Selective Photothermolysis

Leon Goldman was seminal in beginning and motivating the use of medical and surgical lasers but the direction of laser use was related to the industrial lasers provided to us. Micromanipulators, fiberoptics, scanners, and microscopic couplers were all cleverly invented accessories for the main item but the main item was never designed from the ground up for altering specific pathogenic targets, that is, not until 1983. The second most remarkable seminal event for laser surgery was the optical construct, which allowed us to understand the nature of the amount of thermal or acoustic alteration that was minimally necessary to produce our biologic result. Not only could we select a target and an appropriate laser using the target's relative absorption characteristics but we could also construct a laser putting out a burst of light corresponding in its duration to the thermal relaxation time of the target. This combination of selection by absorption and by size became the theory of selective photothermolysis as elaborated by Anderson and Parrish (4,5) (Fig. 1.18). It was the first of many modeling constructs around which medical lasers would be manufactured. The courtship of laser industry and laser surgeons, which had begun after the institution of ASLMS, was now ready for the full-fledged partnership of marriage. Now laser surgeons could request industry machines capable of specific tasks. The pulsed dye laser for vascular lesions was the first of these many instruments (228-235). Though shifted from its original experimental format of 577 nm (236,237), 360 ms pulses, and 5 mm spot size to 585 nm (235,238-244) and 450 ms and now up to 600 nm and 20 ms pulses with 5, 7, and 10 mm spot sizes, it allowed for rapid treatment of large areas—perhaps 100 times faster than the argon laser had been. Pain was usually not severe enough to require anesthesia except in children. There was almost no thermal damage to the epidermis except mild crusting by days 3-4 postoperative and thus no second-degree burn injury and essentially no risk of either hypertrophic or flat opaque scar. In the mid- to late 1980s it very quickly became the vascular laser of choice despite the simultaneous appearance of other quasi-continuous yellow lasers (205 -207,245 -248). Because of its greater safety and specificity it was widely offered to children who for the most part (74,76,77,80,241,249,250) had been denied continuous or quasi-continuous laser treatments. The dramatic impact of a laser able to treat deformed children without scarring and with a "100% cure rate" (240) was earth-shaking.

Figure 1.18 R. Rox Anderson, MD, conceptualizer of "selective photothermolysis." (Courtesy, Wellman Laboratories of Photomedicine.)

What actually happened was unfortunate as this drama had an adverse side as well. Tan et al.'s enthusiastic report in the widely publicized New England Journal of Medicine had the public convinced that the laser was painless and 100% effective, thus putting all cutaneous laser surgeons on the spot trying to re-explain that neither scenario was true. This laser has been documented to clear PWS in only 40% of patient populations (251) with repeated treatments, though the remainder of patients are very significantly improved. As initially with the carbon dioxide laser, hyperbole was fashioning unrealistic public demand.

The second adverse sequel was that this industry-surgeon marriage meant that there was an increasingly important role that the medical-industrial complex would play, not just in the delivery of care, but also in its cost since the new lasers represented hundreds of thousands of dollars in investment to be paid off by the laser surgeon. There was, as well, the possible perversion of scientific methodology and reporting by not-so-subtle conflicts of interest such as special deals in pricing of lasers, free or loaned lasers, research grants, surgeons acting as spokespersons in advertising routines for companies; these same laser surgeons would then be called upon to present or publish new data in what the audience was supposed to think represented no conflict of interest. For the first time it would not be egos or ideas under attack by skeptical laser audiences but the very ethics and truthfulness of the presenters. This was a nasty and unexpected challenge to honest scientific methodology; vocal controversy and insult became an unfortunate coparticipant at laser meetings as evidenced by chairmen's forewarning to their panelists at the 1998 ASLMS about personal (ad hominem) attacks.

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