Biomedical subjects
Publications and source records attributed to M Dressel.
Cutting and drilling of bone- and meniscus tissue were performed using a XeCl-excimer laser combined with a tapered fiber. Ablation speed on meniscus tissue is already sufficient, the thermal damage of the adjacent tissue is minimal. Increasing of energy transmission through special fibers promises higher ablation rates also on hard biological tissue and that promoted the interest in lasers again for accident surgeons.
Our experiments on transmitting high-power excimer laser pulses through optical fibers and our investigations on excimer laser ablation of hard tissue show the feasibility of using the excimer laser as an additional instrument in general and accident surgery involving minimal invasive surgery. By combining XeCl-excimer lasers and tapered fused silica fibers we obtained output fluences up to 32 J/cm2 and ablation rates of 3 microns/pulse of hard tissue. This enables us to cut bone and cartilage in a period of time which is suitable for clinical operations. Various experiments were carried out on cadavers in order to optimize the parameters of the excimer laser and fibers: e.g., wavelength, pulse duration, energy, repetition rate, fiber core diameter. The surfaces of the cut tissue are comparable to cuts with conventional instruments. No carbonisation was observed. The temperature increase is below 40 degrees C in the tissue surrounding the laser spot. The healing rate of an excimer laser cut is not slower than mechanical treatments; the quality is comparable.
In an experimental investigation we examined the possibility to create an open pathway between the anterior chamber and Schlemm's canal by excimer laser ablation of the trabecualr meshwork (AT) in enucleated eyes. A quartzfiber was directed through the anterior chamber to the opposite chamber angle. With an energy of 0.3-1.5 mJ and wavelengths of 248 and 308 nm pores were easily made into the trabecular meshwork leading to a direct connection between the anterior chamber and Schlemm's canal. This result was confirmed by histologic examination of the globes. The trabecular meshwork has disappeared completely. The surrounding tissue reveals only minimal thermal effects due to the laser burns. With the same method cyclodialysis and basal iridectomy may be performed. The operation is simple and effects can be placed with great accuracy.
In 20 guinea pigs 4 test areas were treated with a standard surfactant vehicle twice weekly for 3 weeks. In another 20 animals the same treatment was carried out with the addition of 1% cadmium sulfide on one area, of 10% coal tar distillate on another, 2% ichthyol sodium on the 3rd and 1% Omadine MDS on the 4th. At the end of the test in both animal collectives the number of mitoses in the basal cells of the epidermis (Colcemid method) and the thickness of the epidermis (microscopically) were determined in each of the 4 test areals. All 4 agents lead to a significant inhibition of mitoses compared with the surfactant vehicle. Coal rat also produces an acanthosis. The mitosis inhibition supports the opinion that these agents are suitable for the treatment of dandruff.
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