Histological Comparison of Two Different Fractional Photothermolysis Devices Operating at 1,550 nm

Background: There are a wide variety of fractional resurfacing devices that are available and it is important to understand the tissue effect of different devices at different parameters to ensure a well-controlled treatment. Thus, we have chosen to characterize and compare two different fractional laser devices, the Fraxel SR750 and SR1500 (re:store (TM)) (Solta Medical, Hayward, CA). While the SR750 has a fixed focus spot diameter, the SR1500 features an internally controlled zoom optic allowing for an adjustable spot size. Materials and Methods: Exposures were performed in vitro on human skin samples at 37 C. The exposures were performed for the SR750 at pulse energies between 6 and 40 mJ at 125 MTZ/cm(2) with up to 20 passes, and for the SR1500 between 6 and 100 mJ, at Treatment Level 7 and 8 passes. The skin samples then were processed for serial frozen sectioning, stained with Nitro-Blue-Tetrazolium-Chloride (NBTC) and lesion depth and width was determined. Results: Mean lesion depth was significantly greater for lesions treated with the SR1500 laser compared to the SR750 at pulse energies of 6, 10, 30, and 40 mJ (P < 0.001) with a borderline difference at 20 mJ. Mean lesion width was comparable for energies up to 20 mJ and relatively increased for the SR1500 for higher energies. The depth-to-width ratio (DWR) was in general higher for the SR1500, reaching significance at 6, 10, and 40 mJ. Conclusion: We have characterized the lesion depth and width for the for two different Fractional Photothermolysis devices (SR750 vs. SR1500). The device with the adjustable spot size (SR1500 or Fraxel re:store (TM)) provides generally deeper lesions at the same energy level. It remains to be shown whether increased lesion depth improves efficacy for certain clinical applications. Lasers Surg. Med. 42:32-37, 2010. (C) 2010 Wiley-Liss, Inc.