Comparison of pulsed CO2 laser ablation at 10.6 microm and 9.5 microm.
OBJECTIVE
The pulsed CO2 laser has received attention because of its successful application to dermatologic surgery and burn debridement surgery. Despite impressive results, tissue removal using pulsed CO2 laser irradiation has not been optimized. We examined the ablation processes by performing mass removal and thermal injury experiments at wavelengths where tissue water is the primary absorber (10.6 microm), and where water and collagen have comparable absorption (9.5 microm).


METHODS
Samples of porcine reticular dermis were irradiated with 180-ns laser pulses at either wavelength. Tissue removal was measured using a digital balance. Thermal injury was assessed using a microscope with a calibrated reticle after hematoxylin and eosin staining.


RESULTS
Tissue removal using 10.6-microm radiation resulted in a heat of ablation of 3,740 J/g, an ablation threshold of 1.15 J/cm2, and a zone of thermal injury of 53 microm. By contrast, tissue removal using 9.5-microm radiation resulted in a heat of ablation of 3,330 J/g, an ablation threshold of 1.47 J/cm2, and a zone of thermal injury of 34 microm. The differences in ablation threshold and thermal injury were statistically significant.


CONCLUSIONS
Pulsed CO2 laser irradiation at 9.5 microm removes tissue more efficiently and with a smaller zone of thermal injury than at 10.6 microm.
Wellman Laboratories of Photomedicine, Harvard Medical School, Massachusetts General Hospital, Boston 02114, USA. bugzy@mit.edu
B P
BP
Payne
N S
NS
Nishioka
B B
BB
Mikic
V
V
Venugopalan
D000818:Animals; D002056:Burns / Q000209:etiology / Q000473:pathology; D062109:Dermatologic Surgical Procedures; D006358:Hot Temperature / Q000009:adverse effects; D053685:Laser Therapy / Q000009:adverse effects / Q000379:methods*; D016018:Least-Squares Analysis; D012044:Regression Analysis; D012867:Skin / Q000473:pathology; D013499:Surface Properties; D013552:Swine