Jenifer Serafin Kennedy

Skin resurfacing using an ultrasonic surgical aspirator

The ultrasonic aspirator is essentially a vibrating tip whose ultrasonic frequencies fragment soft tissues, before aspirating it away from the surgical field. In the case of skin, the softer epidermis absorbs the vibrating tips impact force so as to fragment it, whereas the more elastic and collagenous dermis reflects it. Understanding this, a chronic study to compare a skin resurfacing laser (Coherent, Palo Alto, CA) and an ultrasonic surgical aspirator (CUSA) (Valleylab Inc., Boulder, CO) as a skin resurfacing tool was performed using an in-vivo pigmented porcine model. Gross and histopathologic evaluations were made of the lesions removed at 0, 1, 3, 6, 11, 21, and 56 days post procedure. The laser parameters utilized constant power (60 W) and spot size but the number of passes was varied from 1 to 4 passes. This simulated typical minimal to maximal clinical laser treatments. CUSA parameters were then chosen so as to imitate the various laser passes. On sacrifice gross evaluations showed similar levels of healing, using lesion color and scab formation as the method of evaluation. Histological analysis showed evidence of thermal effects with both devices and that some but not all CUSA settings were comparable to the laser. In short, ultrasonic technology may have the potential to provide a controlled method of selectively removing the epidermal skin layer during resurfacing.

Controlled radio frequency vessel sealing system for surgical applications

A radio frequency tissue welding system has been developed for occlusion of vessels during surgery. The system is designed to replace commonly used mechanical clip and suture ligation techniques. Other energy based ligation techniques are limited to use on small structures (<EQ 2 mm) due to slow heating, unreliable sealing, and charring/sticking to the forceps. The system consists of forceps and an RF electrosurgery generator, both of which are specifically designed for optimal tissue sealing. The method combines optimal pressure delivery to the tissue and energy delivery consisting of a high heat cycle, a low heat cycle and a cooling cycle. The generator output is also voltage limited and delivers high current in order to remodel the collagen in approximately 5 seconds with no sticking or charring. The vessel sealing system was compared to other energy based ligation techniques including ultrasonic sealing and other bipolar systems. The pressure required to burst the vessel was used for comparison. Average burst pressures on 3 - 7 mm arteries were 126 +/- 154 mmHg, 607 +/- 314 mmHg, and 913 +/- 304 mmHg for ultrasonic, standard bipolar, and vessel sealing, respectively. Histologic evaluation showed vessel wall fusion and minimal thermal damage to adjacent tissues for the vessel sealing system.

A simplified, low power system for effective vessel sealing

The first bipolar vessel sealing system was developed nearly 15 years ago and has since become standard of care in surgery. These systems make use of radio frequency current that is delivered between bipolar graspers to permanently seal arteries, veins and tissue bundles. Conventional vessel sealing generators are based off traditional electrosurgery generator architecture and deliver high power (150-300 Watts) and high current using complex control and sense algorithms to adjust the output for vessel sealing applications. In recent years, a need for small-scale surgical vessel sealers has developed as surgeons strive to further reduce their footprint on patients. There are many technical challenges associated with miniaturization of vessel sealing devices including maintaining electrical isolation while delivering high current in a saline environment. Research into creating a small, 3mm diameter vessel sealer revealed that a highly simplified generator system could be used to achieve excellent results and subsequently a low power vessel sealing system was developed. This system delivers 25 Watts constant power while limiting voltage (≤ Vrms) and current (≤ Amps) until an impedance endpoint is achieved, eliminating the use of complicated control and sensing software. The result is optimized tissue effect, where high seal strength is maintained (> 360mmHg), but seal times (1.7 ± 0.7s versus 4.1 ± 0.7s), thermal spread (<1mm vs ≤2mm) and total energy delivery are reduced, when compared to an existing high power system.