to 85%) for distinguishing benign and malignant lesions. MRI and CT had similar sensitivity (P = 0.822) and specificity (P = 0.096), but MRI was more specific than EUS (80% vs. 75%, P < 0.05). Studies including only contrast‐enhanced MRI were more sensitive than those including unenhanced exams (P < 0.05). MRI sensitivity and specificity did not differ for mucinous lesions (P = 0.537 and P = 0.384, respectively) or for studies at risk of bias (P = 0.789 and P = 0.791, respectively).
Data Conclusion
MRI and CT demonstrate comparable accuracy for diagnosing malignant pancreatic cystic lesions. EUS is less specific than MRI, which suggests that, in some cases, management should be guided by MRI findings rather than EUS.
Level of Evidence
3
Technical Efficacy Stage
2
Background
The detection of liver metastases is important for pancreatic cancer curative treatment eligibility. The data suggest that magnetic resonance imaging (MRI) is more sensitive than computed ...tomography (CT) for the diagnosis of pancreatic cancer liver metastases. However, MRI is not currently recommended in multiple published guidelines.
Purpose
To perform a comparative diagnostic test accuracy systematic review and meta‐analysis comparing CT and MRI for pancreatic cancer liver metastases detection.
Study Type
Systematic review and meta‐analysis.
Data Sources
MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Scopus, and multiple radiology society meeting archives were searched until November 2018. Comparative design studies reporting on liver CT and MRI accuracy for detection of pancreatic cancer liver metastases in the same cohort were included.
Field Strength
1.5T or 3.0T.
Assessment
Demographic, methodologic, and diagnostic test accuracy data were extracted. Risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS)‐2 tool.
Statistical Tests
Accuracy metrics were obtained using bivariate random‐effects meta‐analysis. The impact of different covariates on accuracy estimates was assessed using a meta‐regression model. Covariates included modality, study design, tumor characteristics, risk of bias, and imaging protocols.
Results
Fourteen studies including 987 patients with pancreatic cancer (205 with liver metastases) were included. Sensitivity for CT and MRI was 45% (confidence intervals 95% CI 21–71%) and 83% (95% CI 74–88%), respectively. Specificity for CT and MRI was 94% (95% CI 84–98%) and 96% (95% CI 93–97%), respectively. The greater observed sensitivity of MRI was preserved in the meta‐regression model (P = 0.01), while no difference in specificity was detected (P = 0.16). CT sensitivity was highest for triphasic and quadriphasic examinations compared to single phase or biphasic protocols (P = 0.03). Most studies were at high risk of bias.
Data Conclusion
MRI is more sensitive than CT for pancreatic cancer liver metastases detection, accounting for confounding variables. Consideration of this finding in clinical practice guidelines is recommended.
Level of Evidence
3
Technical Efficacy Stage
3
Medical imaging diagnostic test accuracy research is strengthened by adhering to best practices for study design, data collection, data documentation, and study reporting. In this review, key ...elements of such research are discussed, and specific recommendations provided for optimizing diagnostic accuracy study execution to improve uniformity, minimize common sources of bias and avoid potential pitfalls. Examples are provided regarding study methodology and data collection practices based on insights gained by the liver imaging reporting and data system (LI‐RADS) individual participant data group, who have evaluated raw data from numerous MRI diagnostic accuracy studies for risk of bias and data integrity. The goal of this review is to outline strategies for investigators to improve research practices, and to help reviewers and readers better contextualize a study's findings while understanding its limitations.
Level of Evidence
5
Technical Efficacy
Stage 3
