Abstract
Sentinel lymph node biopsy has been widely used in cancer treatment to assess lymph node metastasis at early stages. It has been reported that this procedure has an accuracy of greater than 95% in the evaluation of lymph node metastasis in patients with stage N0 carcinoma, especially in patients with malignant melanoma or breast carcinoma. Surgeons trace the sentinel lymph node using a gamma probe that can provide radioactivity counts in the operating theater. As surgeons are unable to visualize increased radioactivity with spatial resolution, a small gamma camera can be used for this purpose at the time of the biopsy. However, sentinel lymph nodes with increased accumulation cannot be defined with anatomical resolution. The blue-dye technique is often combined with the radioisotope method to improve sentinel lymph node detection. However, the blue-dye technique only enables the visualization of lymph flow and sentinel nodes within the incision area. Near-infrared (NIR) imaging using indocyanine green (ICG) was recently introduced as a new option for imaging sentinel lymph nodes due to deeper penetration of photons into living tissue. We developed a dual-modality imaging system, polyamidoamine (PAMAM)-coated silica nanoparticles loaded with 99mTc and ICG, for depicting deeply situated sentinel nodes and fluorescent nodes and to enable simultaneous visualization at anatomical resolution. We conducted animal studies to test the feasibility and utility of this dual-modality imaging system. Furthermore, we are conducting a molecular target imaging study to detect sentinel lymph node metastasis. We also review recent developing molecular imaging modalities for depicting sentinel lymph node metastasis.
