This exchange is expected to reduce contrast media concentration in lumens after intraductal injection. Previous in this laboratory demonstrated contrast media exchange between blood vessels and the lumens of mammary ducts. As a first step, the pilot study reported here was performed on non-transgenic FVB/N mice that do not have detectable cancer.
#BOX SHOT 3D V2.9.4 SOFT SERIAL#
Serial imaging following intra-ductal injection of contrast media could provide information concerning cancer initiation and progression, as well as the normal development of mammary glands and changes during the menstrual cycle. The goal of the present work was to develop and test MRI methods that will later be used to study the development of early in situ cancers growing in mammary ducts. Therefore, high resolution 3D MRI ductography has the potential to provide unique and important information.
In addition, the excellent soft tissue contrast of MRI can provide important information regarding the relationship of ducts and in situ cancers to surrounding tissue including blood vessels and lymph nodes. High resolution volumetric imaging is important because of the complexity of the ductal-alveolar tree that converges into a central duct at the nipple. Previous approaches to ‘ductography’ in mice have not involved high resolution three-dimensional (3D) MRI. In addition, an IVIS bioluminescence system has been used to visualize inflammation in glands and ducts.
Ducts have also been imaged in genetically-engineered mice expressing fluorescent proteins using Olympus OV100 Fluorescence Imaging, as well as using neutral red dye and a variety of fluorescent dyes. In addition, intra-ductal injections of dyes have been used in conjunction with optical imaging, microscopy, and digital photography to evaluate duct architecture, and changes in architecture associated with various pathologies. Techniques for intra-ductal injection in mice are well worked out and have been used for injection of cancer cells to produce in situ cancers. ‘Ductography’ using both X-ray and MRI has been frequently used in clinical practice to increase sensitivity to ductal anatomy, cancer and other pathologies. However, due to limited MRI spatial resolution, it was difficult to visualize the mouse mammary gland ductal architecture in those studies. This previous work relied on conventional imaging including contrast enhanced MRI to detect cancers. recently reported on serial magnetic resonance imaging (MRI) of murine mammary cancer in SV40 Tag mice as it progressed from the in situ to the invasive stage. Transgenic mouse models of human breast cancer provide important insights in the pathways and mechanism of breast cancer initiation and progression. The methods described here could be adapted for injection of specialized contrast agents to measure metabolism or target receptors in normal ducts and ducts with in situ cancers. In spoiled gradient echo T1-weighted images, the signal-to-noise ratio of regions identified as enhancing mammary ducts following contrast injection was significantly higher than that of muscle (p < 0.02) and significantly higher than that of contralateral mammary ducts that were not injected with contrast media (p < 0.0001). MRI showed the mammary gland ductal structure clearly. Trypan blue staining was well distributed throughout the ductal tree. High resolution 3D T1-weighted images were acquired on a 9.4T Bruker scanner after sacrifice to eliminate motion artifacts and reduce contrast media leakage from ducts. To prevent washout of contrast media from ducts due to perfusion, and maximize the conspicuity of ducts on MRI, mice were sacrificed one minute after injection. Approximately 20–25uL of a Gadodiamide/Trypan blue/saline solution was injected slowly over one minute into the nipple and duct. A 34G, 45° tip Hamilton needle with a 25uL Hamilton syringe was inserted into the tip of the nipple.
Female FVB/N mice age 12–20 weeks (n = 12), were used in this study. The purpose of this study was to use high resolution 3D MRI to study mouse mammary gland ductal architecture based on intra-ductal injection of contrast agents.