Quantification of liver fat content in liver and primary liver lesions using triple-echo-gradient-echo MRI.

OBJECTIVES: To quantify and compare the fat fraction of background liver and primary liver lesions using a triple-echo-gradient-echo sequence. M&M: This IRB-approved study included 128 consecutive patients who underwent a liver MRI for lesion characterization. Fat fraction from the whole lesion volume and the normal liver parenchyma were computed from triple-echo (consecutive in-phase, opposed-phase, in-phase echo times) sequence. RESULTS: Forty-seven hepatocellular carcinoma (HCCs), 25 hepatocellular adenomas (HCAs), and 56 focal nodular hyperplasia (FNH) were included. The mean intralesional fat fraction for various lesions was 7.1% (range, 0.5-23.6; SD, 5.6) for HCAs, 5.7% (range, 0.8-14; SD, 2.9) for HCCs, and 2.3% (range, 0.8-10.3; SD, 1.9) for FNHs (p = 0.6 for HCCs vs HCA, p < 0.001 for FNH vs HCCs or HCA). A fat fraction threshold of 2.7% enabled distinction between HCA and FNH with a sensitivity of 80% and a specificity of 77%. The mean normal liver parenchyma fat fraction was lower than the intralesional fat fraction in the HCC group (p = 0.04) and higher in the FNH group (p = 0.001), but not significantly different in the HCA group (p = 0.51). CONCLUSION: Triple-echo-gradient-echo is a feasible technique to quantify fat fraction of background liver and primary liver lesions. Intralesional fat fraction obtained from lesion whole volume is greater for HCCs and HCA compared to FNH. When trying to distinguish FNH and HCA, an intralesional fat fraction < 2.7% may orient toward the diagnosis of FNH. KEY POINTS: • Triple-echo technique is feasible to quantify intralesional fat fraction of primary liver lesions. • Whole volume intralesional fat fraction is greater for HCCs and HCA compared to FNH. • An intralesional fat fraction < 2.7% may orient toward the diagnosis of FNH.

Acute post-traumatic muscle atrophy on CT scan predicts prolonged mechanical ventilation and a worse outcome in severe trauma patients.

BACKGROUND: The aim of present study was to assess the association between acute post-traumatic atrophy (APTMA) determined on psoas computed tomography [CT] scan and the duration of mechanical ventilation and outcomes in severe trauma patients. METHODS: A retrospective analysis of severe trauma patients (Injury Severity Score [ISS], >15) hospitalized in the intensive care unit (ICU) for more than 7 days between January 2010 and December 2015 was performed. The psoas muscle index (PMI) was measured on admission and at delayed CT scan. ΔPMI was calculated as the percentage PMI loss between these two scans. Three groups were defined and compared a posteriori using the quartiles of the ΔPMI values: low (lower quartile), moderate, and severe (higher quartile) APTMA groups. Linear regression analysis was performed to predict the duration of mechanical ventilation, of catecholamines, length of stay (LOS) in the ICU and hospital, and complications were assessed. RESULTS: A total of 114 trauma patients were included (median age, 40 years; [IQR, 25-54 years]; ISS, 33 [IQR, 25-41]). Based on the ΔPMI determination, 29 patients were allocated in the low APTMA group (range ∆PMI, 0%-6%), 56 in the moderate APTMA group (range ∆PMI, 6%-18%), and 29 in the APTMA group (range ∆PMI, ≥19%). Severity of APTMA was significantly associated with the duration of mechanical ventilation and catecholamines, ICU and hospital LOS (P<0.001). Delayed pneumonia (P=0.006) and other delayed infections (P=0.014), as well as thromboembolic events (P=0.04) were statistically associated with the severity of APTMA, whereas mortality did not differ between the three groups (P=0.20). Using linear regression analysis, each ∆PMI increase of 1% was significantly associated with 0.90 supplementary days of mechanical ventilation (P<0.001), 0.29 supplementary days of catecholamines (P<0.001) and 0.82 supplementary days of hospitalization (P<0.001). All these statistical associations were confirmed in multivariate analysis (P<0.001). CONCLUSION: Acute muscle atrophy diagnosed on CT scan by psoas area measurement (ΔPMI) was strongly associated with poor outcomes in severe trauma patients.

Reader performances in breast lesion characterization via DBT: One or two views and which view?

PURPOSE: To compare the performance in breast lesion characterization of one-view mediolateral (MLO) digital mammography plus digital breast tomosynthesis (DM-DBT) versus one-view craniocaudal (CC) DM-DBT versus two-view DM-DBT. MATERIALS AND METHODS: The institutional review board approved this retrospective study conducted on 138 women from the population of a previous prospective multicenter study, with 69 consecutive patients with benign or high-risk lesions and 69 randomized patients with breast cancer, all confirmed at pathology. Four radiologists (two senior and two junior) blinded to the clinical, mammographic and pathological data independently reviewed the MLO DM-DBT views, the CC DM-DBT views and the MLO + CC DM-DBT views using the American College of Radiology Breast Imaging-Reporting and Data System criteria for index lesion characterization. Areas under the receiver were calculated and compared for each reader and imaging protocol. RESULTS: No significant differences in breast cancer characterization were observed between single MLO and CC views for all the readers. The added value of a second view was statistically significant for characterization in pooled data and for junior readers but not for senior readers (p ranging from 0.15 to 0.57 depending on the view and the senior reader). Finally, in 4 breast cancer cases, lesions were only detectable on the CC DM-DBT view in two cases and on the MLO DM-DBT view in the two other cases. CONCLUSION: Our results support the use of two-view DM-DBT for breast lesion characterization when the readers are inexperienced. There is no significant difference between CC and MLO views when diagnosis is performed with one view.

Imaging of appendicitis: Tips and tricks.

Acute appendicitis is one of the most common surgical emergencies worldwide. Over the past 30 years, imaging has become central to the diagnosis of appendicitis, reducing both negative appendicectomy rate and healthcare expenses. Appendicitis can be challenging in many ways for radiologists with various clinical presentations, complications and differential diagnoses. The aim of this review is to present a step-by-step reasoning with key findings, tips and tricks leading to the diagnosis of appendicitis and its complications. The first steps are with the use of the appropriate imaging modality (US, CT and MRI) to locate the appendix in abdominal cavity and to identify the features of appendicitis and its complications through specific imaging signs. The next steps are to eliminate an unusual morphology of the appendix that may simulate acute appendicitis and to recognize an unusual imaging presentation of appendicitis. Then, to corroborate the diagnosis of appendicitis, the last step is to rule out any differential diagnoses mainly from the genitourinary and gastrointestinal tracts. Following these steps can help to accurately diagnose appendicitis and its complications.