Imaging of the Mouse Lymphatic Sinus during Early Stage Lymph Node Metastasis Using Intranodal Lymphangiography with X-ray Micro-computed Tomography

Purpose: Lymph node (LN) metastasis is detected prior to distant metastasis in many types of cancer. Detecting early stage LN metastasis can improve treatment outcomes. However, there are few clinical imaging modalities capable of diagnosing metastatic LNs of clinical N0 status (i.e., before their volume increases) with high precision. Here, we report a new method for diagnosing metastatic LNs of clinical N0 status in a mouse model of LN metastasis. Procedures: The method involved using intranodal lymphangiography with x-ray micro- computed tomography (micro-CT). Contrast agent was injected into an upstream LN to deliver it to a downstream LN, which was then removed and analyzed by micro-CT. Results: We found that using an intranodal injection rate of 10–60 μl/min filled the lymphatic sinus of the downstream LN with contrast agent, although the accumulation of contrast agent in the upstream LN increased with a faster injection rate. Furthermore, breast cancer cells growing in the lymphatic sinus of the downstream LN (which was of clinical N0 status) impeded the flow of contrast agent from the upstream LN, resulting in areas deficient of contrast agent in the metastatic downstream LN. The formation of defect areas in the downstream LN manifested as a difference in position between the centroid of the entire LN area and the centroid of the region that filled with contrast agent. Conclusion: The present study indicates that intranodal lymphangiography with micro-CT has the potential to be used as a new method for diagnosing metastatic LNs of clinical N0 status.