Background
Lymph node staging of ductal adenocarcinoma of the pancreatic head (PDAC) by cross-sectional imaging is limited. The aim of this study was to determine the diagnostic accuracy of expanded criteria in nodal staging in PDAC patients.
Methods
Sixty-six patients with histologically confirmed PDAC that underwent primary surgery were included in this retrospective IRB-approved study. Cross-sectional imaging studies (CT and/or MRI) were evaluated by a radiologist blinded to histopathology. Number and size of lymph nodes were measured (short-axis diameter) and characterized in terms of expanded morphological criteria of border contour (spiculated, lobulated, and indistinct) and texture (homogeneous or inhomogeneous). Sensitivities and specificities were calculated with histopathology as a reference standard.
Results
Forty-eight of 66 patients (80%) had histologically confirmed lymph node metastases (pN+). Sensitivity, specificity, and Youden’s Index for the criterion “size” were 44.2%, 82.4%, and 0.27; for “inhomogeneous signal intensity” 25.6%, 94.1%, and 0.20; and for “border contour” 62.7%, 52.9%, and 0.16, respectively. There was a significant association between the number of visible lymph nodes on preoperative CT and lymph node involvement (pN+, p = 0.031).
Conclusion
Lymph node staging in PDAC is mainly limited due to low sensitivity for detection of metastatic disease. Using expanded morphological criteria instead of size did not improve regional nodal staging due to sensitivity remaining low. Combining specific criteria yields improved sensitivity with specificity and PPV remaining high.
Background: Conventional magnetic resonance enterography is limited in differentiating active inflammation and fibrosis in lesions of Crohn's disease (CD), thus providing a restricted basis for therapeutic decision making. Magnetic resonance elastography (MRE) is an emerging imaging tool that differentiates soft tissues on the basis of their viscoelastic properties. The aim of this study was to demonstrate the feasibility of MRE in assessing the viscoelastic properties of small bowel samples and quantifying differences in viscoelastic properties between healthy ileum and ileum affected by CD.
Methods: Twelve patients (median age: 48 years) were prospectively enrolled in this study between September 2019 and January 2021. Patients of the study group (n=7) underwent surgery for terminal ileal CD, while patients of the control group (n=5) underwent segmental resection of healthy ileum. MRE of ileal tissue samples of surgical specimens from both groups was performed in a compact tabletop MRI scanner. Penetration rate (a in m/s) and shear wave speed (c in m/s) were determined as markers of viscosity and stiffness for vibration frequencies f of 1,000, 1,500, 2,000, 2,500, and 3,000 Hz. Additionally, damping ratio γ was deduced, and frequency-independent viscoelastic parameters were calculated using the viscoelastic spring-pot model.
Results: Penetration rate a was significantly lower in CD-affected ileum compared to healthy ileum for all vibration frequencies (P<0.05). Consistently, damping ratio γ was higher in CD-affected ileum, averaged over all frequencies (healthy: 0.58±0.12, CD: 1.04±0.55, P=0.03), as well as at 1,000 and 1,500 Hz individually (P<0.05). Spring-pot-derived viscosity parameter η was also significantly reduced in CD-affected tissue (2.62±1.37 versus 10.60±12.60 Pa·s, P=0.02). No significant difference was found for shear wave speed c between healthy and diseased tissue at any frequency (P>0.05).
Conclusions: MRE of surgical small bowel specimens is feasible, allowing determination of viscoelastic properties and reliable quantification of differences in viscoelastic properties between healthy and CD-affected ileum. Thus, the results presented here are an important prerequisite for future studies investigating comprehensive MRE mapping and exact histopathological correlation including characterization and quantification of inflammation and fibrosis in CD.
