Anatomical Effects of Axillary Nodes Dissection on Rat Lymphatic System Model: Indocyanine Green Mapping and Dissection.

BACKGROUND: Axillary nodes dissection (AND) is an important risk factor for the appearance of breast cancer-related lymphedema (BCRL). The anatomy and pathophysiology leading to the development of BCRL after AND are not completely understood. Despite the existence of lymphedema models after AND, none of them were able to create lymphedemas without additional chemical inflammatory drugs or auxiliary physical techniques (radiotherapy). In this study, we aimed to describe the anatomical changes of AND on a rat's front leg before and after a new surgery technique. METHODS AND RESULTS: AND was performed on seven Wistar rats with a new, posterior surgical approach. Indocyanine green mapping was done before and after surgery to detect "normal and secondary superficial lymphatic pathways" of the operated rat's front legs. Twelve months after surgery, dissections were performed. Subcutaneous blue dye injection of the hand was used to observe superficial and deep lymphatic pathways. Postsurgery, an acute edema of arm and shoulder appeared and persisted for 14-21 days. However, none of the rats showed a chronic secondary lymphedema. In two cases, seromas also appeared. All rats showed substitution functional lymphatic pathways as perforating lymph vessels around the surgical sites. CONCLUSION: This is the first description of perforating lymph vessels as lymphatic substitution pathways after AND on rats. These results help to understand why a chronic secondary lymphedema could not be created in rats after AND without additional chemical or physical interventions.

Potential Heating Effect in the Gravid Uterus by Using 3-T MR Imaging Protocols: Experimental Study in Miniature Pigs.

Purpose To determine the changes in temperature within the gravid miniature pig uterus during magnetic resonance (MR) imaging at 3 T. Materials and Methods The study received ethics committee approval for animal experimentation. Fiber-optic temperature sensors were inserted into the fetal brain, abdomen, bladder, and amniotic fluid of miniature pigs (second trimester, n = 2; third trimester, n = 2). In the first trimester (n = 2), the sensors were inserted only into the amniotic fluid (three sacs per miniature pig, for a total of six sacs). Imaging was performed with a 3-T MR imager by using different imaging protocols in a random order for animal, each lasting approximately 15 minutes. The first regimen consisted of common sequences used for human fetal MR examination, including normal specific absorption rate (SAR). The second regimen consisted of five low-SAR sequences, for which three gradient-echo sequences were interspersed with two diffusion-weighted imaging series. Finally, a high-SAR regimen maximized the radiofrequency energy deposition (constrained by the 2-W per kilogram of body weight SAR limitations) by using five single-shot turbo spin-echo sequences. Differences in temperature increases between the three regimens and between the three trimesters were evaluated by using one-way analysis of variance. The maximum cumulative temperature increase over 1 hour was also evaluated. Results Low-SAR regimens resulted in the lowest temperature increase (mean ± standard deviation, -0.03°C ± 0.20), normal regimens resulted in an intermediate increase (0.31°C ± 0.21), and high-SAR regimens resulted in the highest increase (0.56°C ± 0.20) (P < .0001). Mean temperature increase in the third trimester was 0.38°C ± 0.27, with no significant differences compared with the first (0.23°C ± 0.27) and second (0.25°C ± 0.32) trimesters (P = .07). The cumulative temperature increase over 1-hour imaging time with high SAR can reach 2.5°C. Conclusion In pregnant miniature pigs, the use of 3-T magnets for diagnostic MR imaging with normal SAR regimens does not lead to temperature increases above 1°C if imaging time is kept below 30 minutes. Longer imaging time, especially with high-SAR regimens, can lead to an increase of 2.5°C. (©) RSNA, 2015 Online supplemental material is available for this article.