Evaluation of lymph node metastases in gastric cancer using magnetic resonance imaging with ultrasmall superparamagnetic iron oxide (USPIO): diagnostic performance in post-contrast images using new diagnostic criteria.

BACKGROUND

We assessed the value of magnetic resonance imaging (MRI), using ultrasmall superparamagnetic iron oxide (USPIO) with new diagnostic criteria, in the evaluation of regional lymph node metastases in gastric cancer.

METHODS

Thirty-one patients with gastric cancer were enrolled. 1000 lymph nodes were dissected during surgery, and of these, 519 nodes (51.9%) were identified by currently used MRI imaging analysis. We evaluated lymph nodes on USPIO-post-contrast T2*-weighted images using the following two criteria: (1) we diagnosed the nodes on T2*-weighted images according to conventional criteria, where a node having an overall low signal intensity (pattern A) was nonmetastatic, while a node having partial (pattern B) or overall (pattern C) high signal intensity was metastatic; (2) we subdivided pattern B nodes on T1-weighted images using the new criteria, in which a node for which the high-intensity area on T2*-weighted images was not defined as adipose tissue on T1-weighted images (pattern B1) was metastatic, while a node for which the high-intensity area was defined as adipose tissue (pattern B2) was nonmetastatic.

RESULTS

(1) The results using the conventional criteria were 96.2% sensitivity, 92.5% specificity, 76.3% positive predictive value (PPV), 99.0% negative predictive value (NPV), and 93.3% accuracy. (2) The results using the new criteria were 96.2% sensitivity, 98.3% specificity, 90.1% PPV, 99.0% NPV, and 97.1% accuracy.

CONCLUSION

The assessment of lymph node metastases from USPIO-post-contrast MRI alone using the new criteria was useful in the diagnosis of regional lymph node metastases in gastric cancer.