Assessment of lymph node metastases by contrast-enhanced MR imaging in a head and neck cancer model

Prognostic Value of Radiologic Extranodal Extension in Human Papillomavirus-Related Oropharyngeal Squamous Cell Carcinoma

Objective

To determine whether radiologic extranodal extension (ENE) appearing on pretreatment CT and MRI could predict the prognosis in patients with human papillomavirus (HPV)-related oropharyngeal squamous cell carcinoma (OPSCC).

Materials and Methods

The study population was obtained from a historical cohort diagnosed with HPV-related OPSCC. A total of 134 OPSCC patients who had a metastatic lymph node on pretreatment CT or MRI were included, and radiologic ENE was evaluated by two experienced head and neck radiologists. Kaplan-Meier and multivariate Cox regression analyses were performed to evaluate the impact of radiologic ENE on progression-free survival (PFS). The diagnostic performance of CT and MRI for the diagnosis of ENE was also evaluated in patients who underwent neck dissection.

Results

Seventy patients (52.2%) showed radiologic ENE-positive findings. Although patients showing radiologic ENE had a worse 3-year PFS (83.7% vs. 95.3%, p = 0.023), the association between radiologic ENE and PFS was not statistically significant on multivariate analysis (p = 0.141; hazard ratio, 2.68; 95% confidence interval, 0.72–9.97). CT or MRI had a sensitivity of 62%, specificity of 77.8%, and accuracy of 71.9% for predicting pathologic ENE.

Conclusion

Radiologic ENE on CT or MRI did not predict poor PFS in patients with HPV-related OPSCC, although there was a trend towards worse PFS. Further studies are warranted to determine whether radiologic ENE is a useful imaging biomarker to risk-stratify patients with HPV-related OPSCC.

Role of Quantitative Dynamic Contrast-Enhanced MRI in Evaluating Regional Lymph Nodes With a Short-Axis Diameter of Less Than 5 mm in Rectal Cancer

OBJECTIVE

The aim of this study was to discriminate metastatic from nonmetastatic regional lymph nodes (LNs) with short-axis diameters of less than 5 mm in rectal cancer using quantitative parameters derived from dynamic contrast-enhanced (DCE) MRI.

SUBJECTS AND METHODS

Sixty-five LNs from 122 patients were evaluated, including malignant LNs (n = 27) and benign LNs (n = 38). The following parameters were assessed: the forward volume transfer constant (K^trans), reverse volume transfer constant (k_ep), fractional extravascular extracellular space volume (Ve), short-axis diameter, long-axis diameter, and short- to long-axis diameter ratio. ROC curves were used to analyze statistically significant parameters.

RESULTS

Metastatic LNs exhibited a lower K^trans than did nonmetastatic LNs (p < 0.001), but the other parameters were not significantly different between the two groups. The AUC of the K^trans was 0.732, with a 95% CI of 0.610-0.854, and the diagnostic cutoff value was 0.088 min^-1 (sensitivity, 60.5%; specificity, 81.5%).

CONCLUSION

K^trans had moderate diagnostic performance in assessing small regional LNs in rectal cancer and appears to be a useful predictor when distinguishing malignant LNs from benign LNs only by morphology is difficult.

Fat-suppressed gadolinium-enhanced isotropic high-resolution 3D-GRE-T1WI for predicting small node metastases in patients with rectal cancer

Background

To investigate the application value of fat-suppressed gadolinium-enhanced isotropic high-resolution 3D-GRE-T1WI in regional nodes with different short-axis diameter ranges in rectal cancer, especially in nodes ≤5 mm.

Methods

Patients with rectal adenocarcinoma confirmed by postoperative histopathology were included, and all the patients underwent preoperative 3.0 T rectal magnetic resonance imaging (MRI) and total mesorectal excision (TME) within 2 weeks after an MR scan. The harvested nodes from specimens were matched with nodes in the field of view (FOV) of images for a node-by-node evaluation. The maximum short-axis diameters of all the visible nodes in the FOV of images were measured by a radiologist; the morphological and enhancement characteristics of these nodes were also independently evaluated by two radiologists. The χ² test was used to evaluate differences in morphological and enhancement characteristics between benign and malignant nodes. The enhancement characteristics were further compared between benign and malignant nodes with different short-axis diameter ranges using the χ² test. Kappa statistics were used to describe interobserver agreement.

