Nanoparticles in sentinel lymph node mapping

Abstract

The lymph nodes and lymphatic vessels are more difficult to access than most vascular structures. Interstitial injection of imaging agents is often necessary to opacify the lymphatics. Traditionally, radionuclide methods of sentinel node imaging have dominated this field, however, limitations in resolution and exposure to radiation have encouraged the development of newer imaging methods. Among these are magnetic resonance lymphography in which a Gadolinium labeled nanoparticle is injected and imaged providing superior anatomic resolution and assessment of lymphatic dynamics. Optical imaging employing various nanoparticles including quantum dots also provide the capability of mapping each lymphatic basin in another "color". Taken together this "toolbox" of lymphatic imaging agents is poised to improve our understanding of the lymphatic system.

FIGURE 1 |

Anterior and lateral planar images of the chest obtained after the intradermal injection of radiotracer in the skin overlying the primary tumor. The large area of intense radiotracer uptake in the right breast corresponds to the injection site. The sentinel lymph node is clearly noted in the right axilla (arrowheads).

FIGURE 2 |

Dynamic (top row) and static images of the chest obtained after the subdermal injection of radiotracer around the peri-areolar area. Radiotracer is noted draining to a sentinel lymph node in the left axilla (arrowheads). Echelon lymph nodes or a lymphatic channel starts to appear medial to the sentinel node.

FIGURE 3 |

Modern gamma probe system currently in use for sentinel lymph node detection (Nuclear Fields Corp., Des Plaines, Illinois).

FIGURE 4 |

In vivo visualization spectral fluorescence imaging of lymphatic drainage of a mouse with five carboxyl Qdots (565, blue; 605, green; 655, yellow; 705, magenta; 800, red) injected intracutaneously into the middle digits of the bilateral upper extremities, the bilateral ears, and at the median chin. Five primary draining lymph nodes are simultaneously demonstrated with different colors through the skin in the in vivo image.

FIGURE 5 |

Whole body three dimensional MR lymphangiogram (maximal intensity projection) of a normal mouse. PAMAM-G8 was injected intracutaneously into middle phalanges of all four limbs. Arrows indicate enhanced lymph nodes and lymphatic vessels. (Adapted with permission from Ref 70. Copyright 2006 Wiley Periodicals Inc).

FIGURE 6 |

Magnetic resonance imaging (MRI) and near-infrared (NIR) optical images of a sentinel lymph node of breast cancer in a mouse obtained with a MRI-NIR optical hybrid nano-sized contrast agent G6-Cy5.5 (left upper). Invivo (right upper) and intra-operative (right lower) images are shown along with a schematic illustration of the imaging method (left lower). (Adapted with permission from Ref 70. Copyright 2006 Wiley Periodicals Inc).