MRI Detection of Intratumoral Fat in Colorectal Liver Metastases After Preoperative Chemotherapy

Fat fraction and R2 * values of various liver masses: Initial experience with 6-point Dixon method on a 3T MRI system

Purpose

To assess the feasibility of the 6-point Dixon method for evaluating liver masses. We also report our initial experience with the quantitative values in various liver masses on a 3T system.

Materials and methods

Of 251 consecutive patients for whom 6-point Dixon was employed in abdominal magnetic resonance imaging scans between October 2020 and October 2021, 117 nodules in 117 patients with a mass diameter of more than 1 cm were included in the study. Images for measuring the proton density fat fraction (PDFF) and R2 * values were obtained using the iterative decomposition of water and fat with echo asymmetry and least-squares estimation-quantitative technique for liver imaging. Two radiologists independently measured PDFF (%) and R2 * (Hz). Inter-reader agreement and the differences between readers were examined using intra-class correlation coefficient (ICC) and the Bland-Altman method, respectively. PDFF and R2 * values in differentiating liver masses were examined.

Results

The masses included hepatocellular carcinoma (n = 59), cyst (n = 20), metastasis (n = 14), hemangioma (n = 8), and others (n = 16). The ICCs for the region of interest (mm2), PDFF, and R2 * were 0.988 (95 % confidence interval (CI): 0.983, 0.992), 0.964 (95 % CI: 0.949, 0.975), and 0.962 (95 % CI: 0.941, 0.975), respectively. The differences of measurements between the readers showed that 5.1 % (6/117) and 6.0% (7/117) for PDFF and R2 * , respectively, were outside the 95 % CI.

Conclusion

Our observation indicates that the 6-point Dixon method is applicable to liver masses.

MRI Findings of Liver Parenchyma Peripheral to Colorectal Liver Metastasis: A Potential Predictor of Long-term Prognosis

Background Gadoxetic acid (Gd-EOB-DTPA)-enhanced MRI is superior to CT in the detection of colorectal liver metastases (CRLMs) smaller than 10 mm. However, few studies have used MRI findings to predict patients' long-term prognosis. Purpose To investigate the relationship between Gd-EOB-DTPA-enhanced MRI findings in the liver parenchyma peripheral to CRLM and both pathologic vessel invasion and long-term prognosis. Materials and Methods This retrospective study included patients who underwent Gd-EOB-DTPA-enhanced MRI before curative surgery for CRLM, without neoadjuvant chemotherapy, between July 2008 and June 2015. Early enhancement, reduced Gd-EOB-DTPA uptake, and bile duct dilatation peripheral to the CRLM at MRI were evaluated by three abdominal radiologists. All tumor specimens were reevaluated for the presence or absence of portal vein, hepatic vein, and bile duct invasion. Predictors of recurrence-free survival (RFS) and overall survival (OS) after surgery were identified with Cox proportional hazard model with the Bayesian information criterion. Previously reported prognosticators were selected for multivariable analyses. The median follow-up period was 60 months (range, 9-127 months). Results Overall, 106 patients (mean age, 65 years ± 12 [standard deviation]; 68 men) with 148 CRLMs were evaluated. Bile duct dilatation peripheral to the tumor was associated with pathologic portal vein invasion (sensitivity, 12 of 50 [24%]; specificity, 89 of 98 [91%]; P = .02), bile duct invasion (sensitivity, eight of 19 [42%]; specificity, 116 of 129 [90%]; P = .001), poor RFS (P = .03; hazard ratio [HR] = 2.4 [95% confidence interval {CI}: 1.3, 4.2]), and poor OS (P = .01; HR = 2.4 [95% CI: 1.2, 4.9]). For RFS and OS, early enhancement and reduced Gd-EOB-DTPA uptake peripheral to the CRLM were eliminated by means of variable selection in the multivariable analysis, but the combination of these findings with bile duct dilatation provided a predictor of poor OS (P = .001; HR = 3.3 [95% CI: 1.6, 6.8]). Conclusion MRI signal intensity changes peripheral to the colorectal liver metastasis were predictors of long-term prognosis after curative surgery without neoadjuvant chemotherapy. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Bashir in this issue.