Results

A total of 441 nodes from 70 enrolled patients were included in the evaluation, of which 111 nodes were metastatic. Approximately 85.5 and 95.6% of benign nodes were found to have obvious enhancement and homogeneous or mild-heterogeneous enhancement, respectively, whereas approximately 89.2 and 85.1% of malignant nodes showed moderate or mild enhancement and obvious-heterogeneous or rim-like enhancement, respectively. The area under the receiver operating characteristic (ROC) curve (AUC) values of the enhancement degree for identifying the overall nodal status, nodes ≤5 mm and nodes > 5 mm and ≤ 10 mm were 0.887, 0.859 and 0.766 for radiologist 1 and 0.892, 0.823 and 0.774 for radiologist 2, respectively. The AUCs of enhancement homogeneity were 0.940, 0.928 and 0.864 for radiologist 1 and 0.944, 0.938 and 0.842 for radiologist 2, respectively. Nodal border and signal homogeneity were also of certain value in distinguishing metastatic nodes.

Conclusions

Enhancement characteristics based on fat-suppressed gadolinium-enhanced isotropic high-resolution 3D-GRE-T1WI were helpful for diagnosing metastatic nodes in rectal cancer and were a reliable indicator for nodes ≤5 mm.

Orbital lymphoproliferative disorders (OLPDs): value of MR imaging for differentiating orbital lymphoma from benign OPLDs

BACKGROUND AND PURPOSE

Accurate discrimination of orbital lymphoma from benign orbital lymphoproliferative disorders is crucial for treatment planning. We evaluated MR imaging including DWI and contrast-enhanced MR imaging for differentiating orbital lymphoma from benign orbital lymphoproliferative disorders.

MATERIALS AND METHODS

Forty-seven histopathologically proved orbital lymphoproliferative disorders (29 orbital lymphomas and 18 benign orbital lymphoproliferative disorders) were evaluated. Two board-certified radiologists reviewed visual features on T1-weighted, fat-suppressed T2-weighted, diffusion-weighted, and contrast-enhanced MR images. For quantitative evaluation, ADC and contrast-enhancement ratio of all lesions were measured and optimal cutoff thresholds and areas under curves for differentiating orbital lymphoma from benign orbital lymphoproliferative disorders were determined using receiver operative characteristic analysis; corresponding sensitivities and specificities were calculated.

RESULTS

Multivariate logistic regression analysis showed that ill-defined tumor margin (P = .003) had a significant association with orbital lymphoma whereas the "flow void sign" (P = .005) and radiologic evidence of sinusitis (P = .0002) were associated with benign orbital lymphoproliferative disorders. The mean ADC and contrast-enhancement ratio of orbital lymphomas were significantly lower than those of benign orbital lymphoproliferative disorders (P < .01). An ADC of less than 0.612 × 10(-3) mm(2)/s and a contrast-enhancement ratio of less than 1.88 yielded areas under curves of 0.980 and 0.770, sensitivity of 94.1% and 95.5%, and specificities of 93.3% and 80.0% for predicting orbital lymphoma, respectively.

CONCLUSIONS

Some characteristic MR imaging features and quantitative DWI and contrast-enhanced MR imaging are useful in further improving the accuracy of MR imaging for differentiation of orbital lymphoma from benign orbital lymphoproliferative disorders.

Discrimination of metastatic lymph nodes in patients with gastric carcinoma using diffusion-weighted imaging

PURPOSE

To determine the accuracy of diffusion-weighted imaging (DWI) in discrimination of metastatic lymph nodes (LNs) in gastric carcinoma with rigorous histopathological correlation.

MATERIALS AND METHODS

With Institutional Review Board (IRB) approval, 28 patients with gastric carcinoma underwent magnetic resonance imaging (MRI) and DWI before surgery. LNs were resected at surgery and thereafter submitted for histopathological analyses. All histopathologically identified LNs (≥ 5 mm) that exactly matched the location and size of nodes on MRI/DWI were submitted to lesion-by-lesion analyses. Short-axis diameter, border irregularity, enhanced patterns, and apparent diffusion coefficient (ADC) values of each LN were recorded. Each measurement was compared between metastatic and benign LNs, confirmed by nodal histopathology. A receiver operating characteristic (ROC) curve was generated to evaluate the capability of morphological and ADC measurements in distinguishing metastatic lymph nodes.

