Thermographic study of laser on arteries

Diamond shaped optical fiber delivery system

BACKGROUND

Optical fibers are generally used with a flat cut end. The adaptation of a coaxial exit of a refrigerated gas near the distal tip of the optical fiber cools the tissue where the laser beam is applied and reduces the injury of thermal effects on biological tissue.

MATERIALS AND METHODS

We have changed the flat end geometry of the fiber's end to a pyramidal end shape (named: Diamond tip). In this project we have evaluated the new shape of the fiber's end using laboratory tests and in real conditions. We have examined the emission pattern in the air and in water as well as its performance in surgery.

RESULTS

With the new shape better results were obtained: higher power density, more utilizations of the same fiber (after sterilization) resulting in economical savings. The diamond tip is characterized by greater mechanical resistance then conical tip delivery systems. The greater resistance of the Diamond tip prevents optical fiber breakage during surgery. The delivered system can be reshaped by a trained hospital physician and reused. Our experience shows that delivery systems intended by the producer to one use only can be converted, by reshaping their tips, to highly performing delivery systems, which can be reused many times. In addition less power was needed, with less tissue penetration. The thermal effect was minimized and higher mechanical resistance was achieved, which allowed reusing the fiber more than six times. The special structure of the faces of the optical fiber diamond tip eased its sliding.

CONCLUSION

The Diamond tip is superior to other fiber end tips by having minimal thermal effects, higher mechanical resistance and by being reused many times.

Cultured human keratinocytes for optical transmission measurement

The challenges of measuring optical properties of human tissues include the thickness of the sample, homogenization, or crystallization from freezing of the tissue. This investigation demonstrates a method to avoid these problems by growing optically thin samples of human keratinocytes as a substitute for ex vivo epidermis samples. Several methods of growth were investigated. Resulting samples were measured on a spectrophotometer for transmission between 300 nm and 2600 nm. The efficacy of the cell growth was confirmed with histological examination of several cultured keratinocyte samples. Limitations were the requirement to measure samples immediately after removal from the incubation environment, and the absence of the irregular structures of normal skin such as hair and glands.

Diamond-shaped optical fiber delivery system

OBJECTIVE

Physicians who use laser systems are looking for new fiberoptic delivery systems with better performance. We searched for a delivery system with high power and with a tip of high durability that may be reused many times.

SUMMARY BACKGROUND DATA

The delivery systems currently found on the market can burn and break easily. The surgeon may either finish the surgery with a damaged delivery system, or have to switch to a new one during surgery, thus increasing the inconvenience and cost of the surgery.

METHODS

Distal tips of fibers used with Nd:YAG and diode lasers have been shaped and polished according to their specific function, including excision, vaporization, and coagulation of tissue.

RESULTS

We have developed several prototypes of optical fiber delivery systems, and in particular, we have developed a prototype of a delivery system, called the Diamond-Shaped Optical Fiber Delivery System, or Diamond. By making the tip of an optical fiber diamond shaped, we are able to obtain greater mechanical resistance than that of other delivery systems that were tested in our laboratory. In the Colorectal Unit, we applied it in surgical procedures such as perianal fistulectomy, hemorrhoidectomy, and excision of condilomata acuminata and pilonidal cyst and sinuses. During cutting and coagulating, the system performed well with no technical problems.

CONCLUSIONS

A new delivery system (Diamond) gave satisfactory performance during surgical operations. Its main component, the diamond-shaped distal end, provided high durability and was reused many times, thus improving the quality of operations and reducing expenses greatly.

Limitations of a thermal camera in measuring surface temperature of laser-irradiated tissues

Thermal cameras are used in research laboratories to measure tissue temperature during laser irradiation. This study was an evaluation of the accuracy of a 3-5 microns thermal camera and two 8-12 microns cameras in detecting the maximum temperatures of small targets. The size of the targets was within the range of laser spot diameters which are used for vessel welding, angioplasty, and dermatology. The response to a sharp thermal edge was measured and analyzed for the three cameras, which had a scanning rate of 30 frames per second. The response of the 3-5 microns camera to reference black body targets of different sizes was also studied. It was found that the detector system required an average of 2.44 microseconds to reach 90% of maximum step response for the 8-12 microns system and 5.85 microseconds for the 3-5 microns system. With a 3 x telescope and a 9.5 inch focal distance close-up lens, the 3-5 microns camera underestimated the temperature of targets smaller than 2.0 mm because of its slow detector response. Although the 8-12 microns camera provides more accurate measurements due to its faster detector response, it still underestimates the temperature of targets smaller than 900 microns, when similar magnification and focal distance are used. Methods to compensate for the inaccuracies are discussed, including empirical correction factors and the inverse filtering technique.