R2* value derived from multi-echo Dixon technique can aid discrimination between benign and malignant focal liver lesions

IDEAL-IQ Magnetic Resonance Imaging Fat Fraction Quantification in Distinguishing Thymic Hyperplasia From Low-Risk Thymoma and Thymic Lymphoma in Adulthood: A Reliability and Efficacy Analysis

OBJECTIVES

Detection of fat content in thymic lesions is essential to differentiate thymic hyperplasia from thymic tumors. This study assesses the reliability and efficacy of "iterative decomposition of water and fat with echo asymmetry and least-squares estimation quantization" IDEAL-IQ magnetic resonance sequence in distinguishing thymic hyperplasia from low-risk thymoma and thymic lymphoma in adulthood.

METHODS

Thirty patients with thymic hyperplasia, 28 low-risk thymomas, and 13 thymic lymphomas were respectively enrolled. All subjects underwent conventional thorax magnetic resonance imaging and IDEAL-IQ sequence. The fat fraction (FF mean and FF total ), signal intensity index, and R2* values of the lesions were compared for differences among 3 groups by the Mann-Whitney U and Kruskal-Wallis tests. Receiver operating characteristic curve analysis was performed to determine the differentiating efficacy.

RESULTS

Both FF mean and FF total values in patients with thymic hyperplasia are significantly higher than those in patients with low-risk thymoma and thymic lymphoma (FF mean : 26.41% vs 1.78% and 1.93%, FF total : 27.67% vs 2.21% and 2.44%; both P  < 0.001), whereas there was no significant difference in these values between low-risk thymomas and thymic lymphomas (both P  > 0.05). Similarly, signal intensity index and R2* values of thymic hyperplasia were significantly higher than those of patients with low-risk thymoma and thymic lymphoma ( P  < 0.001). Receiver operating characteristic curve analysis showed that FF mean had an area under the curve of 0.998, with a cutoff of 4.78% yielding 95.12% sensitivity and 100% specificity, and FF total had an area under the curve of 0.994, with a cutoff of 8.57% yielding 97.56% sensitivity and 96.67% specificity in distinguishing thymic hyperplasia from tumors.

CONCLUSIONS

IDEAL-IQ sequence provides accurate fat quantitative parameters and can differentiate thymic hyperplasia from thymic neoplasms with robust efficacy and reliability.

Differentiation of intrapancreatic accessory spleen from pancreatic neuroendocrine tumor using MRI R2

PURPOSE

To evaluate the performance of R2* in distinguishing intrapancreatic accessory spleens (IPASs) from pancreatic neuroendocrine tumors (PNETs).

METHODS

Two radiologists (R1 and R2) retrospectively reviewed the MRIs of 20 IPAS and 20 PNET patients. IPASs were diagnosed with uptake on 99mTc labeled heat-damaged red blood cell scintigraphy or characteristic findings on CT/MRI and ≥ 12 month-long-stability. PNETs were histopathologically diagnosed with resection. Using McNemar test, sensitivities and specificities of the diagnostic criterion based on R2* mass-to-spleen ratio (MSR) were compared with those of the other criteria using contrast-enhanced (CE) MRI and apparent diffusion coefficient (ADC) MSR.

RESULTS

The study included 40 patients (median age, 54; interquartile range, 43-65; 24 men, 16 women). IPASs exhibited spleen-isointensity on T2WI, late arterial and portal phases, and diffusion-weighted images more frequently than PNETs (p <.05). ADC MSRs were lower (p <.001) and R2* MSRs were higher (p <.001) in IPASs compared to PNETs. For R1, sensitivity and specificity were 45.0% and 100.0% for criterion 1 (spleen-isointensity on CE-MRI); 45.0% and 85.0% for criterion 2 (ADC MSR ≤ 1.08); 90.0% and 95.0% for criterion 3 (0.9 ≤ R2* MSR ≤ 1.7). For R2, 75.0% and 100.0%; 45.0% and 90.0%; 90.0% and 100.0%. Criterion 3 showed higher sensitivity than criterion 1 for R1 (p =.004), and criterion 2 for R1 and R2 (p =.012). There was no difference in specificity.

CONCLUSION

For differentiating IPAS from PNET, R2* showed higher sensitivity than, and similar specificity to CE-MRI and ADC.