Non-ablative cutaneous remodeling with a 1.45µm mid-infrared diode laser: phase I

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Abstract
BACKGROUND : Presented here is phase I of a three-part study of non-ablative cutaneous remodeling with a 1.45 w m diode laser configured with a cryogen spray cooling device. METHODS : Eight men and two women (average age of 67 years) with Fitzpatrick skin phototypes I-IV were treated at postauricular sites. Treatment consisted of one or two passes with a 4mm spot and an average power of 12 W. Heating times ranged from 150 ms to 500ms applied over two to six treatment cycles. One treatment 'cycle' lasted for 100ms and consisted of programmable parallel cryogen spray cooling pulses interspersed with unopposed heating. Biopsies were obtained at baseline, immediately after treatment, and at 2 months. RESULTS : Patients were assessed 1 day, 1 week, 1 month and 2 months after treatment. Treatments were well tolerated with minimal pain, with a trend towards increasing discomfort with longer heating times. Erythema and edema were also mild and short-lived. There was a direct relationship between the degree of erythema and edema, and longer unopposed heating times. Mild hyperpigmentation occurred at only three treatment sites. Epidermal burns usually presented as immediate whitening in 11 of 60 one-pass sites and four of 16 two-pass sites. Whitening was associated with longer unopposed heating times. Atrophic, pitted scars occurred at two single-pass sites and three double-pass sites. Baseline biopsies demonstrated solar elastosis in a 375 w m thick band (mean range from 100 w m to 480 w m deep in the dermis). Immediate post-treatment biopsies demonstrated thermal damage in a 333 w m thick band (mean range from 311 w m to 644 w m deep in the dermis). Finally, dermal fibrosis was observed 2 months after treatment in a 272 w m thick band (mean range from 148 w m to 420 w m deep in the dermis). CONCLUSION : The 1.45 w m diode laser is capable of targeting dermal collagen and stimulating fibrosis at depths where solar elastosis resides. Longer unopposed heating times corresponded to increased erythema, edema, and pain, which were typically mild and short-lived. Epidermal burns can result in pitted scars.