Schlieren imaging: Optical techniques to visualize thermal interactions with biological tissues

During surgical procedures, thermal energy is commonly used to create hemostasis by heating the tissue above coagulation temperatures. During the denaturation of proteins and collagen, microvessels shrink and the passage of blood is blocked. The surgeon can resect diseased tissues from the body with minimal loss of blood. Electrosurgery or diathermia is the standard instrument in the operating room (OR) for surgical incisions or resections. Additionally, various instruments are able to heat tissue locally like lasers, RF needles, and ultrasonically vibrating tips. Each instrument has its unique characteristics and optimal settings depending on the application. Either tissue can be evaporated at a small spot without thermal effect in the direct environment or a large volume is coagulated before resection of, for example, a tumor.