11. Bioengineering and Bio-thermal Fluid Dynamics

In breast cancer, cancer cells are likely to metastasize to the lymph nodes (LNs). LN resection is a well-established treatment; however, it can lead to lymphedema and significantly interfere with daily life. Currently, no definitive treatment is available for lymphedema. Therefore, minimally invasive therapies are highly desirable. One of the promising approaches is to use a combination of near-infrared (NIR) laser and gold nanorods (GNRs). Our previous study obtained the temperature distribution using a porcine liver by combining an NIR laser, GNR, and surface cooling device. It was found that there was no obvious temperature increase at the GNR injection site when the GNRs were injected deeper than 5 mm from the surface. This indicated that the laser propagation length is only several mm in biological tissues. If the tumor was located more than 5 mm, treatment with a laser from outside the body would not be effective. In this study, a prototype fiber-optic probe that could be inserted directly into the body was fabricated. The outer diameter of the probe, whose optical fiber strength was reinforced with SUS, was 0.8 mm. This can be considered a minimally invasive method. As an experimental result using porcine liver, thermal coagulation with a size of approximately 9 mm × 9 mm was obtained during 300 s irradiation at a 1 W laser power. In addition, two experiments, with and without GNR injection, were performed under the same experimental conditions. Clear coagulation was observed with GNRs, whereas no coagulation was observed without GNRs. This preliminary study showed that our prototype probe has the potential to damage tumors located deep in the body, and has a size of approximately 10 mm × 10 mm. The challenge is to reduce the carbonization zone and stabilize the GNRs in biological tissue.

Prof.

Atsuki Komiya