RESULTS

The median ADC value of metastatic nodes was significantly lower (1.28 × 10(-3) mm(2) /sec; interquartile range, 1.20-1.31) than that of benign (1.55; 1.47-1.73) nodes (P < 0.001). DWI showed greater diagnostic accuracy in determining metastatic nodes (AUC = 0.857) than the combined morphological measurements of short-axis, border irregularity, and enhanced patterns (AUC = 0.746, P = 0.03). Adding ADC values to the combined morphologic criteria demonstrated the greatest predictive power (AUC = 0.889).

CONCLUSION

DWI may provide great potential in effective discrimination of metastatic LNs in gastric carcinoma.

Contrast-enhanced ultrasonography of the rabbit VX2 tumor model: Analysis of vascular pathology

The accuracy of diagnosing tumors may be improved significantly by detecting the microvascular distribution. Indeed, contrast-enhanced ultrasonography (CEUS) has shown a distinct advantage in detecting microvasculature. This study aimed to determine the angiogenic characteristics of VX2 tumors in rabbits using CEUS. A total of 17 rabbits were injected with 0.5 ml VX2 cell suspension into the muscles of both hind legs to prepare the VX2 tumor models. At 14, 21, 28 and 35 days after tumor inoculation, CEUS was performed on the rabbits with 0.3 ml SonoVue following a local anesthesia. The pathological findings of the tumors were compared. A total of 12 rabbits survived after being inoculated with the tumor cells and developed a total of 38 tumors. The size of the tumors ranged from 1.12 to 10.85 cm. Using CEUS, all tumors demonstrated rim enhancement with some unenhanced regions. Enhancement began from the peripheral region and quickly showed internal reticular vessels. Regardless of the tumor size or the presence of necrosis, no complete enhancement of the tumors was observed. On microscopic examination, VX2 tumor cells were detected in striated muscles, immature blood capillaries and fibrosis tissues scattered in tumor nests. Immunohistochemical examination revealed that CD34+ cells appeared mainly in the muscles adjacent to vessels. In conclusion, CEUS may be an efficient method to evaluate angiogenesis and blood perfusion in VX2 tumors.

Animal models and molecular imaging tools to investigate lymph node metastases

Lymph node metastasis is a strong predictor of poor outcome in cancer patients. Animal studies of lymph node metastasis are constrained by difficulties in the establishment of appropriate animal models, limitations in the noninvasive monitoring of lymph node metastasis progression, and challenges in the pathologic confirmation of lymph node metastases. In this comprehensive review, we summarize available preclinical animal cancer models for noninvasive imaging and identification of lymph node metastases of non-hematogenous cancers. Furthermore, we discuss the strengths and weaknesses of common noninvasive imaging modalities used to identify tumor-bearing lymph nodes and provide guidelines for their pathological confirmation.

Contrast-enhanced MR imaging of lymph nodes in cancer patients

The accurate identification and characterization of lymph nodes by modern imaging modalities has important therapeutic and prognostic significance for patients with newly diagnosed cancers. The presence of nodal metastases limits the therapeutic options, and it generally indicates a worse prognosis for the patients with nodal metastases. Yet anatomic imaging (CT and MR imaging) is of limited value for depicting small metastatic deposits in normal-sized nodes, and nodal size is a poor criterion when there is no extracapsular extension or focal nodal necrosis to rely on for diagnosing nodal metastases. Thus, there is a need for functional methods that can be reliably used to identify small metastases. Contrast-enhanced MR imaging of lymph nodes is a non-invasive method for the analysis of the lymphatic system after the interstitial or intravenous administration of contrast media. Moreover, some lymphotrophic contrast media have been developed and used for detecting lymph node metastases, and this detection is independent of the nodal size. This article will review the basic principles, the imaging protocols, the interpretation and the accuracies of contrast-enhanced MR imaging of lymph nodes in patients with malignancies, and we also focus on the recent issues cited in the literature. In addition, we discuss the results of several pre-clinical studies and animal studies that were conducted in our institution.