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Small recurrent hepatocellular carcinoma (HCC) can show atypical imaging patterns, and a specific diagnostic algorithm for HCC is lacking. This study aimed to better characterize postoperative recurrent HCCs <20 mm in size with gadoxetic acid-enhanced magnetic resonance imaging (MRI). We evaluated 373 newly developed nodules after hepatectomy in 204 HCC patients with chronic hepatitis B virus infection. The diagnostic performance of Liver Imaging Reporting and Data System (LI-RADS) version 2018 was calculated with gadoxetic acid-enhanced MRI to characterize recurrent HCC. Modified diagnostic algorithms were proposed by combining significant imaging biomarkers related to subcentimeter and 10-19 mm recurrence, and the algorithms were then compared with the LI-RADS system. A total of 256 recurrent HCCs (108 recurrent HCCs <10 mm in size; 148 recurrent HCCs 10-19 mm in size) were confirmed via histology or follow-up imaging. Nonrim arterial phase hyperenhancement (APHE) and 3 LI-RADS ancillary features (AFs; hepatobiliary phase hypointensity, mildmoderate T 2 hyperintensity, and restricted diffusion) were significantly related to recurrent HCCs <20 mm in size according to a multivariate analysis. For subcentimeter recurrence, combining at least 2 of the 3 AFs only achieved better specificity (sensitivity, 83.3%; specificity, 87.7%) than the LR-4 category (sensitivity, 88.9%, P = 0.21; specificity, 70.8%, P = 0.006). For 10-19 mm recurrences, combining nonrim APHE and at least 1 of the 3 AFs achieved only a significantly enhanced sensitivity of 85.1% but a lower specificity of 86.5% compared with the LR-5 category (sensitivity: 63.5%, P < 0.001; specificity: 94.2%, P = 0.13). In conclusion, the diagnostic algorithms for subcentimeter and 10-19 mm recurrent HCCs should be stratified. Combining at least 2 AFs demonstrated comparable sensitivity with significantly enhanced specificity compared with the LR-4 category for characterizing subcentimeter recurrence. Liver Transplantation 26 751-763 2020 AASLD.Recurrence of hepatocellular carcinoma (HCC) after hepatectomy is a common issue that occurs in more than 70% of patients at 5 years. (1,2) Dynamic contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) are commonly performed to establish further evaluation of indeterminate observations. Repeated hepatic resection, liver transplantation, and thermal ablation are recommended for treating recurrent HCCs. (3,4) In particular, percutaneous ultrasound (US)/MRI fusion-guided thermal ablation are safe and effective treatment modalities for subcentimeter recurrent HCC. (5) Indeterminate nodules <20 mm in size are probably benign in screening populations Wang et al.

Background Recently, a prototype 5.0 T whole‐body MRI scanner was developed. A 5.0 T diffusion‐weighted imaging (DWI) may help overcome the issues that limit 3.0 T DWI. Purpose To evaluate the feasibility of 5.0 T high‐field DWI in the upper abdomen and assess the agreement of the apparent diffusion coefficient (ADC) with that from 3.0 T abdominal DWI. Study type Prospective proof of concept. Population Nine volunteers (mean ± SD age: 37.3 ± 7.0 years, 8 M), eight healthy and one with liver and kidney cysts. Field strength/Sequence 3.0 T and 5.0 T; respiratory‐triggered spin‐echo echo‐planar‐imaging (SE‐EPI)‐based DWI sequence. Assessment Subjective image quality scores. The ADC values in abdominal organs (liver, pancreas, spleen, and kidney) were measured by two observers for evaluating the interobserver and interfield agreement. Statistical Tests Wilcoxon‐rank sum test, Bland–Altman analysis, intraclass correlation coefficients (ICCs), and coefficients of variation (CVs). Results The 5.0 T DWI displayed an increase in subjective image quality score compared to 3.0 T DWI without the significant difference (3.0 T DWI: 3.50 ± 0.47, 5.0 T DWI: 3.72 ± 0.42, P = 0.157). Both the interfield and interobserver agreements of ADC values were substantial to excellent (ICCs = 0.640–0.902). For all four upper abdominal organs, there were no significant differences between the ADC values measured by two observers and between the ADC values of 3.0 T and 5.0 T DWI (P = 0.134–1.000). The CVs of ADC measurements from 3.0 T and 5.0 T DWI were all less than 15.0% (6.7%–14.2%). Data Conclusion The substantial to excellent agreements between the ADC values measured with 3.0 T and 5.0 T DWI for liver, pancreas, spleen, and kidney suggested that 5.0 T DWI can be applied for abdominal imaging. The ADC values from 5.0 T abdominal DWI hold the potential to serve as the quantitative markers for clinical investigations. Evidence Level 2 Technical Efficacy Stage 1